Biology subjects

McConnell, N. J.

Publications and source records attributed to McConnell, N. J..

3 recordsLinked to original sources

bioRxiv2025

Environmental modifications of dung beetle larvae shape their growth and life history.

Organisms are not just passive recipients of environmental pressures but are able to shape the environment they experience. Yet, the mechanisms and the evolutionary implications of such niche construction remain poorly understood. Here, we study these effects in the gazelle dung beetle (Digitonthophagus gazella). Larvae of this species develop in an underground brood chamber (a so-called brood ball) consisting of cow dung which serves as a sole source of food for a single developing larva. Throughout its development, the larva extensively modifies its environment by constantly eating, regurgitating, and shaping particle sizes within the brood ball. Previous research suggests that these larval manipulations increase environmental quality and nutrient availability. However, how larval modifications affect larval growth and how these modifications differ between species remain poorly understood. We studied the impact of larval environmental modifications by transplanting eggs into previously modified or unmodified environments, whilst controlling for the confounding effect of maternally derived microbes. Additionally, we also studied how D. gazella larvae grow in an environment that was modified by a different species (Onthophagus binodis) to investigate species-specific differences of niche construction. Counter to expectations, we found that larval modifications by conspecifics did not confer a fitness benefit to D. gazella. However, surprisingly, individuals developing in a brood ball that was modified by a heterospecific individual emerged significantly quicker. These findings thus provide mixed support for the hypothesis that environmental modifications by a larva enhance its growth. Our research adds to the growing literature on the complex interactions between organisms and their environment and how those interactions feedback on organismal development and performance.

animal behavior and cognition↗

bioRxiv2025

The external rumen of dung beetles: Complex interactions between larvae and their ontogenetic environments shape growth and life history

Organisms are not just passive recipients of environmental pressures but are able to shape the environment they experience. However, the mechanisms and the evolutionary implications of such niche construction remains poorly understood. Larvae of the gazelle dung beetle (Digitonthophagus gazella) extensively modify their environment and benefit from microbial symbionts to digest their cellulose-rich diet. These modifications are so extensive that previous research suggests that dung beetle larvae establish an "external rumen", where behavioral adaptations promote beneficial symbionts that enhance nutrient availability in the developmental environment. However, the mechanisms underlying these environmental modifications and their impact on species differences remains unclear. To investigate the external rumen hypothesis, we study the impact of larval environmental modifications on adult life-history traits in the dung beetle Digitonthophagus gazella. We did this by transplanting eggs into modified and unmodified environments, whilst excluding maternally derived microbes. Additionally, we include a heterospecific (Onthophagus binodis) manipulated environment to investigate evolution of species-specific effects. Counter to expectations, we find larval modifications by conspecifics did not confer a benefit to D. gazella in any aspect measured. However, surprisingly, focals from heterospecific treatments emerged significantly quicker. Additionally, we highlight the primary condition of the developmental environment as an essential factor in determining fitness benefits compared to any additive environmental effects. Our research adds to the growing literature on organism by environment interactions and demonstrates the relationship between dung beetle larvae and their developmental environment are complex and are not consistent with the presence of a simple external rumen.

animal behavior and cognition↗

bioRxiv2023

Socially plastic responses in females are robust to evolutionary manipulations of adult sex ratio and adult nutrition

BackgroundSocially plastic behaviours are widespread among animals and can have a significant impact on fitness. Here we investigated whether the socially plastic responses of female Drosophila melanogaster can evolve in predictable ways following long term manipulation of adult sex ratio and adult nutrient availability. Previous reports show that female D. melanogaster respond plastically to their immediate same-sex social environment by altering their fecundity, laying fewer eggs after they mate if previously exposed to other females, Fecundity is also highly sensitive to a females immediate nutritional status, being significantly reduced when dietary protein in particular is scarce. On this basis, we predicted that an evolutionary history of exposure to variation in adult sex ratio and adult nutritional environment would select strongly upon a females plastic fecundity responses. ResultsWe used females that had been drawn from replicated lines that had experienced an evolutionary history of male biased, female biased or equal adult sex ratios and either standard or low-quality adult nutrition. We tested the specific predictions that a history of elevated competition among females (in female-biased regimes) would select for increasingly sensitive plastic fecundity responses to the presence of conspecifics, and that these would be magnified under poor nutritional resource regimes. In contrast to the expectations, we found that the plastic responses in females were strikingly robust to perturbations of both sexual competition and nutrient availability and did not differ significantly across any of the evolutionary regimes. The lack of response is not explained by an insufficient strength of selection. For example, among females held in isolation prior to mating, we did observe significant evolutionary responses in virgin egg according to nutritional regime and in virgin egg retention to sex ratio regime. ConclusionThe lack of variation in the existence and magnitude of predicted plasticity is consistent with the idea that the costs of maintaining fecundity plasticity in females are low, benefits high, and that plasticity itself can be hard wired.

evolutionary biology↗