Biogeography: Studying the Distribution of Species Across Space

Part 1: Biogeography: Studying the Distribution of Species Across Space

00:00:07.06 Hi.
00:00:08.06 My name is Uma Ramakrishnan and I'm an associate professor at the National Centre for Biological
00:00:12.22 Sciences in Bangalore, India.
00:00:15.18 This is a research institute where we study biology, and I've come all the way from there
00:00:20.17 to tell you a little bit about biogeography and the work that we do on understanding biodiversity
00:00:27.12 in the Indian subcontinent.
00:00:29.13 So, anywhere you live, if you look outside your window, you'll see many different species.
00:00:35.06 This is biodiversity.
00:00:36.06 And as humans we're fascinated by biodiversity.
00:00:40.16 And biogeography actually is a field which studies the distribution of species and biodiversity
00:00:47.03 across space.
00:00:48.10 And, you know... you know immediately, even as a child, that certain places have more
00:00:56.10 species than others, the species in a particular place seem to be similar, and so on.
00:01:01.05 You observe these things almost naturally.
00:01:04.05 And this is basically how we measure biodiversity and how we study it.
00:01:08.09 We try and quantify biodiversity and look at why places have more biodiversity than
00:01:14.08 do others.
00:01:15.15 So, how do we quantify biodiversity?
00:01:18.11 How do we actually use mathematical ways to study patterns of biodiversity, statistical
00:01:24.19 ways, across the world?
00:01:27.09 So, the first thing we do is we actually count the number of species, right?
00:01:33.09 This is something which has often been controversial in biology.
00:01:36.11 How do we know what is a species?
00:01:38.05 A taxonomist... as humans, we have this desire to put things in boxes and say, this is one
00:01:44.19 species, this is another... and in some cases this might be relatively easy.
00:01:49.03 For example, with apes, you know, the gibbon... gibbons look very different from gorillas
00:01:55.20 and chimpanzees and modern humans.
00:01:57.15 And when we look at their DNA there are several of these differences which are reflected,
00:02:03.01 allowing us to build a phylogenetic tree.
00:02:05.08 We heard about this also, for example, in Scott Edwards' talk.
00:02:09.21 So, this allows us to understand that there are multiple species of apes which look different
00:02:16.24 and are genetically different, distinct, as well.
00:02:20.10 This may not always be the case.
00:02:22.14 For example, this really beautiful examples of a ring species, salamanders in California.
00:02:30.03 It shows you, here, that across their distribution these different salamanders look slightly
00:02:36.08 different and yet similar, right?
00:02:38.04 So, here, speciation or these different species are along a continuum, right?
00:02:44.05 They look slightly different... one looks slightly different from the other and so on.
00:02:48.19 So, it's not always easy to classify species, but, overall, we use various tools: morphology,
00:02:55.19 how species and individuals... how individuals in a population look; genetics, how different
00:03:00.20 or similar their DNA is; and it could be several other forms of behavior -- do they have similar
00:03:06.12 songs, if they're birds, and so on -- and we use all of these bits of information to
00:03:11.19 make an informed guess about whether we think sets of individuals are distinct species or
00:03:17.10 not.
00:03:18.10 For the sake of correctness, I should tell you that the biological species concept proposed
00:03:23.06 by Ernst...
00:03:24.06 Ernst Mayr is what we accept, and this suggests that a species is a group of individuals that
00:03:29.14 can and do interbreed with each other in nature.
00:03:32.11 So, not if you put them together in a zoo, but in nature you do find them interbreeding.
00:03:38.10 And, as we said, species could look similar or different, but at some point we take a
00:03:44.14 call and we say, okay, this is a species and these two populations are not distinct enough
00:03:49.08 to be a species.
00:03:50.17 So, once we have catalogued species -- that's the first thing we have to do, these are our
00:03:55.07 primary data -- we measure biodiversity in units of species.
00:04:00.23 So, how do species actually evolve?
00:04:04.03 I mean, we said, okay, they look different or, you know, they're genetically different.
00:04:09.06 Well, this has also been a field of extensive study in evolutionary biology and you made
00:04:13.16 have seen a talk as part of this series by Hopi Hoekstra, who's actually trying to understand
00:04:18.01 how these differences between how species look/evolve from a genetic perspective, right?
00:04:24.03 Adaptation from a DNA level.
00:04:26.19 But this picture, here, shows you a really simple kind of theoretical idea of speciation.
00:04:33.09 So, the most basic is allopatry, over here, where you can see that there's two pop...
00:04:39.03 there's a population and suddenly, potentially, there's a barrier between two parts of this
00:04:45.03 population, maybe a road came up or there was a... a... a, you know, a rift or something
00:04:50.01 like that, a river.
00:04:52.00 And now, individuals on either side of this barrier develop different adaptations or they
00:04:59.16 become different.
00:05:01.13 And so, when they meet again, say, when this barrier disappears, they don't interbreed
00:05:05.23 with each other.
00:05:06.23 So, this has now resulted in the creation of two species from what was a single population,
00:05:12.24 right?
00:05:13.24 So, this is a case of allopatric speciation, and often what we see most commonly in nature.
00:05:21.13 On the other hand, speciation could theoretically also be sympatric, where you have a new, for
00:05:27.14 some reason, change...
00:05:30.12 ecological change, maybe, or adaptation... of some individuals in one of this... in this
00:05:35.16 population, and this results in differentiation and, over time, these differences became...
00:05:42.05 become so large that these two populations do not interbreed.
00:05:47.06 An example for this is the [unknown] flies, or the apple flies, and the Hawthorn flies,
00:05:53.00 which lay their eggs on different fruits.
00:05:55.23 Apple and Hawthorn [flies] are just coexisting, so they're sympatric, these flies, and yet,
00:06:02.11 you know, they do become... could become different species.
00:06:05.01 There are kinds of shades and grades of these two examples, where you could have speciation
00:06:10.13 in peripatry or parapatry, a creation of a new niche or a certain kind of budding off
00:06:16.24 of a set of individuals and so on, a range expansion.
00:06:21.06 But, basically, the mechanisms are somewhere between sympatry and allopatry.
00:06:26.21 While these are nice examples from a theoretical, hot perspective, what do we know about speciation?
00:06:34.06 So, early on, Dodd did experiments with Drosophila where, you know, different populations of
00:06:41.00 flies were given two different kinds of food and, over time, these two flies... fly populations
00:06:49.23 became differentiated and then they developed mating preferences, so flies from population
00:06:56.16 1 didn't want to mate with flies from population 2 and vice versa.
00:07:00.23 So, this is very important because it shows that not only did they become different, they
00:07:06.17 developed reproductive preferences and, potentially, reproductive isolation -- what's most important
00:07:13.04 for the lack of gene flow of mating, in the end, between two species.
00:07:18.00 So, now I'll go... we go back to biogeography, which is basically the distribution of species
00:07:26.14 on our planet, right?
00:07:28.08 So, how do we actually study this?
00:07:30.17 In a sense, it's one of those... the most basic things.
00:07:34.04 Even before people thought about DNA or evolution, a lot of naturalists walked all over the world
00:07:41.19 and did surveys and catalogued interesting things about biodiversity.
