Biogeography: Historical and Contemporary Perspectives, Slides of Theory of Evolution

Download Biogeography: Historical and Contemporary Perspectives and more Slides Theory of Evolution in PDF only on Docsity! Lecture 17: Biogeography Cont’d Historical Biogeography: Fossil Record: e.g. How assess disjunct distribution? a) Once widespread, now relictual… e.g. Tapirs - fossil record shows local extinction b) Breakup of Gondwanaland... e.g. Marsupials - S. Am., Aust. Antarctica Docsity.com Systematics very important when fossil record incomplete (always!) Errors are common… e.g. Age/Area Hypothesis: Centre of Origin = Maximum Diversity But, Adaptive Radiations (colonizing spp. adapt to fill niches) Results in lots of diversity in relatively new arrival Docsity.com Phylogeny reflects relationship to source of population A A B A C y x1 x2 z1 z2 Docsity.com Vicariance Model A C B x y x1 z y1, y2 x1 x2 Docsity.com Phylogeny reflects sequence of separation C B B A A z y1 y2 x1 x2 Docsity.com 1) some elements of Mesozoic Gondwanaland - shared with other southern continents e.g. pipid frogs, lungfish Docsity.com 2) Autochthonous (indigenous) groups • arose & diversified after isolation e.g. antbirds, edentates Docsity.com 3) Diversification after mid-Tertiary • Dispersal followed by diversification e.g. cricetid rodents & primates from Africa Docsity.com Glacial Refugia • Pleistocene glaciations • Many taxa survived in refugia & speciated • e.g. western & eastern diamondback rattler Docsity.com Why are some species absent? • Limited dispersal ability • Extinction • Exclusion (competition, predation) Docsity.com Equilibrium of communities In given env’t, max # spp in a community: S = cAz • immigration balanced by extinction • interactions → extinctions • leads to speciation, improved adaptations • slows extinction rate “ evolutionary species equilibrium” Docsity.com