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Sperm competition affects sexual selection intensity on males, but models suggest it cannot affect the relative intensity of sexual selection on males compared to females. However, if sperm competition depresses the payoff for male multiple mating, it could affect the relative intensity of sexual selection and even cause sexual selection to be more intense on females than males (reversal of typical pattern). To evaluate how sperm competition, energy availability, and parental investment affect the intensity of sexual selection on each sex, I constructed a simulation model using the relationship between fecundity and number of mates to estimate sexual selection gradients. Unlike earlier models, I include a trade-off between paternal investment and sperm competition ability. The amount of energy available for reproduction affects the sexual selection gradient for each sex. Reversals in the sex experiencing stronger sexual selection do occur when additional paternal investment reduces a male's ability to compete for fertilizations within females. The shape of the distribution of mates for each sex (determined by mate competition) is also important. Output from the model is qualitatively similar to empirical data from insects with paternal investment. This model challenges previous thinking about the role of sperm competition in sex-role reversal.
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http://dx.doi.org/10.1086/339992 | DOI Listing |
J Fish Biol
September 2025
Department of Marine Renewable Resources, Institute of Marine Science, Barcelona, Spain.
This study investigates whether size-selective harvesting induced heritable changes reflected in epigenetic and reproductive molecular markers in zebrafish (Danio rerio), thereby indicating potential evolutionary responses. We used an experimental harvest model where zebrafish populations were subjected to five generations of size-selective harvesting, followed by eight generations without harvesting in a controlled environment to examine evolutionarily fixed outcomes in response to harvest selection. We assumed the evolutionary adaptations to size-selection to have left a molecular legacy related to sexual development, as previous studies have shown that evolution of reproductive timing is a common response to size-selection.
View Article and Find Full Text PDFArch Sex Behav
September 2025
Department of Psychology, University of Toronto Mississauga, Mississauga, ON, L5L 1C6, Canada.
The kin selection hypothesis (KSH) proposes that same-sex attracted individuals offset their lowered direct reproduction via kin-directed altruism that increases close genetic relatives' reproduction, thereby enhancing inclusive fitness. Retrospective research found that childhood concerns for kin's well-being are elevated among birth-assigned males who are androphilic (i.e.
View Article and Find Full Text PDFMaturitas
August 2025
Turku PET Centre, University of Turku and Åbo Akademi University, Finland; Turku University Hospital, Turku, Finland; Department of Psychology, University of Turku, Finland. Electronic address:
Objectives: Faces and bodies serve as important cues of physical attractiveness and reproductive fitness. Previous studies indicate that there are sex-related differences in the visual processing of erotic stimuli. We investigated gaze patterns and sex differences during sexual perception.
View Article and Find Full Text PDFCurr Opin Urol
September 2025
Department of Surgery, Urology Division, University of Toronto, Toronto, Ontario, Canada.
Purpose Of Review: The expanding range of minimally invasive surgical therapies (MISTs) for benign prostatic hyperplasia (BPH) reflects a growing emphasis on individualized, anatomy-driven treatment that prioritizes symptom relief, reduced morbidity, and preservation of sexual function. This review provides a timely synthesis of MISTs, highlighting innovations in technique, key anatomical considerations, and evolving strategies for patient-centered care in the modern clinical setting.
Recent Findings: Recent studies highlight the expanding role of MISTs, such as UroLift, Rezūm, the temporary implanted nitinol device, Optilume BPH, transperineal laser ablation, and prostatic stents.