00:07:47.17 Alexander von Humboldt was one of these people and he basically did a lot of explorations
00:07:54.10 and studies in South America, and this beautiful illustration he has of this mountain, Chimborazo,
00:08:02.13 in South America, which is a volcanic mountain, which goes really high -- 6200 or so meters
00:08:09.03 -- he shows that, actually, as you go up the mountain, the ecological environment changes
00:08:14.15 dramatically.
00:08:15.15 So, you can see, for example, at the top of this mountain, you have snow, right?
00:08:19.20 And that's not there at the bottom of the mountain; it doesn't seem to be covered with
00:08:24.06 snow at all.
00:08:25.11 So, what Humboldt did was he also catalogued the plants at the... along this mountain.
00:08:32.13 He was a botanist and he said, well, it seems to be that there are very different species,
00:08:37.09 very different sets of species, which occur across this mountain, and this famous and
00:08:41.20 really beautiful illustration he made kind of shows this, shows the community of plants
00:08:46.24 associated with these environmental gradients.
00:08:50.17 And so, Humboldt thought early on that ecology, or differences in habitat, might be important
00:08:57.06 to determine where species are distributed.
00:09:02.03 The father of evolutionary biology, Darwin, also had contributions to thinking about biogeography.
00:09:08.01 So, Darwin, as you know, went on this really long voyage across the world on the Beagle.
00:09:15.21 And he... while he was going on this voyage, he thought about all the species present along
00:09:21.11 this route.
00:09:22.11 And he actually happened to go to South America and then later to the Galapagos Islands, and
00:09:28.21 when he did that he noticed something really interesting.
00:09:31.17 He saw many birds on the Galapagos Islands.
00:09:34.08 They look similar to the ones he'd seen on the mainland and yet different, right?
00:09:39.06 So, Darwin realized that, potentially, the species that occur in a location may be there
00:09:45.16 because of history, because they're colonizing from somewhere close by, and so the finches
00:09:51.19 are similar to those on the mainland and yet they're different.
00:09:59.04 Most interestingly, also, Alfred Russel Wallace, around the same time as Darwin... he was a
00:10:05.03 codiscoverer of the theory of natural selection with Darwin, they chanced upon the idea together,
00:10:10.01 in the same ti... not together, but the same... at similar times... was also a very avid explorer
00:10:16.13 and he also studied distributions of species across the world.
00:10:22.01 And what he did was he actually realized that certain sets of species seemed to be most
00:10:28.20 similar to each other and these sets of species seemed to occur in similar locations, okay?
00:10:34.24 So, he tried to group the species in the world into bins, in a sense, not just one species
00:10:41.21 but sets of species.
00:10:43.06 And he, for example, suggested that all of the Orient, which is Southeast Asia and India,
00:10:50.11 was one biogeographic zone or grouping.
00:10:55.06 And it's interesting to note that, very recently, in 2013, Holt and other authors actually kind
00:11:01.15 of reevaluated Wallace's ideas of these biogeographic zones based on modern DNA phylogeny.
00:11:09.10 So, Alfred Russel Wallace and Darwin are pre-DNA -- they didn't know anything about, you know,
00:11:15.10 the kind of hereditary material that we know so much about today, which we use to study
00:11:19.20 evolution.
00:11:21.03 And they also found very similar results to what Wallace had found so many years ago.
00:11:28.24 So, now we can look, then... we are looking with modern tools of GIS and DNA and so on,
00:11:37.12 and we can now look at biodiversity and ask questions in biogeography.
00:11:42.12 And this actually shows you a distribution of vertebrate species across the world, and
00:11:48.19 you can see immediately, anyone can see, that some areas have more diversity than others,
00:11:55.12 and this tends to be in the tropics.
00:11:57.12 So, of course, here, the colder colors or blues are areas with lower numbers of species
00:12:03.02 and the warmer reds are regions with higher numbers of species.
00:12:08.06 What I'm also going to try and convince you is that if you actually were to plot onto
00:12:13.12 this map mountain rangers, you would see that mountain ranges tend to correlate with areas
00:12:20.04 where there are high species, and we'll come back to this in a little bit.
00:12:25.01 There's other ways to look at species, right?
00:12:28.00 You can just count all of them, but you can also ask whether some places have more restricted-range
00:12:34.22 species, or higher endemism.
00:12:36.24 Do some places have more special species, which are not found anywhere else?
00:12:41.09 This is also an important thing for us to understand when thinking about biog... biogeography
00:12:46.12 and biodiversity.
00:12:47.12 So, we can quantify this by quantifying endemism, or how restricted a species' range is to a
00:12:54.12 geographic location.
00:12:57.05 And when we do this, again, we find, you know, really interesting patterns.
00:13:01.00 We find, for example, superimposing our mountains, again, that endemism, or special species,
00:13:07.23 tend to be found also in areas where there are mountains and, very interestingly, also
00:13:14.18 on islands, okay?
00:13:16.14 So, islands, mountains, and the tropics seem to be important for presence of species.
00:13:25.07 So, how do we actually study why there's more biodiversity in a particular location?
00:13:30.14 So, okay... so, why may there be more species in a particular place?
00:13:34.12 Well, clearly there's more speciation there.
00:13:38.03 Maybe there's less extinction.
00:13:39.20 Speciation increases the number of species while extinction might decrease the number
00:13:44.00 of species.
00:13:45.00 So, clearly, the balance or diversification... the balance between speciation and extinction
00:13:51.12 must be high.
00:13:52.12 There must be a net positive rate or diversification.
00:13:56.08 And we can actually quantify speciation rate and extinction by looking at phylogenies.
00:14:02.09 And so, in this paper, Rolland et al tried to do this, and what we did was they contrasted
00:14:08.16 the net accumulation of biodiversity, or diversification, amongst the tropics and amongst the temperate
00:14:16.01 regions.
00:14:17.10 And what you can see here, in this really beautiful graph is, if you look at speciation,
00:14:23.04 it's higher in the tropics, extinction seems to be much higher in the temperate regions,
00:14:30.06 and so, overall, on an average, it appears like diversification -- that's net diversification
00:14:36.07 over there -- is much higher in the tropics.
00:14:39.05 So, this suggests that the tropics are cradles of diversity, which means that new species
00:14:48.12 are being created here, right?
00:14:50.12 They're also museums -- there's less extinction, so they retain these species over longer periods
00:14:56.18 of time.
00:14:57.18 So, because they're both cradles and museums, tropic regions, overall, tend to have higher
00:15:03.05 biodiversity.
00:15:04.05 Islands, as we pointed out earlier, are also a really interesting case.
00:15:10.00 This is a very interesting figure from a review, a recent review, by Losos and Ricklefs, where
00:15:15.24 they actually suggest a model for how something like this may happen.
00:15:20.07 They basically verbalized what Darwin thought those many years ago, that you may have a
00:15:25.10 finch which moves from the mainland onto one island.
00:15:29.23 These islands are different and so it manages to disperse to all these islands over time.
00:15:35.10 And then, slowly, these finches or birds maybe differentiate over time, they become adapted
00:15:42.23 to the conditions on that particular island.
00:15:46.04 And then, maybe, if there's further speciation in allopatry, you have recolonization of these
