Archaeal and Bacterial Diversity and Distribution Patterns in Mediterranean-Climate Vernal Pools of Mexico and the Western USA.

Biogeographic patterns in microorganisms are poorly understood, despite the importance of microbial communities for a range of ecosystem processes. Our knowledge of microbial ecology and biogeography is particularly deficient in rare and threatened ecosystems. We tested for three ecological patterns in microbial community composition within ephemeral wetlands-vernal pools-located across Baja California (Mexico) and California (USA): (1) habitat filtering; (2) a latitudinal diversity gradient; and (3) distance decay in community composition. Paired water and soil samples were collected along a latitudinal transect of vernal pools, and bacterial and archaeal communities were characterized using 16S rDNA sequencing. We identified two main microbial communities, with one community present in the soil matrix that included archaeal and bacterial soil taxa, and another community present in the overlying water that was dominated by common freshwater bacterial taxa. Aquatic microbial communities were more diverse in the north, and displayed a significant but inverted latitudinal diversity pattern. Aquatic communities also exhibited a significant distance-decay pattern, with geographic proximity, and precipitation explaining part of the community variation. Collectively these results indicate greater sensitivity to spatial and environmental variation in vernal pool aquatic microbial communities than in soil microbial communities. We conclude that vernal pool aquatic microbial communities can display distribution patterns similar to those exhibited by larger organisms, but differ in some key aspects, such as the latitudinal gradient in diversity.

Biogeographic Patterns of Arbuscular Mycorrhizal Fungal Communities Along a Land-Use Intensification Gradient in the Subtropical Atlantic Forest Biome.

Information concerning arbuscular mycorrhizal (AM) fungal geographical distribution in tropical and subtropical soils from the Atlantic Forest (a global hotspot of biodiversity) are scarce and often restricted to the evaluation of richness and abundance of AM fungal species at specific ecosystems or local landscapes. In this study, we hypothesized that AM fungal diversity and community composition in subtropical soils would display fundamental differences in their geographical patterns, shaped by spatial distance and land-use change, at local and regional scales. AM fungal community composition was examined by spore-based taxonomic analysis, using soil trap cultures. Acaulospora koskei and Glomus were found as generalists, regardless of mesoregions and land uses. Other Acaulospora species were also found generalists within mesoregions. Land-use change and intensification did not influence AM fungal composition, partially rejecting our first hypothesis. We then calculated the distance-decay of similarities among pairs of AM fungal communities and the distance-decay relationship within and over mesoregions. We also performed the Mantel test and redundancy analysis to discriminate the main environmental drivers of AM fungal diversity and composition turnover. Overall, we found significant distance-decays for all land uses. We also observed a distance-decay relationship within the mesoregion scale (< 104 km) and these changes were correlated mainly to soil type (not land use), with the secondary influence of both total organic carbon and clay contents. AM fungal species distribution presented significant distance-decays, regardless of land uses, which was indicative of dispersal limitation, a stochastic neutral process. Although, we found evidence that, coupled with dispersal limitation, niche differentiation also played a role in structuring AM fungal communities, driven by long-term historical contingencies, as represented by soil type, resulting from different soil origin and mineralogy across mesoregions.

Diazotrophs Show Signs of Restoration in Amazon Rain Forest Soils with Ecosystem Rehabilitation.

