Predicting distributions of known and unknown reptile species in Madagascar.

Despite the importance of tropical biodiversity, informative species distributional data are seldom available for biogeographical study or setting conservation priorities. Modelling ecological niche distributions of species offers a potential solution; however, the utility of old locality data from museums, and of more recent remotely sensed satellite data, remains poorly explored, especially for rapidly changing tropical landscapes. Using 29 modern data sets of environmental land coverage and 621 chameleon occurrence localities from Madagascar (historical and recent), here we demonstrate a significant ability of our niche models in predicting species distribution. At 11 recently inventoried sites, highest predictive success (85.1%) was obtained for models based only on modern occurrence data (74.7% and 82.8% predictive success, respectively, for pre-1978 and all data combined). Notably, these models also identified three intersecting areas of over-prediction that recently yielded seven chameleon species new to science. We conclude that ecological niche modelling using recent locality records and readily available environmental coverage data provides informative biogeographical data for poorly known tropical landscapes, and offers innovative potential for the discovery of unknown distributional areas and unknown species.

Diversity, above-ground biomass, and vegetation patterns in a tropical dry forest in Kimbi-Fungom National Park, Cameroon.

RESEARCH HIGHLIGHTS: This study is one of few detailed analyses of plant diversity and vegetation patterns in African dry forests. We established permanent plots to characterize plant diversity, above-ground biomass, and vegetation patterns in a tropical dry forest in Kimbi-Fungom National Park, Cameroon. Our results contribute to long-term monitoring, predictions, and management of dry forest ecosystems, which are often vulnerable to anthropogenic pressures. BACKGROUND AND OBJECTIVES: Considerable consensus exists regarding the importance of dry forests in species diversity and carbon storage; however, the relationship between dry forest tree species composition, species richness, and carbon stock is not well established. Also, simple baseline data on plant diversity are scarce for many dry forest ecosystems. This study seeks to characterize floristic diversity, vegetation patterns, and tree diversity in permanent plots in a tropical dry forest in Northwestern Cameroon (Kimbi-Fungom National Park) for the first time. MATERIALS AND METHODS: We studied associations between above-ground biomass and species composition, and how different vegetation types vary in terms of species composition, diversity, and carbon storage, in a dry forest in Kimbi-Fungom National Park, Cameroon. Vegetation was inventoried in 17 permanent 1-ha plots. Allometric equations were used to calculate above-ground biomass and carbon. RESULTS: We found an average of 269.8 tree stems ha-1 and 43.1 species ha-1. Five vegetation types: semi-deciduous, gallery, mixed vegetation, secondary and the grassland/woody savanna forest were classified using TWINSPAN analysis. The five vegetation types had an average above-ground biomass of 149.2 t ha-1 and 74.6 tC ha-1 of carbon in the 17 ha analyzed. Canonical correspondence analysis (CCA) showed the importance of semi-deciduous forest over grassland/woody savanna forest. CONCLUSIONS: This study demonstrated that the forest of the Kimbi-Fungom National Park is poor in plant diversity, biomass, and carbon, highlighting the need to implement efficient management practices. Fine-scale inventory data of species obtained in this study could be useful in developing predictive models for efficient management of tropical dry forests.

The ecology of chronic wasting disease in wildlife.

Prions are misfolded infectious proteins responsible for a group of fatal neurodegenerative diseases termed transmissible spongiform encephalopathy or prion diseases. Chronic Wasting Disease (CWD) is the prion disease with the highest spillover potential, affecting at least seven Cervidae (deer) species. The zoonotic potential of CWD is inconclusive and cannot be ruled out. A risk of infection for other domestic and wildlife species is also plausible. Here, we review the current status of the knowledge with respect to CWD ecology in wildlife. Our current understanding of the geographic distribution of CWD lacks spatial and temporal detail, does not consider the biogeography of infectious diseases, and is largely biased by sampling based on hunters' cooperation and funding available for each region. Limitations of the methods used for data collection suggest that the extent and prevalence of CWD in wildlife is underestimated. If the zoonotic potential of CWD is confirmed in the short term, as suggested by recent results obtained in experimental animal models, there will be limited accurate epidemiological data to inform public health. Research gaps in CWD prion ecology include the need to identify specific biological characteristics of potential CWD reservoir species that better explain susceptibility to spillover, landscape and climate configurations that are suitable for CWD transmission, and the magnitude of sampling bias in our current understanding of CWD distribution and risk. Addressing these research gaps will help anticipate novel areas and species where CWD spillover is expected, which will inform control strategies. From an ecological perspective, control strategies could include assessing restoration of natural predators of CWD reservoirs, ultrasensitive CWD detection in biotic and abiotic reservoirs, and deer density and landscape modification to reduce CWD spread and prevalence.