00:15:52.23 different birds across these different islands, now, and further speciation.
00:15:56.23 So, islands are really nice because they're actually models to study speciation.
00:16:02.12 So, because they're small and they're in the ocean, environmental conditions can vary very
00:16:08.01 dramatically on islands, and any of you who've been to an island know it's suddenly raining
00:16:12.15 or suddenly there's a storm, so it's... they're very easy to see environmental changes on.
00:16:18.17 At the same time, because there are many islands, often, in a sea, there are natural barriers
00:16:24.15 which exist between islands, so we can clearly see a role for history -- there's a mainland
00:16:30.13 close by -- ecology -- differences between islands or within an island -- and things
00:16:36.22 like dispersal, right, where differences can actually come based on islands across space.
00:16:42.15 So, let's look at a couple of examples of speciation and its study on islands.
00:16:48.23 So, you know, one of the most biodiverse islands we have in the world is Madagascar.
00:16:56.15 It's a really interesting place because it has a very unique set of species found nowhere
00:17:01.21 else.
00:17:02.21 And I show you, here, a map of... of... a picture of birds -- these are called vangas
00:17:11.03 -- and these have diversified on Madagascar.
00:17:12.23 So, you can see, below, there, there's a map which shows the different kind of ecological
00:17:18.22 conditions or habitats within Madagascar.
00:17:21.12 And, here, you can see a phylogeny, a DNA-based tree, of all these birds, which allows us
00:17:28.02 to infer who evolved from whom, and who colonized which environment first, and so on.
00:17:34.12 And so here we can see an example of ecological speciation, right?
00:17:39.21 Diversification of these birds into different niches, different habitats on this island
00:17:45.23 of Madagascar.
00:17:46.23 And, actually, if you look at Madagascar, there's also incredibly rich vertebrate diversity,
00:17:55.01 in terms of reptiles and amphibians, and these maps on this side actually show you those
00:18:01.06 types of diversity.
00:18:02.09 They show you where there are more or less species, and you can see, for example, that
00:18:07.09 diversity tends to be high in some environments -- higher that, say, in other.
00:18:11.23 So, wetter environments, which you can see below, actually tend to have higher diversity
00:18:16.13 than drier environments.
00:18:17.17 So, again, examples of ecologically driven speciation within an island, and a place with
00:18:24.13 high biodiversity.
00:18:27.11 On the other hand, you can also have geographic examples of speciation.
00:18:31.05 So, here we see these insects on the Hawaiian island chain.
00:18:37.07 So, the nice thing about the Hawaiian island chain is the different islands have different
00:18:42.12 ages, right?
00:18:43.21 So, the oldest island is Kauai and the youngest island is Hawaii, and you can look and see
00:18:52.07 this, also, in the phylogeny.
00:18:54.00 So, for example, the authors have very nicely colored these islands in different colors
00:19:01.04 and the insects found on those islands are in the phylogeny in the same color.
00:19:05.16 So, if you look down, for example, you can see... you can this order, you can see green,
00:19:11.03 orange, purple, blue, and red, right?
00:19:15.17 So, in terms of time, the oldest island is green and then there's orange and then there's
00:19:21.22 purple and then there's blue and then there's red.
00:19:24.09 And you can see that reflected in the phylogenetic tree as well.
00:19:28.11 So, speciation has progressed with time and you have these different islands being colonized
00:19:34.17 and these different species diverging across the Hawaiian island chain.
00:19:39.12 So, lineages, or sets of individuals which are closer together from a DNA perspective,
00:19:45.22 are related on an island, younger lineages are on younger islands, and genetic data kind
00:19:51.16 of helps us explore the history of speciation on these islands.
00:19:56.24 So, now...
00:19:59.08 I've been kind of alternating between mountains and islands, slipping in the fact that mountain
00:20:04.21 ranges have high biodiversity.
00:20:06.21 Why was I doing this?
00:20:08.05 Well, it turns out as Humboldt showed us, and this is an example from the U.S., the
00:20:15.22 Southwest, mountains also have "islands", they have habitat islands.
00:20:21.06 As you go up a mountain, you can see that the habitat or the ecology actually changes
00:20:27.00 -- higher parts of the mountain are different than the lower parts of the mountain.
00:20:32.09 And so you might imagine that, ecologically, species would become adapted to live in these
00:20:38.10 specialized environments.
00:20:40.13 And then, if you looked at the mountain range, that's like a set of islands, kind of like
00:20:45.17 Hawaii in a sense, right?
00:20:48.00 So, it might be interesting to try and explore patterns of speciation, or the accumulation
00:20:53.15 of biodiversity, in mountain chains.
00:20:57.07 And this is what I'm going to talk to you about in terms of our research, but the best
00:21:00.20 part of it all is the history of this speciation is actually written in the DNA of these species,
00:21:07.19 of the populations which actually live on these islands.
00:21:11.11 A way to look at their past is through sequencing their DNA.
00:21:15.23 Umm... this is also important; it's not just fun.
00:21:19.12 But, uhh... you know, our existence as humans is critically dependent on biodiversity.
00:21:25.09 There are many studies which show us, now, that human well-being, not just from an aesthetic
00:21:31.03 perspective, but in terms of our ecosystem services and many, many things, is critically
00:21:35.21 dependent on biodiversity, and this allows us to really prioritize studying areas of
00:21:42.18 high biodiversity.
00:21:44.05 It's important to us; it's not just interesting.
00:21:47.16 And these can be classified globally as biodiversity hotspots, not just regions where there is
00:21:53.15 higher... high biodiversity, but also regions where there are threats to this biodiversity.
00:21:59.10 And two of the regions I'm going to talk to you about today happen to be biodiversity
00:22:03.07 hotspots -- the Western Ghats, which is in India and Southern India, and the Himalayas,
00:22:09.03 which is the in the northern part of Asia.
00:22:10.23 So, uhh...
00:22:12.00 I guess what I'm trying to say is that, you know, we're really interested in understanding
00:22:16.06 biodiversity, but it's also critically important from a conservation perspective.
00:22:20.11 This understanding, we hope, will help us to think about how we can save these species
00:22:26.02 in the future.
00:22:27.02 So, I'll just summarize and uhh... kind of give a leap into our research questions, which
00:22:32.17 I'm going to talk about in the next part of this talk.
00:22:36.09 Biodiversity is higher in the tropics, in mountain ranges, and in islands, and the barriers
00:22:42.12 which cause allopatric speciation, or the creation of biodiversity, could be physical
00:22:47.07 or ecological.
00:22:49.19 But what still remains for us to explore is whether what's driving speciation is really
00:22:56.02 different or the same in various locations across the world.
00:23:00.01 And you saw, for example, that study... you know... from Madagascar on vangas, right?
00:23:07.19 It's a particular type of bird.
00:23:10.02 But you could also think about this from the perspective of all the species which live
00:23:14.06 in a location.
00:23:15.15 Do they all respond similarly to these different barriers or changes in ecology?
00:23:22.07 How generalizable are these patterns?
00:23:24.22 How important are physical differences?
00:23:26.07 Are they more important to some species versus others, or not?
00:23:30.21 And this is what I'm going to talk about in the next talk.
00:23:34.02 Thank you.

