The effects of tropical forest fragmentation on frugivorous and nectarivorous bats were studied on recent islands created by the flooding of a dam in French Guiana. Study sites include forest islands isolated by water, and control plots in nearby continuous forest. Studies began 1y before the onset of forest fragmentation and encompassed the first 3y after flooding. Forest fragmentation greatly modified the diversity and abundance of bats. Changes occurred more rapidly in the smallest fragments than in the largest one, and trends were remarkably similar among all the studied islands. Bat captures in islands were characterised by the scarcity of understorey frugivores. Differences in home range size and foraging strategies may explain why understorey fruit bat species are more sensitive to fragmentation than canopy ones. Changes in the frugivorous bat community may have indirect consequences on both the demographic and the genetic structures of plant populations inside forest fragments.

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Summary1. Species richness is a state variable of some interest in monitoring programmes but raw species counts are often biased due to imperfect species detectability. Therefore, monitoring programmes should quantify detectability for target taxa to assess whether it varies over temporal or spatial scales. We assessed the potential for tropical bat monitoring programmes to reliably estimate trends in species richness. 2. Using data from 25 bat assemblages from the Old and New World tropics, we estimated detectability for all species in an assemblage (mean proportion of species detected per sampling plot) and for individual species (species-specific detectability). We further assessed how these estimates of detectability were affected by external sources of variation relating to time, space, survey effort and biological traits. 3. The mean proportion of species detected across 96 sampling plots was estimated at 0AE76 (range 0AE57-1AE00) and was significantly greater for phytophagous than for animalivorous species. Species-*Correspondence author. E-mail: cmeyer@fc.ul.pt 1365-2664.2011.01976.x Ó 2011 The Authors. Journal of Applied Ecology Ó 2011 British Ecological Society averaged detectability for phytophagous species was influenced by the number of surveys and season, whereas the number of surveys and sampling methods [ground-or canopy-level mist nets, harp traps and acoustic sampling (AS)] most strongly affected estimates of detectability for animalivorous bats. Species-specific detectability averaged 0AE4 and was highly heterogeneous across 232 species, with estimates ranging from 0AE03 to 0AE84. Species-level detectability was influenced by a range of external factors such as location, season, or sampling method, suggesting that raw species counts may sometimes be strongly biased. 4. Synthesis and applications. Due to generally high species-specific detection probabilities, Neotropical aerial insectivorous bats proved to be well suited for monitoring using AS. However, for species with low detectability, such as most gleaning animalivores or nectarivores, count data obtained in bat monitoring surveys must be corrected for detection bias. Our results indicate that species-averaged detection probabilities will rarely approach 1 unless many surveys are conducted. Consequently, long-term bat monitoring programmes need to adopt an estimation scheme that corrects for variation in detectability when comparing species richness over time and when making regional comparisons. Similar corrections will be needed for other species-rich tropical taxa. Journal of AppliedEcology 2011, 48, 777-787 doi: 10.1111/j.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. The present study compares breeding parameters and adult survival rate in a herring gull colony before and after the closing of a large refuse tip where breeders used to find most of their food. During the first study period (1983-88) food of human origin was abundant and virtually always available. During the second period (1989-90) such food was scarce. 2. The annual adult survival rate was time-dependent. It varied from 0-826 (SE = 0.031) in 1987-88 to 0-975 (SE = 0-022) in 1985-86. The average survival rate calculated for 1983-90 was 0-881 (SE = 0-014).There was no significant difference in adult survival between males and females. The closure of the refuse tip was not followed by a significant decrease in adult survival rate. 3. After the refuse tip was closed, mean clutch size and mean production of young per breeding pair decreased by 6-7% and 49 1%, respectively. Mean adult body weight decreased by 4-6% for males and by 4-7% for females. 4. The proportion of non-breeders among former breeders and the proportion of 3and 4-year-old individuals among ringed birds did not change after closure of the tip. 5. The results are discussed in terms of the life-history theory, which predicts that in long-lived species a decrease in food supply should affect fecundity before affecting adult survival.

Incomplete reproductive isolation promotes gene flow between diverging taxa. However, any gene encoding for traits involved in the reproductive barriers will be less prone to introgression than neutral markers. Comparing introgression rates among loci is thus informative of the number and functions of loci involved in the reproductive barriers. This study aimed at identifying possible mechanisms of restriction to gene flow across a zone of recent secondary contact between Larus argentatus and Larus cachinnans by comparing introgression patterns for nine microsatellite loci, a fragment of mitochondrial DNA and a set of phenotypic traits. The low linkage disequilibrium between neutral nuclear markers indicated introgression without any barrier to gene flow. However, asymmetric introgression of mitochondrial DNA suggested that interspecific crosses may be more successful in one direction. The introgression rate for phenotypic traits was variable and low compared to neutral molecular markers. This was particularly evident in colouration of bare parts: individuals with intermediate colouration were scarcer in sympatry than expected if the genomes recombined freely. We hypothesized that one of these variables, the orbital ring colour, may play a role in mate choice, acting as an incomplete premating barrier through assortative mating. This study emphasizes that multilocus approaches are useful to discriminate among possible mechanisms responsible for the maintenance of hybrid zones.