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Coping with aridity is a physiological challenge for all organisms, including freshwater ones. Aridity shapes distributions of aquatic species at fine and large geographical scales. Specifically, for aquatic beetles, the desiccation resistance of the adults is a potential constraint for the colonisation of arid regions.We assessed the congruence between the fundamental and realised aridity niche in eight species of a Palearctic lineage of water beetles (subgenus Lumetus, genus Enochrus, family Hydrophilidae). We also estimated the relative explanatory capacity of aridity‐related versus other environmental variables in species distributions.Most of the species, even those most sensitive to desiccation stress in laboratory experiments, occur in areas with high aridity within the Palearctic region. Our results suggest a lack of association between the physiological (desiccation resistance) and environmental distance matrix (realised aridity niche), or between either of these and phylogenetic distances. Aridity‐related variables had generally a similar explanatory capacity in explaining the distribution of species than non‐related ones.Our results indicate that desiccation resistance has not been an important physiological constraint for the colonisation of arid environments by this clade and suggest that other non‐physiological factors are more important in shaping their distributions along aridity gradients. The studied beetle lineage might conserve a high basal desiccation resistance from relatively recent terrestrial ancestors, which could have provided a physiological advantage for the colonisation of arid areas. Further research could shed light on whether these unexpected results are common to other groups of aquatic insects living in arid areas or are particular to this group of beetles. [ABSTRACT FROM AUTHOR]

Studying the environmental characteristics of the localities in which different taxa have been observed could help to estimate probable niche differences. Previous studies on local distribution and reproductive behavior of the two subspecies of Canthon rutilans support their allopatry. Here we estimated the geographical distribution of these taxa to examine the congruency between the environmental characteristics of the occurrence localities derived from geographical and local data, in order to facilitate the future study of the causal factors that are more likely to explain their segregation. To do so, a database including most of the available distributional information about these subspecies was compiled. The data derived from 23 environmental variables in the occurrence cells were used to estimate those variables with different mean values among the two subspecies, and also to generate distributional maps reflecting the probable distribution of the two subspecies. Ten variables have statistically significant different values among both subspecies. Canthon rutilans rutilans would be present in colder places, living in the high elevation localities of the Atlantic Forest or Pampas biomes, whereas C. rutilans cyanescens seems to be restricted to lowland forested areas. Probable distribution maps show geographical sympatry in almost half of the distribution range of C. r. rutilans. As former results suggest that they are in allopatry at a local scale, these results propose that fine‐grain environmental factors would be promoting the segregation of taxa, but also that coarse‐grain data should be used with caution when the aim is to estimate niche differences. [ABSTRACT FROM AUTHOR]