Part 2: Biogeography and Speciation in Indian Mountain Ranges

00:00:07.05 Hi.
00:00:08.05 I'm Uma Ramakrishnan.
00:00:09.19 I'm at the National Centre for Biological Sciences in Bangalore, where we do basic science
00:00:15.06 research, and I'm going to tell you today about some research we've been doing in my
00:00:19.14 lab for the last several years.
00:00:21.18 So, in the first part of the talk, I discussed biogeography and how we study patterns of
00:00:28.01 speciation across the world.
00:00:30.09 What I'm going to do in this part of the talk is focus on two examples of speciation, one
00:00:37.03 in more detail and the other just touch upon it, about speciation in mountain ranges associated
00:00:43.06 with the Indian subcontinent, which is where I live.
00:00:46.06 So, we started out with this beautiful picture of biodiversity across the world, and realizing
00:00:53.20 that biodiversity seems to be high in certain locations.
00:00:58.07 And now I'm going to zoom in on the Indian subcontinent and, as you can probably see,
00:01:03.05 there's two particular kinds of places where biodiversity appears to be high, here.
00:01:09.06 These are the Himalayan mountains -- you can see that... you know, like a comet of yellow
00:01:13.22 radiating out of Southeast Asia -- and in the South the Western Ghats -- the small sliver
00:01:20.22 of yellow down the coast in the West.
00:01:24.07 So, these are two mountain ranges, the Himalayas, of course, many of you are familiar with.
00:01:30.03 The less-known Western Ghats, a really old mountain range in the southern part of the
00:01:36.23 Indian subcontinent.
00:01:38.11 So, what is it about these mountain ranges which seems to allow for speciation and the
00:01:45.02 presence of high biodiversity, here?
00:01:48.03 So, let's abstract this a bit, this is what we always do as evolutionary biologists; we
00:01:52.21 take a really complex problem and we think, how can we break this down to something really
00:01:57.23 simple, right?
00:01:59.04 So, you think of a mountain range and you know, if you've been on any mountain top,
00:02:04.05 that the top part of the mountain tends to be really cold, whereas the bottom part of
00:02:09.06 the mountain is hotter, right?
00:02:11.21 So, if you think of a mountain, the environments are different as you go up the mountain.
00:02:18.00 And so you could imagine, then, that, over time, you would have populations which live
00:02:24.02 in the cold and wet part of the mountain, as well as down at the base of the mountain
00:02:29.10 in the hotter, kind of wetter parts -- we're talking about the tropics, remember, that's
00:02:33.23 why it's hot, right?
00:02:36.16 But, over... you can imagine, though, that mountain tops have smaller areas, right?
00:02:42.21 So, imagine you have a mountain -- it's a triangle.
00:02:45.09 The top of the mountain has a smaller area and the next top of the mountain is further
00:02:50.09 away than the base of the mountain, which could be more continuous, right?
00:02:55.15 So, you can imagine, then, that the base mountain populations are more continuous, right?
00:03:01.17 There's less barriers, potentially, between them, these populations, than those which
00:03:07.05 live on the top of the mountain.
00:03:09.12 Now, such species that live on mountain tops are actually called montane species -- they're
00:03:15.14 adapted to living in... on mountain tops.
00:03:18.23 A very classic example are pikas.
00:03:21.11 Many of you are familiar with them.
00:03:23.00 Pikas are a classic story, also, for climate change, because as the climate warms, since
00:03:28.08 they live on the top of the mountain, they have nowhere to go and they simply go extinct.
00:03:33.17 So, what we are going to ask is about a question, about the evolution of montane bird communities
00:03:41.14 in the Western Ghats.
00:03:42.20 So, what I'm showing you here is an elevational profile of the Western Ghats.
00:03:48.03 What I've done is I've taken a cross-section of this mountain from the north all the way
00:03:53.15 going to the south, and you can see the mountain range is going up and down, up and down, all
00:03:59.23 the way from the north to the south.
00:04:02.08 So, it so happens that above about 200...
00:04:05.06 1200 meters or so in elevation, the habitat changes, and it becomes like what you see
00:04:11.16 over here.
00:04:13.02 These habitats are called sholas.
00:04:14.22 They are mixtures of grasslands and forests.
00:04:17.11 You can see there's actually rhododendron here, which is a very cold-adapted species,
00:04:23.00 and it tends to be cold and drizzly and wet for most parts of the year.
00:04:27.17 So, these montane habitats make the species which live here special -- montane species.
00:04:33.22 But if you look a bit more closely, you can see that, in this elevational profile, there
00:04:39.21 seem to be three kind of barriers where the mountain really dips down and goes back up.
00:04:46.15 And so what we decided to do when we're studying this problem is just say, well, let's just
00:04:51.11 look at the effect of these barriers -- how do these barriers... do they drive allopatric
00:04:57.21 speciation?
00:04:58.21 Do they cause differentiation?
00:05:00.24 And how does it affect the entire set of birds which live in these montane habitats in the
00:05:06.03 Western Ghats?
00:05:07.03 So, because there's three barriers, right -- one, two, three -- you have four populations
00:05:13.10 on the sides of these barriers.
00:05:14.20 So, how do we actually study this?
00:05:16.22 How do we look for the effect of a barrier?
00:05:20.15 So, remember, we go back to DNA.
00:05:22.14 That's where the story of evolution is recorded.
00:05:25.22 And if we were to sample birds from across these four populations and build a phylogeny,
00:05:32.01 build a set of relationships between A, B, C, and D, we would expect to see certain things.
00:05:38.00 For example, if all the barriers were important, right, if it was like the Hawaiian chain of
00:05:44.03 islands, where each island has a different history, in a sense, and species are related
00:05:49.10 on that island, you would expect to see A as distinct from B and C as distinct from
00:05:55.11 D -- all four separate.
00:05:58.03 On the other hand, it could be that some barriers are not important.
00:06:02.16 So, for example, A and B could be together, because this particular barrier is not that
00:06:08.02 much of a barrier at all, and C and D could be separate.
00:06:11.21 And, similarly, you could have two populations -- A and B together, and C and D together.
00:06:17.07 And, finally, no effect of any barrier.
00:06:20.10 These are birds, after all, maybe they just flew?
00:06:23.16 And so we would have A, B, C, D, all together, all mixed up, no impact of the mountain being
00:06:30.01 a place where there's ecological differences between species.
00:06:34.10 So, I'm going to just show you these barriers a little bit better.
00:06:39.20 Since you haven't been to the Western Ghats, it's actually nice to see these on Google
00:06:43.10 Earth, for example.
00:06:44.10 What we've done in this slide is we've colored the montane environment, so you can actually
00:06:48.20 see that's the extent of the area that the montane species could occupy.
00:06:54.07 And you can see the barrier between A and B, which is marked over there as well.
00:07:00.09 You can see, for example, the much deeper barrier between B and C.
00:07:05.10 This is actually a break in the mountain range, it's called the Palghat Gap, and there's an
00:07:09.24 extinct river which used to flow through here.
00:07:12.09 You can see that... you know, how the mountains actually break there.
00:07:16.06 And, finally, the barrier between C and D. So, also notice that the area of the populations
00:07:23.02 on either sides are actually quite different in these different cases, but we'll get to
00:07:27.12 that later.
00:07:28.13 This particular barrier is called the Shencottah Gap, which separates C and D. So, what did
00:07:34.09 we do?
00:07:35.09 How did we actually do this research?
00:07:36.09 So, it's a... really, a lot of fun.
00:07:38.07 We actually go to these mountains, we go high up onto these mountains, and we catch 24 species
