Reproductive isolation, morphological and ecological differentiation among cryptic species of Euchlanis dilatata, with the description of four new species

Abstract

Morphological approaches may not provide sufficient resolution for species delineation. Thus, we used an integrated approach that included molecular and ecological characters as well as morphological features to gain a better estimate of species diversity and to improve our understanding of the speciation process within rotifers. Previously, seven putative cryptic species were found within Euchlanis dilatata complex based on a nuclear marker. Here, we investigated reproductive isolation, variation in trophi morphology, and life history characteristics among representatives of some of these species. Mating success between each cryptic species was 0–1.1%; lower than that of positive controls (intra-clonal: 15.6–43.9%). SEM trophi images representing individuals from all seven lineages were used for morphometric analyses. Using Discriminant Analysis, 64% of individuals were correctly assigned to cryptic species. Five clonal lineages, each representing a putative species, were used in life table experiments with varying temperature and conductivity. Age-specific fecundity increased under high temperature and life expectancy decreased under high temperature and high conductivity. There was variation among cryptic species in some life table characteristics, such as life expectancy and generation time. Applying an integrative taxonomy approach, we examined the boundaries between E. dilatata cryptic species and described four of them as new species.