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Disentangling the multiple factors controlling species diversity is a major challenge in ecology. Island biogeography and environmental filtering are two influential theories emphasizing respectively island size and isolation, and the abiotic environment, as key drivers of species richness. However, few attempts have been made to quantify their relative importance and investigate their mechanistic basis. Here, we applied structural equation modelling, a powerful method allowing test of complex hypotheses involving multiple and indirect effects, on an island‐like system of 22 French Guianan neotropical inselbergs covered with rock‐savanna. We separated the effects of size (rock‐savanna area), isolation (density of surrounding inselbergs), environmental filtering (rainfall, altitude) and dispersal filtering (forest‐matrix openness) on the species richness of all plants and of various ecological groups (terrestrial versus epiphytic, small‐scale versus large‐scale dispersal species). We showed that the species richness of all plants and terrestrial species was mainly explained by the size of rock‐savanna vegetation patches, with increasing richness associated with higher rock‐savanna area, while inselberg isolation and forest‐matrix openness had no measurable effect. This size effect was mediated by an increase in terrestrial‐habitat diversity, even after accounting for increased sampling effort. The richness of epiphytic species was mainly explained by environmental filtering, with a positive effect of rainfall and altitude, but also by a positive size effect mediated by enhanced woody‐plant species richness. Inselberg size and environmental filtering both explained the richness of small‐scale and large‐scale dispersal species, but these ecological groups responded in opposite directions to altitude and rainfall, that is positively for large‐scale and negatively for small‐scale dispersal species. Our study revealed both habitat diversity associated with island size and environmental filtering as major drivers of neotropical inselberg plant diversity and showed the importance of plant species growth form and dispersal ability to explain the relative importance of each driver. [ABSTRACT FROM AUTHOR]

Islands are geographically defined as land masses completely surrounded by water, and island systems have been used as models for many biogeographic, ecological, and evolutionary theories ever since Darwin's pioneering efforts. However, their biological definition is complex. Over the past few decades these theories have been applied to many study systems that only share some geographic features with island systems. These features include spatial fragmentation, limited area, spatial and temporal isolation from adjacent parts of the system, and low connectivity between different parts within the system, to mention just a few. These systems vary in their form, the matrix that surrounds them, the factors defining their borders, the extent of insularity they impose on the different taxa, and their geological similarity to different types of actual islands. Here, I seek to understand whether such island‐like systems (ILS) function biologically as true islands. In the first part, I describe the wide diversity of ILS suggested in the literature and the variation in the features that define their insularity. In the second part, I review the extent to which the main theories of island biology are applicable to these systems: species–area and species–isolation relationships, community composition, evolutionary radiations, and the extent of endemism and genetic diversity. In the third and final part, I suggest a new conceptual framework within which to classify and study the biology of ILS, as well as practical future research directions. I conclude that the term 'biological island' is a multi‐faceted concept, loosely related to its geographical definition. As ILS are often less isolated than true islands, and their biological patterns are only partly similar to those of true islands (and even this is true only for some ILS) the use of the term 'island' to describe any isolated habitat is therefore inappropriate. [ABSTRACT FROM AUTHOR]

Background:There is limited understanding about bird dispersal behaviour and seedling distribution of endangered tree species in patchy environments, although these processes are important for plant species persistence. Aims:We tested how patch features affected bird behaviour and seed dispersal, and thus seedling distribution of the endangered Chinese yew tree (Taxus chinensis). Methods:In the present study, we combined field data of bird dispersal behaviour and GIS-based information to elucidate the influence of spatial features of habitat patches on bird dispersal behaviour, and the resulting effects on the seedling distribution of the endangered Chinese yew in two patchy habitats. Results:Our results showed that the only seed source patch could attract eight bird species for dispersal at the two sites. Post-foraging movements of bird dispersers was strongly related to both topography and the relative locations of habitat patches. Yew seedlings aggregated only at the seed source and bamboo recruitment patches, which was affect by both the spatial distribution of recruitment patches and patch use by dispersers. Conclusions:Our results emphasise that bamboo patches in both patchy environments provide the necessary conditions for germination of yew seeds, and the post-foraging behaviour of dispersers determines seed deposited in these patches. Our study highlights the importance of the dispersal behaviour of frugivorous birds in the successful regeneration and colonisation of yew populations in patchy habitats. [ABSTRACT FROM PUBLISHER]

Understanding how often individuals should move when foraging over patchy habitats is a central question in ecology. By combining optimality and functional response theories, we show analytically how the optimal movement rate varies with the average resource level (enrichment) and resource distribution (patch heterogeneity). We find that the type of functional response predicts the effect of enrichment in homogeneous habitats: enrichment should decrease movement for decelerating functional responses, but increase movement for accelerating responses. An intermediate resource level thus maximises movement for type-III responses. Counterintuitively, greater movement costs favour an increase in movement. In heterogeneous habitats predictions further depend on how enrichment alters the variance of resource distribution. Greater patch variance always increases the optimal rate of movement, except for type-IV functional responses. While the functional response is well established as a fundamental determinant of consumer-resource dynamics, our results indicate its importance extends to the understanding of individual movement strategies. [ABSTRACT FROM AUTHOR]

We investigated the aggregation model of coexistence as a potential mechanism explaining patterns of coexistence between container mosquitoes Aedes albopictus and Aedes aegypti in southern Florida, USA. Aedes aegypti coexists with the invasive A. albopictus in many locations despite being an inferior resource competitor under most conditions. In agreement with aggregation theory we observed significant intraspecific aggregation of A. albopictus in all six field sites sampled in southern Florida in 2009. Quantitative results suggest that larval distributions of A. albopictus across containers are sufficiently aggregated to permit persistence of the inferior competitor A. aegypti. We tested whether observed levels of A. albopictus aggregation would significantly improve A. aegypti population performance in a controlled laboratory competition experiment manipulating A. albopictus aggregation while holding mean densities constant. We quantified A. aegypti's estimated rate of population change for replicate, multi-container cohorts in response to increasing A. albopictus aggregation across the cohorts. Aedes albopictus aggregation treatments produced J statistics for aggregation that spanned the range observed in the field study. We demonstrate a positive linear relationship between intraspecific aggregation of the superior competitor A. albopictus and estimated rate of population change for cohorts of the inferior A. aegypti. Thus, aggregation of A. albopictus at levels comparable to those observed in nature appears to be sufficient to reduce significantly the competitive impact of A. albopictus on multi-container cohorts of A. aegypti, and may therefore contribute to local coexistence of these competitors. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the effect of red wood ants Formica polyctena s.l. Foerst. on the spatial distribution of carabids and describe mechanisms of the ant–beetle interactions at the individual level. Fifteen carabid species were found in the foraging territory of an ant colony. The difference in the numbers of carabids in ant-controlled and ant-free territories was maximal in July, when the ants were most active. Measurements of running speed, duration of stops, and individual trajectories showed significant alterations in the behaviour of beetles in the ant-controlled territory. Experiments with a binary Y-shaped labyrinth showed that different carabid species used species-specific sets of behavioural tactics for avoiding conflict with ants. Pterostichus magus and P. oblongopunctatus, which are comparable with red wood ants in body length and speed of movement, possess the most effective stereotyped tactics in combination with a flexible behaviour. Such properties allow these species to penetrate ant foraging territory and partly avoid interference competition. [Copyright &y& Elsevier]