Jorge Galindo-González

Evolution of the Sweet Taste Receptor Gene Tas1r2 in Bats

Taste perception is an important component of an animals fitness. The identification of vertebrate taste receptor genes in the last decade has enabled molecular genetic studies of the evolution of taste perception in the context of the ecology and dietary preferences of organisms. Although such analyses have been conducted in a number of species for bitter taste receptors, a similar analysis of sweet taste receptors is lacking. Here, we survey the sole sweet taste-specific receptor gene Tas1r2 in 42 bat species that represent all major lineages of the order Chiroptera, one of the most diverse groups of mammals in terms of diet. We found that Tas1r2 is under strong purifying selection in the majority of the bats studied, with no significant difference in the strength of the selection between insect eaters and fruit eaters. However, Tas1r2 is a pseudogene in all three vampire bat species and the functional relaxation likely started in their common ancestor, probably due to the exclusive feeding of vampire bats on blood and their reliance on infrared sensors rather than taste perception to locate blood sources. Our survey of available genome sequences, together with previous reports, revealed additional losses of Tas1r2 in horse, cat, chicken, zebra finch, and western clawed frog, indicating that sweet perception is not as conserved as previously thought. Nonetheless, we found no common dietary pattern among the Tas1r2-lacking vertebrates, suggesting different causes for the losses of Tas1r2 in different species. The complexity of the ecological factors that impact the evolution of Tas1r2 calls for a better understanding of the physiological roles of sweet perception in different species.

FRUGIVOROUS BATS IN ISOLATED TREES AND RIPARIAN VEGETATION ASSOCIATED WITH HUMAN-MADE PASTURES IN A FRAGMENTED TROPICAL LANDSCAPE

Abstract Conversion of tropical rain forest to pasture and cropland often leads to a loss of local species. However, information on the role of some isolated elements of the fragmented landscape on maintaining biodiversity is lacking. This study, carried out in human-made pastures in Veracruz, Mexico, demonstrated the year-round presence of frugivorous bats in isolated trees inside pastures and in riparian corridors of vegetation among pastures. During a 1-year study (October 1995 through September 1996), we captured 652 bats belonging to 20 species, representing 56% of the total species recorded for the area. Higher abundance and diversity of bats were recorded for riparian sites than for isolated trees. Of the bats we captured, 82% were frugivorous, 15% insectivorous, 2% nectarivorous-frugivorous, and 2% sanguivorous. Bats visited isolated trees regardless of tree species or phenological state. Abundance decreased with distance from the nearest forest fragment. We discuss how riparian corridors and isolated trees in pastures might contribute to maintaining diversity of frugivorous bats and plants in a fragmented landscape.

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.

Seed Dispersal Among Three Different Vegetation Communities in the Huasteca Region, Mexico, Analyzed from Bat Feces

Seed dispersal is a key process for plant colonization and for the establishment of many plant populations in tropical environments. A large proportion of all tropical woody plants with fruits and seeds depend on frugivorous vertebrates for their dispersal, and frugivorous bats are essential for the dispersal of seeds from many tropical plants. Many of these plants are important for vegetative regeneration after disturbances. Our main goal was to document the process of seed dispersal through feces-seed analysis by the bat community among semi-deciduous, evergreen, and secondary forests in the ‘Huasteca’ region of San Luis Potosí, Mexico. We hypothesized that bats would disperse seeds among all three forest types, and thus predicted that we would find seeds from both early and late successional stages in bat feces in all three forest types. In each of three replicate sites representative of each of these forest types, we trapped bats with mist-nets and collected their feces with seeds. A total of 558 individuals from eight frugivorous bat species were captured. The most abundant species were Sturnira ludovici, Glossophaga soricina and Artibeus jamaicensis. We documented seeds in bat feces from 16 plant species belonging to four families: Moraceae, Piperaceae, Solanaceae, and Myrtaceae; 43% were pioneer species, and thus important for the initial stages of regeneration, and 37% were species of late successional stages. Seeds in bat feces were found in similar proportions in all forest types, thus contributing to the regeneration of highly deforested habitats in the Huasteca region. To maintain the entire mutualistic network between bats and plant species, diverse bat communities are important.

Tropical Secondary Forest Management Influences Frugivorous Bat Composition, Abundance and Fruit Consumption in Chiapas, Mexico

Most studies on frugivorous bat assemblages in secondary forests have concentrated on differences among successional stages, and have disregarded the effect of forest management. Secondary forest management practices alter the vegetation structure and fruit availability, important factors associated with differences in frugivorous bat assemblage structure, and fruit consumption and can therefore modify forest succession. Our objective was to elucidate factors (forest structural variables and fruit availability) determining bat diversity, abundance, composition and species-specific abundance of bats in (i) secondary forests managed by Lacandon farmers dominated by Ochroma pyramidale, in (ii) secondary forests without management, and in (iii) mature rain forests in Chiapas, Southern Mexico. Frugivorous bat species diversity (Shannon H’) was similar between forest types. However, bat abundance was highest in rain forest and O. pyramidale forests. Bat species composition was different among forest types with more Carollia sowelli and Sturnira lilium captures in O. pyramidale forests. Overall, bat fruit consumption was dominated by early-successional shrubs, highest late-successional fruit consumption was found in rain forests and more bats consumed early-successional shrub fruits in O. pyramidale forests. Ochroma pyramidale forests presented a higher canopy openness, tree height, lower tree density and diversity of fruit than secondary forests. Tree density and canopy openness were negatively correlated with bat species diversity and bat abundance, but bat abundance increased with fruit abundance and tree height. Hence, secondary forest management alters forests’ structural characteristics and resource availability, and shapes the frugivorous bat community structure, and thereby the fruit consumption by bats.

Tropical rain-forest matrix quality affects bat assemblage structure in secondary forest patches

Abstract We studied Phyllostomidae bat assemblage structure in patches of secondary forest dominated by the pioneer tree Ochroma pyramidale, largely (>85%) or partially (<35%) surrounded by a matrix of tropical rain forest, to test 3 hypotheses: the highest bat diversity and richness is observed in the matrix rain forest in comparison to secondary forest patches; the proportion of rain forest surrounding secondary forest positively affects bat diversity and richness; and canopy openness is an important structural variable negatively affecting bat abundance. Rain-forest control sites had the highest bat species diversity and richness, and contributed more to total diversity than did secondary forest. Bat diversity was similar between secondary forest patches largely enclosed by rain forest and their controls, but higher diversity, richness, and contribution to total diversity were recorded in largely enclosed patches compared to partially enclosed patches. Partially enclosed patches were dominated by 2 small, frugivorous understory bat species (Carollia sowelli and Carollia perspicillata), whereas largely enclosed patches were dominated by 2 large-bodied, canopy-dwelling, frugivorous bats (Artibeus lituratus and Artibeus jamaicensis), which primarily feed on figs, a tree species that is abundant in rain forest. Bat diversity, richness, and contribution to total diversity were positively correlated with the proportion of area with rain forest, and bat abundance was negatively correlated with canopy openness. Resumen Estudiamos el ensamble de murciélagos de la familia Phyllostomidae en parches de vegetación secundaria dominada por árboles pioneros de Ochroma pyramidale (Malvaceae) en dos condiciones de vegetación circundante, aquellos mayormente rodeados por una matriz de bosque tropical (>85%), y los rodeados parcialmente (<35%). Se testearon 3 hipótesis: la matriz de bosque tropical que rodea parches de vegetación secundaria presenta una mayor diversidad y riqueza de murciélagos en comparación con la vegetación secundaria; la proporción de bosque tropical que rodea a la vegetación secundaria favorece la diversidad, riqueza y abundancia de murciélagos sensibles al disturbio; y el incremento en la apertura del dosel disminuye la abundancia de murciélagos. Los sitios de control de bosque tropical, presentaron la mayor diversidad y riqueza de murciélagos y contribuyeron mayormente a la diversidad total. En los parches de vegetación secundaria mayormente rodeados de bosque tropical se encontró que la diversidad de murciélagos fue similar a las áreas de control de bosque tropical. Sin embargo, los parches de vegetación secundaria mayormente rodeados por bosque tropical presentaron mayor diversidad y riqueza de murciélagos y contribuyeron a la diversidad total en comparación con parches de vegetación secundaria parcialmente rodeados por bosque tropical. Los parches de vegetación secundaria parcialmente rodeados por bosque tropical, estuvieron dominados por 2 especies murciélagos frugívoros pequeños característicos de la vegetación secundaria (Carollia sowelli y Carollia perspicillata) mientras que los parches mayormente rodeados por bosque estuvieron dominados por 2 especies de murciélagos frugívoros grandes (Artibeus lituratus y Artibeus jamaicensis), típicos de vegetación madura que se alimentan principalmente de higos (Ficus spp.), un árbol abundante del bosque tropical. La diversidad, riqueza y la contribución total a la diversidad estuvieron correlacionadas positivamente con la proporción de bosque tropical, mientras que la abundancia de murciélagos fue negativamente correlacionada con la apertura de dosel.

Deforestation Impacts on Bat Functional Diversity in Tropical Landscapes

Functional diversity is the variability in the functional roles carried out by species within ecosystems. Changes in the environment can affect this component of biodiversity and can, in turn, affect different processes, including some ecosystem services. This study aimed to determine the effect of forest loss on species richness, abundance and functional diversity of Neotropical bats. To this end, we identified six landscapes with increasing loss of forest cover in the Huasteca region of the state of Hidalgo, Mexico. We captured bats in each landscape using mist nets, and calculated functional diversity indices (functional richness and functional evenness) along with species richness and abundance. We analyzed these measures in terms of percent forest cover. We captured 906 bats (Phyllostomidae and Mormoopidae), including 10 genera and 12 species. Species richness, abundance and functional richness per night are positively related with forest cover. Generalized linear models show that species richness, abundance and functional richness per night are significantly related with forest cover, while seasonality had an effect on abundance and functional richness. Neither forest cover nor season had a significant effect on functional evenness. All these findings were consistent across three spatial scales (1, 3 and 5 km radius around sampling sites). The decrease in species, abundance and functional richness of bats with forest loss may have implications for the ecological processes they carry out such as seed dispersal, pollination and insect predation, among others.

Can a fast-growing early-successional tree (Ochroma pyramidale, Malvaceae) accelerate forest succession?

Species-specific traits of trees affect ecosystem dynamics, defining forest structure and understorey development. Ochroma pyramidale is a fast-growing tree species, with life-history traits that include low wood density, short-lived large leaves and a narrow open thin crown. We evaluated forest succession in O. pyramidale-dominated secondary forests, diverse secondary forests, both 10–15 y since abandonment, and rain forests by comparing height, density and basal area of all trees (> 5 cm dbh). Furthermore, we compared species richness of understorey trees and shrubs, and basal area and density of trees of early- and late-successional species ( 15%) and leaf litter (> 10 cm) were both highest in O. pyramidale forests, which positively affected density of understorey trees and shrubs and negatively affected density of late-successional trees. In conclusion, O. pyramidale forests presented structural features similar to those of rain forest, but this constrained the establishment of understorey tree species, especially late-successional species, decreasing successional development

Present and future potential distribution of the endemic Perote ground squirrel (Xerospermophilus perotensis) under different climate change scenarios

Abstract The current distribution of the endemic Perote ground squirrel (Xerospermophilus perotensis) and its future potential response to climate change have not been addressed. Thus, in this work, we focus on both aspects of this species by means of ecological niche modeling, using different general circulation models and Intergovernmental Panel on Climate Change emission scenarios. Because the species’ life history includes a hibernation period, we performed two different sets of analysis: one considering the whole annual cycle and another considering only the species’ active season. According to our results, the current potential distribution of X. perotensis extends further out of the Oriental Basin, to which the species is endemic. Future projections vary among different climatic scenarios and data sets used in the modeling process, but virtually all of them project a substantial encroachment of the species’ potential distribution area by 2050. Our models suggest that, compared with species that are active throughout the year, X. perotensis, being a seasonal species, could be affected by climate change, increasing the risk of extinction. This may pose a serious threat to the Perote ground squirrel’s persistence throughout the following decades.

First report of a hard fruit in the diet of Centurio senex (Chiroptera: Phyllostomidae) in Mexico

Abstract Recently it was proposed that Centurio senex specializes on hard fruit because of its strong bite compared to other similar-sized frugivorous bats; however, this hypothesis has not been tested. We tested the hardness of 5 fruit species eaten by bats, including Sideroxylon capiri (Sapotaceae), here reported for the 1st time as part of the diet of C. senex. Results show that S. capiri is the hardest fruit of the species evaluated. This is the 1st evidence of C. senex eating hard fruit in the wild, which supports the theory of a skull adapted to eating hard fruit. Resumen Recientemente se planteó que Centurio senex se especializa en frutos duros, ya que posee una fuerte mordida comparada con otros murciélagos frugívoros de talla similar; aunque no se ha probado. Pusimos a prueba la dureza de 5 especies de frutos consumidos por murciélagos, incluyendo Sideroxylon capiri (Sapotaceae), que reportamos por primera vez en la dieta de C. senex. Los resultados muestran que S. capiri es la especie con semilla más dura de las estudiadas. Esta es la primera evidencia del consumo de un fruto duro por C. senex en la naturaleza, lo cual apoya la teoría de un cráneo adaptado para el consumo de frutos duros.