Explore the vast range of titles available.

A new species, Onthophagus contrapositus (Coleoptera: Scarabaeidae: Scarabaeinae: Onthophagini), belonging to the New World O. dicranius species group is described and illustrated. Photographs of cephalic and pronotal configurations of all known females are presented for the first time to ease identification. A replacement name is proposed, Onthophagus kohlmanni new name, for the secondary junior homonym Onthophagus xiphias Solís and Kohlmann, 2003. On décrit la nouvelle espèce Onthophagus contrapositus (Coleoptera: Scarabaeidae: Scarabaeinae: Onthophagini) appartenant au groupe O. dicranius. Des photographies de la configuration de la tête et du pronotum de toutes les femelles de ce complexe en vue dorsale sont présentées afin de faciliter la détermination de la nouvelle espèce. Un nom de remplacement, Onthophagus kohlmanni nouveau nom de remplacement, est proposé pour l’homonyme secondaire plus récent Onthophagus xiphias Solís and Kohlmann, 2003.

Many dung beetle communities are characterized by species that share very similar morphological, ecological, and behavioral traits and requirements yet appear to be stably maintained. Here, we document that the morphologically nearly indistinguishable, sympatric, and syntopic tunneling sister species Onthophagus taurus and Onthophagus illyricus may be avoiding competitive exclusion by nesting at remarkably different soil depths. Intriguingly, we also find rapid divergence in preferred nesting depth across native and recently established O. taurus populations. Furthermore, geometric morphometric analyses reveal that both inter- and intraspecific divergences in nesting depth are paralleled by similar changes in the shape of the primary digging appendages, the fore tibiae. Collectively, our results identify preferred nesting depth and tibial shape as surprisingly evolutionarily labile and with the potential to ease interspecific competition and/or to facilitate adaptation to local climatic conditions.

Invasive species may be more capable of adjusting to climate warming via phenotypic plasticity than native species since plasticity is thought to increase invasion success. Physiological plasticity via acclimation is one way in which organisms can adjust their thermal tolerance in response to temperature change, but few studies have addressed whether invasive species have greater thermal plasticity compared to native congeners. Here we investigated whether thermal plasticity via temperature acclimation varies between two Onthophagus dung beetle species, the non-native Onthophagus taurus and the native Onthophagus hecate , collected from both Florida and Tennessee, USA. We expected the non-native O. taurus to demonstrate greater plasticity than the native O. hecate ; we also predicted that beetles from Florida would have reduced plasticity since their environment is less thermally variable. To examine thermal plasticity, we measured shifts in time until loss of function (i.e., leg mobility) following acclimation to hot or cold temperature treatments. We found that non-native O. taurus from Florida acclimated to warm temperatures, increasing time to loss of function following warm treatments; unexpectedly, O. taurus from Tennessee showed no warm acclimation ability. Onthophagus hecate did not acclimate to warm temperatures in either location. In contrast, both species showed similar levels of cold acclimation. Taken together, our results suggest that the non-native species,  O. taurus , will be more capable of using physiological adjustments to respond to climate warming than the native species, O. hecate.

The potential sex-specific differences in animal personality traits (i.e., consistent inter-individual variation in observed behavior) are an active field of inquiry in behavioral ecology. Sexual horn dimorphism, a special type of trait divergence where males develop large and elaborate horns, presents an opportunity to test whether sex-specific morphologies covary with changes in personality expression. We compared the activity personality trait between sexes in two dung beetle species: hornless Onthophagus ruficapillus and sexually horn dimorphic Onthophagus furcatus . We measured speed and distance moved in artificially constructed circular tracks to simulate physical activity in brood tunnels. Both measures were positively correlated and showed moderate levels of repeatability in two species, hence representing a personality axis. Sex-specific differences in locomotory performance emerged only in the horn dimorphic O. furcatus : males exhibited a more active personality than females. Season, body size, and the interaction of body size with sex did not alter the observed activity levels. Finally, O. furcatus not only showed stronger relationship between the activity measures, but it also presented lower within-individual variation for both metrics. Our results contribute to the growing body of literature on how consistent individual differences can either interact with or be a result of sex-based biological processes.

To complete their development, diverse animal species rely on the presence of communities of symbiotic microbiota that are vertically transmitted from mother to offspring. In the dung beetle genus Onthophagus, newly hatched larvae acquire maternal gut symbionts by the consumption of a maternal fecal secretion known as the pedestal. Here, we investigate the role of pedestal symbionts in mediating the normal development of Onthophagus gazella. Through the stepwise removal of environmental and maternal sources of microbial inoculation, we find that pedestal microbiota can enhance both overall growth and developmental rate in O. gazella. Further, we find that the beneficial effects of symbionts on developmental outcomes are amplified in the presence of ecologically relevant temperature and desiccation stressors. Collectively, our results suggest that the pedestal may provide an adaptive function by transmitting beneficial microbiota to developing dung beetle larvae and that the importance of microbiota for developmental and fitness outcomes may be context dependent.

