Classification and distribution of functional groups of birds and mammals in Mexico

There has been a recent exponential growth in the study of functional trait ecology. Nonetheless, the study of functional traits and functional groups has been limited for terrestrial vertebrates. We conducted a classification update of functional groups (FG) of birds and mammals in Mexico, and determined the distribution patterns of FG species richness in different ecosystems nationwide. We selected six functional traits (feeding habit, locomotion, feeding substrate and technique, activity period, seasonality, and body size) obtained for 987 and 496 species of birds and mammals, respectively. A cophenetic correlation analyses resulted in values of 0.82 for the bird species dendrogram, and 0.79 for the mammal species dendrogram showing that the structures adequately reflected the similarity between observations. We obtained 52 FG for birds, assembled into 9 broader groups based on their feeding habits (16 invertivores, 6 carnivores: 5 herbivores, 9 aquatic vertivore/invertivore, 5 granivores, 1 scavenger, 3 nectarivores, 4 frugivores, and 3 omnivores). We obtained 35 FG for mammals, assembled into 9 broader groups based on their feeding habits (4 granivores, 10 herbivores, 1 nectarivore, 4 frugivores, 8 invertivores, 3 omnivores, 2 aquatic vertivore/invertivore, 1 hematophagous, and 2 carnivores). Overall, the distribution of FG species richness for birds and mammals gradually increased from the Nearctic to the Neotropical region, following a typical latitudinal species richness pattern. Few FG of migratory birds, and FG of granivore and herbivore mammals showed more species in the Nearctic and in the transitional regions. Our study provides a baseline for identifying ecological functions of species of birds and mammals in different ecosystems in Mexico, and contributes to understand the relationship between species diversity, community structure and ecosystem functioning. Identifying spatial patterns of functional trait diversity is important as biodiversity loss has a negative impact on ecosystem functioning and provision of environmental services.

Clinical trial to determine whether the timing of tranexamic acid administration influences perioperative bleeding in total knee arthroplasty

BACKGROUND AND OBJECTIVES

The ideal timing of tranexamic acid administration in total knee arthroplasty with tourniquet remains unclear. Our primary objective was to prove if administering it before surgical incision, instead of before releasing the tourniquet, reduces postoperative bleeding. A second objective was to determine whether a second dose reduces post-operative bleeding.

MATERIAL AND METHODS

A prospective, double-blind clinical trial was performed on 212 patients scheduled for total knee arthroplasty. They were randomised into 4 groups. Tranexamic acid was administered before the surgical incision in "pre-induction groups" (1 and 2), and just before the tourniquet release in "pre-release groups" (3 and 4). Groups 2 and 4 received a second dose 3h post-surgery. Main outcome was postoperative bleeding (visible blood loss and calculated total bleeding). Secondary outcomes were haemoglobin variations, complications and transfusion rate.

RESULTS

The mean calculated total bleeding was 1563ml (95%CI: 1445-1681) in preinduction groups versus 1576ml (95%CI: 1439-1713) in pre-release groups (P=0.9); 1579ml (95%CI: 1452-1706) in single-dose groups versus 1559ml (95%CI: 1431-1686) in double-dose groups (P=0.82). One patient was transfused. The mean haemoglobin at discharge was 10.4g/dl (95%CI: 10.2-10.7) in singledose groups versus 10.8 (95%CI: 10.6-11.1) in double-dose groups (P=0.06).

CONCLUSIONS

There were no differences in bleeding or transfusion regarding the time of tranexamic acid administration. The second dose had not impact on outcomes.

TRIAL REGISTRATION

EudraCT 2016-000071-24.

Diversidad de escarabajos tigre (Carabidae: Cicindelinae) en México

Se describen la riqueza y diversidad beta de escarabajos tigre (Carabidae: Cicindelinae) en las 3 regiones y 14 provincias biogeográficas de México. Con información de bases de datos, colecciones entomológicas y literatura publicada se recabaron 6,501 registros pertenecientes a 4 tribus, 16 géneros y 122 especies de cicindelinos distribuidas en México. A nivel nacional, el estimador Chao1 predijo 128 especies, por lo que el inventario estaría completo en 95%. Las provincias con la mayor riqueza fueron el Desierto Chihuahuense, Tierras Bajas del Pacífico y Veracruzana, mientras que la menor riqueza se registró en las provincias Californiana, Tamaulipas y Península de Yucatán. Se estimó la diversidad beta y sus componentes de recambio y anidamiento entre regiones y entre provincias biogeográficas. La mayor diversidad beta se presentó entre las provincias de la Zona de Transición Mexicana. En la mayoría de los casos, el recambio fue el principal componente de la diversidad beta. Este trabajo describe la distribución de las especies de cicindelinos en las provincias biogeográficas del país, pero a escala local aún son necesarios estudios para entender la ecología de estos insectos, los factores que determinan sus patrones de distribución y sus respuestas a los cambios ambientales. 

