Biology subjects

Fitzpatrick, J. L.

Publications and source records attributed to Fitzpatrick, J. L..

4 recordsLinked to original sources

bioRxiv2026

Evolutionarily labile pachytene piRNAs target an altered set of mRNAs in male hybrids of house mouse subspecies

During male meiosis-I of placental mammals, [~]30-nucleotide pachytene PIWI-interacting RNAs (piRNAs) are expressed to regulate genes required for sperm function. Pachytene piRNA genes evolve rapidly. Whether rapid evolutionary turnover of pachytene piRNAs is under positive selective pressure remains enigmatic. Here, we investigate the evolutionary rate of pachytene piRNA genes over a short evolutionary timescale using geographically isolated mouse subspecies. We demarcate the genes producing postnatal piRNAs in PWK/PhJ and CAST/EiJ. Comparative genomics reveals 16 subspecies-specific pachytene piRNA loci underscoring how labile pachytene piRNA genes are even during short evolutionary timescale. We report a highly abundant CAST/EiJ-specific pi17-CAST locus defying the notion that young pachytene piRNA genes do not produce abundant piRNAs. In fact, male hybrids from the reciprocal crossing C57BL/6J and CAST/EiJ produce pi17-CAST piRNAs almost exclusively from the CAST/EiJ allele suggesting that species-specific nucleotide variants are sufficient to turn a locus into piRNA source. Intriguingly, hybrid males with reduced fertility features retain distinct piRNA-mRNA pairs compared to parents. Our work reveals that rapidly evolving pachytene piRNAs can gain or lose targets in the hybrid males of closely related mammalian species.

evolutionary biology↗

bioRxiv2025

Male social dominance affects access to mates but not female mate choice in a livebearing fish

Male-male competition and female mate choice are often assumed to act in concert, with male social dominance serving as a reliable cue in female choice reflecting overall male quality. However, few studies have explicitly disentangled the effects of male competition and female mate choice, leaving gaps in our understanding of how these processes interact to shape male fitness. Here, we experimentally separated the effects of male-male competition and female mate choice in the pygmy halfbeak Dermogenys colletei, a small freshwater fish, to test whether i) male social dominance drives access to females in the presence and absence of direct male-male competition, and ii) females prefer socially dominant males. Our results show that dominant males monopolized access to females, spending more time courting females and engaging in more courtship behaviors. Additionally, female halfbeaks did not show a preference for dominant males, providing no evidence that females use male dominance when assessing males. Overall, these findings highlight that when male-male competition facilitates mate monopolization there may be less scope for pre-copulatory female mate choice.

animal behavior and cognition↗

bioRxiv2025

Habitat complexity alters the strength of sexual selection on brain size in a livebearing fish

Animals often reproduce in complex environments, which should generate selection for both enhanced detectability in signaling traits and improved cognitive processing abilities. However, the extent to which signaling and cognitive traits have evolved to overcome the challenges of interacting in complex habitats remains understudied. We examined whether habitat complexity influences sexual selection in the pygmy halfbeak, Dermogenys collettei, a small livebearing freshwater fish. Using free-swimming arenas, we created low- and high-complexity environments and observed mating behaviors in mixed-sex groups. While the opportunity for sexual selection did not differ significantly between environments for either sex, we observed positive selection gradients for both male and female brain size in open arenas, but not in complex habitats. Interestingly, no clear selection on male or female ornamentation was detected in either environment. Our findings suggest that habitat complexity may limit selection pressures on cognitive traits, such as brain size, without significantly affecting visual ornamentations role in mating success.

animal behavior and cognition↗

bioRxiv2025

Inbreeding preference emerges in female guppies in a socially complex setting

Animals are typically expected to avoid mating with relatives due to the costs associated with incestuous matings. Yet for more than four decades, theoretical models have consistently suggested that animals should tolerate, or even prefer, mating with relatives under a broad range of conditions. However, empirical studies that evaluate inbreeding avoidance under alternative social and sexual contexts remain scarce. Here, we investigate how experimental variation in sexual and social complexity influence precopulatory inbreeding avoidance behaviors in the guppy Poecilia reticulata, a species known to experience inbreeding depression. In an integrated set of experiments, we examined if sexual and affiliative behaviors of virgin and experienced females and males were differentially directed towards either related or unrelated individuals. In simplistic social interactions, neither virgin nor experienced females or males showed a preference for related or unrelated partners. In contrast, we detected sex-specific responses to relatives in the more sexually and socially complex free-swimming arenas. Females exhibited a stronger preference towards related males regardless of mating experience, while male preference remained unchanged. Overall, these findings challenge previous reports of preference shifts between virgin and experienced female guppies and suggest that inbreeding avoidance behaviors may be less prevalent in complex social environments than previously thought.

animal behavior and cognition↗