Integrative taxonomy of freshwater ostracodes (Crustacea: Ostracoda) of the Yucatán Peninsula, implications for paleoenvironmental reconstructions in the northern Neotropical region

As a first step, we analyzed the congruence of two genes of different inheritance, the mitochondrial COI (cytochrome c-oxidase subunit 1), and the nuclear 18S rDNA (small-subunit rDNA). Second, we tested the lineages discriminated for concordant differentiation in morphology, using morphometry of the carapace and typological analysis of the appendages. The third step assessed the association of occurrences and abundances of lineages to environmental variables. The integration of these methods revealed six hidden species within clades previously considered as a single widely distributed nominal species. Of these, Cypretta elongata sp. nov. and Alicenula yucatanensis sp. nov. are herein formally named and described given their morphological distinctness. Three species of Cypridopsis: Cypridopsis sp. [Ca1 ECO-CH-Z-09396], Cypridopsis sp. [Ca2 ECO-CH-Z-09398], Cypridopsis sp. [Ca3 ECO-CH-Z-09401] and a species that may represent a new genus, Cyprididae sp. [Ca1 ECO-CH-Z-09402], are allocated to a confirmed candidate full species status. Cypretta maya and Cypretta sp., considered a priori as separate species, are recognized as a single species with phenotypic plasticity, attributed to its broad ecological tolerances. For paleoenvironmental reconstructions these results have relevance because the particular carapace morphology of the new species can be correlated with specific ecological traits, thus constituting a potential tool for refining interpretations of fossil assemblages.