Spatio-temporal climate change contributes to latitudinal diversity gradients.

The latitudinal diversity gradient (LDG), where the number of species increases from the poles to the Equator, ranks among the broadest and most notable biodiversity patterns on Earth. The pattern of species-rich tropics relative to species-poor temperate areas has been recognized for well over a century, but the generative mechanisms are still debated vigorously. We use simulations to test whether spatio-temporal climatic changes could generate large-scale patterns of biodiversity as a function of only three biological processes-speciation, extinction and dispersal-omitting adaptive niche evolution, diversity-dependence and coexistence limits. In our simulations, speciation resulted from range disjunctions, whereas extinction occurred when no suitable sites were accessible to species. Simulations generated clear LDGs that closely match empirical LDGs for three major vertebrate groups. Higher tropical diversity primarily resulted from higher low-latitude speciation, driven by spatio-temporal variation in precipitation rather than in temperature. This suggests that spatio-temporal changes in low-latitude precipitation prompted geographical range disjunctions over Earth's history, leading to high rates of allopatric speciation that contributed to LDGs. Overall, we show that major global biodiversity patterns can derive from interactions of species' niches (fixed a priori in our simulations) with dynamic climate across complex, existing landscapes, without invoking biotic interactions or niche-related adaptations.

Phylogeography and population genetics of the Amethyst-throated Hummingbird (Lampornis amethystinus).

We analyzed mitochondrial DNA sequence variation across 69 Amethyst-throated Hummingbirds (Lampornis amethystinus), comparing with samples of related taxa. Although this group shows discrete phenotypic variation in throat color among populations in Oaxaca and Guerrero (Mexico), the only phylogeographic structure observed was between phenotypically similar populations north and south of the Isthmus of Tehuantepec. As such, it appears that throat color variation is of recent origin and likely based only on minor genetic differences.

Ecological niche and geographic distribution of the Chagas disease vector, Triatoma dimidiata (Reduviidae: Triatominae): Evidence for niche differentiation among cryptic species.

The principal vector of Chagas disease in Central America, Triatoma dimidiata, shows considerable diversity of habitat, phenotype, and genotype across its geographic range (central Mexico to southern Ecuador), suggesting that it constitutes a complex of cryptic species. However, no consistent picture of the magnitude of ecological differentiation among populations of this complex has yet been developed. To assess ecological variation across the complex, we broadened the geographic coverage of phylogeographic data and analyses for the complex into Colombia and Mexico, with additional nuclear (ITS-2) and mitochondrial (ND4) DNA sequences. This information allowed us to describe distributions of previously documented clades in greater detail: Group I, from central Guatemala south to Ecuador; Group II, across Mexico south through the Yucatán Peninsula to Belize and northern Guatemala; and Group III, in northern Guatemala, Belize, and the Yucatán Peninsula. Using ecological niche modeling, we assessed ecological niche differentiation among the groups using four hypotheses of accessible areas (M) across the distribution of the complex. Results indicated clear niche divergence of Group I from Group II: the speciation process thus appears to have involved genetic and ecological changes, suggesting divergence in populations in response to environmental conditions.

Potential for spread of the white-nose fungus (Pseudogymnoascus destructans) in the Americas: use of Maxent and NicheA to assure strict model transference.

