The Oriental Hornet (Vespa orientalis L.): a Threat to the Americas?

Invasive alien species generate adverse ecological, economic and social impacts in the invaded area. This is particularly alarming as the establishment of alien species shows no sign of saturation worldwide. Among invasive alien species, social wasps of the Vespidae family are well known to negatively impact the biodiversity and economy in the invaded areas. In 2020, an established population of the Oriental Hornet (Vespa orientalis L.) was detected in central Chile. This finding represents the first successful establishment of an insect of the genus Vespa in South America and rises an alarm about its potential spread in the Americas. Here, we performed an ecological niche modelling approach using Global Biodiversity Information Facility (GBIF) and literature occurrences for V. orientalis and a set of environmental variables, to identify the suitable areas for the species outside its native range. The highest suitability values were predicted mostly in warm temperate regions and some arid regions of the world, with humid subtropical, Mediterranean, semi-arid or desert climates. In the Americas, we identified four main regions as moderately or highly suitable for the oriental hornet: the Gulf of Mexico and some areas in western California in the USA, central west Chile and the north-western region of Argentina. When we complemented GBIF occurrences with data from the literature, the potential areas of invasions became broader. Based on our results, we recommend the implementation of early warning monitoring schemes including citizen science initiatives to prevent the invasion of the oriental hornet.

Biogeographical affinity shapes relationships between ecological and phylogenetic mammal diversity and associations with their environmental correlates in the Americas.

We evaluate the role of biogeographical affinity in shaping relationships between ecological diversity as a proxy of functional diversity and phylogenetic diversity and their association with environmental variation, across tropical and temperate latitudes of the Americas. If environmental niches are evolutionarily conserved, high mammal taxa of tropical and temperate affinity will show consistent differences in these relationships. Accordingly, mammal groups of tropical affinity (old-autochthonous: marsupials and xenarthrans; and mid-Cenozoic immigrants: hystricognaths and primates) show stronger positive correlations between ecological and phylogenetic diversity within the tropics than those from extra-tropical latitudes where newcomers from North America (artiodactyls) show the strongest positive correlations. The other group of newcomers (carnivorans), however, show a peak in the association that include both tropical and extra-tropical latitudes of South America. Climate predominates over topographic relief in structuring the spatial variation of ecological and phylogenetic mammal diversity. The environmental structuring of ecological and phylogenetic mammal diversity across the Americas is more complex than expected from a latitudinal diversity gradient. Dry seasonal tropical habitats generated considerable heterogeneity in relationships between ecological and phylogenetic diversity and their association with environmental correlates. We conclude that biogeographical affinity and regional associations between the different components of diversity and the environment should be considered for a comprehensive explanation of covariation between ecological and phylogenetic diversity on a continental scale.

The latitudinal diversity gradient in South American mammals revisited using a regional analysis approach: The importance of climate at extra-tropical latitudes and history towards the tropics.

The latitudinal diversity gradient has been considered a consequence of a shift in the impact of abiotic and biotic factors that limit species distributions from the poles to the equator, thus influencing species richness variation. It has also been considered the outcome of evolutionary processes that vary over geographical space. We used six South American mammal groups to test the association of environmental and evolutionary factors and the ecological structuring of mammal assemblages with spatial variation in taxonomic richness (TR), at a spatial resolution of 110 km x 110 km, at tropical and extra-tropical latitudes. Based on attributes that represent what mammal species do in ecosystems, we estimated ecological diversity (ED) as a mean pairwise ecological distance between all co-occurring taxa. The mean pairwise phylogenetic distance between all co-occurring taxa (AvPD) was used as an estimation of phylogenetic diversity. Geographically Weighted Regression analyses performed separately for each mammal group identified tropical and extra-tropical high R2 areas where environmental and evolutionary factors strongly accounted for richness variation. Temperature was the most important predictor of TR in high R2 areas outside the tropics, as was AvPD within the tropics. The proportion of TR variation accounted for by environment (either independently or combined with AvPD) was higher in tropical areas of high richness and low ecological diversity than in tropical areas of high richness and high ecological diversity. In conclusion, we confirmed a shift in the impact of environmental factors, mainly temperature, that best account for mammal richness variation in extra-tropical regions, whereas phylogenetic diversity best accounts for richness variation within the tropics. Environment in combination with evolutionary history explained the coexistence of a high number of ecologically similar species within the tropics. Consideration of the influence of contemporary environmental variables and evolutionary history is crucial to understanding of the latitudinal diversity gradient.

