Genetic Bottlenecks Driven by Population Disconnection

Abstract: Connectivity among populations plays a crucial role in maintaining genetic variation at a local scale, especially in small populations affected strongly by genetic drift. The negative consequences of population disconnection on allelic richness and gene diversity (heterozygosity) are well recognized and empirically established. It is not well recognized, however, that a sudden drop in local effective population size induced by such disconnection produces a temporary disequilibrium in allelic frequency distributions that is akin to the genetic signature of a demographic bottleneck. To document this effect, we used individual‐based simulations and empirical data on allelic richness and gene diversity in six pairs of isolated versus well‐connected (core) populations of European tree frogs. In our simulations, population disconnection depressed allelic richness more than heterozygosity and thus resulted in a temporary excess in gene diversity relative to mutation drift equilibrium (i.e., signature of a genetic bottleneck). We observed a similar excess in gene diversity in isolated populations of tree frogs. Our results show that population disconnection can create a genetic bottleneck in the absence of demographic collapse.     

Localization of a Contact Zone between Two Highly Divergent Mitochondrial DNA Lineages of the Brown Bear Ursus arctos in Scandinavia

In Europe the brown bear ( Ursus arctos ) is represented by two different mitochondrial DNA (mtDNA) lineages, which probably diverged about 0.85 million years ago. Scandinavia has been colonized by representatives of both lineages, from the north (eastern lineage) and from the south (western lineage), and now bears occur primarily in four main regions called female concentration areas. For management purposes the localization of the contact zone between these two genotypes is important. Using hairs as a source of DNA, 127 individual brown bears from throughout the Scandinavian populations were assayed for lineage assignment. A part of the mtDNA control region was amplified via the polymerase chain reaction, and the product was either sequenced (14 individuals) or digested with two diagnostic restriction endonucleases (113 individuals). Fifty-six and 71 bears were assigned to the western and eastern lineages, respectively. The geographic distribution of the two genotypes allowed precise localization of the contact zone. Only two males from each lineage had crossed the border between the two lineages. We used dispersal data from bears radio-marked as yearlings to determine whether potential mtDNA introgressions agreed with the dispersal behavior of bears. The males in the "wrong" areas were all within the 95th-percentile dispersal distance from the "correct" area. Females were more philopatric than males, and none were found in the wrong areas. The two female concentration areas flanking the contact zone were 134 km apart. Thus, radiotelemetry results on dispersal distances could explain the occurrence of the males in the wrong genetic area. In the absence of information concerning possible male-mediated gene flow, a conservative management approach would be to consider the southern and the three northern female concentration areas as two distinct conservation units.     

Testing the Value of Six Taxonomic Groups as Biodiversity Indicators at a Local Scale

Abstract:  We examined six groups of taxa—woody plants, aquatic and terrestrial herpetofauna, small terrestrial birds, orchids, and Orthoptera—to determine their efficiency as biodiversity indicators in the Dadia Reserve in northern Greece. We investigated the indicator value of each group by examining the degree of congruence of its species-richness pattern with that of the other groups and the efficiency of its complementary network in conserving the other groups and biodiversity. The two techniques differed in many respects in their outputs, but they both showed woody plants as the best biodiversity indicator. There was in general low congruence in the species richness patterns across the different groups. Significant relationships were found between woody plants and birds, Orthoptera and terrestrial herpetofauna, and birds and aquatic herpetofauna. None of the optimal complementary networks of the groups we examined protected all species of the other groups. Nevertheless, the complementary network of woody plants adequately conserved all groups except orchids. We conclude that the principle of complementarity must be integrated into the methodology of evaluating an indicator. In an applied context, our results provide a scientific background on which to base a biomonitoring program for the Dadia Reserve. In a wider scope, if the group of woody plants prove an adequate biodiversity indicator for other Mediterranean areas as well, this will be important because it will facilitate conservation-related decisions for the entire Mediterranean region.     

