Putative causes and consequences of MHC variation within and between locally adapted stickleback demes
Bibliographic record
Abstract
Genes of the major histocompatibility complex (MHC) have been a source of considerable research interest, owing in large part to the growing body of evidence that they may be subject to both natural and sexual selection. However, much remains to be learned about the dynamics of MHC genes in subdivided populations, particularly those characterized by divergent ecological pressures. In this study, we attempt to disentangle the relative roles of both parasite-mediated selection and MHC-mediated mate choice in an open estuarine system inhabited by two parapatric, adaptively divergent threespine stickleback (Gasterosteus aculeatus) demes. We sequenced the putative peptide-binding region (PBR) of an estimated four Class IIβ loci from 127 individuals, identifying 329 sequence variants (276 translated amino acid sequences). Demes differed significantly both in the frequency of MHC alleles and in the communities of helminth parasites infecting resident sticklebacks. Strong signatures of natural selection were inferred from analyses of codon substitutions, particularly in the derived (freshwater) rather than the ancestral (marine) deme. Relationships between parasite load and MHC diversity were indicative of balancing selection, but only within the freshwater deme. Signals of MHC-mediated mate choice were weak and differed significantly between demes. Moreover, MHC-mediated mate choice was significantly influenced by environmental salinity and appeared of secondary importance to tendencies towards assortative mating. We discuss the implications of these findings in respect to ecological adaptation and the potential demographic consequences of possible outcomes of MHC-mediated mate choice.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".