A study in contrasts: two extensive Neotropical radiations

Lessa et al. (2014) make a compelling casefor systematic exploration of genomes inthe diverse South American rodent fauna.Not only do the caviomorph and sigmod-ontine rodents comprise a sizable portionof the continental fauna, but they haveradiated into virtually all available habi-tats and have adopted practically all of thelife modes exploited by rodents elsewhere.Both are diverse and demonstrably mono-phyletic, offering great insights into theevolutionary transitions underlying thesepresumably adaptive radiations. Here wecomment on the non-South Americanportions of these radiations, as well asthe broader phylogenetic context of theserodents, recent work on Caribbean taxa,and historical biogeography.Although both rodent radiationsflourished in South America, neitheris confined there, as clearly noted by theauthors.BothgroupsextendfarintoNorthAmerica, reaching the Arctic Ocean inthe case of the caviomorph