00:07:45.20 of birds, individuals from 24 species, and I show you all of these birds here.
00:07:51.23 I've tried to highlight in black boxes the ones which are endemic -- remember, we talked
00:07:56.23 about endemism in the first part?
00:07:59.01 These are special to the Western Ghats; they only live here, the don't live anywhere else.
00:08:04.21 And what we do is we set up these nets and catch species in the nets.
00:08:09.15 Don't worry, it doesn't hurt the birds at all.
00:08:11.22 It's like a pouch -- they just fall in and then we take them out, we take measurements,
00:08:16.10 and we use a capillary to take a small bit of blood from the bird wing, and then we let
00:08:21.17 them go.
00:08:23.00 We then come back to the lab, sequence DNA, and we come to the results to try and understand
00:08:29.17 patterns of speciation.
00:08:30.21 So, just for formality, we sample over 1,000 individuals, but the data I report is from
00:08:36.19 about 300-plus individuals and about 5,000 base pairs of genetic data.
00:08:42.19 So, what are the patterns we see across this community?
00:08:46.10 So, just step back for a minute and think... okay, these 24 species of birds, very different...
00:08:52.01 our question is, how are they responding to this mountain range?
00:08:55.21 How are these barriers impacting these species?
00:08:59.00 So, remember, it's possible that the mountain doesn't matter to these species at all, right,
00:09:04.18 and they are all mixed up, A, B, C, D. Or, we could have one major barrier, that's the
00:09:10.20 Palghat Gap, you saw that barrier, it really seems like a break in the mountain.
00:09:14.24 Or we could have shades and grades of two barriers, or all three being barriers.
00:09:21.07 So, while these schematics or these phylogenies are nice models for us to think about the
00:09:26.15 results, what did we actually find?
00:09:29.14 I'm showing you, here, a figure from our paper where we tried to represent the essence of
00:09:35.03 what we found.
00:09:36.21 It's a bit easier to understand this way than to look at, you know, 24 phylogenies.
00:09:42.03 What I'm showing you here is that, for 14 of the 24 species, we found no pattern at
00:09:48.01 all -- it appeared as if the mountain didn't exist for these birds.
00:09:51.22 They appeared to be continuous.
00:09:53.09 By continuous, I mean in terms of genetic differentiation across this mountain range.
00:10:00.23 But, for 10 of the 4... of the 24 species, it appeared like there were breaks or genetic
00:10:07.20 differences caused by being on these mountain tops.
00:10:11.14 And it turns out that for all of these 10 species, the deepest valley, deepest, widest
00:10:18.16 valley, the Palghat Gap, which sandwiches this mountain range, appears to be the most
00:10:25.01 impactful.
00:10:26.01 So, that's what we show over here, that, you know, for 10 of these 24 species, this break,
00:10:33.04 which we represent as a break in this line, correlates spatially with the Palghat Gap,
00:10:38.15 okay?
00:10:39.15 So, this particular barrier seems to cause the most genetic differentiation, suggesting
00:10:45.01 that it is important in terms of species evolution across the community.
00:10:51.01 What was even more interesting was, when we look at these other barriers, the next deepest
00:10:56.02 barrier or, you know, the second most important from a physical perspective, the Shencottah
00:11:01.10 Gap, it appears that, of those 10 species, 3 -- these 3 over here -- were impacted by
00:11:08.20 the Shencottah Gap.
00:11:09.21 So, the deepest valley had the largest impact and the next deeper valley had slightly less
00:11:18.10 of an impact.
00:11:20.00 And it impacted species which were a subset of those earlier 10 species.
00:11:25.06 And, finally, the shallowest valley, which is the Chaliyar River valley, had the most...
00:11:31.02 has a minimal impact and it affected only 1 species, again, a complement of those 10.
00:11:36.22 So, putting this in a Venn diagram, sometimes easier for us to understand that way, 10 species,
00:11:43.05 in blue, were impacted by the Palghat Gap.
00:11:46.04 3 of those 10, a subset, were impacted by the Shencottah Gap.
00:11:50.21 And 1 of those 3 was impacted by the shallowest, Chaliyar River valley.
00:11:55.08 So, now, it's not just interesting that this was a nested pattern, but what was also interesting
00:12:01.10 was that time was also nested, in the sense that the deepest valley had... was the oldest
00:12:11.01 divergence, corresponded to the oldest divergences on that phylogeny.
00:12:14.22 Remember when we talked about Hawaii, it was like the oldest splits were between the oldest
00:12:21.05 islands?
00:12:22.05 Similarly, here, it appeared like populations on either side of the Palghat Gap were most
00:12:28.03 different in terms of evolutionary time as well.
00:12:31.11 And you can see that in this figure over here, that the oldest divergences were across the
00:12:37.19 Palghat Gap, following that the Shencottah Gap, and the most recent divergences were
00:12:43.24 across the Chaliyar River valley.
00:12:46.04 So, in terms of actual amount of time, this was all in the last few millions of years.
00:12:52.12 So, we can map when these divergences were for all these 10 species and look at that
00:12:59.10 a bit more carefully.
00:13:00.14 So, that's what is shown in this graph, here.
00:13:03.04 I'm just showing you, for all those 10 species, when did they diverge across the Palghat Gap,
00:13:10.08 okay?
00:13:11.08 And while 2 of these are relatively older, a majority of them are relatively recently,
00:13:17.13 in a time period which we call the Pleistocene.
00:13:20.15 And this is where climate comes in.
00:13:22.14 So, what I show you here is, now, how temperature has been changing over time.
00:13:28.01 We know this from various other sources of information, from sediment cores, for example,
00:13:32.11 and this is a global pattern, okay?
00:13:34.03 So, it's not just about the Western Ghats.
00:13:36.13 Globally, in the last 2 or so million years, temperature has changed very, very dramatically.
00:13:43.04 And that is called the Pleistocene, this period of time.
00:13:47.14 And so, several authors have suggested that this may be why we see lots of diversification
00:13:53.22 or changes, dynamic changes, in the Pleistocene.
00:13:57.22 Why might these temperature fluctuations impact our birds in the Western Ghats?
00:14:01.16 Well, remember, I told you these are montane birds -- they like on mountain tops.
00:14:07.00 Mountain tops are cold and wet.
00:14:09.13 When the temperature changes, the extent of the mountain top, in a sense, the habitat,
00:14:15.09 the mountain habitat, could be shifted down or up.
00:14:19.05 If it's warmer, it goes up; if it's colder, it may come down.
00:14:23.09 And so, when it comes down, in those periods, these species may be more connected, whereas
00:14:27.19 when it's warmer they may be less connected.
00:14:30.01 So, you can imagine the Pleistocene as a period of isolation and connection, isolation and
00:14:36.09 connection, much like sea level changes and how island could be connected or isolated
00:14:41.11 when sea levels went up or down.
00:14:43.16 So, to summarize, here, the patterns we see are nested, but also linked to climate.
00:14:50.24 So, the physical barriers matter, but climate is impacting how much of a barrier these valleys
00:14:57.12 actually are.
00:14:59.03 We also found, actually, from our phylogenetic data, that two of the species we're looking
00:15:04.21 at were actually cryptic, in the sense that it turned out, for example, the laughing thrush,
00:15:12.06 when we looked at its phylogeny, over here, there's actually 4 populations of laughing
00:15:18.04 thrushes, which are distinct enough to be 4 species.
00:15:22.14 So, remember those A, B, C, D?
00:15:24.23 So, it turns out that every laughing thrush on A is dis... is distinct from that on B,
00:15:31.09 is distinct from C, and so on.
00:15:34.00 And when you put these into a larger bird phylogeny, you put them along with their sisters,
00:15:38.23 it seems like they're very different.
00:15:41.08 They're so different that we think this benefits... they be called a new genus -- they're not
