Development, environmental change, and dispersal abilities in living and extinct mammals

This is Dromiciops gliroides, the living representative of the marsupial clade that dispersed back to South America from Australia.

Photo attribution: By José Luis Bartheld from Valdivia, Chile (Monito del Monte) [CC BY 2.0  (https://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

How do development and ecology interact to shape the dispersal abilities of species?  What environments do marsupials and placentals dominate in today, where they overlap, and how does this differ from their ranges in the deep past?  How have their current and former distribution and dispersal histories influenced their ecological diversification?

Project Description

How do development and ecology interact to shape the dispersal abilities of organisms? The earliest fossils for both marsupial and placental mammals are known from the Late Jurassic/Early Cretaceous of China, and both clades were extensively distributed across the northern hemisphere until the K/Pg mass extinction.  By the earliest Cenozoic, both groups had dispersed into South America, and shortly thereafter, marsupials further dispersed across Antarctica into Australia (and at least one lineage also dispersed back across this route).  Since then, marsupials have been largely isolated in South America and Australia, going extinct in their former range and persisting only in these landmasses that were islands for much of the Cenozoic. In contrast, placentals now dominate most of the globe.  These groups have extensive convergences in ecology and morphology but very divergent reproductive strategies, which have long been considered the cause of their differential evolutionary patterns and their different dispersal histories through regions such as Antarctica, but these hypotheses are largely untested, leaving their current distribution unexplained.

Marsupials and placentals are sister clades with widely divergent evolutionary histories.  Despite many ecological and morphological convergences, marsupials make up only 5% of extant diversity and are largely limited to Australia and South America, while placental dominate across the globe.  Despite this differential success, marsupials dominate in some environments, and apparently showed greater dispersal abilities in the early Cenozoic, in comparison to co-existing placentals.  These differences have been long attributed to the unusual reproductive strategy of marsupials, which may confer advantages in periods of environmental stress (easy abandonment of highly undeveloped young), compared to placentals.  In this project, the student will conduct an extensive analysis of modern and fossil mammal ecological niches, ranges, and dispersal abilities and will combine this with data on palaeoclimate through the Cenozoic and Late Cretaceous to answer the fundamental question of how ecology and development interact to shape the evolutionary histories of these major mammalian clades.

Aims of the Project

The aims of the project are to 1) quantify the range and ecological niches of living marsupial and placental mammals, 2) infer dispersal abilities of living taxa with regard to ecology and development, 3) quantify the ranges and extrapolate the niches of extinct marsupials and placentals in South America and Australia, 4) generate a comprehensive model combining data from paleoclimate, ecological niches, and known ranges to interrogate the cause for differential dispersal of marsupials and placentals in deep time.

Specialised skills required

The prospective student should have experience in R.  Some experience with ArcGIS and vertebrate biology or palaeobiology is preferred but not necessary.  Training will be provided.

Please contact Erin Saupe erin.saupe@earth.ox.ac.uk and Anjali Goswami a.goswami@nhm.ac.uk

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