Homogenization of terrestrial mammals in fragmented rainforests: the loss of species turnover and its landscape drivers

Understanding the factors and mechanisms shaping differences in species composition across space and time (β-diversity) in human-modified landscapes has key ecological and applied implications. This topic is, however, challenging because landscape disturbance can promote either decreases (biotic homogenization) or increases (biotic differentiation) in β-diversity. We assessed temporal differences in intersite β-diversity of medium-bodied and large-bodied mammals in the fragmented Lacandona rainforest, Mexico. We hypothesized that, given the relatively short history of land-use changes in the region, and the gain and loss of some species caused by landscape spatial changes, β-diversity would increase through time, especially its nestedness component. We estimated β-diversity between 24 forest sites (22 forest patches and two continuous forest sites) in 2011 and 2017 to assess whether β-diversity is decreasing or increasing in the region, and calculated its turnover and nestedness components to understand the mechanisms responsible for changes in β-diversity, separately assessing mammal groups with different body mass, feeding guild, and habitat specialization. We then related such temporal changes in β-diversity to temporal changes in five landscape variables (forest cover, matrix openness, number of patches, edge density and interpatch distance) to identify the landscape drivers of β-diversity. In contrast with our expectations, β-diversity decreased over time, suggesting an ongoing biotic homogenization process. This pattern was mostly driven by a decrease in species turnover in all mammal groups, especially in landscapes with decreasing forest cover and increasing forested matrices. Although the nestedness component showed a three-fold increase through time, species turnover was 22 and six times higher than nestedness in 2011 and 2017, respectively. The decreased turnover appears to be driven by an increase in dispersal (i.e., spillover) of native species among patches. The prevalence of species turnover over nestedness indicates that different forest sites have a fairly distinct subset of species (i.e., high complementarity in species composition). Therefore, conserving all remaining forest patches and increasing forest cover is of utmost importance to effectively maintain β-diversity and conserve the total diversity (γ) of mammal assemblages in this Mesoamerican biodiversity hotspot.

Taxonomic and phylogenetic beta diversity of cricetid rodents in Oaxaca, southern Mexico

Understanding the ecological and historical causes and processes that shape biodiversity distribution patterns remains a challenging and fundamental task in biogeography, ecology, and evolution. To address this issue, taxonomic and phylogenetic β diversity can help us to assess the importance of ecological and historical factors that structure these biotic patterns. To make inferences about the processes underlying current spatial patterns in communities of Cricetidae across the state of Oaxaca, Mexico, their taxonomic and phylogenetic β diversity were assessed jointly. Our aims were: 1) to examine taxonomic and phylogenetic β diversity and their turnover and nestedness components among physiographic subprovinces; 2) to test for statistical significance of observed phylogenetic β diversity against the expected values of a null model; and 3) to evaluate if these metrics were correlated with geographical distance. We obtained the species composition for 12 subprovinces based on distribution models for 49 cricetid species present in Oaxaca, then carried out a maximum likelihood analysis to estimate their phylogenetic relationships. Our results show that the taxonomic and phylogenetic dissimilarities mainly were explained by the turnover component of species and lineages. In almost all pairwise comparisons, the null model approach revealed random patterns for phylogenetic β diversity values and its components. Mantel correlation models showed that the values of total taxonomic and phylogenetic diversity and their components are correlated with the geographical distances between subprovinces. Our results suggest that both taxonomic and phylogenetic β diversity are explained by the interplay between biogeographical history from southern Mexico, and the recent speciation processes in cricetid rodents. Given that speciation processes are allopatric for most cricetid taxa, the high values of spatial turnover can be explained by the small ranges of species, coupled with current abiotic conditions that act as filters, promoting specialization of species on particular conditions. Our results show the importance of the phylogenetic approach to unravel the multidimensional spatial patterns of biodiversity.

