How has the biogeography of Gondwanan mammalian clades varied over deep time?

我提议的项目将专注于解决冈德瓦南哺乳动物支系的生物地理趋势。具体地说，我将定量比较有袋类和胎盘类进行洲际扩散的可能性，这可以解释它们的分离分布。南美洲和澳大拉西亚在始新世之前都毗邻南极洲，许多分支不断分散在三大洲之间(例如Rguero等人)。2014年，Goin等人。2015年)。因此，重要的物理障碍不太可能阻止有袋类和胎盘类在冈瓦那建立同质分布。因此，我最初的假设是，哺乳动物在冈瓦那的扩散主要是由生态位的限制和生态位之间的相互作用决定的，进而建立了今天有袋类和胎盘动物分布的基线。我将具体测试以下几点：a)我假设更适合栖息地的‘扩散走廊’促进了支系的扩散。为了测试这一点，我将模拟中、新生代在澳大拉西亚、南美洲和南极洲的有袋类和胎盘动物的栖息地适宜性。B)我假设，具有更大生态位宽度的支系是那些本来可以在大陆之间更成功地扩散的支系，实际上是那些在今天更有能力分散的支系。因此，我将研究澳大拉西亚、南美洲和南极洲胎盘动物和有袋类群的生态位宽度有何不同(例如，Garcia-Navas和Rodriguez-Rey 2019)。C)我假设，澳大拉西亚有袋类动物已经占据了其他地方胎盘动物占据的整个生态位。我计划对此进行测试，也许会在这个过程中展示有袋类动物在南美和其他地方在生态上被排除在外的程度。D)最后，我假设有袋类通常表现出更大的生态位保守主义--一个支系保持一致的生态位的趋势(例如，Crisp和Cook 2012)--解释了至少对它们的多样性和生物地理的一些限制。因此，我将比较有袋类和胎盘支系中的生态位保守主义。

My proposed project will focus on resolving biogeographical trends in Gondwanan mammalian clades. Specifically, I will quantitatively compare the potential for marsupials and placentals to engage in intercontinental dispersal, which could explain their disjunct distributions. South America and Australasia were both adjacent to Antarctica until the Eocene, with many clades continuously dispersing between the three continents (e.g. Reguero et al. 2014, Goin et al. 2015). Thus, it is unlikely that significant physical barriers prevented marsupials and placentals from establishing a homogenous distribution across Gondwana. As such, my initial hypothesis is that mammalian dispersal across Gondwana was dictated primarily by the limitations of and interactions among ecological niches, establishing in turn a baseline from which the present-day distributions of marsupials and placentals originated. I will specifically test the following: A) I hypothesize that the dispersal of clades was facilitated by 'dispersal corridors' of more suitable habitat. To test for this, I will model the habitat suitability for marsupials and placentals in Australasia, South America and Antarctica during the Mesozoic and Cenozoic. B) I hypothesize that clades with greater niche breadths were those that could have dispersed more successfully between continents, and indeed those more capable of dispersing in the present-day. Consequently, I will examine how niche breadths of placentals and marsupial groups differ in Australasia, South America and Antarctica (e.g. Garcia-Navas and Rodriguez-Rey 2019). C) I hypothesize that Australasian marsupials have filled the entire range of niches occupied by placentals elsewhere. I plan to test for this, perhaps demonstrating in the process the extent to which marsupials have been ecologically excluded in South America and elsewhere. D) Finally, I hypothesize that marsupials generally show greater niche conservatism - a tendency for a clade to retain a consistent ecological niche (e.g. Crisp and Cook 2012) - explaining at least some limitations to their diversity and biogeography. Thus, I will compare niche conservatism in marsupials and placental clades.