Biology subjects

Rohner, P. T.

Publications and source records attributed to Rohner, P. T..

9 recordsLinked to original sources

bioRxiv2026

Genotype-by-environment-by-environment (GxExE) interactions have the potential to shape adaptation in response to multiple stressors

Rapid adaptation in complex environments depends not only on the amount of genetic variation, but also on patterns of covariation among traits targeted by selection. Anthropogenic stressors create rapidly changing and multifaceted environments and provide powerful systems in which to investigate the potential for adaptation to multiple coinciding stressors. We investigate the combined effects of heat and chemical stress on survival in the black scavenger fly, Sepsis neocynipsea, and determine the genetic basis for resistance. In a fully factorial experiment, we expose isofemale lines to combinations of heat stress and ivermectin, a veterinary antiparasitic to which these flies are naturally exposed in agricultural landscapes. Using a Bayesian quantitative genetic approach, we estimate broad-sense genetic variation and cross-environmental genetic correlations. First, we show that these two stressors have synergistic effects on survival, with heat stress exacerbating the lethal effects of ivermectin. Second, we find that the largest component of genetic variation is the response to heat and ivermectin in combination (genotype-by-environment-by-environment; GxExE). Third, cross-environmental genetic correlations are weak, implying that relative genetic performance is dependent on the specific combination of stressors. Together, these results suggest that incorporating GxExE is essential for understanding adaptive potential in multi-stressor environments.

evolutionary biology↗

bioRxiv2025

The impact of microplastic contamination in cow manure on reproductive behavior and larval survival in the dung beetle Onthophagus taurus

Microplastics are an emerging environmental hazard on a global scale. Their detection in agricultural environments is of particular concern not only for food contamination, but also because microplastics negatively impact detritivores and their ecosystem functioning. Dung beetles in particular provide vital ecosystem services in agricultural environments and are often vulnerable to anthropogenic hazards, but whether they are affected by microplastics remains unclear. Here, we test whether artificial contamination of cow dung with thermoplastic polyurethane (TPU) has the potential to affect the juvenile development and maternal behavior of the bull-headed dung beetle Onthophagus taurus. Dung beetles exhibited high mortality when exposed to elevated concentrations of TPU. In addition, females were equally likely to provision offspring with TPU-spiked (and lethal) cow dung as with control dung, suggesting that females cannot differentiate between highly toxic microplastic-contaminated and uncontaminated cow dung. Our findings highlight potentially severe consequences for dung beetles if microplastics persist and accumulate, although the levels of exposure in the field are unknown. Although the direct environmental hazards and the mechanisms mediating the negative impacts of TPU microplastics remain to be assessed, this study suggests that microplastics may negatively impact dung beetles and their ecosystem services. Future work assessing exposure levels in the field as well as dung beetles potential to evolve resistance against microplastic pollution will be necessary to assess the long-term impact of microplastic presence on dung beetle ecosystem functioning.

ecology↗

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↗

bioRxiv2025

Life history evolution of insects in response to climate variation: seasonal timing versus thermal physiology

Climate adaptation in insects can proceed via responses in life history traits and their thermal plasticity, and through phenological shifts mediated by responses to photoperiodic cues ("photoperiodism"). While, experimental studies demonstrate evolutionary potential for both modes of adaptation, it remains unclear how evolution will unfold in natural populations, limiting our ability to predict how insects will respond to climate change. Here we review the literature and perform an analysis of published studies revealing that photoperiodism for diapause induction evolves predictably along latitude, with high-latitude populations entering diapause earlier. In contrast, although a few species showed clinal variation in life history and thermal plasticity, the direction of these clines were not consistent across taxa. This suggests that while insect life history and physiological adaptation to temperature can evolve, phenological shifts via evolution of photoperiodism is likely to be a more common and predictable response to future climate change.

ecology↗

bioRxiv2025

Macroevolution of fly wings proceeds along developmental lines of least resistance

