Undervalued habitat or impoverished guild? Exploring the scarcity of
living semiaquatic sigmodontine rodents
Abstract
Sigmodontines (Rodentia: Cricetidae), the largest living radiation of
Neotropical rodents (90 genera, 489 species), show about 10% having
specializations related to a semiaquatic habitat. In addition, this mode
of life is unequally distributed among the several clades which compose
the subfamily, concentrated in the Ichthyomyini and in a few
large-bodied Oryzomyini. The observed taxonomical and geographical
pattern is here discussed in a biogeographical historical context. As
working hypothesis is advanced that the risk of predation (exerted by
animalivorous fresh-water vertebrates) shaped and limited since the late
Miocene the semiaquatic performance of the subfamily. Moreover, by
exploring the fossil record can also be argued that during the
Pleistocene is registered an important number of amphibious
sigmodontines extinctions. Therefore, the scarcity of living semiaquatic
sigmodontine rodents can be attributed to a combination of an
undervalued habitat (mostly by risk of predation) plus a recent
pauperization (by a sum of biological extinctions) of the members of
that guild. A shallow comparison of the sigmodontine case against murids
suggests that continental waterbodies resulted partially refractory to
muroid colonizations.