#Evol2017 catch-up: Biome turnover and body size evolution in Australian vertebrates

A week after the closing day of the 2017 Evolution Meetings, the Molecular Ecologists have all dispersed from Portland. Still, the conference was so big that there’s a lot we missed the first time around — many great talks were scheduled against each other. Fortunately, hundreds of talks were recorded on video and posted online, so it’s possible to go back and catch up with them all. Over the next few days, we’ll highlight some recommendations from the conference’s well-organized YouTube channel.

I didn’t see Ian Brennan’s “Late Miocene biome turnover constrained body size evolution across Australian vertebrates” at the meeting, but I really liked the video (clear and beautiful). It’s totally not my field, but I found it super cool. Here’s the abstract from the online program, and then the video.

Climatic trends may influence macroevolutionary trajectories via abiotic and biotic paths. Evidence from mass extinction events suggest rapid climatic oscillations can influence ecological diversification by opening niche space and precipitating adaptive radiation. However, dramatic climatic events represent infrequent deviations from extended periods of protracted climate change and biome turnover. Our understanding of the macroevolutionary impacts of the intervening periods of gradual change remain limited. In contrast to rapid perturbations, gradual climatic change may constrain ecological diversification by making conditions favorable for allopatric and nonadaptive speciation. The degree to which this response is congruent among ecologically different groups also remains unknown. I tested these concepts using a series of fossil-calibrated, species-level phylogenies, and continuous morphological and discrete ecological data for six diverse Australian vertebrate radiations encompassing mammals, birds, and reptiles. To observe temporal trends in the frequency and timing of cladogenetic dispersal events among biomes, and investigate a Late Miocene shift in dispersal patterns, I used a likelihood method for reconstructing ancestral states and modelling cladogenetic dispersal event types (sympatry, allopatry, vicariance). I then compiled body size data for each group, and using maximum likelihood, modelled the temporal trend in body size evolution by comparing standard evolutionary models against novel models which account for a shift in the mode of size evolution in the Miocene. I compared the results of biogeographic and body size modelling, principally temporal shifts in trends, and suggest that coincident timing of changes indicate that Miocene cooling and aridification restricted niche diversification of these diverse radiations. Bounded morphological divergence during the late Miocene coincided with elevated rates of allopatric, particularly vicariant, speciation, characterizing a shift from adaptive to nonadaptive processes during a period of considerable biome transition. These findings suggest that niche evolution can be constrained not only by biotic interactions, but also by gradual abiotic change.

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About Rob Denton

I'm a Postdoctoral Fellow in the Department of Molecular and Cell Biology at UConn. I'm most interested in understanding the evolutionary/ecological consequences of strange reproduction in salamanders (unisexual Ambystoma). Topics I'm likely to write about: population and landscape genetics, mitonuclear interactions, polyploidy, and reptiles/amphibians.
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