Effects of Forest Fragmentation on a Dung Beetle Community in French Guiana

Abstract:  Fragmentation is the most common disturbance induced by humans in tropical forests. Some insect groups are particularly suitable for studying the effects of fragmentation on animal communities because they are taxonomically and ecologically homogenous. We investigated the effects of forest fragmentation on a dung beetle species community in the forest archipelago created in 1994–1995 by the dam of Petit Saut, French Guiana. We set and baited an equal number of pitfall traps for dung beetles on three mainland sites and seven island sites. The sites ranged from 1.1 to 38 ha. In 250 trap days, we captured 50 species in 19 genera. Diversity indices were high (2.18–4.06). The lowest diversity was on the small islands and one mainland site. Species richness and abundance were positively related to fragment area but not to distance from mainland or distance to the larger island. The islands had lower species richness and population than mainland forest, but rarefied species richness was relatively invariant across sites. There was a marked change in species composition with decreasing fragment that was not caused by the presence of a common fauna of disturbed-area species on islands. Small islands differed from larger islands, which did not differ significantly from mainland sites. Partial correlation analyses suggested that species richness and abundance of dung beetle species were positively related to the number of species of nonflying mammals and the density index of howler monkeys ( Alouatta seniculus ), two parameters positively related to fragment area.     

Use of Large‐Scale Acoustic Monitoring to Assess Anthropogenic Pressures on Orthoptera Communities

Biodiversity monitoring at large spatial and temporal scales is greatly needed in the context of global changes. Although insects are a species‐rich group and are important for ecosystem functioning, they have been largely neglected in conservation studies and policies, mainly due to technical and methodological constraints. Sound detection, a nondestructive method, is easily applied within a citizen‐science framework and could be an interesting solution for insect monitoring. However, it has not yet been tested at a large scale. We assessed the value of a citizen‐science program in which Orthoptera species (Tettigoniidae) were monitored acoustically along roads. We used Bayesian model‐averaging analyses to test whether we could detect widely known patterns of anthropogenic effects on insects, such as the negative effects of urbanization or intensive agriculture on Orthoptera populations and communities. We also examined site‐abundance correlations between years and estimated the biases in species detection to evaluate and improve the protocol. Urbanization and intensive agricultural landscapes negatively affected Orthoptera species richness, diversity, and abundance. This finding is consistent with results of previous studies of Orthoptera, vertebrates, carabids, and butterflies. The average mass of communities decreased as urbanization increased. The dispersal ability of communities increased as the percentage of agricultural land and, to a lesser extent, urban area increased. Despite changes in abundances over time, we found significant correlations between yearly abundances. We identified biases linked to the protocol (e.g., car speed or temperature) that can be accounted for ease in analyses. We argue that acoustic monitoring of Orthoptera along roads offers several advantages for assessing Orthoptera biodiversity at large spatial and temporal extents, particularly in a citizen science framework. El Uso de Monitoreos Acústicos a Gran Escala para Estudiar las Presiones Antropogénicas sobre Comunidades de Orthoptera     

Releasing Adults versus Young in Reintroductions: Interactions between Demography and Genetics

Abstract:  We integrated genetics and demography into population modeling in the context of species restorations, in which both the origin of released individuals and the management strategy may influence the success of introduction. Through an explicit individual-based simulation approach, we investigated the effects of the age of released individuals by exploring the relative merits of releasing juveniles or adults to establish populations. We included the effect of genetic variability responsible for inbreeding depression and mutational meltdown. Our general analysis uncovered an interaction between the age of founders and the extent of intrapopulation fitness variability, which substantially influenced the efficiency of selection in populations founded by juveniles and had subsequent positive consequences for long-term persistence compared with the case in which adults were released. We then applied the model to the case of the reintroduction of the Griffon Vulture ( Gyps fulvus fulvus ) to southern France, for which post-release data were available. The demographic aspects of this reintroduction were already analyzed and published, suggesting that it is more efficient to release adults than juveniles, despite an observed reduction of demographic parameters following the release of adults. In that context, the inclusion of genetic considerations qualitatively changes the conclusion, predicting reduced long-term extinction risk if juveniles rather than adults are released.     

Joint Effects of Inbreeding and Local Adaptation on the Evolution of Genetic Load after Fragmentation

Abstract: Disruption of gene flow among demes after landscape fragmentation can facilitate local adaptation but increase the effect of genetic drift and inbreeding. The joint effects of these conflicting forces on the mean fitness of individuals in a population are unknown. Through simulations, we explored the effect of increased isolation on the evolution of genetic load over the short and long term when fitness depends in part on local adaptation. We ignored genetic effects on demography. We modeled complex genomes, where a subset of the loci were under divergent selection in different localities. When a fraction of the loci were under heterogeneous selection, isolation increased mean fitness in larger demes made up of hundreds of individuals because of improved local adaptation. In smaller demes of tens of individuals, increased isolation improved local adaptation very little and reduced overall fitness. Short‐term improvement of mean fitness after fragmentation may not be indicative of the long‐term evolution of fitness. Whatever the deme size and potential for local adaptation, migration of one or two individuals per generation minimized the genetic load in general. The slow dynamics of mean fitness following fragmentation suggests that conservation measures should be implemented before the consequences of isolation on the genetic load become of concern.     

Devising Local Sustainable Development Indicators: from technical issues to bureaucratic stakes. The Greater Lyons experience

The paper will draw on the experience of Greater Lyons (France) in the development and implementation of air quality indicators in the framework of an environmental monitoring body, created in 1992. The analysis shows a patent discrepancy between the strength of the political support enjoyed by the monitoring body at its creation and its gradual confinement within the administrative structure of Greater Lyons. In fact, developing and using indicators raises not only technical issues but also political and bureaucratic stakes. The experience provides food for thought as regards the emergence of sustainable development issues within large and complex structures such as that of Greater Lyons. The paper points out that if indicators are hybrid objects, monitoring bodies, which are supposed to devise and promote them, are hybrid as well: their management, in terms of aims, means and position within the administrative body, is at least as important as their so-called ‘technical’ function.     

Relative Contributions of Sampling Error in Initial Population Size and Vital Rates to Outcomes of Population Viability Analysis

Abstract:  We evaluated the relative contributions of sampling error (randomly chosen standard errors applied as 0–30% of parameter estimates) in initial population size and vital rates (survival and reproduction) to the outcome of a simulated population viability analysis for grizzly bears (  Ursus arctos ). Error in initial population size accounted for the largest source of variation (model II analysis of variance, F _25,5= 10.8, p = 0.00001) in simulation outcomes, explaining 60.5% of the variance. In contrast, error in vital rates contributed little to simulation outcomes ( F _25,5= 0.61, p = 0.70), accounting for only 2.4% of model variation. Reduced global variation in vital rates, as a result of independent random sampling of annual deviates for each parameter, likely contributed to the results. Errors in estimates of initial population size, if ignored in PVA, have the potential to leave managers with estimates of population persistence that are of little value for making management decisions.