Richard D. Stevens

Aim: Phylogenetic niche conservatism, the tendency of closely related species to retain ancestral ecological traits, has gained considerable interest, yet the lack of integration across independent evaluation methods has hindered our understanding of whether niches are conserved or dynamic. Such an understanding is especially relevant for taxa of conservation concern, such as crocodylians (order Crocodylia). This study assessed niche conservatism among New World crocodylians by combining ensemble species distribution models, phylogenetics, and standard metrics of geographic and environmental niche overlap. Location: America. Major Taxa: Order Crocodylia. Methods: We estimated species' climatic niches in geographic and environmental dimensions to assess overlap patterns and quantified associations between niche overlap and phylogenetic patristic distance using the Mantel test and phylogenetic independent contrast (PIC). Results: Overlap analyses in geographic and environmental spaces revealed climatic niche differentiation across the clade, suggesting divergent environmental preferences among species. The relationship between phylogenetic patristic distance and climatic niche overlap assessed via Mantel tests revealed a significant negative correlation with geographic niche overlap ( ρ = −0.361, p = 0.005), but no evidence for associations with environmental niche overlap (Schoener's D: ρ = −0.079, p = 0.184; Hellinger's I: ρ = −0.063, p = 0.250), suggesting that more distantly related species overlap less geographically. In contrast, the relationship assessed using PIC revealed no evidence for associations between phylogenetic distance and either geographic ( ρ = −0.200, p = 0.579) or environmental niche overlap (D: ρ = −0.294, p = 0.41; I: ρ = −0.319, p = 0.369). Conclusions: We found no strong or consistent evidence for phylogenetic conservatism in climatic niches across both geographic (inverse relationship) and environmental (no relationship) dimensions in New World crocodylians. This study enhances our understanding of niche dynamics and highlights the value of integrating niche modelling with phylogenetic analyses to detect biogeographic and evolutionary patterns.

Sustainable human–wildlife coexistence requires a mechanistic understanding of the many ways that humans affect animals. However, progress is hampered by the lack of accessible data measuring the dynamic presence of people. Here, we leverage mobile-device data to disentangle how human presence and landscape modification differentially influence the use of geographic and environmental space for 37 mammal and bird species across the United States. Human presence affected more than 65% of species, with substantial variation across species. For ~60% of species that responded to human activities, the effects were interdependent—animals tended to react more strongly to human presence in less modified habitats. Our results demonstrate that human presence and landscape modification have complex combined effects on wildlife, which need to be considered for effective management.

Phenotypic variation can assume multiple forms including sexual dimorphism, geographic and subspecific differences, or morphological clines along environmental gradients. Importantly, these sources of variation may interact, especially across large spatial and/or temporal extents. Moreover, subspecies delineations are often based on discontinuities in phenotypic variation thought to represent distinct populations. We examined phenotypic variation within Myotis velifer, a bat species distributed across the southwestern United States and Mexico to Honduras. We measured a series of cranial characters from 195 specimens from 98 sites of the 3 currently recognized subspecies (M. v. incautus, M. v. magnamolaris, and M. v. velifer) to identify potential differences among sexes and subspecies. We also used multivariate analyses to relate variation in cranial characteristics to spatial and environmental gradients. We found significant differences in cranial characters among subspecies, but no differences between sexes and no sex-by-subspecies interactions. We also demonstrated that spatial gradients but not subspecies designation or sex explained significant unique variation in cranial morphology. Climatic gradients were primarily characterized by larger phenotypes in environments with more variable temperatures. Results from this work question existing subspecific designations for this species as well as demonstrate the importance of accounting for geographic clines when examining phenotypic variation in the context of subspecific delineation.

The lowland tapir (Tapirus terrestris) is distributed throughout much of South America and is considered a keystone species because it fulfills crucial ecological roles in tropical forests. Tapirs are associated with forest ecosystems and water bodies throughout their geographic range. In the Orinoquia region of Colombia, tapirs are found in natural savannahs and in dense, gallery, and riparian forests. Although there is data available on tapir natural history, basic knowledge is still lacking across much of its distribution. This research generated a baseline of tapir distribution to assess habitat use and conservation areas across the Orinoquia. We built a database of 110 individual occurrences from camera trap sampling conducted in the departments of Arauca, Casanare, Vichada, and Meta. We built candidate models using the Wallace 2.1.3 R package and selected the best-performing models, which we then implemented in Maxent 3.4.4 to obtain the final distribution outputs. Precipitation seasonality and land cover were the most important variables for tapir distribution, and areas of dense gallery and riparian forests in good conservation state were found to be highly suitable habitats, especially in Arauca and Vichada. Tapir populations likely became locally extinct in the southern part of the department of Casanare. Our results constitute the first approximation of the distribution of the lowland tapir for the Orinoquia region of Colombia. It is necessary to generate additional regional and local data to allow for a more precise evaluation of distribution in these heterogeneous landscapes. The findings of this study provide useful information for conservation strategies and highlight the need for further research to better understand the distribution and habitat use of the lowland tapir in this region.

