Extinction risk and body size have been found to be related in various vertebrate groups, with la... more Extinction risk and body size have been found to be related in various vertebrate groups, with larger species being more at risk than smaller ones. We checked whether this was also the case for snakes by investigating extinction risk–body size relationships in the New World's Colubroidea species. We used the IUCN Red List risk categories to assign each species to one of two broad levels of threat (Threatened and Non-Threatened) or to identify it as either Data Deficient or Not-Evaluated by the IUCN. We also included the year of description of each species in our analysis as this could affect the level of threat assigned to it (earlier described species had more time to gather information about them, which might have facilitated their evaluation). Also, species detectability could be a function of body size, with larger species tending to be described earlier, which could have an impact in extinction risk–body size relationships. We found a negative relationship between body size and description year, with large-bodied species being described earlier. Description year also varied among risk categories, with Non-Threatened species being described earlier than Threatened species and both species groups earlier than Data Deficient species. On average, Data Deficient species also presented smaller body sizes, while no size differences were detected between Threatened and Non-Threatened species. So it seems that smaller body sizes are related with species detectability, thus potentially affecting both when a species is described (smaller species tend to be described more recently) as well as the amount of information gathered about it (Data Deficient species tend to be smaller). Our data also indicated that if Data Deficient species were to be categorized as Threatened in the future, snake body size and extinction risk would be negatively related, contrasting with the opposite pattern commonly observed in other vertebrate groups.
The historical contingencies of biological invasions may have important consequences for final in... more The historical contingencies of biological invasions may have important consequences for final invasion outcomes. Here, we characterize the variations in the realized niche during the invasions of the bull-headed dung beetle Onthophagus taurus (Coleop-tera: Scarabaeidae) from its native Mediterranean range following accidental (Eastern North America) as well as deliberate (Western North America, Western Australia, and Eastern Australia) releases into novel, exotic ranges approximately 50 years ago. Specifically, we examined whether the climatic responses of exotic O. taurus have diverged from those characterizing their native range, and if so, to what degree and in what dimensions. We found that when compared to the native range, all exotic populations exhibited similar overlap proportions regardless of invasion history. However, more detailed analysis of climatic niche features showed that all three deliberately established populations were characterized by overall similar climatic niche features, whereas the accidentally-established Eastern North American populations have undergone significant changes in their climatic niche. Specifically, when
Extinction risk and body size have been found to be related in various vertebrate groups, with la... more Extinction risk and body size have been found to be related in various vertebrate groups, with larger species being more at risk than smaller ones. We checked whether this was also the case for snakes by investigating extinction risk–body size relationships in the New World's Colubroidea species. We used the IUCN Red List risk categories to assign each species to one of two broad levels of threat (Threatened and Non-Threatened) or to identify it as either Data Deficient or Not-Evaluated by the IUCN. We also included the year of description of each species in our analysis as this could affect the level of threat assigned to it (earlier described species had more time to gather information about them, which might have facilitated their evaluation). Also, species detectability could be a function of body size, with larger species tending to be described earlier, which could have an impact in extinction risk–body size relationships. We found a negative relationship between body size and description year, with large-bodied species being described earlier. Description year also varied among risk categories, with Non-Threatened species being described earlier than Threatened species and both species groups earlier than Data Deficient species. On average, Data Deficient species also presented smaller body sizes, while no size differences were detected between Threatened and Non-Threatened species. So it seems that smaller body sizes are related with species detectability, thus potentially affecting both when a species is described (smaller species tend to be described more recently) as well as the amount of information gathered about it (Data Deficient species tend to be smaller). Our data also indicated that if Data Deficient species were to be categorized as Threatened in the future, snake body size and extinction risk would be negatively related, contrasting with the opposite pattern commonly observed in other vertebrate groups.
The historical contingencies of biological invasions may have important consequences for final in... more The historical contingencies of biological invasions may have important consequences for final invasion outcomes. Here, we characterize the variations in the realized niche during the invasions of the bull-headed dung beetle Onthophagus taurus (Coleop-tera: Scarabaeidae) from its native Mediterranean range following accidental (Eastern North America) as well as deliberate (Western North America, Western Australia, and Eastern Australia) releases into novel, exotic ranges approximately 50 years ago. Specifically, we examined whether the climatic responses of exotic O. taurus have diverged from those characterizing their native range, and if so, to what degree and in what dimensions. We found that when compared to the native range, all exotic populations exhibited similar overlap proportions regardless of invasion history. However, more detailed analysis of climatic niche features showed that all three deliberately established populations were characterized by overall similar climatic niche features, whereas the accidentally-established Eastern North American populations have undergone significant changes in their climatic niche. Specifically, when
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Papers by Bruno Vilela