Biology subjects

Berg, E. C.

Publications and source records attributed to Berg, E. C..

4 recordsLinked to original sources

bioRxiv2021

Genetic and thermal variation influences adaptation to fluctuating temperature in the seed beetle, Callosobruchus maculatus

Climate change is associated with both the increase in mean and variability of thermal conditions. The use of more realistic thermal regimes is therefore the most appropriate laboratory method to correctly predict population responses to thermal heterogeneity. However, both the long- and short-term implications of evolving under such conditions are not well understood. Here, we examined the effect of fluctuating daily temperatures on several key life history traits in the seed beetle, Callosobruchus maculatus, that was exposed to a short-term thermal switch into a novel environment. Populations were kept for 19 generations at one of two temperatures: constant control temperature (T=29{degrees}C) or a fluctuating daily cycle (Tmean=33{degrees}C, Tmax=40{degrees}C, and Tmin=26{degrees}C) and were subsequently exposed to a switch to the opposite condition. We found that beetles that had evolved in stressful environments were smaller in size when switched to a constant 29{degrees}C and had far greater reproductive fitness compared to beetles from both the constant control and continuously stressful 33{degrees}C environments. This suggests that beetles raised in environments with stressful fluctuating temperatures were more phenotypically plastic and had greater genetic variability than control treatment beetles and indicates that populations that experience fluctuations in temperature may be better able to respond to short-term changes in environmental conditions.

evolutionary biology↗

bioRxiv2021

Inbreeding reduces fitness of seed beetles under thermal stress

Human-induced environmental change can influence populations both at the global level through climatic warming and at the local level through habitat fragmentation. As populations become more isolated, they can suffer from high levels of inbreeding which contributes to a reduction in fitness, termed inbreeding depression. However, it is still unclear if this increase in homozygosity also results in a corresponding increase in sensitivity to stressful conditions, which could intensify the already detrimental effects of environmental warming. Here, in a fully factorial design, we assessed the life-long impact of increased mutation load and elevated temperature on key life history traits in the seed beetle, Callosobruchus maculatus. We found that beetles raised at higher temperatures had far reduced fitness and survival than beetles from control temperatures. Importantly, these negative effects were exacerbated in inbred beetles as a result of increased mutation load, with further detrimental effects manifesting on individual hatching probability and lifetime reproductive success. These results reveal the harmful impact that increasing temperature and likelihood of habitat fragmentation due to anthropogenetic changes in environmental conditions could have on populations of organisms worldwide.

evolutionary biology↗

bioRxiv2020

An experimental test of information use by North American wood ducks (Aix sponsa): external habitat cues, not social visual cues, influence initial nest-site selection

Birds may use a variety of cues to select a nest site, including external information on habitat structure and nest site characteristics, or they may rely instead on social information obtained directly or indirectly from the actions of conspecifics. We used an experimental manipulation to determine the extent to which a California population of the wood duck (Aix sponsa) used social information gleaned from visual cues inside nest boxes that might indicate the quality or occupancy of that site. Over two nesting seasons, we manipulated the contents of newly installed boxes to simulate one of three states: (1) presence of wood duck eggs, indicating current use of a nest site; (2) presence of down and shell membranes, indicating a previously successful nest; and (3) control nests with fresh shavings indicating an unused box. In addition, we measured habitat characteristics of the area surrounding each box to assess the use of external, non-social information about each nest site. We found no evidence that females laid eggs preferentially, or that conspecific brood parasitism was more likely to occur, in any of the treatments. In contrast, nest site use and reproductive traits of wood ducks did vary with vegetation cover, and orientation and distance of the box from water. Our results suggest that personal information, not social information, influence initial nest site selection decisions when females are unfamiliar with a site. Social cues likely become increasingly important once nest sites develop their own history, and a population becomes well established. Significance StatementIn selecting a nest site, birds may use many types of information, including habitat characteristics, their own previous breeding experience, or social cues inadvertently provided by other individuals of the same or different species. We examined information use in a Californian population of wood ducks by experimentally manipulating the visual cues within nest boxes and found that females did not use internal box cues to direct their nesting behaviors, appearing to rely on key habitat characteristics instead. These results contrast with previous studies of this system, suggesting that females may change the cues they use depending on their prior experience with a particular area. In the nest-site selection literature, there appears to be a divergence between research on passerines versus waterfowl, and we advocate unifying these perspectives.

animal behavior and cognition↗

bioRxiv2019

Kin selection and sexual conflict: male relatedness and familiarity do not affect female fitness in seed beetles

Theory maintains that kin selection can mediate sexual conflict because within-group male relatedness should reduce male-male competition, thereby reducing collateral harm to females. We tested whether male relatedness and familiarity can lessen female harm in the seed beetle Callosobruchus maculatus. Neither male relatedness nor familiarity influenced female lifetime reproductive success or individual fitness. However, male relatedness, but not familiarity, marginally improved female survival. Because male relatedness improved female survival in late life when C. maculatus females are no longer producing offspring, our results do not provide support for the role of kin selection in mediating sexual conflict. The fact that male relatedness improves the post-reproductive part of female life cycle strongly suggests that the effect is non-adaptive. We discuss adaptive and non-adaptive mechanisms that could result in reduced female harm in this and previous studies and suggest that cognitive error is a likely explanation.

evolutionary biology↗