The establishment of cattle ranches throughout the world has prompted the release of dung beetles as biological control agents that reduce pasture fouling and control dung‐breeding flies. One of these beetles, Digitonthophagus gazella (Fabricius) (Coleoptera: Scarabaeidae), that is native to southeast Africa, has been introduced into the Americas, Australia, and New Zealand. Distribution records for this species have been used to develop climate models of potential future establishment. Recent studies, however, identify D. gazella as a complex of seven species. Taking into account this revision, and the clear identification of the records belonging to the actual D. gazella, we developed environmental models to identify factors that have contributed to the establishment of this species across regions and habitats. We compared the environmental conditions of D. gazella in its native range against those in the regions where the species has or has not established. Our results indicate that D. gazella is still absent in certain parts of Central and South America and parts of Africa where it could potentially establish. We speculate that its distribution in Africa is limited by competitive exclusion. The introduction of D. gazella in America is relatively recent, such that the full extent of its distribution has probably yet to be realized. In Australia and North America, D. gazella is present in regions not predicted according to its native environmental conditions. This discrepancy may reflect a lack of competitive exclusion, phenotypic plasticity, and/or genetic adaptation. Our analyses suggest that the species has the ability to adapt to a wide range of environmental conditions that are extremely different from those in their native region. The species represents a useful case study to indicate that an introduced species may expand its realized niche beyond what is expected based on apparent environmental limits in the species native range. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mediterranean ectothermic insect species active under cold conditions are rare. • Chelotrupes momus is an endemic and apterous species active during winter nights. • Results indicate that this species is active without the need to warm its body. • The exoskeleton of this species may facilitate the absorbance of infrared radiation. • This would constitute an example of a "hotter-is-not-better" thermal strategy. While there are numerous examples of thermogenesis processes in poikilothermic insects that maintain a stable temperature for a certain time and in certain parts of the body, there is a lack of information on ectothermic insect species capable of remaining active under "cold" conditions that would be challenging for other species. Such a thermal strategy would imply the existence of a metabolism that can operate at different temperatures without the need to increase body temperature when experiencing cold environmental conditions. This "hotter-is-not-better" thermal strategy is considered ancestral and conjectured to be linked to the origin and evolution of endothermy. In this study, we examined the thermal performance of a large-bodied dung beetle species (Chelotrupes momus) capable of being active during the winter nights in the Iberian Mediterranean region. Field and laboratory results were obtained using thermocamera records, thermocouples, data loggers and spectrometers that measured ultraviolet, visible and near-infrared wavelengths. The thermal data clearly indicated that this species can remain active at a body temperature of approximately 6 °C without the need to warm its body above ambient temperature. Comparing the spectrophotometric data of the species under study with that from other previously examined dung beetle species indicated that the exoskeleton of this particular species likely enhances the absorption of infrared radiation, thereby implying a dual role of the exoskeleton in both heat acquisition and heat dissipation. Taken together, these results suggest that this species has morphological and metabolic adaptations that enable life processes at temperatures that are typically unsuitable for most insect species in the region. [ABSTRACT FROM AUTHOR]

Background: 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. Methods: Onthophagus coenobita (Herbst) and O. medius (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. Results: 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. Discussion: 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. [ABSTRACT FROM AUTHOR]

The altitudinal gradient in diversity of dung beetles (Scarabaeidae) was studied in a Mediterranean mountain chain located in Central Anatolia to (i) determine if there are altitudinal differences between the main taxonomic groups, (ii) describe the seasonal variations in these assemblages and (iii) assess whether closed habitats influence dung beetle diversity differentially at different altitudes. Beetles were collected throughout a year at 14 localities between 469 and 1810 m above sea level in three different types of habitats. Dung beetle assemblages at 400 to 1200 m did not vary greatly in species richness, abundance and biomass. However, they varied in composition, with the assemblages dominated by species of Scarabaeinae up to 900 m, whereas in the mid-mountain assemblages (from 900 m to 1600 m) the numbers of species of Aphodiinae was higher. The decline with increase in altitude in richness, abundance and biomass of both small and large species of Scarabaeinae up to 1500 m, together with the constancy of these parameters in the case of Aphodiinae, accounts for the changes in the composition from the lowland to mid-mountain localities. Unlike at other Mediterranean localities, the open/closed structure of the habitat only slightly influences these assemblages independently of altitude or season. The general seasonal pattern follows the classical Mediterranean bimodal pattern associated with summer drought, but the patterns are more complex when the seasonal responses of the different groups and at different localities are analysed separately. We propose that the interplay between local climatic conditions (mainly temperature) and evolutionary conserved species preferences accounts for both the current seasonal and altitudinal gradients and the changes in species composition in terms of Aphodiinae and Scarabaeinae. [ABSTRACT FROM AUTHOR]