Generation of Priority Research Questions to Inform Conservation Policy and Management at a National Level

Abstract: Integrating knowledge from across the natural and social sciences is necessary to effectively address societal tradeoffs between human use of biological diversity and its preservation. Collaborative processes can change the ways decision makers think about scientific evidence, enhance levels of mutual trust and credibility, and advance the conservation policy discourse. Canada has responsibility for a large fraction of some major ecosystems, such as boreal forests, Arctic tundra, wetlands, and temperate and Arctic oceans. Stressors to biological diversity within these ecosystems arise from activities of the country's resource‐based economy, as well as external drivers of environmental change. Effective management is complicated by incongruence between ecological and political boundaries and conflicting perspectives on social and economic goals. Many knowledge gaps about stressors and their management might be reduced through targeted, timely research. We identify 40 questions that, if addressed or answered, would advance research that has a high probability of supporting development of effective policies and management strategies for species, ecosystems, and ecological processes in Canada. A total of 396 candidate questions drawn from natural and social science disciplines were contributed by individuals with diverse organizational affiliations. These were collaboratively winnowed to 40 by our team of collaborators. The questions emphasize understanding ecosystems, the effects and mitigation of climate change, coordinating governance and management efforts across multiple jurisdictions, and examining relations between conservation policy and the social and economic well‐being of Aboriginal peoples. The questions we identified provide potential links between evidence from the conservation sciences and formulation of policies for conservation and resource management. Our collaborative process of communication and engagement between scientists and decision makers for generating and prioritizing research questions at a national level could be a model for similar efforts beyond Canada.     

Assessment of Management to Mitigate Anthropogenic Effects on Large Whales

United States and Canadian governments have responded to legal requirements to reduce human‐induced whale mortality via vessel strikes and entanglement in fishing gear by implementing a suite of regulatory actions. We analyzed the spatial and temporal patterns of mortality of large whales in the Northwest Atlantic (23.5°N to 48.0°N), 1970 through 2009, in the context of management changes. We used a multinomial logistic model fitted by maximum likelihood to detect trends in cause‐specific mortalities with time. We compared the number of human‐caused mortalities with U.S. federally established levels of potential biological removal (i.e., species‐specific sustainable human‐caused mortality). From 1970 through 2009, 1762 mortalities (all known) and serious injuries (likely fatal) involved 8 species of large whales. We determined cause of death for 43% of all mortalities; of those, 67% (502) resulted from human interactions. Entanglement in fishing gear was the primary cause of death across all species (n = 323), followed by natural causes (n = 248) and vessel strikes (n = 171). Established sustainable levels of mortality were consistently exceeded in 2 species by up to 650%. Probabilities of entanglement and vessel‐strike mortality increased significantly from 1990 through 2009. There was no significant change in the local intensity of all or vessel‐strike mortalities before and after 2003, the year after which numerous mitigation efforts were enacted. So far, regulatory efforts have not reduced the lethal effects of human activities to large whales on a population‐range basis, although we do not exclude the possibility of success of targeted measures for specific local habitats that were not within the resolution of our analyses. It is unclear how shortfalls in management design or compliance relate to our findings. Analyses such as the one we conducted are crucial in critically evaluating wildlife‐management decisions. The results of these analyses can provide managers with direction for modifying regulated measures and can be applied globally to mortality‐driven conservation issues. Evaluación del Manejo para Mitigar Efectos Antropogénicos sobre Ballenas Mayores     

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     

Testing Decision Rules for Categorizing Species’ Extinction Risk to Help Develop Quantitative Listing Criteria for the U.S. Endangered Species Act

Lack of guidance for interpreting the definitions of endangered and threatened in the U.S. Endangered Species Act (ESA) has resulted in case‐by‐case decision making leaving the process vulnerable to being considered arbitrary or capricious. Adopting quantitative decision rules would remedy this but requires the agency to specify the relative urgency concerning extinction events over time, cutoff risk values corresponding to different levels of protection, and the importance given to different types of listing errors. We tested the performance of 3 sets of decision rules that use alternative functions for weighting the relative urgency of future extinction events: a threshold rule set, which uses a decision rule of x% probability of extinction over y years; a concave rule set, where the relative importance of future extinction events declines exponentially over time; and a shoulder rule set that uses a sigmoid shape function, where relative importance declines slowly at first and then more rapidly. We obtained decision cutoffs by interviewing several biologists and then emulated the listing process with simulations that covered a range of extinction risks typical of ESA listing decisions. We evaluated performance of the decision rules under different data quantities and qualities on the basis of the relative importance of misclassification errors. Although there was little difference between the performance of alternative decision rules for correct listings, the distribution of misclassifications differed depending on the function used. Misclassifications for the threshold and concave listing criteria resulted in more overprotection errors, particularly as uncertainty increased, whereas errors for the shoulder listing criteria were more symmetrical. We developed and tested the framework for quantitative decision rules for listing species under the U.S. ESA. If policy values can be agreed on, use of this framework would improve the implementation of the ESA by increasing transparency and consistency. Evaluando Reglas de Decisión para Categorizar el Riesgo de Extinción de Especies con el Fin de Desarrollar de Criterios Cuantitativos de Alistamiento en el Acta de Especies en Peligro de los EE. UU.