Deforestation Thresholds for Phyllostomid Bat Populations in Tropical Landscapes in the Huasteca Region, Mexico

Abstract

The loss and degradation of forests in tropical regions have modified tree cover, creating deforested landscapes. It has been suggested that there are thresholds in these landscapes beyond which the diversity, distribution, abundance, and fitness of different biological groups can be affected. In this study, the ecological habitat thresholds were detected for eight populations of phyllostomid bats along an environmental gradient of forest loss in the Huasteca region, Mexico. At a local scale, we analyzed canopy loss, and we also detected these thresholds at the landscape level, as a function of forest remnant area at three scales with radii of 1, 3 and 5 km. The data were analyzed using the Threshold Indicator Taxa ANalysis (TITAN) method for detecting indicator species along gradients. The bats exhibited three different types of response to habitat loss: 1) Leptonycteris yerbabuenae, Chiroderma salvini, Sturnira hondurensis, and Artibeus lituratus were more abundant where canopy cover was present at the local site, even though the landscape had been deforested; 2) Sturnira parvidens and Artibeus jamaicensis required tree cover at all spatial scales; and 3) Glossophaga soricina and Desmodus rotundus are species that might be locally abundant in habitats with little canopy, but both species need landscapes that have not been deforested. In conclusion, these populations of phyllostomid bats were sensitive to deforestation in different ways, their response to the habitat loss gradient varying among species and with spatial scale.Keywords: habitat loss, tropical forests, ecological thresholds, Chiroptera, Phyllostomidae Resumen La pérdida y degradación de selvas en las zonas tropicales han modificado la cobertura vegetal creando paisajes deforestados, en los que se ha sugerido que existen umbrales a partir de los cuales la diversidad, distribución, abundancia y adecuación de distintos grupos biológicos pueden verse afectadas. En este trabajo se detectaron los umbrales ecológicos del hábitat para ocho poblaciones de murciélagos filostómidos a lo largo de un gradiente ambiental de pérdida de selvas; a escala local en función de la cobertura del dosel y a escala de paisaje en función del área con vegetación forestal remanente, en tres escalas de 1, 3 y 5 km de radio. Para analizar los datos se utilizó el método Threshold Indicator Taxa ANalysis (TITAN), que se basa en la detección de especies indicadoras en gradientes. Los murciélagos tuvieron tres tipos de respuesta a la pérdida de hábitat: 1) Leptonycteris yerbabuenae, Chiroderma salvini, Sturnira hondurensis y Artibeus lituratus son más abundantes en zonas con cobertura de dosel, aunque el paisaje se encuentre deforestado, 2) Sturnira parvidens y Artibeus jamaicensis requieren de cobertura vegetal en todas las escalas espaciales analizadas y, 3) Glossophaga soricina y Desmodus rotundus pueden ser abundantes en hábitats con poca vegetación a escala local, pero requieren de paisajes no deforestados. En conclusión, se observó que las poblaciones de murciélagos ...

Deforestation Impacts on Bat Functional Diversity in Tropical Landscapes

“…Currently, cattle ranching and crop cultivation have resulted in the disappearance of 50% of the natural vegetation cover [29]. More details and a map of the study area can be found in [26]. …”

“…Six sampling sites were selected, separated by a minimum of 10 km to ensure their spatial independence [26]. While these sites cover a representative gradient of deforestation, neither sites with 100% of their original forest cover intact, nor those that have been totally transformed into anthropogenic habitats were included because they are not present in the region.…”

“…and Glossophaga soricina , respectively) respond to habitat loss [32]. Other studies have used the same methodology of circular landscape units with 1, 3 and 5 km radius to evaluate the influence of habitat loss on bats [24, 26, 33–34]. In each landscape unit, we quantified the area occupied by each cover type using the program ArcView 3.2.…”

“…Although very little is known about the movement patterns of Neotropical bats, we know that species can respond differently to anthropogenic disturbance owing to differences in their vagility, food and roost requirements, and their life history attributes [16, 25]. Moreover, in our study area we found that bats exhibit different thresholds to habitat loss depending on the spatial scale [26]. Some bats are more abundant in cluttered canopy sites, even though the landscape had been deforested; other species might be locally abundant in habitats with little canopy, but need landscapes that have not been deforested; and a third group of species require tree cover at all spatial scales [26].…”

“…Moreover, in our study area we found that bats exhibit different thresholds to habitat loss depending on the spatial scale [26]. Some bats are more abundant in cluttered canopy sites, even though the landscape had been deforested; other species might be locally abundant in habitats with little canopy, but need landscapes that have not been deforested; and a third group of species require tree cover at all spatial scales [26]. Thus, to evaluate the effect of forest loss on the taxonomic and functional diversity of bats, here we follow a multiscale approach.…”