Patterns Of Native Species Richness Research Articles

Island biogeography of native and alien plant species: Contrasting drivers of diversity across the Lesser Antilles

AbstractAimUnderstanding the factors driving the diversity of alien and native species on islands is crucial for predicting the spread of alien species and for proposing management practices to protect the unique native biodiversity that often occurs in insular ecosystems. The main objective of this study was to evaluate whether native and alien plant species respond similarly to natural biogeographic and human‐related drivers.LocationLesser Antilles, Caribbean.MethodsWe compiled a dataset with the verified status of native and alien plant species occurring on 15 islands across the Lesser Antilles. We assessed the relationship of native and alien plant species richness and identified the biogeographic and socio‐economic variables that best explain the diversity patterns of both alien and native species on these islands by combining correlation analysis and generalized linear models.ResultsThe final dataset comprises a total of 2,438 plant species with 1,825 native species and 613 alien species. For the 15 islands analysed, native and alien species richness is strongly and positively correlated, but different variables explained their diversity patterns. We found that biogeographic drivers such as island area, elevation and distance to the mainland best explain patterns of native species richness. On the other hand, alien species richness was well predicted by a combination of geographic and socio‐economic variables, with per capita gross domestic product (GDP) and island area having the strongest effect. Species composition of alien floras is also significantly influenced by the historical colonial identity of these islands.Main conclusionsWhile native species are clearly associated with biogeographic variables, alien species are strongly influenced by variables related to human activities and therefore anthropogenic disturbance processes. Modification of natural areas by human activities can result in high alien species richness even on islands with high native species richness.

Non-native fishes and native species diversity in freshwater fish assemblages across the United States

The proliferation of non-native species in North American freshwater ecosystems is considered a primary threat to the integrity of native community structure. However, a general understanding of consistent and predictable impacts of non-native species on native freshwater diversity is limited, in part, because of a lack of broad-scale studies including data from numerous localities across multiple drainages. This study uses data from 751 localities collected during the United States Geological Survey (USGS) National Water Quality Assessment (NAWQA) program to examine the influence of non-native fish species on native freshwater fish assemblages across the United States. In general, no significant differences in native fish richness and diversity measures were detected between sites with only native species and sites containing non-native species. However, at sites with non-native species, the number of non-native species present was negatively correlated with native species richness and Shannon diversity and positively correlated with native evenness. Non-native piscivores were negatively correlated with native species richness and Shannon diversity and positively correlated with native evenness. Native piscivores were positively correlated with native richness and diversity and negatively correlated with native evenness at sites with only native species. Our results suggest that from a superficial perspective, native species richness and diversity are not different among sites with and without non-native species. However, when patterns of native species richness and diversity are examined at sites containing non-native species, correlations between non-native and native species richness and diversity imply the expected negative effect of invasive taxa. Additionally, non-native piscivores appear to have a significant negative effect on native taxa and possibly represent a novel selective force on naive native prey.

Filling in the gaps: modelling native species richness and invasions using spatially incomplete data

ABSTRACTDetailed knowledge of patterns of native species richness, an important component of biodiversity, and non‐native species invasions is often lacking even though this knowledge is essential to conservation efforts. However, we cannot afford to wait for complete information on the distribution and abundance of native and harmful invasive species. Using information from counties well surveyed for plants across the USA, we developed models to fill data gaps in poorly surveyed areas by estimating the density (number of species km−2) of native and non‐native plant species. Here, we show that native plant species density is non‐random, predictable, and is the best predictor of non‐native plant species density. We found that eastern agricultural sites and coastal areas are among the most invaded in terms of non‐native plant species densities, and that the central USA appears to have the greatest ratio of non‐native to native species. These large‐scale models could also be applied to smaller spatial scales or other taxa to set priorities for conservation and invasion mitigation, prevention, and control efforts.