On the cover
Roycroft EJ, Nations JA, Rowe KC. 2020. Environment predicts repeated body size shifts in a recent radiation of Australian mammals, Evolution 74:3, 694-695.
Our new paper made the cover of the March issue of Evolution! This lovely little Notomys is part of Melbourne Museum’s Live Exhibits. Photo by David Paul.
Closely related species that occur across steep environmental gradients often show clear body size differences. Generally, species living in colder habitats or environments tend to be larger, while species in hotter habitats are smaller. This pattern is predicted by a biogeographic principle called ‘Bergmann’s Rule’.
We were interested in looking at this pattern in the Australian endemic Pseudomys Division, a recent radiation of small mammals that live across a diverse range of habitats in Australia – from the arid central desert to wet forest in mountains!
In our new paper we collated body size data and occurrence records for 31 species in the Pseudomys Division and used Bayesian phylogenetic models to test whether the biome and environmental conditions each species lives in can predict their body size.
Our results show that body size in these species predictably increases in the mesic biome and decreases in arid and monsoon biomes, in concordance with Bergmann’s rule. It is possible that we see this pattern due to the thermoregulatory benefits for species that live in cold environments – i.e., being larger helps to keep you warm in the cold, while being smaller helps to dissipate heat in the hot! There are also more resources available in colder, wetter forest habitats than in the arid desert; which also likely contributes to this pattern.