BackgroundFully asexually reproducing taxa lack outcrossing. Hence, the classic Biological Species Concept cannot be applied.Methodology/Principal FindingsWe used DNA sequences from the mitochondrial COI gene and the nuclear ITS2 region to check species boundaries according to the evolutionary genetic (EG) species concept in five morphospecies in the putative ancient asexual ostracod genera, Penthesilenula and Darwinula, from different continents. We applied two methods for detecting cryptic species, namely the K/θ method and the General Mixed Yule Coalescent model (GMYC). We could confirm the existence of species in all five darwinulid morphospecies and additional cryptic diversity in three morphospecies, namely in Penthesilenula brasiliensis, Darwinula stevensoni and in P. aotearoa. The number of cryptic species within one morphospecies varied between seven (P. brasiliensis), five to six (D. stevensoni) and two (P. aotearoa), respectively, depending on the method used. Cryptic species mainly followed continental distributions. We also found evidence for coexistence at the local scale for Brazilian cryptic species of P. brasiliensis and P. aotearoa. Our ITS2 data confirmed that species exist in darwinulids but detected far less EG species, namely two to three cryptic species in P. brasiliensis and no cryptic species at all in the other darwinulid morphospecies.Conclusions/SignificanceOur results clearly demonstrate that both species and cryptic diversity can be recognized in putative ancient asexual ostracods using the EG species concept, and that COI data are more suitable than ITS2 for this purpose. The discovery of up to eight cryptic species within a single morphospecies will significantly increase estimates of biodiversity in this asexual ostracod group. Which factors, other than long-term geographic isolation, are important for speciation processes in these ancient asexuals remains to be investigated.

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Two new species of semiterrestrial darwinulid ostracods, both belonging to the pagliolii -lineage of the genus Vestalenula , are described here. Vestalenula botocuda sp. nov ., collected from moist mud in a rain forest remnant, is an enigmatic species, as it combines valve characters of the boteai-lineage with soft part features of the danielopoli-lineage within the genus. Vestalenula irajai sp. nov ., found in several types of semiterrestrial habitats, is closely related to V. pagliolii in its soft part morphology, but has more elongated valves, with straight dorsal and ventral margins running parallel to each other. The description of these new species confirms the relatively high levels of endemicity and diversity in Southern Hemisphere Vestalenula and challenges earlier classifications of this group.

Five new species and a new genus of terrestrial ostracods from Brazil are described: Callistocypris mckenziei sp. nov., Callistocypris rossettii sp. nov., Terrestricypris wurdigae sp. nov., Caaporacandona shornikovi gen. et sp. nov. and Caaporacandona iguassuensis gen. et sp. nov. This is the first time that Callistocypris Shornikov, 1980 and Terrestricypris Shornikov, 1980 have been found since their original description from the Solomon Islands. The family Terrestricyprididae Shornikov is here lowered to the rank of tribe within the Candoninae; this tribe comprises Terrestricypris, Terrestricandona Danielopol & Betsch, 1980 (from Madagascar) and Caaporacandona gen. nov. Putative heterochronic character evolution within this tribe (in valves A1 and A2) is compared to a parallel evolutionary pathway in another group of terrestrial ostracods, the Mesocypridini. The similarity between the terrestrial ostracod faunas of Brazil and the Western Pacific Islands (including New Zealand) and the dissimilarity between those of Africa and South America is indicated. The putative causality of the prevalence of asexual reproduction in terrestrial ostracods is briefly discussed. © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society, 2005, 145, 145–173.

The occurrence and abundance of darwinulid ostracods, as well as environmental factors influencing these patterns, were investigated in the alluvial valley of the upper Paraná River. Ostracods were sampled from several substrates, like littoral sediments and pleuston, which included several aquatic macrophytes species, from 31 localities (lentic and lotic) belonging to different riverine systems. Eight darwinulid species were found, representing all genera from this family. Alicenula serricaudata, Vestalenula pagliolii, and Penthesilenula brasiliensis were the most common species. Cluster analysis based on the composition and abundance of darwinulid communities revealed the presence of five associations. Darwinula stevensoni, Vestalenula botocuda, and Penthesilenula aotearoa were almost exclusive to lotic environments. A Mantel multiple test showed that the occurrence and distribution of darwinulid ostracods were significantly related to types of habitat and systems, but not to abiotic variables. It thus seems that the hydrodynamic fluctuations of these environments are probably more important to darwinulid distribution than the limnological characteristics. Keywords

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Of the three superfamilies of Ostracoda present in fresh water, only the Cytheroidea had thus far no records in terrestrial environments. Here, we report on a new genus and species, Intrepidocythere ibipora n. gen. n. sp., of the ostracod superfamily Cytheroidea, from forest leaf litter in São Paulo State, Brazil. Judging from morphological similarities, this new genus is believed to be closely related to the genus Elpidium. Possible pathways that led to the colonisation of terrestrial habitats are discussed, and an overview is given on the distribution of the known terrestrial ostracod lineages. The present findings strengthen the idea that terrestrial ostracods are more common than previously thought, at least in tropical areas.

Asexual lineages lack the means to purge their genomes of (deleterious) mutations through recombination. Evolutionary theory thus predicts that such lineages will be prone to early extinction. In brooding animals, brood selection might provide a mechanism to counter the accumulation of mutations. Of the three putative ancient asexual animal groups, only the darwinulid ostracods are brooders. Here, we test the incidence of egg and juvenile abortion in a darwinulid species, Penthesilenula brasiliensis, under two temperature treatments. Part of the offspring is released without brooding (close to 30% in one treatment). The majority of these aborted eggs hatches and develops. As it is unlikely that females are such bad judges of offspring quality, either the surviving animals will present deficiencies later on in development (brood selection) or early egg release can be a (bet-hedging) strategy to increase fecundity in favourable conditions.