Strong sexual selection has been reported to both enhance and hinder the adaptive capacity and persistence of populations when exposed to novel environments. Consequently, how sexual selection influences population adaption and persistence under stress remains widely debated. Here, we present two empirical investigations of the fitness consequences of sexual selection on populations of the Indian meal moth, exposed to stable or gradually increasing temperatures. When faced with increasing temperatures, strong sexual selection was associated with both increased fecundity and offspring survival compared with populations experiencing weak sexual selection, suggesting sexual selection acts to drive adaptive evolution by favouring beneficial alleles. Strong sexual selection did not, however, delay extinction when the temperature became excessively high. By manipulating individuals' mating opportunities during fitness assays, we were able to assess the effect of multiple mating independently from the effect of population-level sexual selection, and found that polyandry has a positive effect on both fecundity and offspring survival under increasing temperatures in those populations evolving with weak sexual selection. Within stable temperatures, there were some benefits from strong sexual selection but these were not consistent across the entire experiment, possibly reflecting changing costs and benefits of sexual selection under stabilizing and directional selection. These results indicate that sexual selection can provide a buffer against climate change and increase adaptation rates within a continuously changing environment. These positive effects of sexual selection may, however, be too small to protect populations and delay extinction when environmental changes are relatively rapid.

The effect of sexual selection on species persistence remains unclear. The cost of bearing ornaments or armaments might increase extinction risk, but sexual selection can also enhance the spread of beneficial alleles and increase the removal of deleterious alleles, potentially reducing extinction risk. Here we investigate the effect of sexual selection on species persistence in a community of 34 species of dung beetles across a gradient of environmental disturbance ranging from old growth forest to oil palm plantation. Horns are sexually selected traits used in contests between males, and we find that both horn presence and relative size are strongly positively associated with species persistence and abundance in altered habitats. Testes mass, an indicator of post‐copulatory selection, is, however, negatively linked with the abundance of species within the most disturbed habitats. This study represents the first evidence from a field system of a population‐level benefit from pre‐copulatory sexual selection.

March 2021Field-collected samples Rhizoglyphus robini were collected from onions from fields in various locations from Poland (Krakόw, collected in 1998, Kwiejce, collected in 2017 and Mosina, collected in 2017 and then reared in the laboratory under standard laboratory conditions (23°C, >90% humidity) Ethics oversightNo ethical approval is needed for working with Rhizoglyphus robini Note that full information on the approval of the study protocol must also be provided in the manuscript.

Agricultural expansion is a primary driver of biodiversity decline in forested regions of the tropics. Consequently, it is important to understand the conservation value of remnant forests in production landscapes. In a tropical landscape dominated by oil palm (Elaeis guineensis), we characterized faunal communities across eight taxa occurring within riparian forest buffers, which are legally protected alongside rivers, and compared them to nearby recovering logged forest. Buffer width was the main predictor of species richness and abundance, with widths of 40-100 m on each side of the river supporting broadly equivalent levels of biodiversity as compared to logged forest. However, width responses varied markedly among taxa, and buffers often lacked forestdependent species. Much wider buffers than are currently mandated are needed to safeguard most species. The largest biodiversity gains are achieved by increasing relatively narrow buffers. To provide optimal conservation outcomes in tropical production landscapes, we encourage policy makers to prescribe width requirements for key taxa and different landscape contexts.

1. Temperature change is an often-assumed, but rarely tested, mechanism by which sensitive species may decline in forest landscapes following habitat degradation, fragmentation and destruction.2. Traits mediate how species respond to environmental change, with physiological, morphological and behavioural traits key to determining the response of ectotherms to temperature.3. We collected data on traits linked to thermal sensitivity (critical thermal maxima, body size, cuticle lightness and pilosity) for 46 dung beetle species (Scarabaeinae) in a forest-oil palm mosaic in Malaysian Borneo. By combining these data with a largescale community sampling campaign (>59,000 individuals sampled from >600 traps) and an airborne Light Detection and Ranging-derived thermal map, we investigated how traits mediate species-and community-level responses to temperature. 4. Using hierarchical models, we found that critical thermal maxima predicted how species respond to maximum temperatures. These results were mirrored in communitylevel analyses alongside similar patterns in other thermal traits. Increased body size and decreased pilosity were associated with higher temperatures, while cuticle lightness showed a complex relationship with temperature across the disturbance gradient. 5. Our findings highlight the potential mechanisms by whichforest specialists decline in human-modified landscapes, resulting in changes to community patterns and processes.