Dung consumption and removal is a fundamental ecological process carried out by dung beetles that drive soil nutrient cycling and associated ecosystem services. In this study, the removal rate of small droppings by dung beetles was estimated in natural subtropical rainforests of southern Brazil located along an elevational gradient, in order to understand the factors influencing variation in dung removal. To do that, the comparative explanatory capacity of three main types of variables was quantified: assemblage characteristics, local climatic and habitat conditions, and seasonal variation. The complete disappearance of dung within 48 h after deposition occurs in 73% of occasions. The highest explanatory capacity correspond to the combined effects of the three types of variables; however, average air temperature during the sampling period, total volume of dung beetles collected in the traps in which dung removal was measured, and the seasonal transition from summer to winter were the most important and representative predictors of dung removal. Thus, the dung nutrient incorporation into the soil will most likely be greater during spring‐summer conditions, when the air temperature at the time of dung deposition is high and the biomass of the dung beetle assemblage is bigger. The disappearance of small droppings by dung beetle activity within 48 h after deposition is widespread in subtropical Atlantic Rainforests. The highest explanatory capacities accounting for dung removal correspond to the combined effects of three predictors: assemblage characteristics, local environmental conditions, and seasonal effects. Thus, incorporation of dung nutrients into the soil most likely is greatest during spring‐summer conditions, when air temperature at the time of dung deposition is high, and biomass of the dung beetle assemblage is high. [ABSTRACT FROM AUTHOR]

A basic aim of ecology is to understand the determinants of organismal distribution, the niche concept and species distribution models providing key frameworks to approach the problem. As temperature is one of the most important factors affecting species distribution, the estimation of thermal limits is crucially important for inferring range constraints. It is expectable that thermal physiology data derived from laboratory experiments and species' occurrences may express different aspects of the species' niche. However, there is no study systematically testing this prediction in a given taxonomic group while controlling by potential phylogenetic inertia. We estimate the thermal niches of twelve Palaearctic diving beetles species using physiological data derived from experimental analyses in order to examine the extent to which these coincided with those estimated from distribution models based on observed occurrences. We found that thermal niche estimates derived from both approaches lack general congruence, and these results were similar before and after controlling by phylogeny. The congruence between potential distributions obtained from the two different procedures was also explored, and we found again that the percentage of agreement were not very high (~60%). We confirm that both thermal niche estimates derived from geographical and physiological data are likely to misrepresent the true range of climatic variation that these diving beetles are able to tolerate, and so these procedures could be considered as incomplete but complementary estimations of an inaccessible reality. [ABSTRACT FROM AUTHOR]

Predictions from individual distribution models for Mexican Geotrupinae species were overlaid to obtain a total species richness map for this group. A database (GEOMEX) that compiles available information from the literature and from several entomological collections was used. A Maximum Entropy method (MaxEnt) was applied to estimate the distribution of each species, taking into account 19 climatic variables as predictors. For each species, suitability values ranging from 0 to 100 were calculated for each grid cell on the map, and 21 different thresholds were used to convert these continuous suitability values into binary ones (presence-absence). By summing all of the individual binary maps, we generated a species richness prediction for each of the considered thresholds. The number of species and faunal composition thus predicted for each Mexican state were subsequently compared with those observed in a preselected set of well-surveyed states. Our results indicate that the sum of individual predictions tends to overestimate species richness but that the selection of an appropriate threshold can reduce this bias. Even under the most optimistic prediction threshold, the mean species richness error is 61% of the observed species richness, with commission errors being significantly more common than omission errors (71 ± 29 versus 18 ± 10%). The estimated distribution of Geotrupinae species richness in Mexico in discussed, although our conclusions are preliminary and contingent on the scarce and probably biased available data. [ABSTRACT FROM AUTHOR]

It is well known that biodiversity data from historical inventories presents important geographic and taxonomic biases. Due to this, current knowledge on the distribution of most species could be incomplete and biased. We assess how the biases in historical biodiversity data might affect the description of the environmental niche of the species, using exhaustive data on the distribution of dung beetles in Madrid as a case study. We describe the historical process of survey and compare such historical data with the results of an exhaustive survey, identifying the environmental biases in the historical surveys during different periods, and assessing the completeness of the environmental niche of the species provided by historical data through time. Events like the Spanish Civil War affect the tempo and spread of surveys, but the exhaustive work since 1970 provides a good, though incomplete, coverage of the region by 1998. In spite of this, the biases in historical data result in a limited knowledge about the niche of an important number of species. Although nearly a half of the species had the 100% of their niche covered by data in 1998, roughly a third had less than 75%, nearly a fourth less than 50%, and 18 species had to be excluded from the analyses due to the lack of data. Our results point out that data from non-standardized inventories often provide an incomplete description of the environmental responses of most species. Due to this, we highlight that currently predictive models of species distributions present some limitations, since the results of models based in partial information about the environmental niche of the species will be compromised. Therefore, the biases in the available data must be evaluated before constructing predictive maps of species distributions, and taken into account when drawing conclusions or conservation strategies from these maps. [ABSTRACT FROM AUTHOR]

