Ecological strategies in the ancient asexual animal group Darwinulidae (Crustacea, Ostracoda)

Abstract

Summary We investigated the relationship between geographical distribution and ecological tolerance within the ancient asexual family Darwinulidae. Distribution maps were compiled based on data from the literature, the Non‐marine Ostracod Distribution in Europe database and personal collections. Ecological tolerance was assessed experimentally by exposing individual ostracods to a combination of eight different salinities (range from 0 to 30 g L−1) and three different temperatures (10, 20 and 30 °C). The type species of the family, Darwinula stevensoni, is ubiquitous and cosmopolitan; the two species Penthesilenula brasiliensis and Microdarwinula zimmeri also have an intercontinental distribution. Two other darwinulid species tested here (Vestalenula molopoensis and P. aotearoa) are known only from their type localities. The latter is also true for most extant darwinulids. Darwinula stevensoni and P. brasiliensis had a broad salinity tolerance, tolerating distilled water and also salinity up to 25–30 g L−1, whereas the maximum salinity tolerance of V. molopoensis was 12 g L−1 and of P. aotearoa, 20 g L−1. The results indicate that both ecological specialists and generalists, as well as intermediate forms, exist in the Darwinulidae and that taxa with the broadest ecological tolerance also have the widest distribution.