The creation of mega-hydropower dams inundates vast lowland areas, causing widespread environmental impacts in tropical forest regions. Few studies, however, have taken advantage of these newly fragmented landscapes to examine the effects of habitat insularization on arthropod faunas. Here, we assess how dung beetle assemblages respond to 30 years of post-isolation history in forest islands within a major hydroelectric reservoir in Central Amazonia. We sampled 30 of the 3546 islands created by this reservoir, and three neighbouring forest sites. We collected a total of 865 individuals representing 34 dung beetle species and 15 genera. Remarkably, one third of all islands had been entirely defaunated of dung beetles in terms of overall occupancy. Isolation was the single best predictor of dung beetle species richness, followed by the interaction between isolation and island area, and these variables were key determinants of the relict species composition. Isolation was the most important predictor of dung beetle abundance, but area alone was the main predictor of abundance when the dominant species was excluded. We predicted species richness across all 3546 islands, indicating that 61.5% of all islands likely retain only a single ‘super-tramp’ species (Onthophagus osculatii). These community disassembly patterns were likely aggravated by the marked hostility of the open-water matrix combined with the poor flight dispersal capacity of dung beetles over wide gaps between insular forests. As such, the overwhelming number of small, isolated islands created by major dams has profound effects on regional forest biodiversity, including wholesale local extinctions in detritivore assemblages and their ecosystem functions.

The exoskeleton of an insect could be an important factor in the success of its evolutionary process. This reaches its maximum expression in beetles, which constitute the most diversified animal taxon. The involvement in the management of environmental radiation could be one of the most important functions of the exoskeleton due to the passive contributions to the thermoregulation of body temperature. We study whether the elytra of two sympatric and closely related beetle species respond differentially to the radiation of distinct wavelengths in agreement with their ecological preferences. (Herbst) and (Kugelaan) occupy different habitats and environmental conditions (shaded vs. unshaded from solar radiation). The potential adaptive variations to thermoregulation under these different ecological conditions were studied using the responses of their exoskeletons to radiation of different wavelengths (ultraviolet, visible and near-infrared). For these two species, the amounts of the three wavelengths that were reflected, transmitted or absorbed by the exoskeleton were measured using of a spectrophotometer. In addition, the darkness and thickness of the elytra were examined to determine whether these two features influence the management of radiation by the exoskeleton. Both species differ in the management of visible and near-infrared radiation. In agreement with habitat preferences, the species inhabiting shaded conditions would allow infrared and visible radiation to penetrate the elytra more easily to heat internal body parts, while the elytra of the heliophilous species would have increased absorbance of these same types of radiation. An increase in body size (and therefore in elytron thickness) and the quantity of dark spots may serve as barriers against exogenous heat gain. However, the maintenance of between-species differences independent of the effects of these two morphological features led us to suspect that an unconsidered elytron characteristic may also be affecting these differences. The results of the involvement of the exoskeleton thickness and spots in the thermoregulation of insects opens new research lines to obtain a better understanding of the function of the exoskeleton as a passive thermoregulation mechanism in Coleoptera.

The origins of novel complex phenotypes represent one of the most fundamental, yet largely unresolved, issues in evolutionary biology. Here we explore the developmental genetic regulation of beetle horns, a class of traits that lacks obvious homology to traits in other insects. Furthermore, beetle horns are remarkably diverse in their expression, including sexual dimorphisms, male dimorphisms, and interspecific differences in location of horn expression. At the same time, beetle horns share aspects of their development with that of more traditional appendages. We used larval RNA interference-mediated gene function analysis of 3 cardinal insect appendage patterning genes,dachshund, homothorax, and Distal-less, to investigate their role in development and diversification of beetle horns within and between species. Transcript depletion of all 3 patterning genes generated phenotypic effects very similar to those documented in previous studies that focused on general insect development. In addition, we found that Distal-less and homothorax, but not dachshund, regulate horn expression in a species-, sex-, body region-, and body size-dependent manner. Our results demonstrate differential co-option of appendage patterning genes during the evolution and radiation of beetle horns. Furthermore, our results illustrate that regulatory genes whose functions are otherwise highly conserved nevertheless retain the capacity to acquire additional functions, and that little phylogenetic distance appears necessary for the evolution of sex- and species-specific differences in these functions.

Size and shape constitute fundamental aspects in the description of morphology. Yet while the developmental-genetic underpinnings of trait size, in particular with regard to scaling relationships, are increasingly well understood, those of shape remain largely elusive. Here we investigate the potential function of the Notch signaling pathway in instructing the shape of beetle horns, a highly diversified and evolutionarily novel morphological structure. We focused on the bull-headed dung beetle Onthophagus taurus due to the wide range of horn sizes and shapes present among males in this species, in order to assess the potential function of Notch signaling in the specification of horn shape alongside the regulation of shape changes with allometry. Using RNA interference-mediated transcript depletion of Notch and its ligands, we document a highly conserved role of Notch signaling in general appendage formation. By integrating our functional genetic approach with a geometric morphometric analysis, we find that Notch signaling moderately but consistently affects horn shape, and does so differently for the horns of minor, intermediate-sized, and major males. Our results suggest that the function of Notch signaling during head horn formation may vary in a complex manner across male morphs, and highlights the power of integrating functional genetic and geometric morphometric approaches in analyzing subtle but nevertheless biologically important phenotypes in the face of significant allometric variation.