1,721,086 research outputs found
FIGS 7–9 in Epizoic rotifers (Rotifera: Monogononta, Bdelloidea) from the gill chambers of Potamon fluviatile (Herbst, 1785)
No full textFIGS 7–9. Trophi of Lecane branchicola, SEM pictures. (7) Rami and unci, ventral view. (8) Fulcrum and rami, dorsal view. (9) Manubrium. Scale bar: 2 µm.Published as part of Fontaneto, D., Segers, H. & Melone, G., 2004, Epizoic rotifers (Rotifera: Monogononta, Bdelloidea) from the gill chambers of Potamon fluviatile (Herbst, 1785), pp. 1225-1232 in Journal of Natural History 38 (10) on page 1228, DOI: 10.1080/0022293031000155197, http://zenodo.org/record/465850
Using DNA taxonomy to investigate the ecological determinants of plankton diversity: explaining the occurrence of Synchaeta spp. (Rotifera, Monogononta) in mountain lakes
No full text1. The occurrence of unresolved complexes of cryptic species may hinder the identification of the main ecological drivers of biodiversity when different cryptic taxa have different ecological requirements.
2. We assessed the reliability of the influence of ecological drivers on the occurrence of Synchaeta species (monogonont rotifers) in seventeen water bodies of the Trentino-South Tyrol region in the Eastern Alps. To do so, we compared the results by using unresolved complexes of cryptic species, as is common practice in limnological studies based on morphological taxonomy, and by resolving cryptic complexes, possible by DNA taxonomy.
3. The DNA taxonomy approach we used to identify cryptic species was the generalized mixed Yule coalescent (GMYC) model. We, thus, investigated the relationship between the environment and the occurrence of Synchaeta by multivariate ordination using two definitions of the units of diversity, namely (i) unresolved species complexes (morphospecies) and (ii) putative cryptic species (GMYC entities). Our expectation was that solving complexes of cryptic species could provide more information than using morphospecies.
4. DNA taxonomy provided higher taxonomical resolution than morphological taxonomy. As expected, environmental-based multivariate ordination on cryptic species explained a significantly higher proportion of variance than the one on morphospecies. Occurrence of GMYC entities was related to total phosphorus (TP), whereas no relationship could be found between morphospecies and the environment. Moreover, different cryptic species within the same morphospecies showed different, and even opposite, preferences for TP. Additionally, the large geographical distribution of haplotypes and cryptic species indicated the absence of limiting barriers to dispersal in Synchaeta
Cryptic diversity within the rotifer Polyarthra dolichoptera along an altitudinal gradient
No full textCryptic species (species that are difficult or impossible to distinguish morphologically) are found worldwide and neglecting them may hamper our understanding of species-environment relationships. The rotifer Polyarthra dolichoptera occurs across wide environmental gradients, indicating the potential for a cryptic species complex. We used P. dolichoptera as a model to investigate spatial patterns and relationships of cryptic species with environmental variables along a broad altitudinal gradient.
We sequenced 575 specimens of Polyarthra from 42 waterbodies from Germany, Hungary and Italy sampled in summer. Thirty-five lakes were distributed along an altitudinal gradient (250–2564 m a.s.l.) in a geographically restricted area, the Trentino–South Tyrol region, Italy, and one lake (Lake Tovel) was sampled in two basins and at different depths year-round to investigate temporal and spatial patterns of cryptic species. We used the Generalised Mixed Yule Coalescent model to delimit cryptic species (GMYC entities) based on a phylogenetic tree and related their presence/absence to space and the environment by applying Mantel tests and variance partitioning.
We found twelve GMYC entities of P. dolichoptera. In variance partitioning, most explained variability was attributed to the interaction between space and altitude and by environmental variables and geographical space alone. However, by splitting the data into sets of low- and high-altitude lakes, the strong effect of altitude was removed; conductivity and silica played a major role in high-altitude lakes, whereas neither environment nor space were related to entity occurrence in low-altitude lakes. In Lake Tovel, three cryptic entities were found that did not show spatial segregation; however, two entities showed temporal segregation while the third one occurred throughout the year.
