Accurate mapping of species distributions is a fundamental goal of modern biogeography, both for basic and applied purposes. This is commonly done by plotting known species occurrences, expert-drawn ...range maps or geographical estimations derived from species distribution models. However, all three kinds of maps are implicitly subject to uncertainty, due to the quality and bias of raw distributional data, the process of map building, and the dynamic nature of species distributions themselves. Here we review the main sources of uncertainty suggesting a code of good practices in order to minimize their effects. Specifically, we claim that uncertainty should be always explicitly taken into account and we propose the creation of maps of ignorance to provide information on where the mapped distributions are reliable and where they are uncertain.
Species distribution models (SDM) are commonly used to obtain hypotheses on either the realized or the potential distribution of species. The reliability and meaning of these hypotheses depends on ...the kind of absences included in the training data, the variables used as predictors and the methods employed to parameterize the models. Information about the absence of species from certain localities is usually lacking, so pseudo-absences are often incorporated to the training data. We explore the effect of using different kinds of pseudo-absences on SDM results. To do this, we use presence information on Aphodius bonvouloiri, a dung beetle species of well-known distribution. We incorporate different types of pseudo-absences to create different sets of training data that account for absences of methodological (i.e. false absences), contingent and environmental origin. We used these datasets to calibrate SDMs with GAMs as modelling technique and climatic variables as predictors, and compare these results with geographical representations of the potential and realized distribution of the species created independently. Our results confirm the importance of the kind of absences in determining the aspect of species distribution identified through SDM. Estimations of the potential distribution require absences located farther apart in the geographic and/or environmental space than estimations of the realized distribution. Methodological absences produce overall bad models, and absences that are too far from the presence points in either the environmental or the geographic space may not be informative, yielding important overestimations. GLMs and Artificial Neural Networks yielded similar results. Synthetic discrimination measures such as the Area Under the Receiver Characteristic Curve (AUC) must be interpreted with caution, as they can produce misleading comparative results. Instead, the joint examination of ommission and comission errors provides a better understanding of the reliability of SDM results.
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.
1. Global warming may especially affect ectothermic insect species, making it necessary to forecast the capacity of these species to cope with climatic changes.
2. In this study, we use circular ...statistics to examine the seasonal plasticity of 32 dung beetle species in 17 localities of a mountain Iberian assemblage. We assume that the high variability between localities in the seasonal patterns for the same species suggests that seasonal plasticity could minimise the demographic effects of climate change on local populations.
3. Our results suggest that the populations of at least one‐third of the dung beetle species could partially adapt to the effects of climate change by modifying their phenological occurrence, and that the degree of concentration of the seasonal occurrences is generally maintained independently of the locality. However, we have not detected clear seasonal pattern variations or a clear effect of environmental temperature on seasonal variations in around two‐thirds of the studied species.
4. The dung beetle assemblages of this mountain region will experience deep changes in the future. Plasticity in seasonal patterns does not seem to be associated with species characteristics such as high‐rank taxonomic identity, body weight, or geographical distribution. Only the general functional character of species would have some explanatory power. Endophagic Aphodiidae dung beetle species would be more capable than hypophagic species in mitigating the effects of climate change by modifying their phenological traits, whereas that Scarabaeidae hypophagic species may cope better with these climatic changes without having to change their seasonal activities.
We examine the seasonal plasticity of 32 dung beetle species in 17 Iberian localities, assuming that a high spatial variability in seasonal patterns could minimise the effects of climate change.
One‐third of the studied species modify spatially their seasonal occurrence, but we have not detected a clear effect of environmental temperature on seasonal variations in around two‐thirds of the species.
Plasticity in seasonal patterns does not seem to be associated with species characteristics. Only the general functional character of species would have some explanatory power.
Aim: The method used to generate hypotheses about species distributions, in addition to spatial scale, may affect the biodiversity patterns that are then observed. We compared the performance of ...range maps and MaxEnt species distribution models at different spatial resolutions by examining the degree of similarity between predicted species richness and composition against observed values from well-surveyed cells (WSCs). Location: Mexico. Methods: We estimated amphibian richness distributions at five spatial resolutions (from 0.083° to 2°) by overlaying 370 individual range maps or MaxEnt predictions, comparing the similarity of the spatial patterns and correlating predicted values with the observed values for WSCs. Additionally, we looked at species composition and assessed commission and omission errors associated with each method. Results: MaxEnt predictions reveal greater geographic differences in richness between species rich and species poor regions than the range maps did at the five resolutions assessed. Correlations between species richness values estimated by either of the two procedures and the observed values from the WSCs increased with decreasing resolution. The slopes of the regressions between the predicted and observed values indicate that MaxEnt overpredicts observed species richness at all of the resolutions used, while range maps underpredict them, except at the finest resolution. Prediction errors did not vary significantly between methods at any resolution and tended to decrease with decreasing resolution. The accuracy of both procedures was clearly different when commission and omission errors were examined separately. Main conclusions: Despite the congruent increase in the geographic richness patterns obtained from both procedures as resolution decreases, the maps created with these methods cannot be used interchangeably because of notable differences in the species compositions they report.
Protected areas (PAs) are intended to preserve natural places, aiming to sustain ecosystem functionality and preserve biodiversity. However, PAs are spatially static, while major threats to ...biodiversity, such as climate and land-use change, are dynamic. The climatic conditions represented in a PA could vanish in the future and appear in other places more or less far away from the PA; these places could be considered as recipient areas potentially suited to receive propagules from the source PAs, which tend to lose the climatic conditions that motivated their protection. This study estimates the current and future climatic representativeness of mainland Iberian national parks by identifying future areas with a similar climate to those existing now in the parks and taking into account the degree of anthropogenic alteration and protection. We identify a network of ecological corridors connecting Iberian national parks with their recipient areas, as well as discriminating those most conflicting areas that impede network connectivity due to their degree of land-use transformation. Our results identify important areas for maintaining the climatic representativeness of Iberian national parks in the future, showing a substantial reduction in the climatic representativeness of the Iberian national parks. Although most of the recipient areas now have forest and semi-natural land uses and more than half of their whole area has protected status, current land uses in the Iberian Peninsula severely obstruct the corridor network connecting the parks and recipient areas.
