Biology subjects

Jennions, M. D.

Publications and source records attributed to Jennions, M. D..

5 recordsLinked to original sources

bioRxiv2024

Does early-life food shortage alter the effect of elevated temperature on female life history?

O_LIGlobal warming is reducing prey availability in many aquatic systems, raising questions about the combined effects of higher temperatures and lower food availability on fish life histories and reproductive output. C_LIO_LIIn ectotherms, higher temperatures accelerate growth and promote an earlier onset of reproduction. However, when fish have less food during development, resource depletion might constrain these temperature-driven processes. C_LIO_LIWe manipulated water temperature (24 or 28{degrees}C) and early-life food availability (control or restricted) for female guppies (Poecilia reticulata). We measured how both factors affected key life history traits (growth, reproduction, survival, self-maintenance). C_LIO_LIHigher temperature significantly affected female life histories. Females at 28{degrees}C matured at a larger size, but then grew more slowly and produced fewer, smaller offspring than females at 24{degrees}C. The effect of temperature on reproduction persisted even after controlling for body size, suggesting there was a shift in the fecundity-size relationship. C_LIO_LIAdult mortality was greater at 28{degrees}C. Higher temperature also resulted in a longer gut, potentially enhancing resource acquisition, but a higher temperature did not affect immunity or telomere length of the surviving females. C_LIO_LIEarly-life food shortage affected very few traits, except for a weak interaction with temperature that affected total fecundity. At 28{degrees}C, females that experienced early-life food restriction produced fewer offspring than females with continual food supply. No such diet effect occurred at 24{degrees}C. C_LIO_LIOur results suggest that tropical fish may be severely impacted by increased temperatures (i.e., decreased reproduction with increased morality), but are likely to be resilient to brief periods of food limitations during early development. C_LIO_LIInterestingly, early-life food shortage caused a reduction in total offspring number but only at 28{degrees}C, suggesting that global prey decline might exacerbate the negative effects of a warming climate on stock recruitment of tropical fish. C_LI

ecology↗

bioRxiv2024

Effects of inbreeding and elevated rearing temperatures on strategic sperm production

Males often strategically modify their rate of sperm production based on the social context, but it remains unclear how environmental and genetic factors shape this plasticity. In freshwater ecosystems, high ambient temperatures often lead to isolated pools of hotter water in which inbreeding occurs. Higher water temperatures and inbreeding can impair fish development, potentially disrupting sperm production. We used guppies (Poecilia reticulata) to investigate how developmental temperature (26 {degrees}C or 30 {degrees}C) and male inbreeding status (inbred, outbred) influence sperm production in the absence or presence of a female (i.e., sperm priming response). We also tested if sperm priming was affected by whether the female was a relative (sister), and whether she was inbred or outbred. A higher rearing temperature had no effect on the rate of sperm production or the priming response. Inbred males produced significantly more sperm in the presence of an unrelated, outbred female than when no female was present. Conversely, outbred males did not alter sperm production in response to female presence or relatedness. In addition, inbred males showed marginally greater sperm production when exposed to an unrelated female that was outbred rather than inbred, but no difference when exposed to an inbred female that was unrelated versus related. Together, only inbred males increased sperm production in response to the presence of a female, but this depended on her being outbred. This suggests stronger sexual selection on inbred males to allocate ejaculate resources, perhaps due to greater benefits when mating with outbred females in better condition.

evolutionary biology↗

bioRxiv2024

Fluctuating salinity during development impacts fish productivity

Climate change is elevating salinity levels in many freshwater systems, and more erratic rainfall is increasing variation in salinity. Consequently, many species now experience more extreme developmental environments. Resultant shifts in developmental trajectories could change key life history traits that persist into adulthood. To date, however, how variation in salinity affects the life histories of freshwater species has been neglected despite its implications for fisheries. We ran a large-scale experiment with a global pest, the mosquitofish (Gambusia holbrooki), and manipulated the salinity experienced by juveniles: freshwater (0{per thousand}), stable salinity (10{per thousand}) or fluctuating salinity (0-20{per thousand}; mean = 10 {per thousand}). Fish developing in stable, high salinity grew faster and matured earlier, albeit with a decline in male telomeres and female gut development. Stable high salinity resulted in larger adult body size in females, but not males, which increased female fecundity. Conversely, fluctuations in salinity induced fish to grow more slowly and lowered female fecundity. Crucially, several of the long-term effects of salinity fluctuations were sex-specific, more adversely affecting females than males. We highlight that environmental variability alters an organisms vulnerability to stressors, with implications that should be considered if we wish to understand the impact of climate change on population dynamics.

ecology↗

bioRxiv2024

Experimental evidence that investment into ejaculation and mating effort impose different life history trade-offs

When males compete, sexual selection favors reproductive traits that increase their mating or fertilization success (pre- and post-copulatory sexual selection). It is assumed that males face a trade-off between these two types of sexual traits because they both draw on investment from the same pool of resources. Consequently, investment into mate acquisition or ejaculation should create similar trade-offs with other key life history traits. Tests of these assumptions are exceedingly rare. Males only ejaculate after they mate, and investment into ejaculation is therefore highly correlated with mating effort. Consequently, little is known about how each component of reproductive investment affects a males future performance. Here, we ran an experiment using a novel technique to distinguish the life history costs of mating effort and ejaculation for mosquitofish (Gambusia holbrooki). We compared manipulated males (mate without ejaculation), control males (mate and ejaculate) and naive males (neither mate nor ejaculate) continuously housed with a female and two rival males. We assessed their growth, somatic maintenance, mating and fighting behavior, and sperm traits after 8 and 16 weeks. Past mating effort significantly lowered a males future mating effort and growth, but not his sperm production; while past sperm release significantly lowered a males future ejaculate quantity, but not his mating effort. These findings challenge the assumption that male reproductive investment draws from a common pool of resources such that, all else being equal, greater mating effort reduces ejaculate investment, and vice versa. Instead, we provide clear evidence that investment in traits under pre- and post-copulatory sexual selection have different trait-specific effects on subsequent male reproductive performance that occur both early and late in life.

evolutionary biology↗

bioRxiv2020

The role of maternal effects on offspring performance in familiar and novel environments

Maternal effects are an important evolutionary force that may either facilitate adaptation to a new environment or buffer against unfavourable conditions. The degree of variation in traits expressed by siblings from different mothers is frequently sensitive to environmental conditions. This could generate a Maternal-by-Environment interaction (MxE) that could inflate estimates of Genotype-by-Environment effects (GxE). We aimed to test for environment-specific maternal effects (MxE) using a paternal full-sib/half-sib breeding design in the seed beetle Callosobruchus maculatus, where we split and reared offspring from the same mother on two different bean host types - original and novel. Our quantitative genetic analysis indicated that maternal effects were very small on both host types for all the measured life-history traits. There was also little evidence that maternal oviposition preference for a particular host type predicted her offsprings performance on that host. Further, additive genetic variance for most traits was relatively high on both hosts. While there was higher heritability for offspring reared in the novel host, there was no evidence for GxEs, and most cross-host genetic correlations were positive. This suggests that offspring from the same family ranked similarly for performance on both host types. Our results point to a genetic basis of host adaptation in the seed beetle, rather than maternal effects. Even so, we encourage researchers to test for potential MxEs because, due to a lack of testing, it remains unclear how often they arise.

evolutionary biology↗