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Aim: Understanding 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. Location: Lesser Antilles, Caribbean. Methods: We 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. Results: The 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 conclusions: While 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. [ABSTRACT FROM AUTHOR]

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This article compares four different models describing the dependence of species richness on area, maximum altitude in the island and its latitude, based on data on orchid richness. It discusses correlation of area and altitude of the highest peak with the number of orchid species present on an island, and the relationship using the generalized linear model approach with the response variable as the number of orchids.

The level of invasion (number or proportion of invasive species) in a given area depends on features of the invaded community, propagule pressure, and climate. In this study, we assess the invasive flora of nine islands in the West Indies to identify invasion patterns and evaluate whether invasive species diversity is related to geographical, ecological, and socioeconomic factors. We compiled a database of invasive plant species including information on their taxonomy, origin, pathways of introduction, habitats, and life history. This database was used to evaluate the similarity of invasive floras between islands and to identify invasion patterns at regional (West Indies) and local (island) scales. We found a total of 516 alien plant species that are invasive on at least one of the nine islands studied, with between 24 to 306 invasive species per island. The invasive flora on these islands includes a wide range of taxonomic groups, life forms, and habitats. We detected low similarity in invasive species diversity between islands, with most invasive species (>60%) occurring on a single island and 6% occurring on at least five islands. To assess the importance of different models in predicting patterns of invasive species diversity among islands, we used generalized linear models. Our analyses revealed that invasive species diversity was well predicted by a combination of island area and economic development (gross domestic product per capita and kilometers of paved roadways). Our results provide strong evidence for the roles of geographical, ecological, and socioeconomic factors in determining the distribution and spread of invasive species on these islands. Anthropogenic disturbance and economic development seem to be the major drivers facilitating the spread and predominance of invasive species over native species. [ABSTRACT FROM AUTHOR]

The metapopulation concept is widely established in population biology. It predicts that the likelihood of colonization of an empty patch is positively correlated with its connectivity, because colonizers from occupied patches will be more likely to reach an empty patch if they are closer to it. Another prediction is that the likelihood of extinction of an occupied patch will be negatively correlated with its connectivity to other patches, as the occupied patch can be 'reinforced' by immigrants from patches that are close by. We tested these predictions using an extensive data set for an epiphytic orchid, Lepanthes rupestris from Puerto Rico. Our data did not support the first prediction, but we found that the likelihood of extinction is negatively correlated with patch connectivity. We hypothesize that this might be because most orchid seeds are wind dispersed and seeds that do not fall immediately below the mother plant are uniformly distributed after a steep leptokurtic distribution. We predict that taxa with similar seed and gene flow characteristics should show similar patterns in the association between colonization/extinction rates and patch connectivity. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175, 598-606. [ABSTRACT FROM AUTHOR]

Evolutionary models estimating phenotypic selection in character size usually assume that the character is invariant across reproductive bouts. We show that variation in the size of reproductive traits may be large over multiple events and can influence fitness in organisms where these traits are produced anew each season. With data from populations of two orchid species, Caladenia valida and Tolumnia variegata, we used Bayesian statistics to investigate the effect on the distribution in fitness of individuals when the fitness landscape is not flat and when characters vary across reproductive bouts. Inconsistency in character size across reproductive periods within an individual increases the uncertainty of mean fitness and, consequently, the uncertainty in individual fitness. The trajectory of selection is likely to be muddled as a consequence of variation in morphology of individuals across reproductive bouts. The frequency and amplitude of such changes will certainly affect the dynamics between selection and genetic drift. [ABSTRACT FROM AUTHOR]