Three new cryptic species of the freshwater zooplankton genus Holopedium (Crustacea: Branchiopoda: Ctenopoda), revealed by genetic methods
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Bibliographic record
Abstract
Molecular approaches have greatly advanced our understanding of species diversity and biogeography in the cladoceran crustaceans. Here, we provide the first large-scale examination of taxonomic diversity in the genus Holopedium Zaddach, 1855, by characterizing patterns of allozyme, mtDNA, and morphological variation from a total of 193 sites from three continents, including collections from near the type localities for the two generally recognized species, Holopedium gibberum Zaddach, 1855, and Holopedium amazonicum Stingelin, 1904. Allozyme data were only available for North American samples but revealed the presence of four species. Divergence patterns in the mitochondrial cytochrome c oxidase subunit I (COI) gene supported those species, as well as a fifth taxon endemic to South America. The five putative species are separated by substantial sequence (8.7–24.5%) and allozyme (0.36–1.54 Nei’s distance) divergences, while intraspecific genetic diversity was generally limited in comparison. Although two of these species exhibited little morphological differentiation from their closest relatives, and diagnostic traits were not found among the characters considered, a population-level approach revealed significant morphological differences among all pairs of taxa. We therefore present both an allozyme key and a morphological/geographic key to all species, as well as new or augmented descriptions for all five species. H. gibberum s.s. is distributed in Europe and across arctic North America, while its cryptic sister species, H. glacialis n. sp., is widely distributed across temperate North America. H. amazonicum s.s. is apparently restricted to the Amazon basin, H. atlanticum n. sp. occurs in lakes along the eastern margin of North America, while H. acidophilum n. sp. occurs sporadically across North America along a narrow band of middle latitudes. Due to high morphological variability within species, as well as the detection of cryptic diversity, we suggest that genetic analyses should be performed on populations from other geographic regions and should always accompany the recognition of new species of Holopedium.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it