The degree of completeness of the western Palaearctic inventory of the genus Aphthona and the factors that have determined the process of species description in the region were analysed. The historic species accumulation curve shows no asymptotic trend so no accurate estimations could be made of the number of species to be discovered in the future, but the shape of the curve indicates that a significant proportion of the taxa remains yet-to-be-described and thus further taxonomic effort will be needed. In order to optimise this taxonomic work, several morphologic, trophic and geographic variables of Aphthona species were analysed, in a search for the factors that have influenced the probability of discovery of taxa and thus to estimate the characteristics of the yet-to-be-described species. General Regression Models and variation partitioning were used to assess the influence on the process of species description of body size and colour, trophic range, number of host plants, geographic range size, maximum and minimum latitude and longitude. Morphological variables are not statistically significant in explaining the variation in the year of description, whereas trophic and geographic variables are essential determinants. The pure effects of geographic range size, trophic variables and geographic location of taxa are negligible, but the shared effects between the three groups of variables account for important portions of the variation; the whole model explains 64% of the variance. Widely distributed and trophic generalist species living in northern and western areas of the western Palaearctic region were described first. Extrapolation of the observed pattern should yield an estimate of the probable features and location of the yet-to-be-described species. New Aphthona should be searched for southwards and eastwards, distributed in small areas and living on a single, or very few, host plants. [ABSTRACT FROM AUTHOR]

This study analyses the effect of resource availability (i.e. sheep dung) on dung beetle communities in an arid region of Central Spain, both at regional and at local scales. A total of 18 sites within 600 km2 were sampled for the regional analysis and 16 sites within the 30 km2 of an Iberian municipality were sampled for the local analysis. Spatial and environmental characteristics of sampling sites were also compiled at both scales, including measures of grazing activity (livestock density at regional scale, and two counts of rabbit and sheep dung at local scale). At a regional scale, any environmental or spatial variable can help to explain the variation in abundance. However, species richness was related to summer precipitation and composition was related to elevation. At local scale, abundance is not significantly related to any of the environmental variables, but species richness was related to the local amount of sheep dung (27% of variance). The amount of dung in a 2-km buffer around the site accounts for 27–32% of variance in abundance and 60–65% of variance in species richness. The presence of the flock with the highest sheep density explains 53% of abundance variability and 73% of species richness variance. A cluster analysis of localities identified two main groups, one characterized by a lower abundance and species richness that can be considered a nested subsample of the species-rich group. The mean and maximum amount of sheep dung in the sites separated by less than 2 km are the only significant explanatory variables able to discriminate both groups. These results suggest that grazing intensity (and the associated increase in the amount of trophic resources) is a key factor in determining local variation in the diversity and composition of dung beetle assemblages. However, dung beetle assemblages are not spatially independent at the analysed resolution, and the amount of dung in the surroundings seems to be more important for locally collected species than the dung effectively found in the site. Although differences in the availability and quantity of trophic resources among nearby sites could be affecting the population dynamics and dispersion of dung beetles within a locality, sites with larger populations, and greater species numbers would not be able to exercise enough influence as to bring about a complete local faunistic homogenization. [ABSTRACT FROM AUTHOR]