Biological nitrogen fixation can be an important source of nitrogen in tropical forests that serve as a major CO2 sink. Extensive deforestation of the Amazon is known to influence microbial communities and the biogeochemical cycles they mediate. However, it is unknown how diazotrophs (nitrogen-fixing microorganisms) respond to deforestation and subsequent ecosystem conversion to agriculture, as well as whether they can recover in secondary forests that are established after agriculture is abandoned. To address these knowledge gaps, we combined a spatially explicit sampling approach with high-throughput sequencing of nifH genes. The main objectives were to assess the functional distance decay relationship of the diazotrophic bacterial community in a tropical forest ecosystem and to quantify the roles of various factors that drive the observed changes in the diazotrophic community structure. We observed an increase in local diazotrophic diversity (α-diversity) with a decrease in community turnover (ß-diversity), associated with a shift in diazotrophic community structure as a result of the forest-to-pasture conversion. Both diazotrophic community turnover and structure showed signs of recovery in secondary forests. Changes in the diazotrophic community were primarily driven by the change in land use rather than differences in geochemical characteristics or geographic distances. The diazotroph communities in secondary forests resembled those in primary forests, suggesting that at least partial recovery of diazotrophs is possible following agricultural abandonment.IMPORTANCE The Amazon region is a major tropical forest region that is being deforested at an alarming rate to create space for cattle ranching and agriculture. Diazotrophs (nitrogen-fixing microorganisms) play an important role in supplying soil N for plant growth in tropical forests. It is unknown how diazotrophs respond to deforestation and whether they can recover in secondary forests that establish after agriculture is abandoned. Using high-throughput sequencing of nifH genes, we characterized the response of diazotrophs' ß-diversity and identified major drivers of changes in diazotrophs from forest-to-pasture and pasture-to-secondary-forest conversions. Studying the impact of land use change on diazotrophs is important for a better understanding of the impact of deforestation on tropical forest ecosystem functioning, and our results on the potential recovery of diazotrophs in secondary forests imply the possible restoration of ecosystem functions in secondary forests.

Diversity patterns of free-living nematode assemblages in seagrass beds from the Cuban archipelago (Caribbean Sea).

Diversity patterns of free-living marine nematodes in tropical seagrass beds are understudied. Here, we describe the species richness and assemblage composition of nematodes in 13 seagrass sites covering the whole Cuban archipelago. Nematodes were collected from Thalassia testudinum seagrass beds and identified to species level. We provide a checklist of nematode species from seagrass beds. The species richness of nematode assemblages is high, with 215 species, 138 genus, 35 families, seven orders and two classes. That γ-diversity is higher than other studies and points to seagrass beds as diversity hotspots of free-living marine nematodes. Local species richness in seagrass bed sites is about 57 ± 17 species and broadly similar across the sites, despite the environmental heterogeneity. The geographical distance plays a weak, but significant, role on the decay of similarity likely affected by limited dispersal of nematodes. The pairwise similarity values, related to poor-coloniser nematodes, were twice more affected by the distance than those related to good-colonisers, possibly due to differential success of transport and settlement.

How do bat, rodent, and marsupial communities respond to spatial and environmental gradients? Insights from a deconstruction of mammal beta diversity from the Atlantic Forest of South America.

Space and environment are fundamental in influencing the community structure. However, their relative influences vary according to species' biological characteristics. Here we test whether differences in life-history traits mainly linked to dispersal abilities influence bat, rodent and marsupial beta diversity along spatial and environmental gradients. We expect bat beta diversity to be weakly related with space in comparison to dispersal-limited rodents and marsupials. Using data from communities distributed along the Atlantic Forest of South America, we calculated the total beta diversity and its turnover and nestedness components for each group. We estimated the strength of correlation of beta diversity and its components along spatial and environmental gradients, comparing their importance within and between groups. Space had the higher influence on rodent and marsupial beta diversity. For bats, both gradients influenced similarly their community composition. Between taxa, the influence of these gradients did not differ for rodents and marsupials, while bats presented a stronger relationship with environment compared to non-volant small mammals. Also, all groups presented a similar influence of the spatial gradients on their community structure, despite their differences in dispersal abilities. Our results suggest that differences in biological characteristics partially influence the community structure of these mammals, with their responses along space likely reflecting similar biogeographical dynamics affecting their distribution. Overall, our results improve the understanding of the processes structuring these communities, highlighting the benefits of comparative analyses within a beta diversity perspective to better understand the influence of multiple processes on the community assembly along geographical gradients.