Natural history collections are repositories of biodiversity specimens that provide critical infrastructure for studies of mammals. Over the past 3 decades, digitization of collections has opened up the temporal and spatial properties of specimens, stimulating new data sharing, use, and training across the biodiversity sciences. These digital records are the cornerstones of an “extended specimen network,” in which the diverse data derived from specimens become digital, linked, and openly accessible for science and policy. However, still missing from most digital occurrences of mammals are their morphological, reproductive, and life-history traits. Unlocking this information will advance mammalogy, establish richer faunal baselines in an era of rapid environmental change, and contextualize other types of specimen-derived information toward new knowledge and discovery. Here, we present the Ranges Digitization Network (Ranges), a community effort to digitize specimen-level traits from all terrestrial mammals of western North America, append them to digital records, publish them openly in community repositories, and make them interoperable with complimentary data streams. Ranges is a consortium of 23 institutions with an initial focus on non-marine mammal species (both native and introduced) occurring in western Canada, the western United States, and Mexico. The project will establish trait data standards and informatics workflows that can be extended to other regions, taxa, and traits. Reconnecting mammalogists, museum professionals, and researchers for a new era of collections digitization will catalyze advances in mammalogy and create a community-curated trait resource for training and engagement with global conservation initiatives.

Los murciélagos del desierto pertenecen a las comunidades de murciélagos más diversas de América del Norte. Innovaciones recientes, como el uso de detectores de murciélagos, para estimar la composición de especies en estos diversos ensamblajes proveen un modo automático de menos trabajo y aparentemente más eficiencia para muestrear comunidades de murciélagos. No obstante, se sabe muy poco a cerca del tipo de régimen temporal de muestreo necesario para asegurarse de obtener estimaciones precisas de la riqueza de especies y las diferencias en actividad entre las especies. Evalué la eficacia de los detectores de murciélagos en cuanto a la estimación de riqueza de especies y actividad relativa en la región Trans-Pecos de Texas. En particular, estimé la composición de especies en tres sitios ubicados en la Sierra del Carmen, examiné el número de noches que el detector de murciélagos debe de operar para establecer la asíntota de la riqueza de especies y la diversidad de actividad. También examiné la probabilidad de encuentro entre especies y las diferencias interespecíficas. Además, comparé cualitativamente la composición de especies basada en datos acústicos con datos obtenidos a partir de redes de niebla tanto en El Carmen como en localidades adyacentes de Big Bend National Park y de Black Gap Wildlife Management Area. Acústicamente se detectaron 17 especies de murciélagos en El Carmen, lo que requirió un promedio de 21 días para estimar con precisión la riqueza de especies y 15 días para la diversidad y uniformidad de las actividades. Las probabilidades de encuentro fueron variables entre especies y fueron necesarios un promedio de 9.49 días para que las especies en general llegaran a la probabilidad de encuentro al valor de uno. Las especies comunes alcanzaron una alta probabilidad de encuentro mucho antes que las especies raras. Los detectores acústicos proveen un medio viable de estimación de riqueza de especies y diversidad de actividad para los murciélagos del área del Trans-Pecos. Sin embargo, se necesita un esfuerzo substancial para alcanzar estimaciones precisas de la composición de especies. Probablemente la compilación de datos acústicos no remplazará la colección de datos por redes de niebla. Además, la captura de datos acústicos probablemente es mejor cuando se combina y se guía con datos de composición de especies basados en redes de niebla.