Our study showed that P. dolichoptera is a complex of species which distribution is driven by geography and environmental parameters whose importance is different in low- and high-altitude lakes. Considerable unexplained variability points to a major contribution of other variables, potentially in-lake properties such as competition, predation and species behaviou
FIGS 12–15 in Epizoic rotifers (Rotifera: Monogononta, Bdelloidea) from the gill chambers of Potamon fluviatile (Herbst, 1785)
No full textFIGS 12–15. Trophi of Anomopus telphusae, SEM pictures. (12) Cephalic. (13) Caudal view. Trophi of Embata parasitica, SEM pictures. (14) Cephalic. (15) Caudal view. Scale bar: 5 µm.Published as part of Fontaneto, D., Segers, H. & Melone, G., 2004, Epizoic rotifers (Rotifera: Monogononta, Bdelloidea) from the gill chambers of Potamon fluviatile (Herbst, 1785), pp. 1225-1232 in Journal of Natural History 38 (10) on page 1230, DOI: 10.1080/0022293031000155197, http://zenodo.org/record/465850
Vorkommen von kryptischen Synchaeta Arten (Rotifera, Monogononta) in Bergseen in Zusammenhang mit Umweltfaktoren
Full text linkCryptic diversity of Synchaeta spp. (Rotifera, Monogononta) in mountain lakes: relationships with environmental parameters
Full text linkCryptic species (i.e. distinct species that are morphologically similar) may have different ecological requirements and their merging into one species can bias the assessment of the main ecological drivers of biodiversity. We investigated the environmental parameters influencing the occurrence of Synchaeta species (S. pectinata, S. grandis, S. lakowitziana, S. tremula/oblonga - monogonont rotifers) in 17 waterbodies of the Trentino-South Tyrol region in the Eastern Alps. To improve taxonomic resolution in phylogenetic analysis, a marine Synchaeta (i.e. S. cf. cecilia) from the United Kingdom was also sampled and sequences from GenBank were downloaded. While Synchaeta species were morphologically identified based on trophi structure, cryptic species were identified based on the generalised mixed Yule coalescent (GMYC) model. We performed multivariate ordination both for morphospecies (i.e. unresolved complexes of cryptic species), a common practice in limnological studies based on morphological taxonomy, and for putative cryptic species, made possible by DNA taxonomy. We expected that resolving complexes of cryptic species could provide more information than using morphospecies. Out of the overall phylogenetic tree with 48 haplotypes from 203 individuals, the GMYC model indicated the presence of 14 GMYC entities, 11 from lakes in the Eastern Alps, 2 from Canada, and one from the U.K. Synchaeta pectinata showed five GMYC entities and S. tremula showed two; all individuals, for which the identification to S. tremula or S. oblonga was not possible, clustered in one monophyletic clade, here called S. tremula/oblonga, that showed additional evidence of three GMYC entities. Environmental-based multivariate ordination on cryptic species explained a significantly higher proportion of variance than that based on morphospecies. Occurrence of putative cryptic species was mainly related to total phosphorus. Moreover, different cryptic species within the same morphospecies showed different, and even opposite, preferences for total phosphorus. In addition, the same GMYC entity of S. tremula/oblonga found in Trentino-South Tyrol was also present in Canada and the same haplotype of S. pectinata found in Trentino-South Tyrol was also found in the U.K. This wide geographical distribution of haplotypes and cryptic species indicated the absence of dispersal barriers in Synchaet
Sexual species are separated by larger genetic gaps than asexual species in rotifers
Full text linkWhy organisms diversify into discrete species instead of showing a continuum of genotypic and phenotypic forms is an important yet rarely studied question in speciation biology. Does species discreteness come from adaptation to fill discrete niches or from interspecific gaps generated by reproductive isolation? We investigate the importance of reproductive isolation by comparing genetic discreteness, in terms of intra- and interspecific variation, between facultatively sexual monogonont rotifers and obligately asexual bdelloid rotifers. We calculated the age (phylogenetic distance) and average pairwise genetic distance (raw distance) within and among evolutionarily significant units of diversity in six bdelloid clades and seven monogonont clades sampled for 4211 individuals in total. We find that monogonont species are more discrete than bdelloid species with respect to divergence