Parasites of the Brazilian flathead Percophis brasiliensis reflect West Atlantic biogeographic regions.

With the aim of evaluating the utility of marine parasites as indicators of zoogeographical regions in the South West Atlantic, we analyzed data on assemblages of long-lived larval parasites of 488 specimens of Percophis brasiliensis distributed in 11 samples from nine localities covering the entire distribution of the species in the Argentine biogeographical Province. Near half a million long-lived parasite individuals belonging to 17 species present in the whole sample displayed clear latitudinal patterns. Data for parasite assemblages at infracommunity and component community levels were analysed in relation to the geographical distance. Significant similarity decay of parasite assemblages over distance was observed, with those based on abundances and mean abundances showing departures from predicted values of regressions. These departures were represented by higher dissimilarities between samples coming from different zoogeographical regions than between those caught within the same region, independently of the distance separating them. Consequently, zoogeographical regions were identified in a distance-decay context. Multivariate analyses corroborated a close fit of similarity between assemblages to existing zoogeographical classifications. Regressions representing distance decay of similarity, and the identification of their outliers, can therefore shed light on the existence of discontinuities or uniformities in the geographic distribution of parasite assemblages and, in turn, in the zoogeography of their fish hosts.

Mapping distance-decay of cardiorespiratory disease risk related to neighborhood environments.

Neighborhood characteristics affect an individual's quality of life. Although several studies have examined the relationship between neighborhood environments and human health, we are unaware of studies that have examined the distance-decay of this effect and then presented the risk results spatially. Our study is unique in that is explores the health effects in a less developed country compared to most studies that have focused on developed countries. The objective of our study is to quantify the distance-decay cardiorespiratory diseases risk related to 28 neighborhood aspects in the Federal District, Brazil and present this information spatially through risk maps of the region. Toward this end, we used a quantile regression model to estimate risk and GIS modeling techniques to create risk maps. Our analysis produced the following findings: i) a 2500 m increase in highway length was associated with a 46% increase in cardiorespiratory diseases; ii) 46,000 light vehicles in circulation (considering a buffer of ≤500 m from residences) was associated with 6 hospital admissions (95% CI: 2.6, 14.6) per cardiorespiratory diseases; iii) 74,000 m2 of commercial areas (buffer ≤1700 m) was associated with 12 hospital admissions (95% CI: 2.2, 20.8); iv) 1km2 increase in green areas intra urban was associated with less two hospital admissions, and; vi) those who live ≤500 m from the nearest point of wildfire are more likely to have cardiorespiratory diseases that those living >500 m. Our findings suggest that the approach used in this study can be an option to improve the public health policies.

Moving beyond abundance distributions: neutral theory and spatial patterns in a tropical forest.

Assessing the relative importance of different processes that determine the spatial distribution of species and the dynamics in highly diverse plant communities remains a challenging question in ecology. Previous modelling approaches often focused on single aggregated forest diversity patterns that convey limited information on the underlying dynamic processes. Here, we use recent advances in inference for stochastic simulation models to evaluate the ability of a spatially explicit and spatially continuous neutral model to quantitatively predict six spatial and non-spatial patterns observed at the 50 ha tropical forest plot on Barro Colorado Island, Panama. The patterns capture different aspects of forest dynamics and biodiversity structure, such as annual mortality rate, species richness, species abundance distribution, beta-diversity and the species-area relationship (SAR). The model correctly predicted each pattern independently and up to five patterns simultaneously. However, the model was unable to match the SAR and beta-diversity simultaneously. Our study moves previous theory towards a dynamic spatial theory of biodiversity and demonstrates the value of spatial data to identify ecological processes. This opens up new avenues to evaluate the consequences of additional process for community assembly and dynamics.

Richness of tiger moths (Lepidoptera: Arctiidae) in the Brazilian Cerrado: how much do we know?

