Wilson's warbler comprises three subspecies separated into two geographic groups: C. p. pusilla that breeds in eastern North America; and C. p. pileolata and C. p. chryseola that breed in western North America. Given the differences between the groups in genetics, morphology, habitat use, and population decline, we tested for ecological niche similarity in both their breeding and wintering distribution using niche modeling based on temperature and precipitation data. We first conducted an inter-prediction approach considering the percent of summer and winter localities of one group that are predicted by the potential distribution of the alternate group. We also applied a null model approach that compares self-predictions and pseudoreplicates of each group to indicate similarity, divergence, or indeterminate niche overlap. Finally, we compared ecological distances between and within groups using the Gower similarity equation. We found that the western group had an ecological niche of broader climatic conditions, while the eastern group had a narrower ecological niche. The interprediction approach showed that, for both summering and wintering ranges, ecological niche models of the western group predicted ∼50% of the observed distribution of the eastern group, whereas eastern group models predicted  18% of the western group distribution. The null model approach found that similarity in ecological niches was indeterminate, possibly due to the large area occupied by the two groups; but it suggests a more restricted set of climatic conditions of the eastern group distribution. However, the Gower coefficients demonstrated that the ecological distance between the two geographic groups was larger than the ecological distance within groups, indicating distinct ecological niches. Overall, our results support the hypothesis that the eastern and western groups of Wilson's warbler are two cryptic species; this should be taken into consideration for future analyses, particularly with respect to vulnerability categorization and conservation efforts.

IntroductionThe standardization of sampling protocols is imperative for robustly studying any taxonomic group. Replicable methods allow the comparison of data between different spatial and temporal studies. In the case of dung beetles, one of the best-studied indicator groups in analyses of environmental disturbance, a wide range of collection methodologies are used, from basic pitfall traps to more complex or complementary methods such as mini-Winkler extractor. Also, different types of attractive baits, sampling effort, durations, and designs are used in dung beetle studies. Variations in methodological approaches are particularly noted in the Neotropics, which may be related to the vast number of biological strategies and behavior of dung beetles that inhabit this region. A lack of methodological unification for the Neotropical region makes a cross-sectional analysis of the information impossible.MethodsWe performed a compilation and analytical review of the existing literature for dung beetle sampling in the Neotropics, discussing the most used methodologies, their advantages and disadvantages, and specific cases in which particular models are more efficient.ResultsPitfall traps baited with human excrement are the most common sampling method, but there is a wide range of models and variations in the structure of this trap. The complementary effect generated by flight interception traps, light traps, and direct collections, particularly within microhabitats, is exciting for the potential of finding new species. Some methodologies, such as mini-Winkler extractor, fogging, or very specific baits, are infrequently used.DiscussionThere was a lack of inclusion of spatial and temporal variation among studies. Therefore, it is necessary to consider broader sampling windows, which include different spatial scales, seasons, and years. Finally, we propose a standard protocol for sampling dung beetles in the Neotropics, depending on each objective, and including a basic methodology for obtaining complete local inventories.

Se presenta un estudio de los escarabajos necrófagos (Scarabaeidae y Trogidae) de la región central baja de Veracruz y se compara la composición de su ensamble con otras regiones. Las colectas se realizaron durante la época de lluvias del año 2000 en sitios con remanentes derivados del bosque tropical subcaducifolio perturbado, rodeados con vegetación secundaria y cultivos de la región Apazapan-Jalcomulco establecidos entre 280 y 450 m snm. Se obtuvieron 2135 ejemplares pertenecientes a 3 subfamilias, 7 tribus, 11 géneros y 18 especies de Scarabaeidae y Trogidae que comprenden el 92% de las especies de escarabajos necrófagos posibles de ser encontradas en esa región. Las especies más abundantes fueron: Canthon cyanellus cyanellus, Deltochilum gibbosum sublaeve y Coprophanaeus pluto. La riqueza y abundancia fue mayor al inicio de la época de lluvias y fue disminuyendo gradualmente. Se encontró mayor abundancia en Apazapan que en Jalcomulco. Los escarabajos cavadores superan a los rodadores en riqueza específica en proporción de 3:1en tanto que la proporción en abundancia fue inversa. La actividad de especies nocturnas sobrepasa la de diurnas en la misma proporción. Esta región presenta hasta el 63% de similitud específica y alrededor del 80% de similitud genérica con la región costera de Veracruz, valores comparables con el 56% y el 90% de similitudes respectivas con la parte baja de la Reserva de la Biósfera El Cielo, Tamaulipas.

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