Mexico ants: incidence and abundance along the Nearctic-Neotropical interface

Mexico is one of the most biodiverse countries in the world, with an important proportion of endemism mainly because of the convergence of the Nearctic and Neotropical biogeographic regions, which generate great diversity and species turnover at different spatial scales. However, most of our knowledge of the Mexican ant biota is limited to a few well-studied taxa, and we lack a comprehensive synthesis of ant biodiversity information. For instance, most of the knowledge available in the literature on Mexican ant fauna refers only to species lists by states, or is focused on only a few regions of the country, which prevents the study of several basic and applied aspects of ants, from diversity and distribution to conservation. Our aims in this data paper are therefore (1) to compile all the information available regarding ants across the Mexican territory, and (2) to identify major patterns in the gathered data set and geographic gaps in order to direct future sampling efforts. All records were obtained from raw data, including both unpublished and published information. After exhaustive filtering and updating information and synonyms, we compiled a total of 21,731 records for 887 ant species distributed throughout Mexico from 1894 to 2018. These records were concentrated mainly in the states of Chiapas (n = 6,902, 32.76%) and Veracruz de Ignacio de la Llave (n = 4,329, 19.92%), which together comprise half the records. The subfamily with the highest number of records was Myrmicinae (n = 10,458 records, 48.12%), followed by Formicinae (n = 3,284, 15.11%) and Ponerinae (n = 1,914, 8.8%). Most ant records were collected in the Neotropical region of the country (n = 12,646, 58.19%), followed by the Mexican transition zone (n = 5,237, 24.09%) and the Nearctic region (n = 3,848, 17.72%). Native species comprised 95.46% of the records (n = 20,745). To the best of our knowledge, this is the most complete data set available to date in the literature for the country. We hope that this compilation will encourage researchers to explore different aspects of the population and community research of ants at different spatial scales, and to aid in the establishment of conservation policies and actions. There are no copyright restrictions. Please cite this data paper when using its data for publications or teaching events.

Assembly mechanisms of dung beetles in temperate forests and grazing pastures

The role of deterministic and stochastic mechanisms in community assembly is a key question in ecology, but little is known about their relative contribution in dung beetle assemblages. Moreover, in human modified landscapes these mechanisms are crucial to understand how biodiversity can be maintained in productive agroecosystems. We explored the assembly mechanisms driving dung beetle assemblages in forests and grazed grassland patches, and assessed the role of dung availability, soil hardness and moisture, elevation and land use heterogeneity as environmental predictors of functional diversity. To determine the underlying assembly mechanisms, we estimated functional diversity metrics (functional richness, evenness and divergence) and their departure from the predicted values by null models. We also used GLMs to assess the influence of environmental variables on functional diversity. In most cases, stochastic processes prevailed in structuring dung beetle assemblages and, consequently, environmental variables were not good predictors of dung beetle functional diversity. However, limiting similarity was found as a secondary mechanism with an effect on dung beetle assemblages in grasslands. Our results highlight the importance of stochastic processes that may reflect a metacommunity dynamic. Therefore, restoring landscape connectivity might be more important than habitat quality for the conservation of these functionally diverse beetle assemblages.

Responses of Phyllostomid Bats to Traditional Agriculture in Neotropical Montane Forests of Southern Mexico

Bat communities' responses to land use change in neotropical montane forests have scarcely been studied. We hypothesized that, like in lowland forests, a montane agricultural area will have a lower species richness, abundance, diversity and species composition of understory phyllostomid bats than a native forest (montane cloud forest and pine-oak forest). Monthly surveys over the course of a year gave an overall low species richness and abundance (167 captures corresponding to nine species). We found a slight loss of species richness in agricultural areas with respect to the montane cloud forest (one species) and pine-oak forest (two species). However, differences in abundance were noteworthy: 45% and 73% fewer captures in agricultural areas than in the montane cloud forest and pine-oak forest, respectively. Species diversity was higher in the montane cloud forest than the pine-oak forest, but the diversity of agricultural areas did not differ between the types. Species and guild compositions did not differ between crops and forests. At least for the understory phyllostomid bats, and at the spatial scale studied, traditional management of agricultural areas in the study area and the surrounding matrix could explain the similarity in species richness, composition, and diversity between the agricultural area and native montane forests; however, other indicator groups should be evaluated to understand the effects of habitat loss on montane forests.