The Cerrado biome is located in the central region of Brazil and consists mainly of savanna vegetation. In this study we assessed the richness of tiger moths (Arctiidae) of the Brazilian Cerrado. Specifically, we 1) assessed species richness in one-degree cells in the biome, 2) identified areas where these moths are poorly known, and 3) tested if similarities in species composition are related to geographical distance in the relatively well-sampled areas. We obtained the data mainly from specimens deposited in museums, but we also included additional information from the literature. We compiled 2,321 records belonging to 723 species. Specimens were recorded in 108 localities distributed in 67 one-degree cells. Species occurring exclusively in one or two one-degree cells represented 64% of the total number of species. Sample effort was not uniform in the biome, as there were very few records in the northern region of the Cerrado. The best-sampled one-degree cell had 239 species. Species assemblages were structured in space with a clear trend of localities near one another presenting more similarities in faunal composition than distant localities. This distance decay in similarity was slightly more pronounced along the longitudinal than along the latitudinal distances. We conclude that the Cerrado still remains poorly inventoried for tiger moths, particularly in its northern portion, where many unrecorded species may be found in the future. Despite of this limited knowledge, the best-sampled region indicates that richness of tiger moths in the Cerrado is comparable to the species-rich forest biomes in the Neotropical region.

Richness of tiger moths (Lepidoptera: Arctiidae) in the Brazilian Cerrado: how much do we know?

The Cerrado biome is located in the central region of Brazil and consists mainly of savanna vegetation. In this study we assessed the richness of tiger moths (Arctiidae) of the Brazilian Cerrado. Specifically, we 1) assessed species richness in one-degree cells in the biome, 2) identified areas where these moths are poorly known, and 3) tested if similarities in species composition are related to geographical distance in the relatively well-sampled areas. We obtained the data mainly from specimens deposited in museums, but we also included additional information from the literature. We compiled 2,321 records belonging to 723 species. Specimens were recorded in 108 localities distributed in 67 one-degree cells. Species occurring exclusively in one or two one-degree cells represented 64% of the total number of species. Sample effort was not uniform in the biome, as there were very few records in the northern region of the Cerrado. The best-sampled one-degree cell had 239 species. Species assemblages were structured in space with a clear trend of localities near one another presenting more similarities in faunal composition than distant localities. This distance decay in similarity was slightly more pronounced along the longitudinal than along the latitudinal distances. We conclude that the Cerrado still remains poorly inventoried for tiger moths, particularly in its northern portion, where many unrecorded species may be found in the future. Despite of this limited knowledge, the best-sampled region indicates that richness of tiger moths in the Cerrado is comparable to the species-rich forest biomes in the Neotropical region.

Richness of tiger moths (Lepidoptera: Arctiidae) in the Brazilian Cerrado: how much do we know?

The Cerrado biome is located in the central region of Brazil and consists mainly of savanna vegetation. In this study we assessed the richness of tiger moths (Arctiidae) of the Brazilian Cerrado. Specifically, we 1) assessed species richness in one-degree cells in the biome, 2) identified areas where these moths are poorly known, and 3) tested if similarities in species composition are related to geographical distance in the relatively well-sampled areas. We obtained the data mainly from specimens deposited in museums, but we also included additional information from the literature. We compiled 2,321 records belonging to 723 species. Specimens were recorded in 108 localities distributed in 67 one-degree cells. Species occurring exclusively in one or two one-degree cells represented 64% of the total number of species. Sample effort was not uniform in the biome, as there were very few records in the northern region of the Cerrado. The best-sampled one-degree cell had 239 species. Species assemblages were structured in space with a clear trend of localities near one another presenting more similarities in faunal composition than distant localities. This distance decay in similarity was slightly more pronounced along the longitudinal than along the latitudinal distances. We conclude that the Cerrado still remains poorly inventoried for tiger moths, particularly in its northern portion, where many unrecorded species may be found in the future. Despite of this limited knowledge, the best-sampled region indicates that richness of tiger moths in the Cerrado is comparable to the species-rich forest biomes in the Neotropical region.