Emerging infectious diseases can present serious threats to wildlife, even to the point of causing extinction. Whitenose fungus (Pseudogymnoascus destructans) is causing an epizootic in bats that is expanding rapidly, both geographically and taxonomically. Little is known of the ecology and distributional potential of this intercontinental pathogen. We address this gap via ecological niche models that characterise coarse resolution niche differences between fungus populations on different continents, identifying areas potentially vulnerable to infection in South America. Here we explore a novel approach to identifying areas of potential distribution across novel geographic regions that avoids perilious extrapolation into novel environments. European and North American fungus populations show differential use of environmental space, but rather than niche differentiation, we find that changes are best attributed to climatic differences between the two continents. Suitable areas for spread of the pathogen were identified across southern South America; however caution should be taken to avoid underestimating the potential for spread of this pathogen in South America.

Ecology of North American Triatominae.

In all, 40 native triatomine species and subspecies occur in NA, belonging to six genera from the Triatomini (Triatoma, Paratriatoma, Panstrongylus, Dipetalogaster, Belminus, Eratyrus), and one genus from the Rhodniini (represented by one non-native species Rhodnius prolixus, formerly occurring exclusively in domestic habitats); 28 species are found exclusively in Mexico (and/or Central America), eight are shared between the United States (US) and Mexico, and four occur exclusively in the US. The genus Triatoma is the most diverse with 26 species belonging to the species groups protracta, including the species complexes protracta and lecticularia, and rubrofasciata, which includes the species complexes rubida, phyllosoma and dimidiata. Triatomine species richness declined both at higher (south US) and lower (south of the Istmus of Tehuantepec, Mexico) latitudes. Triatoma species are found predominantly in cropland, grassland, wooded grassland and woodland landscapes. Land cover types were most similar among the lecticularia, protracta, and rubida complexes, in contrast to the phyllosoma and dimidiata species complexes. The land cover types having highest suitability for most species were wooded grassland, followed by woodland for the phyllosoma and dimidiata species complexes, and open and closed shrubland and cropland for the remaining three species complexes. A principal component analysis was used to demonstrate differences in the potential range for use of environmental conditions: protracta and phyllosoma complexes occupy the broadest niches. The present study represents a primary stratification of potential triatomine dispersal areas, based on species and species complexes, and based on predicted niche, a method which has already proven to be highly significant epidemiologically.

Coarse-scale spatial and ecological analysis of tuberculosis in cattle: an investigation in Jalisco, Mexico.

We have tested the hypothesis that coarse-scale environmental features are associated with spatial variation in bovine tuberculosis (BTB) prevalence, based on extensive sampling and testing of cattle in the state of Jalisco, Mexico. Ecological niche models were developed to summarize relationships between BTB occurrences and aspects of climate, topography and surface. Model predictions, however, reflected the distributions of dairy cattle versus beef cattle, and the non-random nature of sampling any cattle, but did not succeed in detecting environmental correlates at spatial resolutions of 1 km. Given that the tests employed seek any predictivity better than random expectations, making the finding of no environmental associations conservative, we conclude that BTB prevalence is independent of coarsescale environmental features.

Phylogeography of the Buarremon brush-finch complex (Aves, Emberizidae) in Mesoamerica.

The Buarremon brush-finches represent a complex suite of populations distributed in the montane New World Tropics from Mexico south to South America. Traditional taxonomic arrangements have separated populations of this genus into three species, based on plumage variation, although plumage patterns are well known to exhibit homoplasy. We present a first detailed phylogeographic and phylogenetic study, focused on Mesoamerican populations, and signal the existence of strong differentiation among populations with a clear geographic structure. We find well differentiated clades for (1) the Sierra Madre Oriental and Sierra Madre del Sur in Oaxaca, (2) western Mexican populations, including the B. brunneinucha populations in the Sierra Madre del Sur and B. virenticeps, (3) Sierra Madre Oriental and Sierra de los Tuxtlas, (4) northern Central America, (5) southern Central America, (6) middle Central America, and (7) South America. We demonstrate a lack of concordance with plumage patterns, and argue for several additional species to be recognized in the complex.