Texas exhibits one of the richest levels of pocket gopher diversity in the United States. Three genera (Cratogeomys, Geomys, and Thomomys) and 11 species are found in Texas. It is not surprising given the diversity of the Texas landscape (ecoregions, life zones, substrates, and vegetation) that these species are further subdivided into 29 subspecies in Texas alone. Pocket gopher distributions are determined by availability of suitable soil types and therefore often occur in small, isolated populations. For some taxa, limited distribution and ultimately small deme sizes result in populations that may require attention from a regulatory and management perspective. For many Texas pocket gopher subspecies, insufficient information exists to make sound recommendations relative to conservation status and needs despite decades of research collecting and evaluating data based on morphometrics, distributions and habitat preferences, karyotypes, allozymes, and mitochondrial DNA. As such, there is precedent for elevating pocket gopher subspecies to species after evaluation of available data, as well as subsuming subspecies into a broader taxonomic group. We used genomic techniques to identify genetically defined operational taxonomic units (OTUs) of pocket gophers to improve knowledge and understanding of pocket gopher distributions within the state. Using tens of thousands of single nucleotide polymorphisms, we determined the number of OTUs in each genus to be 5 for Thomomys bottae subspecies, 8 for Geomys species, and 5 for Cratogeomys castanops subspecies in Texas. In general, these data agree with current taxonomic hypotheses regarding Geomys and C. castanops; however, many T. bottae groups present similar genetic patterns that do not merit subspecies status based on these data, suggesting a more conservative classification of T. bottae in Texas and southeastern New Mexico that could facilitate conservation efforts, should they be necessary.

The degree to which Grinnellian and Eltonian niche characteristics influence species distribution may depend on latitude. Tropical regions are environmentally stable and resource-rich, whereas temperate regions are comparatively less environmentally stable (e.g., environmental filtering). Moreover, phylogenetic niche conservatism could influence distributions by inhibiting the ability for species to colonize environmentally different locations. Herein, we examine relationships between niche characteristics, passerine distributions, and phylogenetic niche conservatism across the latitudinal gradient. We used environmental and climatic variables to characterize Grinnellian niches and diets to characterize Eltonian niches. We conducted variation partitioning with retained components from ordination methods to evaluate the degree of association of Grinnellian and Eltonian niche characteristics with passerine distribution across latitudes. We examined the relationship between phylogenetic signal and niche characteristics with a phylogenetic regression. Passerine distributions were more related to environmental gradients than resources across latitudes. While niche conservatism was prevalent in Eltonian niche characteristics, phylogeny was related to Grinnellian niche characteristics in only 46% of biomes. There was no latitudinal gradient in phylogenetic niche conservatism or the degree to which Eltonian and Grinnellian niche characteristics relate to passerine distribution. Niche conservatism, albeit weak, was present for Grinnellian niche characteristics, thus potentially influencing the expansion of passerine distributions into the northern hemisphere.

Myotis septentrionalis (Northern Long-eared Bat) has recently suffered a >90% decline in population size in North America due to white-nose syndrome (WNS). We assessed genetic diversity, population structure, current effective population size, and demographic history of M. septentrionalis distributed across the United States to determine baseline levels pre-WNS. We analyzed RADseq data from 81 individuals from Kentucky, Louisiana, Michigan, Minnesota, North Carolina, Oklahoma, and Wisconsin. Additionally, we examined population genetic structure using discriminant analysis of principal components, fastStructure, and STRUCTURE. We then estimated effective population size and demographic history using fastsimcoal2. Similar levels of genetic diversity were found across all samples. We found no population genetic structure in the varied analyses from these contemporary samples. The best model for demographic history estimated a rapid population expansion followed by a slower expansion approximately 340,000 years ago. The vagility of M. septentrionalis, along with male dispersal and random mating, may provide a buffer against serious bottleneck effects stemming from rapid population declines due to WNS. This research provides a baseline for tracking and monitoring the influence of WNS on genetic diversity such as potential reduced diversity or increased population structuring in the future.

Con el paso del tiempo se ha hecho evidente que la actividad invernal de los murciélagos norteamericanos es un fenómeno poco estudiado. Utilizando un detector acústico de murciélagos, monitoreé la actividad de los murciélagos tricolor (Perimyotis subflavus) que perchaban en un complejo de alcantarillas de una carretera en el este de Texas, a lo largo de un periodo de 153 días durante las estaciones de otoño, invierno y primavera de 2021–2022. Los murciélagos permanecieron activos aproximadamente el 95% de las noches y dos fue el mayor número de noches consecutivas sin actividad. La actividad de los murciélagos se relacionó considerablemente con la temperatura al atardecer, pero no con la cantidad de iluminación lunar. La mediana de la distribución de actividad nocturna fue mayor, mientras que la desviación y la curtosis fueron menores a temperaturas más altas, lo anterior indica que, a medida que aumentaba la temperatura, los murciélagos permanecían activos más tarde y de manera más uniforme durante la noche. Este extenso periodo de actividad sugiere que P. subflavus no utiliza letargo prolongado (es decir, hibernación) durante el invierno en esta área de Texas.