Romeo A. Saldaña-Vázquez

Abundance responses of frugivorous bats (Stenodermatinae) to coffee cultivation and selective logging practices in mountainous central Veracruz, Mexico

Shifting and permanent cultivation, selective logging, cattle production and coffee plantations are among the most important factors in montane cloud forest conversion and disturbance. Although shaded-coffee plantations can contribute to the preservation of local species richness, abundance of organisms could be determined by habitat resource availability in agricultural landscapes. We compared abundance of Sturnira and Artibeus bats (Phyllostomidae, Stenodermatinae), in shade coffee plantations and disturbed cloud forest fragments, which represent habitats with different chiropterochorous plant density. We also investigated the relationship between bat species abundance and food plant richness, abundance and diversity. We captured 956 bats, 76% in cloud forest fragments and 24% in shaded coffee plantations. Abundance of Sturnira spp. (small bats) was greater in cloud forest than in coffee plantations, but Artibeus spp. (large bats) abundance was similar in both habitats. Chiropterochorous plant abundance was positively related with bat abundance for Sturnira spp., while chiropterochorous plant richness and diversity were negatively related for Artibeus spp. This suggests that frugivorous bats with different morphological and ecological characteristics respond differentially to anthropogenic activities. For landscape management purposes, the maintenance and augmentation of diverse food resources, for frugivorous bats with different foraging requirements in coffee plantations, will benefit the resilience of bats to modification of their natural habitat.

A more efficient technique to collect seeds dispersed by bats

Seeds dispersed and deposited by wind, animals and other dispersal agents are a fundamental component of natural forest succession, plant regeneration and population maintenance, aside from increasing a populations genetic pool in tropical ecosystems (Henry & Jouard 2007, Muscarella & Fleming 2007, Wilson & Traveset 2000). Frugivorous bats and birds are ideal vectors for long-distance seed dispersal; therefore, studies of the food habits of frugivores and the specific identities of the dispersers are essential for understanding ecological patterns and processes in tropical environments. Studies related to succession processes, the frequency, number and composition of seeds dispersed by animals are essential in order to generate new data and hypotheses, consequently the method and quality of obtaining data are important.

The role of extrinsic and intrinsic factors in Neotropical fruit bat–plant interactions

Abstract Understanding the structure and evolution of ecological communities requires an examination of the factors that influence plant–animal mutualistic interactions. These interactions are affected by factors that are both extrinsic and intrinsic to the animals. We used a meta-analysis technique to examine such factors affecting the interactions between frugivorous animals and the plants they feed upon, using 3 common Neotropical frugivorous bat genera (Carollia, Sturnira, and Artibeus) as a model. We assessed whether latitude, altitude, ecoregion, and bat body size were related to the proportions of the most important plant genera in the diet of the bats. Our results show that extrinsic factors did not affect the proportion of Piper in the diet of Carollia. The proportion of Solanum in the diet of Sturnira was positively correlated with latitude and decreased in the mountain, moist, and bahia interior ecoregions. The proportion of Ficus and Cecropia in the diet of Artibeus decreased in high-elevation ecoregions and was negatively correlated with altitude. The large Artibeus species featured more Ficus and Cecropia in their diets compared to the small species of this genus. Our work demonstrates that mutualistic interaction between Neotropical bats and their core plant taxa is mediated by geographic and morphological factors. Resumen Entender la estructura y evolución de las comunidades ecológicas requiere de la evaluación de los factores que influyen en las interacciones mutualistas entre plantas y animales. Estas interacciones son afectadas por factores extrínsecos e intrínsecos a los animales. Usamos técnicas meta-análiticas para evaluar los factores que afectan las interacciones entre animales frugívoros y las plantas que consumen, usando 3 de los géneros más comunes de murciélagos frugívoros Neotropicales (Carollia, Sturnira y Artibeus) como modelos. Evaluamos si la latitud, altitud, ecoregion y tamaño corporal estaban relacionados con la proporción de los géneros de plantas más importantes en la dieta de estos murciélagos. Nuestros resultados muestran que factores extrínsecos no intervienen en la proporción de Piper en la dieta de Carollia. La proporción de Solanum en la dieta de Sturnira se correlaciona positivamente con la latitud, y es menor en las ecoregiones húmedas, montañosas y bahía. La proporción de Ficus y Cecropia en la dieta de Artibeus disminuyó en las ecoregiones de mayor altitud y se correlacionó negativamente con la altitud. Las especies grandes de Artibeus incluyeron más Ficus y Cecropia en su dieta en comparación con las especies pequeñas de ese género. Nuestro trabajo demuestra que las relaciones mutualistas entre murciélagos Neotropicales y las plantas que comprenden el núcleo de su dieta es mediado por factores geográficos y morfológicos.

Does forest fragmentation cause an increase in forest temperature

Forest fragmentation is considered by many to be a primary cause of the current biodiversity crisis. The underlying mechanisms are poorly known, but a potentially important one is associated with altered thermal conditions within the remaining forest patches, especially at forest edges. Yet, large uncertainty remains about the effect of fragmentation on forest temperature, as it is unclear whether temperature decreases from forest edge to forest interior, and whether this local gradient scales up to an effect of fragmentation (landscape attribute) on temperature. We calculated the effect size (correlation coefficient) of distance from forest edge on air temperature, and tested for differences among forest types surrounded by different matrices using meta-analysis techniques. We found a negative edge-interior temperature gradient, but correlation coefficients were highly variable, and significant only for temperate and tropical forests surrounded by a highly contrasting open matrix. Nevertheless, it is unclear if these local-scale changes in temperature can be scaled up to an effect of fragmentation on temperature. Although it may be valid when considering “fragmentation” as forest loss only, the landscape-scale inference is not so clear when we consider the second aspect of fragmentation, where a given amount of forest is divided into a large number of small patches (fragmentation per se). Therefore, care is needed when assuming that fragmentation changes forest temperature, as thermal changes at forest edges depend on forest type and matrix composition, and it is still uncertain if this local gradient can be scaled up to the landscape.

