Sturgeons (Chondrostei: Acipenseridae) and their metazoan parasites: patterns and processes in historical biogeography
Bibliographic record
Abstract
Abstract Aim The historical biogeography of host‐parasite associations is examined in a geologically old group of fishes, the sturgeons (Osteichthyes: Acipenseridae), and their parasite assemblage. Evidence from phylogenetics and biogeographical studies of several parasite groups is used to formulate and evaluate hypotheses about the coevolutionary history of this host‐parasite association and, ultimately, the origin of sturgeons. Location The geographical areas discussed in this study are the temperate regions of North America and Eurasia, including the North Atlantic, North Pacific, Mediterranean and Ponto‐Caspian basins and their drainages. Methods Relationships of parasites in several clades ( Truttaedacnitis , Diclybothriidae, Deropristiidae, Spinitectus and Acrobothriidae) are analysed or re‐analysed using cladistics. These results are combined with hypotheses of relationships of sturgeons and their biogeography. We largely follow an ‘empirical synthetic pattern approach' (Grande & Bemis, 1998) where the search is primarily for broadly congruent patterns, keeping interpretations close to the data and to known or postulated Earth history (palaeogeography). The evidence from the cladistic analyses is first interpreted within the context of vicariance events, but dispersalist scenarios are also discussed where warranted. We also use the concept of Croizat's ‘biogeographical tracks' to characterize broadly congruent distributional patterns. Results Phylogenetic hypotheses and biogeography of parasites indicate three major biogeographical tracks, of which a Holarctic track involving northern and north‐eastern Asian regions and North America is predominant (in Crepidostomum auriculatum, Polypodium hydriforme, Truttaedacnitis, Capillospirura , Diclybothriidae, Amphilina ), with evidence for a recurring basal trans ‐Pacific track (in Truttaedacnitis , Diclybothriidae). Trans‐Atlantic tracks appear to be either independent of (in Deropristidae) or secondarily derived from (in Bothrimonus and Truttaedacnitis sphaerocephala ) a Holarctic track. Evidence from parasites supports the hypothesis of sister relationships between Acipenser medirostris and A. mikadoi , and between A. fulvescens and A. brevirostrum . Main conclusions This host–parasite association was historically structured by colonization and subsequent coevolution. Dispersal and vicariance of acipenserids resulted in small but widespread, highly distinct, monophyletic parasite lineages. Species of such parasite clades remain associated with major and often discrete continental and oceanic formations, and occasionally with related sturgeon species. Biogeographical tracks implicate the Cretaceous and early Tertiary Asian–American peninsula (Beringian region) as a historically important region in the origin and early geodispersion of the parasite fauna. This is consistent with hypotheses of the northern north‐eastern Asian region, or the more inclusive Asian–American peninsula, as a key area in the early diversification of sturgeons and the acquisition of their parasite fauna. The parasite fauna supports the hypothesis of a former continuous distribution of Nearctic and eastern Palaearctic (Siberian) sturgeons that was subsequently fragmented by geological and climatic events, resulting in major displacement of ancestral sturgeon populations in North America. The parasites also reflect a historical connection with marine and brackish water environments that pre‐dates the diversification of sturgeons, indicating that ancestral acipenserids were diadromous.
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How this classification was reachedexpand
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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".