00:15:47.13 truly laughing thrushes, as what they thought they were, people thought they were, but they're
00:15:52.07 something completely different.
00:15:54.15 We suggest that this genus be called Montecincla, and this work is still in revision, but hopefully
00:16:00.18 will be out soon.
00:16:02.20 Another example of cryptic diversity which we uncovered is that of the short wing.
00:16:08.19 So, again, here, you can see that there are 3 populations.
00:16:13.04 A/B is together and it's 1 species, C, and D. And so we suggested that, instead of 1
00:16:19.08 species of short wing, that there be 3 species of short wing, now.
00:16:22.24 And, again, looking at the bigger phylogeny, shortwings are not shortwings at all -- they're
00:16:27.22 actually closer to something else.
00:16:31.05 And so we suggested a name for this genus, Sholicola.
00:16:35.02 So, Sholicola actually means "a bird of the Shola", translated from a local language,
00:16:42.09 and we felt that would be appropriate because, you know, these species are new to us from
00:16:46.23 a DNA perspective, but natives of the Western Ghats, people who live here, have been seeing
00:16:51.23 these birds for many, many years.
00:16:54.07 And so we thought it would be good... nice to name the genus after a local name, in this
00:17:00.22 case.
00:17:01.22 And I should probably just take a minute to tell you, here, that my postdoc, Robin, who
00:17:06.03 did this work, he actually initially got interested in this problem because he heard the birds
00:17:12.00 on either side of these deep valleys and their songs seemed really different.
00:17:17.06 You can see from the illustrations that they do look a little different, but the divergence
00:17:21.23 is on the order of 2 million years, so basically birds on either side of the Palghat Gap have
00:17:27.24 not had gene flow or exchanged genes for over 2 million years.
00:17:34.05 We also got some conservation insights.
00:17:37.08 So, before I... actually, before I jump in, I just should mention that, you know, we talked
00:17:40.19 about quantifying biodiversity in the first part, right, and we said, okay, how do we
00:17:44.21 define species?
00:17:46.02 Well, in trying to understanding speciation in the Western Ghats, we actually learned
00:17:50.17 about... we requantified biodiversity there, we learned about new species there, based
00:17:56.21 on our data.
00:17:57.21 We also learned more information for... which is relevant for conservation.
00:18:02.23 For example, this particular bird, the Nilgiri pipit... many surveys early on had suggested
00:18:10.13 that it occurs in quite a wide distribution.
00:18:13.11 There were suggestions that the distributional range was about 11,000 square kilometers.
00:18:19.08 But when we looked very carefully at our mist net records, where we had actually caught
00:18:25.03 this bird, and looked at it in hand and used DNA to prove that it was a Nilgiri pipit,
00:18:31.13 which is very important, we actually saw that its range was actually much more restricted.
00:18:38.00 This bird seemed to live only in marshy areas about 1,400 meters.
00:18:44.02 And when you look at the total amount of area of that kind of habitat, it reduces to only
00:18:49.13 400 square kilometers.
00:18:50.19 So, when we had a more careful scientific quantification of this biodiversity -- where
00:18:57.09 this bird occurs -- we actually were able to show that it maybe is more threatened than
00:19:03.00 we think it is, than we thought it was.
00:19:05.13 This is a kind of an example of a side benefit and a conservation insight that we got from
00:19:12.03 looking at our data a little bit more carefully.
00:19:14.11 So, to kind of summarize the work on the Western Ghats, it appears the deep valleys are biogeographic
00:19:22.00 barriers for montane species -- they're habitat barriers.
00:19:25.13 The habitat on... as we go down the valley is very different and, potentially, montane
00:19:30.18 species cannot live in those very different habitats.
00:19:33.22 It appears that climate has played a role in shifting these things up and down?
00:19:39.13 Because the divergences appear to correlate with when climate was really changing dramatically
00:19:45.14 across the globe, in the Pleistocene.
00:19:48.01 Umm... and basically.. umm...
00:19:50.21 I guess, you know, what we still don't know is why we see these patterns.
00:19:55.23 Why do certain birds show a stronger pattern than others, for example?
00:20:00.24 Why do some birds not show a pattern at all?
00:20:03.10 Overall, there's a general pattern, but the details of why is something we're still investigating.
00:20:09.01 For example, are certain birds better fliers, and so dis... they... they're able to travel
00:20:14.12 across the barrier irrespective?
00:20:15.21 Or is it something about how plastic they are?
00:20:19.19 Are they able to adapt more easily to non-montane environments?
00:20:24.06 These are the kind of secondary questions which we need to delve into more and we will
00:20:29.07 be doing so in the near future.
00:20:32.06 I think it's also really important... early on, I said, how generalizable are these patterns,
00:20:37.01 right?
00:20:38.01 So, now that I've done this huge amount of field work and, you know, I've done this study,
00:20:42.08 can I say this is a general paradigm?
00:20:44.20 So, can I actually make a prediction for the Western Ghats?
00:20:48.03 Well, one prediction we would make, for example, is that, if you were to look for the two most
00:20:54.05 different individuals, they would always be on either side of the Palghat Gap, okay?
00:21:01.17 And, as... as other researchers kind of work in this area, we hope that they will actually
00:21:08.00 test these predictions, add to them, you know, maybe change them, and say, oh, this is not
00:21:13.18 generalizable to, you know, mammals or centipedes or frogs, but that's what we hope we can generate
00:21:21.12 with this study -- a further study in the Western Ghats.
00:21:24.11 Very recently, there was a paper published on bush frogs.
00:21:28.04 These are really tiny frogs and, if you actually look carefully at this picture over here,
00:21:32.19 it's actually a frog on someone's finger.
00:21:34.23 So, these are really, really tiny frogs, and so clearly their levels of divergence are
00:21:40.02 way higher, because they hardly move, right?
00:21:42.19 But even in this case, this was a phylogeny of bush frogs across the Western Ghats, it
00:21:48.20 turned out that the deepest split in the phylogeny was on either side of the Palghat Gap.
00:21:54.05 So, again, this suggest that the Palghat Gap, this deep valley, this deep barrier, may be
00:22:00.13 a barrier for many other species.
00:22:02.15 So, imagine... it's kind of uhh... really cool to think of this... irrespective of the
00:22:08.21 species you're talking about, if it seems like the shape of the mountain it... is what
00:22:14.02 is driving evolution, that's really cool.
00:22:17.06 From a conservation perspective, you can then say, oh, we need to protect these areas which
00:22:21.24 have the highest diversity, and they should be on either side of this barrier, for example.
00:22:27.16 So, the Western Ghats was a really nice study system because they're a relatively short
00:22:33.20 mountain chain, a linear mountain chain, which is, habitat-wise, pretty unique.
00:22:40.12 So, they're quite wet and they exist in a relatively dry kind of land mass of the Indian
00:22:46.03 subcontinent.
00:22:47.03 So, they're almost like an island mountain chain in a relatively arid landscape.
00:22:51.00 A much more complex and difficult problem is to think about the Himalayas.
00:22:57.10 Now, the Himalayas are amongst the longest mountain ranges in the world.
00:23:02.07 It's certainly the highest, right?
00:23:03.19 We all know that the highest mountains in the world are part of the Himalayan range.
00:23:09.05 And what's also interesting about the Himalayas is they go from the west all the way to the
00:23:15.17 east, and the eastern part of the Himalaya tends to be more tropical.
00:23:20.19 It's closer to the equator because it's more southern than is the western part of the Himalaya,