Ecological Diversity in South American Mammals: Their Geographical Distribution Shows Variable Associations with Phylogenetic Diversity and Does Not Follow the Latitudinal Richness Gradient.

The extent to which the latitudinal gradient in species richness may be paralleled by a similar gradient of increasing functional or phylogenetic diversity is a matter of controversy. We evaluated whether taxonomic richness (TR) is informative in terms of ecological diversity (ED, an approximation to functional diversity) and phylogenetic diversity (AvPD) using data on 531 mammal species representing South American old autochthonous (marsupials, xenarthrans), mid-Cenozoic immigrants (hystricognaths, primates) and newcomers (carnivorans, artiodactyls). If closely related species are ecologically more similar than distantly related species, AvPD will be a strong predictor of ED; however, lower ED than predicted from AvPD may be due to species retaining most of their ancestral characters, suggesting niche conservatism. This pattern could occur in tropical rainforests for taxa of tropical affinity (old autochthonous and mid-Cenozoic immigrants) and in open and arid habitats for newcomers. In contrast, higher ED than expected from AvPD could occur, possibly in association with niche evolution, in arid and open habitats for taxa of tropical affinity and in forested habitats for newcomers. We found that TR was a poor predictor of ED and AvPD. After controlling for TR, there was considerable variability in the extent to which AvPD accounted for ED. Taxa of tropical affinity did not support the prediction of ED deficit within tropical rainforests, rather, they showed a mosaic of regions with an excess of ED interspersed with zones of ED deficit within the tropics; newcomers showed ED deficit in arid and open regions. Some taxa of tropical affinity showed excess of ED in tropical desert areas (hystricognaths) or temperate semideserts (xenarthrans); newcomers showed excess of ED at cold-temperate latitudes in the Northern Hemisphere. This result suggests that extreme climatic conditions at both temperate and tropical latitudes may have promoted niche evolution in mammals.

Large-scale patterns in morphological diversity and species assemblages in Neotropical Triatominae (Heteroptera: Reduviidae)

We analysed the spatial variation in morphological diversity (MDiv) and species richness (SR) for 91 species of Neotropical Triatominae to determine the ecological relationships between SR and MDiv and to explore the roles that climate, productivity, environmental heterogeneity and the presence of biomes and rivers may play in the structuring of species assemblages. For each 110 km x 110 km-cell on a grid map of America, we determined the number of species (SR) and estimated the mean Gower index (MDiv) based on 12 morphological attributes. We performed bootstrapping analyses of species assemblages to identify whether those assemblages were more similar or dissimilar in their morphology than expected by chance. We applied a multi-model selection procedure and spatial explicit analyses to account for the association of diversity-environment relationships. MDiv and SR both showed a latitudinal gradient, although each peaked at different locations and were thus not strictly spatially congruent. SR decreased with temperature variability and MDiv increased with mean temperature, suggesting a predominant role for ambient energy in determining Triatominae diversity. Species that were more similar than expected by chance co-occurred near the limits of the Triatominae distribution in association with changes in environmental variables. Environmental filtering may underlie the structuring of species assemblages near their distributional limits.

Large-scale patterns in morphological diversity and species assemblages in Neotropical Triatominae (Heteroptera: Reduviidae).

We analysed the spatial variation in morphological diversity (MDiv) and species richness (SR) for 91 species of Neotropical Triatominae to determine the ecological relationships between SR and MDiv and to explore the roles that climate, productivity, environmental heterogeneity and the presence of biomes and rivers may play in the structuring of species assemblages. For each 110 km x 110 km-cell on a grid map of America, we determined the number of species (SR) and estimated the mean Gower index (MDiv) based on 12 morphological attributes. We performed bootstrapping analyses of species assemblages to identify whether those assemblages were more similar or dissimilar in their morphology than expected by chance. We applied a multi-model selection procedure and spatial explicit analyses to account for the association of diversity-environment relationships. MDiv and SR both showed a latitudinal gradient, although each peaked at different locations and were thus not strictly spatially congruent. SR decreased with temperature variability and MDiv increased with mean temperature, suggesting a predominant role for ambient energy in determining Triatominae diversity. Species that were more similar than expected by chance co-occurred near the limits of the Triatominae distribution in association with changes in environmental variables. Environmental filtering may underlie the structuring of species assemblages near their distributional limits.