between species but exhibit similar levels of intraspecific variation (species cohesiveness). This pattern arises because bdelloids have diversified into discrete genetic clusters at a faster net rate than monogononts. Although sampling biases or differences in ecology that are independent of sexuality might also affect these patterns, the results are consistent with the hypothesis that bdelloids diversified at a faster rate into less discrete species because their diversification does not depend on the evolution of reproductive isolatio
Biological, chemical, and ecotoxicological assessments using benthos provide different and complementary measures of lake ecological status
No full textThe Water Framework Directive (WFD) aims to monitor continental water bodies in Europe to achieve good ecological status. Indexes based on biological quality elements (BQEs), ecotoxicological tests, and chemical characterizations are commonly used with standardized protocols to assess sediment quality and the associated risks. Here, we compare the results of quality assessment of benthic macroinvertebrates as BQEs as required by theWFDwith the results of ecotoxicological tests and assessment of selected persistent organic pollutants (POPs) in sediments of the same eight water bodies in Italy. The aim was to verify if the assessment of quality through macroinvertebrates through POPs analyses and ecotoxicological tools can yield comparable, overlapping, or complementary results. We used the Benthic Quality Index (BQIES) for macroinvertebrates (two different applications), legacy POPs (dichloro-diphenyl-trichloroethane and metabolites (DDTs) and polychlorinated-biphenyls (PCBs), and the emergence ratio (ER) and development rate (DR) for ecotoxicology. The results showed that the two indices within each approach were highly correlated, but between approaches, each result can lead to a completely different scenario, with rather different results of the assessment of ecosystem quality. The most striking result was that very few significant correlations existed between sediment quality assessment through macroinvertebrates and the risk assessment through analyses of micropollutants and ecotoxicological tests. The highest absolute r-value (0.81) was for the correlation between the BQIESbottom index and PCBs for micropollutants, whereas all other pairwise comparisons between indices had r-values ranging between 0.07 and 0.53. Our analysis calls for a caveat in the blind application of one or only a few indices of water/sediment quality, as the results of a single index may not represent the complexity of a freshwater ecosystem
Exploring motion using geometric morphometrics in microscopic aquatic invertebrates: ‘modes’ and movement patterns during feeding in a bdelloid rotifer model species
Full text linkBackground: Movement is a defining aspect of animals, but it is rarely studied using quantitative methods in microscopic invertebrates. Bdelloid rotifers are a cosmopolitan class of aquatic invertebrates of great scientific interest because of their ability to survive in very harsh environment and also because they represent a rare example of an ancient lineage that only includes asexually reproducing species. In this class, Adineta ricciae has become a model species as it is unusually easy to culture. Yet, relatively little is known of its ethology and almost nothing on how it behaves during feeding. Methods: To explore feeding behaviour in A. ricciae, as well as to provide an example of application of computational ethology in a microscopic invertebrate, we apply Procrustes motion analysis in combination with ordination and clustering methods to a laboratory bred sample of individuals recorded during feeding. Results: We demonstrate that movement during feeding can be accurately described in a simple two-dimensional shape space with three main ‘modes’ of motion. Foot telescoping, with the body kept straight, is the most frequent ‘mode’, but it is accompanied by periodic rotations of the foot together with bending while the foot is mostly retracted. Conclusions: Procrustes motion analysis is a relatively simple but effective tool for describing motion during feeding in A. ricciae. The application of this method generates quantitative data that could be analysed in relation to genetic and ecological differences in a variety of experimental settings. The study provides an example that is easy to replicate in other invertebrates, including other microscopic animals whose behavioural ecology is often poorly known
Is the human population a large-scale indicator of the species richness of ground beetles?
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