Spatial incongruence in the species richness and functional diversity of cricetid rodents

Biodiversity is multidimensional and different mechanisms can influence different dimensions. The spatial distribution of these dimensions can help in conservation decisions through the location of complementary areas with high diversity. We analyzed congruence in spatial patterns of species richness and functional diversity of cricetid rodents in the state of Oaxaca, southern Mexico, at different scales, and environmental variables related. Potential distribution models were produced for 49 species of cricetids in Maxent and superimposed to obtain potential communities in cells of 25, 50,100, 200 and 400 km2. We estimated species richness (SR) and functional diversity (SES.FD) eliminating the species richness effect through null models. The patterns and spatial congruence of species richness and functional diversity are described. The relationships between the environmental variables (elevation, temperature, precipitation, net primary productivity and potential evapotranspiration) and the SR and SES.FD were explored using Generalized Linear Models (GLMs) and Generalized Additive Models (GAMs). The highest species richness was found in mountainous ecosystems while the highest functional diversity was in tropical forests, revealing a spatial incongruence among these components of biodiversity (r = -0.14, p = 0.42; Pearson correlation). The locations of the cells of low congruence varied according to spatial resolution. In univariate models, elevation was the variable that best explained species richness (R2 = 0.77). No single variable explained the functional diversity; however, the models that included multiple environmental variables partially explained both the high and low functional diversity. The different patterns suggest that different historic, ecological and environmental processes could be responsible for the community structure of cricetid rodents in Oaxaca. These results indicate that one great challenge to be met to achieve more effective planning for biological conservation is to integrate knowledge regarding the spatial distribution of different dimensions of biodiversity.

Populations and assemblages living on the edge: dung beetles responses to forests-pasture ecotones

Edge effects alter insect biodiversity in several ways. However, we still have a limited understanding on simultaneous responses of ecological populations and assemblages to ecotones, especially in human modified landscapes. We analyze edge effects on dung beetle populations and assemblages between livestock pastures and native temperate forests (Juniperus and pine-oak forests (POFs)) to describe how species abundances and assemblage parameters respond to edge effects through gradients in forest-pasture ecotones. In Juniperus forest 13 species avoided the ecotones: six species showed greater abundance in forest interior and seven in pasturelands, while the other two species had a neutral response to the edge. In a different way, in POF we found five species avoiding the edge (four with greater abundance in pastures and only one in forest), two species had a neutral response, and two showed a unimodal pattern of abundance near to the edge. At the assemblage level edge effects are masked, as species richness, diversity, functional richness, functional evenness, and compositional incidence dissimilarity did not vary along forest-pasture ecotones. However, total abundance and functional divergence showed higher values in pastures in one of the two sampling localities. Also, assemblage similarity based on species’ abundance showed a peak near to the edge in POF. We propose that conservation efforts in human-managed landscapes should focus on mitigating current and delayed edge effects. Ecotone management will be crucial in livestock dominated landscapes to conserve regional biodiversity and the environmental services carried out by dung beetles.

Effects of a wind farm installation on the understory bat community of a highly biodiverse tropical region in Mexico

Wind energy has rapidly become an important alternative among renewable energies, and it is generally considered clean. However, little is known about its impact at the level of ecological communities, especially in biodiversity hotspots. The Isthmus of Tehuantepec is a highly biodiverse region in Mesoamerica, and has the highest potential for generating wind energy in Mexico. To assess the effects of installing a wind farm on the understory bat community in a landscape of fragmented habitat, we assessed its diversity and composition over four stages of installation (site preparation, construction, and two stages of operation). We captured 919 bats belonging to 22 species. Species richness, functional diversity and phylogenetic diversity decreased during construction and the first stage of operation. However, these components of biodiversity increased during the second stage of operation, and species composition began to resemble that of the site preparation stage. No species considered as sensitive to disturbance was recorded at any stage. This is the first study to reveal the diversity of a Neotropical bat community after wind turbines begin to operate.

Got Dung? Resource Selection by Dung Beetles in Neotropical Forest Fragments and Cattle Pastures

Both the impact of habitat modification on the food preferences of species and its impact on ecosystem functioning are poorly understood. In this study, we analyzed food selection by dung beetles in 80 tropical forest fragments and their adjacent cattle pastures in the Los Tuxtlas Biosphere Reserve, Mexico. Ten pitfall traps were placed at each site, half baited with human dung and the other half with fish carrion. We assessed dung beetle food selection and classified any specialization in resource use quantitatively using a multinomial classification model. We collected 15,445 beetles belonging to 42 species, 8747 beetles (38 species) in forest fragments and 6698 beetles (29 species) in cattle pastures. Twenty-five species were present in both habitats. Of all the beetles captured, 76% were caught in dung traps (11,727 individuals) and 24% in carrion traps (3718 individuals). We found 21 species of dung specialists, 7 carrion specialists, 8 generalists, and 6 species too rare to classify. The bait most frequently selected by beetles in this study was dung in both forests and pastures. Specialists tended to remain specialists in both habitats, while generalists tended to change their selection of bait type depending on the habitat. In summary, our results show that replacing forests with cattle pastures modifies the patterns of resource selection by dung beetles and this could affect ecosystem functioning.

