Vertebrate Biogeography and Evolution

Transcription

1 Vertebrate Biogeography and Evolution Phylogeny, Plate Tectonics, and Climate Less Digitigrady More Location 1 Location 2 Location 3 Location 4

2 Biogeography The study of the distribution of species, organisms, and ecosystems in space and through geological time. (also known as paleobiogeography) Global scale: the study of distributions of continents and intercontinental connections to explain differences in continental-scale faunas and floras. Regional scale: the study of distributions of species and communities according to topography and environment, as well as the role of geographic and climatic barriers in separating species and populations. Local scale: the distribution of species and individual organisms in microhabitats. Biogeography is closely linked to the study of evolutionary processes, phylogeny, and Earth systems changes.

3 Topics Evolutionary processes and biogeography Vicariance biogeography Functional traits and biogeography (ecometrics) Species distribution modeling (climate and biogeography)

4 Two processes of evolution Phyletic or anagenetic change: evolutionary change within a lineage of ancestor-descendant populations. Occurs via natural selection (adaptation) and drift (chance change). Anagenetic change produces diversity of form. Speciation or cladogenesis: the split of one evolving population into two or more evolving populations. Speciation produces numeric diversity, but not necessarily diversity of form. Evolution does, of course, involve both processes and anagenetic change may happen during speciation processes. From Simpson, The Species Concept

5 The logic of natural selection 1. Among individuals within every species there exists considerable variation. 2. Variable features found in parents are passed on to their offspring. 3. Every species produces more young than survive into the subsequent generation, therefore, competition for survival exists within species. 4. If one s individual characteristics give an advantage in the competition, then that individual is more likely to survive into the next generation. 5. The characteristics possessed by the disadvantaged individuals are not passed into subsequent generations, but the characteristics of the advantaged ones are.

6 Two modes of selection Stabilizing selection. Extremes of variation are selected against, causing the population to remain the same over time. Directional selection. Some extremes of variation are selected against, but the opposite extreme is favored by selection, causing the population to change over time.

7 Drift Neutral change that not driven by selection. Drift results from chance sampling of offspring generation from the parent generation and is, thus, a product of population size. Expected change related to drift in a quantitative trait is the square root of the heritable variance in the trait divided by the square root of population size. Produces a random walk or Brownian motion pattern of phenotypic change within a lineage.

8 Species concepts and role of biogeography Biological species concept: Species are groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups. (Ernst Mayr, 1940). Emphasis in BSC is on reproductive isolation because gene flow keeps populations from diverging from one another. Reproductive isolation may be transient, in which case it does not result in permanent speciation, or it may be long term, in which case the populations begin to diverge phyletically. Evolutionary species concept: A species is a lineage (an ancestraldescendant sequence of populations) evolving separately from others and with its own unitary evolutionary roles and tendencies. (George G. Simpson, 1961). Emphasis in ESC is on the long term consequences of breakdown in gene flow, which allows lineages to evolve separately according to selection and drift without influencing each other. Geographic separation is one of the surest ways of maintaining reproductive isolation long enough for this to happen.

9 Biogeographic processes Vicariance: the splitting of a widely distributed species or group by the formation of a new geographic barrier, such as an orogeny, a continental rift, change in course of a river, or change in climate. Dispersal: the movement of a species or group from one region to another, often across a pre-existing geographic barrier. Phylogeny and temporal data are necessary to distinguish between the two Vicariance example Albert and Crampton, 2010

10 South American biogeography Early groups were part of pan- Gondwana fauna, including edentates (sloths and armadillos), paenungulates, and marsupials. (Vicariance) Primates and rodents appear in Oligocene, after continents have split. (Dispersal) North American placentals arrive in early Pliocene (ca 5 mya) when Isthmus of Panama forms. Armadillos, ground sloths, porcupines, and possums move north from South America (Great American Interchange). (Dispersal) Flynn and Wyss, 1998

