by Carl Strang
This week’s literature review focuses on a study of the evolutionary history of the mammalian order Lagomorpha, the rabbits, hares and pikas (the members of this group, by the way, are separate from Rodentia, the rodent order, though the two are closely enough related that there is a term, glires, for the two orders combined). This study was reported in the open on-line journal PLoS ONE.
Ge D, Wen Z, Xia L, Zhang Z, Erbajeva M, et al. (2013) Evolutionary History of Lagomorphs in Response to Global Environmental Change. PLoS ONE 8(4): e59668. doi:10.1371/journal.pone.0059668
Pikas today are represented by relatively few high-altitude dwellers.
In the first half of the Miocene epoch, roughly 25-30 million years ago, pikas were much more widespread and diverse, and were represented by more than 20 genera. This was, however, a time of climatic warming and drying, a major result of which was the spread of grasslands and the evolution of plants physiologically adapted to the new climate. Most pika varieties went extinct, the survivors becoming isolated in higher altitudes or latitudes where they could continue to find plenty of plants with the older physiology that they could eat.
The change benefited the other branch of Lagomorpha, the rabbits and hares, which diversified and expanded their collective range.
Though their diversity has decreased after peaking around 5 million years ago during the transition from the Miocene to the cooler Pliocene, rabbits and hares today remain much more widespread and diverse than the pikas.