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

我提议的项目将集中于解决冈瓦纳哺乳动物分支的地理学趋势。具体来说，我将定量比较有袋动物和胎盘动物从事洲际扩散的潜力，这可以解释它们的间断分布。在始新世之前，南美洲和澳大拉西亚都与南极洲相邻，许多分支不断分散在三大洲之间（例如Reguero等人，2014年，Goin等人，2015年）。因此，这是不可能的，重大的物理障碍，阻止有袋动物和胎盘动物建立一个均匀的分布在冈瓦纳。因此，我最初的假设是，哺乳动物在冈瓦纳大陆的扩散主要是由生态位的限制和相互作用决定的，反过来又建立了一个基线，从这个基线开始，今天的有袋动物和胎盘动物的分布起源。我将具体测试以下内容：A）我假设分支的扩散是由更适合栖息地的“扩散走廊”促进的。为了验证这一点，我将模拟在中新生代期间在澳大拉西亚，南美洲和南极洲的有袋动物和胎盘动物的栖息地适宜性。B）我假设生态位宽度较大的分支是那些可以在大陆之间更成功地分散的分支，而且确实是那些更有能力在今天分散的分支。因此，我将研究胎盘动物和有袋动物群体的生态位宽度在澳大拉西亚，南美洲和南极洲的差异（例如Garcia-Navas和Rodriguez-Rey 2019）。C）我假设澳大拉西亚有袋动物已经填满了其他地方胎盘动物占据的整个生态位范围。我计划对此进行测试，也许在这个过程中展示有袋动物在南美洲和其他地方被生态排斥的程度。D）最后，我假设有袋类动物通常表现出更大的生态位保守性-一个分支保持一致的生态位的趋势（例如Crisp和Cook 2012）-至少解释了它们的多样性和生态地理学的一些限制。因此，我将比较有袋类和胎盘类的生态位保守性。

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.