00:23:27.18 over there.
00:23:28.21 So, now, this is a really challenging problem.
00:23:31.20 Again, we could ask, what is driving speciation, or the accumulation of biodiversity?
00:23:38.14 How has biodiversity been assembled in this incredibly long and complex mountain range?
00:23:45.04 We did a little bit of work on this from a biogeographic perspective, looking at species
00:23:51.03 which occur here and what are the distributions of species.
00:23:54.06 Kind of similar to the stuff we talked about earlier, we were talking about species across
00:23:59.12 the world, but we did this with a specific focus on the Himalayas.
00:24:04.02 So, before we begin to study speciation in this really complex landscape of the Himalayas,
00:24:11.04 let's step back a bit and think about how species are distributed in this area.
00:24:16.03 Let's become biogeographers in the style of Wallace again and think, how many species
00:24:21.12 are where along the Himalayan chain?
00:24:24.02 This figure shows you, for example, species richness, or the numbers of species, in Asia.
00:24:30.18 And you can see immediately, of course, as we already know, now, speciation... species
00:24:36.18 richness, or numbers of species, are higher in the tropic, and Southeast Asia has really
00:24:41.19 high numbers of species, and we seem to have a trail of species going into the Himalayas,
00:24:48.02 so, going west, right?
00:24:50.15 It's like a comet of diversity, decreasing as we go west.
00:24:54.24 So, we also noticed earlier that the Himalayas, while it's an east-west mountain chain, the
00:25:02.12 eastern part of the Himalaya is kind of more south -- it's closer to the tropics -- whereas
00:25:08.01 the western part of the Himalaya is more northern, right?
00:25:10.24 So, maybe this difference in the numbers of species, looking only at the Himalayas, is
00:25:16.16 simply because the eastern part of the Himalaya is more tropical and the western part of the
00:25:21.22 Himalaya is more temperate.
00:25:24.05 This could be the case, but we actually... when we looked at this pattern a bit more
00:25:27.08 closely... we noticed something else.
00:25:29.22 We noticed, again, a nested pattern.
00:25:32.21 So, this just shows you a subset of those data, for rodents.
00:25:39.15 And when we looked at this a little bit further, we saw this nested pattern.
00:25:43.05 So, what I'm showing you, here, is basically a cartoon of species richness and how it's
00:25:49.10 varied in the Himalayas.
00:25:51.21 Imagine that the cell on the extreme, with lots of species, is the eastern-most part
00:25:58.09 of the Himalaya, and as we move from one cell to the other we are going west, okay?
00:26:04.13 So, yes, you can see that the number of species is decreasing, right?
00:26:09.19 But also, it's not just the number of species, it's as if they're losing species.
00:26:14.09 And this pattern is nested, so every cell that is to the west has a complement of the
00:26:22.21 species to the east.
00:26:25.04 And so this suggests that maybe we're kind of losing species as we go from east to west,
00:26:33.22 okay, potentially suggesting a strong role for dispersal, or movement, along this mountain
00:26:42.18 range.
00:26:43.18 Now, that's just a hint that I'm going to give you, but if you wanted to really understand
00:26:47.18 speciation in the Himalayas, as we did for the Western Ghats, we are going to go back
00:26:55.07 and look at DNA, but, just to reorient you, we can also look at this nested pattern with
00:27:01.10 a statistical analysis, and that's what I show here.
00:27:04.22 Again, the east seems to have many more species and complements of those species are found
00:27:10.18 in the west.
00:27:12.00 So, how do we actually test what's happening here.
00:27:15.24 So, remember, we talked about this earlier... uhh... imagine this is a uhh... a cross-section
00:27:21.18 of the Himalaya mountain range.
00:27:25.01 Imagine that there is allopatric speciation, as was the case in the Western Ghats, where
00:27:30.17 you had the valleys causing differentiation and speciation.
00:27:34.21 So, imagine, then, like there, we could actually say, oh, there are these A, B, C, D, E...
00:27:41.13 five population.
00:27:42.15 So, we've actually started work on this, where we're actually, in this case, focusing on
00:27:47.22 small mammals -- these two species or sets of species: rats and Niviventers.
00:27:54.07 They're both part of the rat family, but they're kind of a little smaller than, you know, big
00:28:00.03 mammals.
00:28:01.03 They don't move as much, so may be a better system to study.
00:28:04.05 And what we want to ask is, again, do we see similar patterns as in the Western Ghats.
00:28:09.03 For example, do we see a pattern like this, where we see all rats from A are together
00:28:15.24 with other rats from A, and so on and so forth.
00:28:19.03 Umm...
00:28:20.03 I can't reveal the results to you yet -- this is still in the works -- but I can say that
00:28:25.05 this doesn't seem to be the case.
00:28:26.19 The pattern and story in the Himalayas seems to be a little bit different, and you'll hear
00:28:30.19 more about that soon, actually.
00:28:32.22 So, I'd like to summarize, now.
00:28:36.02 The Western Ghats, as a mountain range, are really interesting, and there seems to be
00:28:41.01 allopatry, or speciation because of deep barriers, the deeper barriers... the deeper the barriers
00:28:49.03 the older the divergences.
00:28:51.00 So, the deepest, widest valleys have disproportionate impact on speciation processes here.
00:28:57.22 This is very important, also, because montane habitats are very threatened.
00:29:03.09 You can see in this picture, for example, the short wing, the bird we talked about earlier,
00:29:08.00 and we did another study... well, you know how we talked about A, B, C, D... well, if
00:29:12.04 you blow up A and you look in more depth at the fragments of forests there, it's actually
00:29:19.15 quite fragmented.
00:29:20.15 So, it turns out that these montane habitats, these high-elevation habitats, are also really
00:29:25.19 good to grow tea in.
00:29:27.03 So, several... you know, several years ago, now, the British actually used these areas
00:29:35.07 to grow tea and, because they started growing tea, the natural montane vegetation was lost,
00:29:41.03 and so now these species exist not just in natural A, B, C, D islands, but islands within
00:29:47.18 these islands, habitat islands, because of fragmentation.
00:29:51.21 And so, we showed, for example, that already these habitat islands are impacting movement
00:29:58.12 of species within them.
00:30:01.05 So, this figure over here actually shows genetic differentiation between natural habitat islands,
00:30:08.22 that is, those separated by valleys, and anthropogenic, or human-created, islands, those created by
00:30:16.19 tea or habitat fragmentation.
00:30:18.19 So, while the Western Ghats is a very interesting case study and a place we need to think about
00:30:25.21 ongoing fragmentation and creation of new islands, the Himalayas seems to be much more
00:30:31.00 complex and maybe dispersal from nearby areas, like Southeast Asia and so on, as suggested
00:30:39.07 by the nestedness, movements from east to west, may be more important in driving species,
00:30:46.12 versus actually what's happening along the Himalayan range itself.
00:30:51.18 So, the Himalayas, unlike the Western Ghats, may be more connected to their environment
00:30:57.07 around them.
00:30:58.11 So, I'm going to stop here and thank the various funding sources we've had.
00:31:05.02 We work in natural areas and so we must work in collaboration with the forest departments
00:31:11.22 in these areas, and we've been very lucky to have incr... very good support in that
00:31:19.07 respect.
00:31:20.07 A lot of this work has been done in collaboration with Sushma Reddy, for example, and several
00:31:28.05 others.
00:31:29.05 We've had funding from the National Geographic, from the Department of Atomic Energy, surprisingly,
00:31:35.01 the Field Museum, and several other places.
00:31:37.23 Of course, I'd like to also thank my parent institution, NCBS, and thanks for listening.