We describe the changes in species richness, rarity and composition with altitude, and explore whether the differences in Scarabaeinae dung beetle composition along five altitudinal transects of the same mountain range are related to altitude or if there are interregional differences in these altitudinal gradients. Field work was carried out on the eastern slope of the eastern Cordillera, Colombian Andes, between Tamá Peak to the north, in the Tamá National Park (07°23′ N, 72°23′ W) and the San Miguel River (00°28′ N, 77°17′ W) to the south. Sampling was carried out between February 1997 and November 1999 in five regions spanning elevation gradients. In each gradient, six sites were chosen at 250 m intervals between 1000 and 2250 m a.s.l. We found a curvilinear relationship between altitude and mean species richness, with a peak in richness at middle elevations. However, the diversity of dung beetle assemblages does not seem to be related to the interregional differences in environmental conditions. The number of geographically restricted species is negatively and significantly related to altitude, with geographically restricted species more frequent at low altitude sites. Ordination delimited the two main groups according to altitude: one with all the highest sites (1750–2250 m a.s.l.) and a second group with the remaining sites (< 1750 m a.s.l.). Analysis of species co-occurrence shows that these dung beetle assemblages seem to be spatially structured when all sites have the same probability of being chosen. In contrast, the spatial structure of species assemblages seems to be random when the probability of choosing any site is proportional to its altitude. The altitude of sites is the main factor that influences the diversity of these dung beetle assemblages. The peak in species richness at middle elevations, the higher number of geographically restricted species at lower altitudinal levels, and the compositional differences along these mountain gradients seem to result from the mixing at these altitudes of dung beetle assemblages that have different environmental adaptations and, probably, different origins. The relevance of altitude in these assemblages is related to the limited role of these Neotropical high altitude environments as centres of refuge and vicariance for a monophyletic group of warm-adapted species, for which the vertical colonization of these high mountain environments by lineages distributed at lower altitudes would have been very difficult. [ABSTRACT FROM AUTHOR]

A phylogeny of the main lineages of dung beetles (Coleoptera: Scarabaeinae) from the Iberian Peninsula was based on partial nucleotide sequences (about 1221 bp) of the mitochondrial cytochrome oxidase I and II genes of 33 taxa. Our phylogenetic analyses confirmed the validity and composition of most of the recognized tribes within the subfamily. Interestingly, the Onitini showed an evolutionary rate significantly higher than that of the other tribes. The molecular phylogeny supports a sister-group relationship of the tribes Onitini and Oniticellini + Onthophagini. A close relationship of Scarabaeini, Gymnopleurini, and Sisyphini is also suggested but lacks bootstrap support. Surprisingly, the Coprini, which had always been related to the Oniticellini and Onthophagini, were placed closer to the Scarabaeini, Gymnopleurini, and Sisyphini. The inferred molecular phylogeny was used to assess the main evolutionary trends of nesting behavior. Our results suggest tentative single origins for both the tunneling and the rolling behaviors, and the possibility that the rolling behavior could have been lost secondarily in Copris. [ABSTRACT FROM AUTHOR]

Beetles are the most successful and diversified animal taxa characterized by the possession of an external pair of sclerotized wings (elytra). Managing electromagnetic radiations could be one of the functions of the exoskeleton. We studied the spectrophotometric response to ultraviolet, visible, and near-infrared radiations of the elytra of seven closely related and sympatric Onthophagus species to examine if the environmental preferences of these species could be associated with the spectrophotometric behaviour of their elytra. Our results indicated that sibling species can drastically differ in their environmental preferences but not in their spectrophotometric responses. However, our results corroborated that there are interspecific differences in the spectrophotometric characteristics of the elytra, which are mainly explained by morphological features. Among the examined morphological variables, darkness seems to be especially relevant as it facilitates the absorbance and obstructs the transmittance of visible and near-infrared radiations. • The elytra of dung beetles have different spectrophotometric characteristics. • Spectrophotometric responses can be explained by morphological features. • Sibling species with a similar spectrophotometric behaviour may differ environmentally. • Darkness could facilitate absorbance and but obstruct transmittance of radiations. [ABSTRACT FROM AUTHOR]