Ecological strategies in the ancient asexual animal group Darwinulidae (Crustacea, Ostracoda (original) (raw)
Related papers
Molecular and morphological phylogeny of the ancient asexual Darwinulidae (Crustacea, Ostracoda)
Hydrobiologia, 2005
The Darwinulidae are the only surviving post-Palaeozoic darwinulocopine family of an extensive radiation that reached its maximum in the Permian. Whereas at least some Palaeozoic darwinulids are known from sexual populations, the surviving lineages after the end-Permian mass extinction have abandoned sex since 200 million years ago. This makes the extant family Darwinulidae one of the few putative ancient asexual groups. Only about 30 species in 5 genera are presently known. The phylogeny of these taxa is here analysed using both morphological characters and molecular data. Twelve characters on valve morphology and 17 characters pertaining to appendages are used to construct the most parsimonious (unrooted) cladogram of 12 species in 5 genera. DNA sequences of one nuclear (ITS1) and a mitochondrial (COI) gene of 6 species in 5 genera are used to construct rooted maximum parsimony trees. Both molecular and morphological trees show a high degree of congruence, indicating that Alicenula and Vestalenula mostly cluster closely together, while Penthesilenula and Microdarwinula constitute a robust group. The position of the monospecific genus Darwinula is more variable, but is mostly closer to the two former genera. Congeneric species always cluster together in the morphological cladograms, and these results thus confirm that the five genera recognised by are good phyletic units. An approximate molecular clock (calibrated with fossil data) indicates that the extant darwinulids share a common ancestor, which lived at least 100 million years ago. Hydrobiologia (2005) 538: 153-165 Ó Springer 2005
Brazilian Journal of Biology, 2009
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 abio...
Cryptic diversity in putative ancient asexual darwinulids (Crustacea: Ostracoda).
Fully asexually reproducing taxa lack outcrossing. Hence, the classic Biological Species Concept cannot be applied. Methodology/Principal Findings We 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/Significance Our 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.
2001
We describe life history traits of the ostracod Darwinula stevensoni through laboratory experiments. This small (about 0.7 mm), ancient, obligate parthenogenetic species appeared to be particulary difficult to handle as its long life cycle (up to 3-4 years) has made lab experiments over several generations very difficult. D. stevensoni is an eurythermal and euryhaline species with low variability in size and shape (both of the carapace and the soft parts). Its genetic variability has also been found to be very low. Survival, clutch size, deposition timing and hatching were evaluated in acclimated and non-acclimated females from seven populations: six from Northern Italy and one from Spain. The samples were collected from three different habitats: four lakes, two streams and one spring. A genetic survey using starch gel electrophoresis had previously revealed that only Glucose phosphate isomerase (Gpi) locus was polymorphic. A clone, homozygous at Gpi locus, is the most common in lacustrine and spring habitats in the whole biogeographic range. Surprisingly, two heterozygous clones dominate in Northern Italian lotic environments. Enzymatic activity of heterozygous and homozygous genotypes at Gpi locus was assayed in order to evaluate the relationship between Gpi activity and fitness. Survival and developmental time were not affected by acclimation, while reproductive potential decreased in acclimated females. In females from running waters, reproduction started later and lasted for a shorter time, clutch size was smaller, and hatching percentage lower than females from lakes. These differences are not directly correlated with differences in enzymatic activities at Gpi locus. This does not rule out an overall genetic control of these characteristics since, in a parthenogenetic species, the whole genome is transmitted without recombination. We stress the intriguing case of D. stevensoni in relation to the concept of the "general purpose genotype".
Why most of the Timiriaseviinae (Ostracoda, Crustacea) became extinct
Geobios, 1979
Mesozoic and Cenozoic species of Timiriaseviinae, like the recent species have ecological and biological properties defining them as k-strategists. The extinction of most of them could be due to the contraction of their niche during the Cyprididae explosion in the Upper Jurassic-Lower Cretaceous. Their narrow ecological tolerance limits and poor dispersion abilities made them very vulnerable during major environmental disturbances. Their low rate of sl)eciation during the Tertiary and Quaternary in Europe did not allow to start a new cycle of diversification. This could be due to the change of the reproductive pattern from bisexual to parthenogenetic.
Zoological Journal of the Linnean Society, 2003
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.
Journal of Limnology and Freshwater Fisheries Research
In order to determine distribution, habitat and ecological preferences of Darwinula stevensoni, data gathered from 102 samples collected in Turkey between 2000 and 2017 was evaluated. A total of 1786 individuals of D. stevensoni were reported from eight different aquatic habitats in 14 provinces in six of seven geographical regions of Turkey. Although there are plenty of samples from Central Anatolia Region, recent form of the species was not encountered. Unlike recent, fossil forms of species were encountered in all geographic regions except Southeastern Anatolia. The oldest fossil record in Turkey was reported from the Miocene period (ca 23 mya). Species occurred in all climatic seasons in Turkey. D. stevensoni showed high optimum and tolerance levels to different ecological variables. Results showed a positive and negative significant correlations of the species with pH (P<0.05) and elevation (P<0.01), respectively. It seems that the ecological preferences of the species are much wider than previously known. Our results suggest that if D. stevensoni is used to estimate past and present environmental conditions, attention and care should be paid on its ecology and distribution.
2004
The clonal structure of apomictic populations of Darwinula stevensoni from Northern Italy lacustrine and riverine habitats has been analysed by allozyme electrophoresis. Thirty two sites were sampled and a total of 748 individuals were analysed. Only one polymorphic locus, Gpi, turned out to have enough variation to be informative. Two thirds of all individuals were homozygous for the most frequent allele but the frequency of this genotype was significantly lower in rivers (16%) than in lakes (92%). As a consequence homozygous clonal females are dominant in lacustrine habitats while heterozygous clonal females are dominant in riverine ones. Differences in genetic structure between habitats were observed even at distances of a few meters. Allele and genotype frequencies are significantly different between Lake Montorfano and its outflow (River Seveso) and between Mantova lakes and their two tributaries, the River Mincio and Corniano Channel. The former is also the outflow of Lake Garda. By laboratory experiments, we previously reported difference between genotypes: homozygous females from Mantova lakes show significantly lower starvation tolerance than heterozygous females from River Mincio. We discuss the hypothesis that habitat segregation is related to this difference. Riverine females should be better adapted to low productivity ecosystems than lacustrine ones.