The specificity of host-bat fly interaction networks across vegetation and seasonal variation

Vegetation type and seasonality promote changes in the species composition and abundance of parasite hosts. However, it is poorly known how these variables affect host–parasite interaction networks. This information is important to understand the dynamics of parasite–host relationships according to biotic and abiotic changes. We compared the specialization of host–bat fly interaction networks, as well as bat fly and host species composition between upland dry forest and riparian forest and between dry and rainy seasons in a tropical dry forest in Jalisco, Mexico. Bat flies were surveyed by direct collection from bats. Our results showed that host–bat fly interaction networks were more specialized in upland dry forest compared to riparian forest. Bat fly species composition was different between the dry and rainy seasons, while host species composition was different between upland dry forest and riparian forest. The higher specialization in upland dry forest could be related to the differences in bat host species composition and their respective roosting habits. Variation in the composition of bat fly species between dry and rainy seasons coincides with the seasonal shifts in their species richness. Our study confirms the high specialization of host–bat fly interactions and shows the importance of biotic and abiotic factors to understand the dynamics of parasite–host interactions.

Digestive capacity predicts diet diversity in Neotropical frugivorous bats

1. Predicting the diet diversity of animals is important to basic and applied ecology. Knowledge of diet diversity in animals helps us understand niche partitioning, functional diversity and ecosystem services such as pollination, pest control and seed dispersal. 2. There is a negative relationship between the length of the digestive tract and diet diversity in animals; however, the role of digestive physiology in determining diet diversity has been ignored. This is especially important in vertebrates with powered flight because, unlike non-flying vertebrates, they have limitations that may constrain gut size. 3. Here, we evaluate the relationship between digestive capacity and diet diversity in Carollinae and Stenodermatinae frugivorous bats. These bats disperse the seeds of plants that are key to Neotropical forest regeneration. 4. Our results show that digestive capacity is a good predictor of diet diversity in Carollinae and Stenodermatinae frugivorous bats (R(2) = 0·77). 5. Surprisingly, the most phylogenetically closely related species were not similar in their digestive capacity or diet diversity. The lack of a phylogenetic signal for the traits evaluated implies differences in digestive physiology and diet in closely related species. 6. Our results highlight the predictive usefulness of digestive physiology for understanding the feeding ecology of animals.

Food intake changes in relation to food quality in the neotropical frugivorous Bat Sturnira ludovici

If nutritional elements of food and the consumers ability to use them can determine an animal diet, we can expect that differences in digestive capacity between animals reflect their dietary breadth. Diet diversity in Neotropical frugivorous bats is based on core plant taxa that present different nutritional compositions and qualities. Sturnira bats eat fruits with high sugar concentration, while Artibeus species eat fruits with lower sugar content. In this study we investigated the intake sugar response of Sturnira ludovici and compare it with the intake response reported for Artibeus jamaicensis. Our results show that S. ludovici was unable to achieve compensatory feeding, ingesting twice the energy when feeding on the most concentrated solution with respect to the more diluted one. This finding suggests the existence of a physiological constraint limiting energy intake when this species feeds on low quality food. Intake response slope value for S. ludovici was lower than the one reported for A. jamaicensis, indicating that S. ludovici is less suited than A. jamaicensis to feed on food with low nutrient content. The role that a physiological limitation could have on the food intake of S. ludovici, and the ecological implications of our findings are discussed.

The effects of seasonality on host–bat fly ecological networks in a temperate mountain cave

Changes in the specialization of parasite-host interactions will be influenced by variations in host species composition. We evaluated this hypothesis by comparing the composition of bats and bat flies within a roost cave over one annual. Five bat and five bat fly species occupied the cave over the course of the study. Bat species composition was 40% different in the rainy season compared with the dry-cold and dry-warm seasons. Despite the incorporation of three new bat species into the cave during the rainy season, bat fly species composition was not affected by seasonality, since the bats that arrived in the rainy season only contributed one new bat fly species at a low prevalence. Bat-bat fly ecological networks were less specialized in the rainy season compared with the dry-cold and dry-warm seasons because of the increase of host overlap among bat fly species during this season. This study suggests that seasonality promote: (1) differences in host species composition, and (2) a reduction in the specialization of host-parasite ecological networks.

Nutrient availability predicts frugivorous bat abundance in an urban environment

Abstract We used a mathematical model based on nutrient availability to predict Artibeus jamaicensis densities in urban parks of a tropical city. Nutrient availability was calculated based on bat-fruit density and the carbohydrate, nitrogen and fats they contain. In addition to nutrient availability, our model considered the capacity of this frugivorous bat to assimilate the nutrients present in the environment. We compared our predictions with bat captures obtained in the same urban parks, in which we measured nutrient availability. Our results show that A. jamaicensis densities were limited by the quantity of nitrogen available in urban parks. Our density-predicting models, based on soluble carbohydrates and fats available, overpredicted the number of A. jamaicensis individuals. Our result indicates that to maintain healthy bat populations in cities, it is important to take into account not only the variety of food available but also its nutrient content and how easy it is for the bat to assimilate them.