Videos in this Talk

Part 1: Biogeography: Studying the Distribution of Species Across Space
Audience:
- Student
- Researcher
- Educators of H. School / Intro Undergrad
- Educators of Adv. Undergrad / Grad
Part 2: Biogeography and Speciation in Indian Mountain Ranges
Audience:
- Researcher
- Educators of Adv. Undergrad / Grad

Speaker: Uma Ramakrishnan

Total Duration: 0:55:54

Recorded: September 2016

All Talks in Evolution

Talk Overview

Everywhere we look we can observe the immense diversity in nature. But how does biodiversity occur in the first place? Dr. Uma Ramakrishnan studies biogeography, the field that analyzes biodiversity across space. In her first talk, Ramakrishnan explains factors that shape biodiversity, and shows that biodiversity is higher in tropics, islands, and mountain ranges.

In her second talk, Ramakrishnan describes the biogeography of the Himalaya and the Indian mountain ranges. Her laboratory studies how gaps in mountain ranges can drive the speciation of birds. By analyzing the DNA of 24 species of birds, Ramakrishnan’s laboratory showed that deeper gaps in the mountain range generated higher levels of speciation and biodiversity of birds. Their research may help us to identify and prevent threats to biodiversity hotspots.

Speaker Bio

Uma Ramakrishnan

Dr. Uma Ramakrishnan is a professor at the National Center for Biological Sciences (NCBS) in Bengaluru, India. Her passion for ecology and evolutionary biology led her to complete a bachelor’s degree in Physics, Chemistry and Math. Ramakrishnan obtained her PhD on population genetics from the University of California, San Diego and continued her postdoctoral training… Continue Reading

Comments

ombuor midenyo says

February 19, 2021 at 7:32 am

good work prof

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Part 1: Biogeography: Studying the Distribution of Species Across Space

Part 2: Biogeography and Speciation in Indian Mountain Ranges

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Speaker Bio

Uma Ramakrishnan

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