Beta Diversity in a Highly Heterogeneous Area: Disentangling Species and Taxonomic Dissimilarity for Terrestrial Vertebrates

Quantifying differences in species composition among communities provides important information related to the distribution, conservation and management of biodiversity, especially when two components are recognized: dissimilarity due to turnover, and dissimilarity due to richness differences. The ecoregions in central Mexico, within the Mexican Transition Zone, have outstanding environmental heterogeneity and harbor huge biological richness, besides differences in the origin of the biota. Therefore, biodiversity studies in this area require the use of complementary measures to achieve appropriate information that may help in the design of conservation strategies. In this work we analyze the dissimilarity of terrestrial vertebrates, and the components of turnover and richness differences, among six ecoregions in the state of Hidalgo, central Mexico. We follow two approaches: one based on species level dissimilarity, and the second on taxonomic dissimilarity. We used databases from the project “Biodiversity in the state of Hidalgo”. Our results indicate that species dissimilarity is higher than taxonomic dissimilarity, and that turnover contributes more than richness differences, both for species and taxonomic total dissimilarity. Moreover, total dissimilarity, turnover dissimilarity and the dissimilarity due to richness differences were positively related in the four vertebrate groups. Reptiles had the highest values of dissimilarity, followed by mammals, amphibians and birds. For reptiles, birds, and mammals, species turnover was the most important component, while richness differences had a higher contribution for amphibians. The highest values of dissimilarity occurred between environmentally contrasting ecoregions (i.e., tropical and temperate forests), which suggests that environmental heterogeneity and differences in the origin of biotas are key factors driving beta diversity of terrestrial vertebrates among ecoregions in this complex area.

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.

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.

Commentary: Do we have a consistent terminology for species diversity? Back to basics and toward a unifying framework

After decades of misusing the term diversity in community ecology, over the last 5 years some papers have offered important advances toward developing a more rigorous mathematical background, which allows us to achieve more clarity in the terminology for the vast range of biological phenomena that have been placed under the umbrella of this term. Some points have been clearly stated in previous papers of this Views and Comments section, and new terms have even been proposed for specific cases, but other issues, such as the need for the prefix true have not been discussed. Our aim is to clarify some of the terms and concepts, the proper use of which appears still to remain unclear, and to provide biologists with a simplified version of the general framework resulting from recent contributions, with an emphasis on identifying points of consensus in the field. We also comment on the possibility of extending the basics of this general framework to other facets of the broad term biodiversity, such as functional or phylogenetic diversity.

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.

Orb-weaving spider diversity in the Iberá Marshlands, Argentina

The Iberá Marshlands RAMSAR reserve, in the northeast of Argentina, is one of the largest and most important wetlands of America. In this study we assess orb-weaving spider (Araneae: Orbiculariae) diversity in this reserve, analyzing different facets of local diversity (species richness, diversity, evenness and taxonomic distinctness), and the contribution of species differentiation (beta diversity) among localities and habitat types to the composition of regional diversity. We found 1657 individuals of 59 orb-weaving spider species/morphospecies. Local diversity differs among the three sampled localities. At the habitat level, the different facets of biodiversity followed a clear pattern, where woodlands have higher species richness, diversity, evenness and taxonomic distinctness than savannas. Savanna sites shared a common spider species composition, while woodland communities have high values of complementarity. Thus, beta diversity has a very high contribution to the regional diversity of the orb-weaving spiders in the Iberá Marshlands. We suggest that conservation management in the reserve should be directed towards promoting natural spatial heterogeneity, giving special protection to habitat mosaics in different localities.

Bolete diversity in two relict forests of the Mexican beech (Fagus grandifolia var. mexicana; Fagaceae)

The current distribution of the endangered Mexican beech [Fagus grandifolia var. mexicana (Martinez) Little] is restricted to relict isolated populations in small remnants of montane cloud forest in northeastern Mexico, and little is known about its associated biota. We sampled bolete diversity in two of these monospecific forests in the state of Hidalgo, Mexico. We compared alpha diversity, including species richness and ensemble structure, and analyzed beta diversity (dissimilarity in species composition) between forests. We found 26 bolete species, five of which are probably new. Species diversity and evenness were similar between forests. Beta diversity was low, and the similarities of bolete samples from within and between forests were not significantly different. These results support the idea that the two forests share a single bolete ensemble with a common history. In contrast, cumulative species richness differed between the forests, implying that factors other than the mere presence of the host species have contributed to shaping the biodiversity of ectomycorrhizal fungi in relict Mexican beech forests.

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.

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.