Sperm competition in three species of ground-dwelling squirrels: intraspecific and interspecific differences
Bibliographic record
Abstract
Sperm competition is a post-copulatory evolutionary process that can affect sperm production, and consequently reproductive success. Successful males may not necessarily be the males with the highest number of sperm. Other traits such as sperm motility or abnormality may also be factors that impact fertilization success, when there is selection for traits that improve the ability of the sperm to reach the egg. Ground squirrels are an ideal group of organisms to address questions of reproduction and fertility because of the large species diversity in the group, a well-documented phylogeny, a high variety of mating systems and their diversity of life history traits. The main objective of my thesis was to investigate sperm competition in ground squirrels, since it is biologically, ecologically, and evolutionary important to recognize what traits influence the fertilizing efficiency of males and how different species maximize their reproductive success through post-copulatory sexual selection. I sampled free-ranging adult male Cape ground squirrels in the Northern Cape and SA Lombard Nature Reserve, Bloemhof, South Africa, Richardson’s ground squirrels in Assiniboine Park Zoo, Winnipeg, Canada, and Barbary ground squirrels of an invasive population on Fuerteventura Island (Canarian archipelago), Spain. Key findings demonstrated: 1. A positive relationship (interspecifically) between operational sex ratio (OSR) and relative testes size (RTS); 2. A negative relationship (intraspecifically) between RTS and sperm concentration in Cape and Richardson’s ground squirrels; 3. Cape ground squirrel males in better body condition produced more sperm and had larger Cowper glands; 4. Sperm length and speed were related in Cape and Richardson’s ground squirrels; 5. Selective pressures may act to decrease sperm head variability among males, or possibly favor different sizes and morphologies of sperm within an ejaculate; 6. Barbary ground squirrels had higher sperm concentration, lower sperm abnormality and larger RTS compared to many other species, suggesting there is no evidence of inbreeding depression on sperm traits in this highly inbred population. This research contributes to advance our understanding of post-copulatory sperm competition in mammals as viewed from an ecological and evolutionary perspective.
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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 | 0.000 |
| 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".