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The marginal value theorem (MVT) provides a framework to predict how habitat modifications related to the distribution of resourcesover patches should impact the realized fitness of individuals and their optimal rate of movement (or patch residence times) across the habitat. The MVT theory has focused on the consequences of changing the shape of the gain functions in some patches, describing for instance, patch enrichment. However, an alternative form of habitat modification is habitat conversion, whereby patches are converted from one existing type to another (e.g., closed habitat to open habitat). In such a case, the set of gain functions existing in the habitat does not change, only their relative frequencies does. This case however has received comparatively little attention. Here we analyze mathematically the consequences of habitat conversion under the MVT. We study how realized fitness and the average rate of movement should respond to changes in the frequency distribution of patch-types and how they should covary. We further compare the response of optimal and non-plastic foragers. We find that the initial pattern of patch exploitation in a habitat, characterized by the regression slope of patch yields over residence times, can help predict the qualitative responses of fitness and movement rate following habitat conversion. We also find that for some habitat conversion patterns, optimal and non-plastic foragers exhibit qualitatively different responses, and that adaptive foragers can have opposite responses in the short- and long-term following habitat conversion. We suggest taking into account behavioral responses may help better understand the ecological consequences of habitat conversion. [ABSTRACT FROM AUTHOR]

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]

Nine Element Occurrences (EOs) of Appalachian Jacob's-ladder Polemonium van-bruntiae in Vermont were recognized in 2002. Presently there are 15 EOs comprising 79 Sub-Element Occurrences (subEOs). The author monitored all 79 subEOs at least once and 31 of them twice between 2004 and 2017. The total number of sexually reproductive stems was 32,300, averaging 2153 per EO and 409 per subEO. Six subEOs had fewer than 10 plants each. More than half the subEOs occurred in wooded seeps; the remainder occurred in wet meadows, alder thickets, northern white cedar swamps or human-altered patchy habitats that mimic seeps. In Vermont the species is currently known only from southeast Addison County. The species is now more populous but only slightly more widely distributed in Vermont than in Deller's account. Increase in numbers is due to discovery of new EOs and subEOs, as well as to population growth of the EOs known since 2002. It remains at risk to the same variety of threats that it was believed subject to in 2002. [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]