Genetic relationships among threespine sticklebacks, Gasterosteus aculeatus
Bibliographic record
Abstract
Threespine sticklebacks (Gasterosteus aculeatus) inhabit both marine and freshwater environments along the Pacific coast of North America, In this study, sticklebacks collected from 73 locations on Vancouver Island, the Sechelt Peninsula and the lower Fraser River Valley of British Columbia, and six sites in northwestern Washington State, were assayed by starch gel electrophoresis in order to examine relationships among and between marine (trachurus) and freshwater (leiurus) populations. Six enzymes, coded for by eight genetic loci, were examined. Of these, two aere monomorphic for the same allele in all populations, the remainder were polymorphic to varying degrees. Laboratory breeding studies employing both marine and freshwater fish as parents confirmed the genetic interpretation of observed variability in isozyme banding patterns. One of the monomorphic enzytaes, isocitrate dehydrogenase, exhibited a sexually dimorphic isozyme pattern. Levels of polymorphism and heterozygosity were slightly higher than average, bat within the range of those characterizing other vertebrate species. In general, genotypic ratios conformed to Hardy-Heinberg expectations, and allele frequencies within populations did not shift over short time periods. Gene frequencies did not vary among sticklebacks of different sizes nor among those caught by different methods from the same population. Gene frequencies at all polymorphic loci were significantly heterogeneous among stickleback populations. Average frequencies at two loci (Pgm and Mdh-3) differed significantly between marine and freshwater fish. In addition, average frequencies at two other loci (Mdh-1 and Ck) were different among sticklebacks inhabiting different types of freshwater environments. Among freshwater populations the Ck ⁸⁵ and Pgm ⁹⁰ alleles displayed clinal geographic variability in frequency, possibly as a result of the differential sampling of various freshwater habitat types in different regions. Allele frequencies at three loci (Pgm, Ck and Pgi-2) differed between marine sticklebacks collected from the Strait of Georgia and those from waters off the vest coast of Vancouver Island. Calculation of Nei’s genetic distance indicated that while marine populations are relatively homogeneous at electrophoretic loci, freshwater populations are highly heterogeneous. The average genetic distance between marine and freshwater populations was similar to that separating pairs of freshwater populations. The genetic distance between freshwater populations was greater between than within watersheds, but allele distributions at individual loci did not differ significantly between two watersheds levels of polymorphism and heterozygosity were relatively high in populations from the ocean, large lakes and low-lying streams, and low in those from small lakes and isolated streams. Both deterministic (natural selection) and stochastic (founder effects and genetic drift) mechanisms can be invoked to explain these patterns. Morphologically and ecologically distinct benthic and limnetic sticklebacks within single lakes, and freshwater and marine sticklebacks within a stream, constituted genetically discrete populations. There was a striking congruence in the patterns of morphological and electrophoretic variability among the populations comprising such 'species pairs'. The results of this study are compatible with the suggestion that freshwater populations of the study area are polyphyletic, and have arisen independently from marine sticklebacks which invaded the region since the last ice age, about 10,000 years ago.
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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 | 0.000 |
| Science and technology studies | 0.001 | 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 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".