Evolutionary change necessitates genetic variation, and a reigning paradigm in biology is that rates of microevolution can be predicted from estimates of available genetic variation within populations. However, the accuracy of such predictions should decay on longer evolutionary timescales, as the influence of genetic constraints diminishes. Here, we show that intrinsic developmental variability and standing genetic variation in wing shape in two distantly related flies, Drosophila melanogaster and Sepsis punctum, are aligned and predict deep divergence in the dipteran phylogeny, spanning >900 taxa and 185 My. This alignment cannot easily be explained by constraint hypotheses unless most of the quantified standing genetic variation is associated with deleterious side-effects and effectively unusable for evolution. However, phenotyping of 71 genetic lines of S. punctum revealed no covariation between wing shape and fitness, lending no support to this hypothesis. We also find little evidence for genetic constraints on the pace of wing shape evolution along the dipteran phylogeny. Instead, correlational selection related to allometric scaling, simultaneously shaping developmental bias and deep divergence in fly wings, emerges as a potential explanation for the observed alignment. This suggests that pervasive natural selection has the potential to shape developmental architectures of some morphological characters such that their intrinsic variability predicts their long-term evolution.

evolutionary biology↗

bioRxiv2024

Context-dependent effects of ivermectin residues on dung insects: Interactions with environmental stressors, size, and sex in a sepsid fly (Sepsis neocynipsea)

Insects associated with livestock dung frequently encounter veterinary medication residues. These residues often have negative effects on insect survival, reproduction, and ecosystem functioning and may contribute to the rapid decline in temperate insect populations. Ivermectin is an antiparasitic drug widely used to treat parasites in livestock. While it has long been recognized that ivermectin effects insect survival, the potential interactive effects between ivermectin exposure and other ecologically relevant abiotic stressors remain poorly understood. Here, we study these effects in the black scavenger fly Sepsis neocynipsea, which depends on cow dung for reproduction. Using a fully factorial design, we test whether the effects of ivermectin exposure on adult survival interact with heat and desiccation stress, and whether these effects depend on size and sex. Ivermectin exposure had strong negative impacts on adult survival, but its effects were stronger in females and large individuals. While heat stress also had a strong effect on adult survival, the combined effects of heat and ivermectin exposure were less severe than the expected additive effects of both stressors applied independently, suggesting some cross-resistance. We did not find an interaction between ivermectin and desiccation stress. Taken together, our findings highlight how the complex interactions between insecticides and abiotic stressors could drive changes in coprophagous insect populations and their ecological functions across different ecosystems and climates.

ecology↗

bioRxiv2024

Vertically inherited microbiota and environment modifying behaviors conceal genetic variation in dung beetle life history

Diverse organisms actively manipulate their (sym)biotic and physical environment in ways that feedback on their own development. However, the degree to which these processes affect microevolution remains poorly understood. The gazelle dung beetle both physically modifies its ontogenetic environment and structures its biotic interactions through vertical symbiont transmission. By experimentally eliminating i) physical environmental modifications, and ii) the vertical inheritance of microbes, we assess how environment modifying behavior and microbiome transmission shape heritable variation and evolutionary potential. We found that depriving larvae from symbionts and environment modifying behaviors increased additive genetic variance and heritability for development time but not body size. This suggests that larvaes ability to manipulate their environment has the potential to modify heritable variation and to facilitate the accumulation of cryptic genetic variation. This cryptic variation may become released and selectable when organisms encounter environments that alter the degree to which they can be manipulated. Our findings also suggest that intact microbiomes, which are commonly thought to increase genetic variation of their hosts, may instead reduce and conceal heritable variation. More broadly, our findings highlight that the ability of organisms to actively manipulate their environment may affect the potential of populations to evolve when encountering novel, stressful conditions.

evolutionary biology↗

bioRxiv2018

Evolution of male costs of copulation in sepsid flies (Diptera: Sepsidae)

Reproduction is well known to be costly for females, but longevity costs of copulations in males are still poorly understood. In particular, the effect of the number of copulations on male longevity is rarely considered. Work on black scavenger flies (Diptera: Sepsidae) showed contrasting results: in Saltella sphondylii the number of copulations is strongly negatively correlated with male longevity, whereas in Sepsis cynipsea mated males did not suffer from reduced longevity. Here we summarize the findings of several studies covering four additional species of sepsid flies from across the phylogenetic tree of sepsids to better understand the evolution of male reproductive costs in this clade. After accounting for the mating system differences between species, we find no evidence for longevity costs in Allosepsis sp., Sepsis fulgens and Themira superba, while in Saltella nigripes multiple copulations drastically reduced longevity. Mapping this trait onto the most current phylogenetic hypothesis for Sepsidae suggests that male cost in Saltella is derived while there is an absence of longevity costs for all other sepsids. We discuss the origin of this novel longevity cost in Saltella in the context of a change in their reproductive strategy, namely the evolution of high polygynandry coupled with unusually brief copulations.

evolutionary biology↗