11 South American biogeography Flynn and Wyss, 1998.

12 Vicariance Biogeography The study of the history of vicariance events, usually at a continental scale, through synthesis of phylogenetic analysis of many groups of organisms and their geographic distributions. Example using frogs and lizards on Gondwanan continents. (from Wiley, 1988, Annual Reviews of Ecology and Systematics, 19: ). Cladogenic events (splits on phylogenetic trees) are mapped onto geographic distribution to find continents (or regions) that are shared. Splits between taxa on different continents are assumed to coincide with splits between the continents due to plate tectonics unless the most parsimonious distribution of taxa indicates otherwise. Similar to parsimony, except continents (or regions) are used as OTUs and shared taxa are used as character states.

13 Edwards et al., Science, 328: G404 Geobiology Spread of grasslands and arid environments in the Miocene Middle Miocene Late Eocene

14 G404 Geobiology Ecometric biogeography Hypsodonty: tooth crown height. High crowns associated with abrasive diets related to arid environments and silicaceous phytoliths in grasses. Bunodont teeth: low crowns, characteristic of browsers Hypsodont teeth: high crowns, characteristic of grazers. Average hyposodonty in a fauna is indicative of the aridity of the region and the amount of grass

15 Changes in proportion of Miocene browsers and grazers Jnais et al., PPP 177: Janis et al., 2002.

16 Miocene geography of hypsodonty Fortelius et al., 2002.

17 Habitat modeling Using climate or environmental data associated with the geographic distribution of a species to predict where it might live in the future or where it has lived in the past. Also known as ecological niche modeling and species distribution modeling. Climate envelope is the range of climate tolerated by the species. Envelope is used to locate areas with suitable climate or habitat. Climate envelope Lawing and Polly, PLoS ONE.

18 Habitat modeling through time Predicted rattlesnake distributions through last three glacial-interglacial cycles Geographic changes in climate were two orders of magnitude greater than adaptive changes of rattlesnakes to climate. Lawing and Polly, PLoS One.

19 Habitat models can be checked against fossil record Predicted glacial distribution of spotted hyena based on habitat models (black shading). Species occurred throughout Europe and Asia as documented by the fossil record (dots). Conclusion: relationship between hyenas and climate was different in the past than in the present. Varela et al., Journal of Biogeography.

20 Scientific papers for further reading Badgley, C Tectonics, topography, and mammalian diversity. Ecogeography, 33: Flynn, J. J. and A. R. Wyss Recent advances in South American mammalian paleontology. TREE, 13: Fortelius, M., J. Eronen, J. Jernvall, L. Liu, D. Pushkina, J. Rinne, A. Tesakov, I. Vislobokova, Z. Zhang, and L. Zhou Fossil mammals resolve regional patterns of Eurasian climate change over 20 million years. Evolutionary Ecology Research, 4: Maguire, K. C. and A. L. Stigall Using ecological niche modeling for quantitative biogeographic analysis: a case study of Miocene and Pliocene Equinae in the Great Plains. Paleobiology, 35: Lawing, A. M. and P.D. Polly Pleistocene climate, phylogeny, and climate envelope models: an integrative approach to better understand species' response to climate change. PLoS ONE, 16: e Polly, P.D., J.T. Eronen, M. Fred, G.P. Dietl, V. Mosbrugger, C. Scheidegger, D.C. Frank, J. Damuth, N.C. Stenseth & M. Fortelius History matters: ecometrics and integrative climate change biology. Proceedings of the Royal Society B, 278: Upchurch, P., C. A. Hunn, and D. B. Norman An analysis of dinosaurian biogeography: evidence for the existence of vicariance and dispersal patterns caused by geological events. Proceedings of the Royal Society, B, 269: Varela, S., J. Rodríguez, and J. M. Lobo Is current climatic equilibrium a guarantee for the transferability of distribution model predictions? A case study of the Spotted hyena. Journal of Biogeography, 36: