Claudia E. Moreno

Negative impacts of human land use on dung beetle functional diversity.

The loss of biodiversity caused by human activity is assumed to alter ecosystem functioning. However our understanding of the magnitude of the effect of these changes on functional diversity and their impact on the dynamics of ecological processes is still limited. We analyzed the functional diversity of copro-necrophagous beetles under different conditions of land use in three Mexican biosphere reserves. In Montes Azules pastures, forest fragments and continuous rainforest were analyzed, in Los Tuxtlas rainforest fragments of different sizes were analyzed and in Barranca de Metztitlán two types of xerophile scrub with different degrees of disturbance from grazing were analyzed. We assigned dung beetle species to functional groups based on food relocation, beetle size, daily activity period and food preferences, and as measures of functional diversity we used estimates based on multivariate methods. In Montes Azules functional richness was lower in the pastures than in continuous rainforest and rainforest fragments, but fragments and continuous forest include functionally redundant species. In small rainforest fragments (<5 ha) in Los Tuxtlas, dung beetle functional richness was lower than in large rainforest fragments (>20 ha). Functional evenness and functional dispersion did not vary among habitat types or fragment size in these reserves. In contrast, in Metztitlán, functional richness and functional dispersion were different among the vegetation types, but differences were not related to the degree of disturbance by grazing. More redundant species were found in submontane than in crassicaule scrub. For the first time, a decrease in the functional diversity in communities of copro-necrophagous beetles resulting from changes in land use is documented, the potential implications for ecosystem functioning are discussed and a series of variables that could improve the evaluation of functional diversity for this biological group is proposed.

Edge-Related Loss of Tree Phylogenetic Diversity in the Severely Fragmented Brazilian Atlantic Forest

Deforestation and forest fragmentation are known major causes of nonrandom extinction, but there is no information about their impact on the phylogenetic diversity of the remaining species assemblages. Using a large vegetation dataset from an old hyper-fragmented landscape in the Brazilian Atlantic rainforest we assess whether the local extirpation of tree species and functional impoverishment of tree assemblages reduce the phylogenetic diversity of the remaining tree assemblages. We detected a significant loss of tree phylogenetic diversity in forest edges, but not in core areas of small (<80 ha) forest fragments. This was attributed to a reduction of 11% in the average phylogenetic distance between any two randomly chosen individuals from forest edges; an increase of 17% in the average phylogenetic distance to closest non-conspecific relative for each individual in forest edges; and to the potential manifestation of late edge effects in the core areas of small forest remnants. We found no evidence supporting fragmentation-induced phylogenetic clustering or evenness. This could be explained by the low phylogenetic conservatism of key life-history traits corresponding to vulnerable species. Edge effects must be reduced to effectively protect tree phylogenetic diversity in the severely fragmented Brazilian Atlantic forest.

Reanálisis de la diversidad alfa: alternativas para interpretar y comparar información sobre comunidades ecológicas.

El indice de entropia de Shannon y otras medidas de complejidad se utilizan frecuentemente para evaluar la diversidad de especies en comunidades ecologicas, aun cuando su comprension es dificil y sus valores no son comparables. En este trabajo se muestra que los numeros efectivos de especies (medidas de diversidad verdadera) permiten obtener una interpretacion intuitiva y facilmente comparable de la diversidad de especies. Se ejemplifica su uso reanalizando los datos de 4 trabajos publicados en la Revista Mexicana de Biodiversidad (realizados en distintos ecosistemas y regiones de Mexico, con distinta resolucion taxonomica y enfocados en distintos grupos biologicos). Se utilizan modelos de estimacion en los que se considera que las muestras son representaciones incompletas de las comunidades. Se explica tambien la manera en que las medidas de diversidad de distinto orden incorporan a las especies segun su abundancia en la comunidad. Los resultados obtenidos pueden resultar de especial interes cuando los valores de diversidad se utilizan para proponer medidas para el manejo de recursos y la conservacion biologica.

Spatial and temporal analysis of α, β and γ diversities of bats in a fragmented landscape

We test a strategy for analyzing species richness in a landscape. This strategy is based on the joint analysis of α (local), β (turnover) and γ (landscape) diversities. We assessed the spatial and temporal relations among α, β and γ diversity of bats (Phyllostomidae and Mormoopidae) in a tropical landscape. In a spatial dimension, γ diversity depends on the α diversity of the most species-rich community. The value of spatial β diversity between habitats was very low. A high α diversity was found in a cornfield, which may be attributed to the reduced extent of the field (compared with a more extensive field) that allows the arrival of individuals from nearby rich communities. In a temporal dimension, within habitat cumulative richness over sampling period may be considerably different from the average richness. These differences are attributed to temporal turnover during short time intervals. Therefore, cumulative richness may be viewed as the temporal equivalent of within-habitat γ diversity, which results of both average α and temporal turnover. We discuss, which value must be taken as an estimate of habitat species richness, the average or the cumulative α, and the implications that this decision can have in the evaluation of biodiversity.

A consistent terminology for quantifying species diversity

There is a genuine need for consensus on a clear terminology in the study of species diversity given that the nature of the components of diversity is the subject of an ongoing debate and may be the key to understanding changes in ecosystem processes. A recent and thought-provoking paper (Jurasinski et al. Oecologia 159:15–26, 2009) draws attention to the lack of precision with which the terms alpha, beta, and gamma diversity are used and proposes three new terms in their place. While this valuable effort may improve our understanding of the different facets of species diversity, it still leaves us far from achieving a consistent terminology. As such, the conceptual contribution of these authors is limited and does little to elucidate the facets of species diversity. It is, however, a good starting point for an in-depth review of the available concepts and methods.

Shortcuts for biodiversity evaluation: a review of terminology and recommendations for the use of target groups, bioindicators and surrogates

The terms related to rapid alternative routes for appraising species diversity (biodiversity assessment shortcuts), through the use of biodiversity target groups, indicator groups and other biodiversity surrogates are examined. Biodiversity target groups are selected for their methodological and taxonomical advantages, and the purpose of their use is the assessment of their own diversity patterns. The focus of biodiversity indicator groups is on assessing the health of the entire ecosystem or a part of it, with respect to a visible phenomenon. Biodiversity surrogates include taxa-for-taxa surrogates, higher taxa, morphospecies and environmental surrogates. These are faster, less expensive routes for assessing general biodiversity patterns as compared with taking complete biological inventories. These concepts are clarified, examples of their use are examined and the published studies that have implemented such shortcuts are also analysed. For the selection of biological groups according to biodiversity research goals we have also proposed general recommendations.

Morphological assembly mechanisms in Neotropical bat assemblages and ensembles within a landscape

Empirical studies on bat assemblages have shown that richness is not appreciably influenced by local processes such as ecological interactions. However, most of these studies have been done in large areas that include high heterogeneity, and they analyse all bat species within such areas, and thus they may be not reflecting local but supra-community conditions. We followed an ecomorphological approach to assess how bat assemblages of species from the families Phyllostomidae and Mormoopidae, and ensembles of frugivorous bats, are assembled in local habitats within a single landscape. We measured the volume of the space defined by wing morphology and quantified the average distance between species within such a volume. Then, we related these measures to local richness. Such relationships were contrasted against relationships with random assemblages to test for statistical differences. At the ensemble level of organization, we found that the frugivorous bat morphological assembly mechanism is different from random patterns, and it corresponds to the volume-increasing model. On the other hand, bat assembly mechanisms may be ubiquitous at the assemblage level, because groups of species coexisting in a local habitat and delimited only by phylogeny include more than one ecological group with no potential to interact. Assembling processes are crucial to an understanding of species diversity in local communities, and ecomorphological analyses are very promising tools that may help in their study.

Response of Neotropical bat assemblages to human land use

Neotropical bats are sensitive to human-induced habitat changes, and some authors believe bats can be used as bioindicators. In the literature, however, the results are disparate. Some results show bat diversity deceases as disturbance increases, whereas others indicate no effect. Determining the general response patterns of bats when they encounter different degrees of human-induced disturbance across the Neotropics would help to determine their usefulness as bioindicators. In a series of meta-analyses, we compared the occurrence frequency of bat species between well-preserved forests and human-use areas. We obtained data through an extensive review of published peer-reviewed articles, theses, and reports. The overall effect size indicated that human-use areas harbored more bat species than well-preserved forests. Different response patterns emerged when meta-analyses were conducted separately by family, feeding habit, vegetation stratum, and conservation status. Our results suggest that bat assemblages display strong responses to forest loss and land-use change and that the direction and magnitude of these responses depends on the bat group under study and the type of disturbance. Our results are consistent with the idea that bats are useful for assessing the effects of habitat changes in the Neotropics. However, with our meta-analyses we could not detect fine differences in bat feeding habits, especially within Phyllostomidae, or elucidate the effect of landscape configuration.

Vertebrate Dissimilarity Due to Turnover and Richness Differences in a Highly Beta-Diverse Region: The Role of Spatial Grain Size, Dispersal Ability and Distance

We explore the influence of spatial grain size, dispersal ability, and geographic distance on the patterns of species dissimilarity of terrestrial vertebrates, separating the dissimilarity explained by species replacement (turnover) from that resulting from richness differences. With data for 905 species of terrestrial vertebrates distributed in the Isthmus of Tehuantepec, classified into five groups according to their taxonomy and dispersal ability, we calculated total dissimilarity and its additive partitioning as two components: dissimilarity derived from turnover and dissimilarity derived from richness differences. These indices were compared using fine (10 x 10 km), intermediate (20 x 20 km) and coarse (40 x 40 km) grain grids, and were tested for any correlations with geographic distance. The results showed that total dissimilarity is high for the terrestrial vertebrates in this region. Total dissimilarity, and dissimilarity due to turnover are correlated with geographic distance, and the patterns are clearer when the grain is fine, which is consistent with the distance-decay pattern of similarity. For all terrestrial vertebrates tested on the Isthmus of Tehuantepec both the dissimilarity derived from turnover and the dissimilarity resulting from richness differences make important contributions to total dissimilarity, and dispersal ability does not seem to influence the dissimilarity patterns. These findings support the idea that conservation efforts in this region require a system of interconnected protected areas that embrace the environmental, climatic and biogeographic heterogeneity of the area.

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.