Aim: Nowadays, large amounts of species distribution data and software for implementing different species distribution modelling methods are freely available through the internet. As a result, ...methodological works that analyse the relative performance of modelling techniques, as well as those that study which species characteristics affect their performance, are necessary. We discuss three important topics that must be kept in mind when modelling species distributions, namely (i) the distinction between potential and realized distribution, (ii) the effect of the relative occurrence area of the species on the results of the evaluation of model performance, and (iii) the general inaccuracy of the predictions of the realized distribution provided by species distribution modelling methods. Location: Unspecific. Methods: Using some recent papers as a basis, we illustrate the three issues mentioned above and discuss the negative implications of neglecting them. Results: Considering a potential-realized distribution gradient, different modelling methods may be arranged along this gradient according to their ability to model any concept. Complex techniques may be more suitable to model the realized distribution than simple ones, which may be more appropriate to estimate the potential distribution. Comparisons among techniques must consider this scenario. The relative occurrence area of the species conditions the results of the evaluation scores, implying that models of rare species will unavoidably yield higher discrimination values. Moreover, discrimination values that are usually reported in the literature may imply considerable over or underestimations of the distribution of the species. Main conclusions: It is extremely important to establish a solid conceptual and methodological framework on which the emergent field of species distribution modelling can stand and develop.
Aim: We investigated changes in dung beetle β-diversity components along a subtropical elevational gradient, to test whether turnover or nestedness-related processes drive the dissimilarity of ...assemblages at spatial and temporal scales. Location: An elevational gradient (200-1,600 m a.s.l.) of the Atlantic Forest in southern Brazil. Methods: We investigated the extent to which β-diversity varied along the elevational gradient (six elevations) at both spatial (among sites at different elevations) and temporal (different months at the same site) scales. We compared both the turnover and nestedness-related dissimilarity of species and genera using multiple-site or multiple-month measures and tested whether these measurements were different from random expectations. Results: A mid-elevation peak in species richness along the elevational gradient was observed, and the lowest richness occurred at the highest elevations. We found two different groups of species, lowland and highland species, with a mixing of groups at intermediate elevations. The turnover component of β-diversity was significantly higher for both spatial (i.e. elevational) and temporal changes in species composition. However, when the data for genera by site were considered, the elevational turnover value decreased in relative importance. Nestedness-related processes are more important for temporal dissimilarity patterns at higher elevation sites. Main conclusions: Spatial and temporal turnover of dung beetle species is the most important component of β-diversity along the elevational gradient. High-elevation assemblages are not subsets of assemblages that inhabit lower elevations, but this relationship ceases when β-diversity is measured at the generic level. Environmental changes across elevations may be the cause of the differential establishment of distinctive species, but these species typically belong to the same higher taxonomic rank. Conservation strategies should consider elevational gradients in case-specific scenarios as they may contain distinct species assemblages in lowlands vs. highlands.
Databases on the distribution of species can be used to describe the geographic patterns of biodiversity. Nevertheless, they have limitations. We studied three of these limitations: (1) inadequacy of ...raw data to describe richness patterns due to sampling bias, (2) lack of survey effort assessment (and lack of exhaustiveness in compiling data about survey effort), and (3) lack of coverage of the geographic and environmental variations that affect the distribution of organisms. We used a biodiversity database (BIOTA-Canarias) to analyze richness data from a well-known group (seed plants) in an intensively surveyed area (Tenerife Island). Observed richness and survey effort were highly correlated. Species accumulation curves could not be used to determine survey effort because data digitalization was not exhaustive, so we identified well-sampled sites based on observed richness to sampling effort ratios. We also developed a predictive model based on the data from well-sampled sites and analyzed the origin of the geographic errors in the obtained extrapolation by means of a geographically constrained cross-validation. The spatial patterns of seed-plant species richness obtained from BIOTA-Canarias data were incomplete and biased. Therefore, some improvements are needed to use this database (and many others) in biodiversity studies. We propose a protocol that includes controls on data quality, improvements on data digitalization and survey design to improve data quality, and some alternative data analysis strategies that will provide a reliable picture of biodiversity patterns.
The seasonal and diel variations of dung beetle species were studied in an Iberian mid-mountain locality to examine the interaction between these two temporal rhythms. We assume that a seasonal ...variation in the diel activity would support the notion that both rhythms may assist in achieving a quick and flexible response when the climatic conditions change. Data coming from 4,104 pitfall traps placed during 15 sampling periods and totalling 30 daily sampling cycles were analysed using circular statistics and General Linear Models. A wide variety of seasonal patterns are observed, highlighting those species with a clear unimodal or spring-autumn bimodal seasonal pattern. However, a midday diel pattern is the norm in most of the species, except in the case of those exhibiting a high body weight that prefer dusk or night periods. We hypothesize that most of the dung beetle species fly at noon to promote the passive heating of their muscle activity and minimize the metabolic energy expenditure. Results only partially support the seasonal variation in diel activity. Diel preferences are mainly manifested at the time of the year in which the abundance is greater. Approximately two-thirds of the considered species exhibit a similar diel activity along their seasonal active period. As consequence, a significant portion of the dung beetle species currently inhabiting Mediterranean mid-mountains are not able to use the daily variation in climatic conditions to limit the inconveniences of climate change.
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