An ecological connectivity network maintains genetic diversity of a flagship wildflower, Pulsatilla vulgaris

Ecological connectivity networks have been proposed as an efficient way to reconnect communities in fragmented landscapes. Yet few studies have evaluated if they are successful at enhancing actual functional connectivity (i.e. realized dispersal or gene flow) of focal species, or if this enhanced connectivity is enough to maintain genetic diversity and fitness of plant populations. Here we test the efficacy of an ecological connectivity network implemented in southern Germany since 1989 to reconnect calcareous grassland fragments through rotational shepherding. We genotyped 1449 individuals from 57 populations and measured fitness-related traits in 10 populations of Puisatilla vulgaris, a flagship species of calcareous grasslands in Europe. We tested if the shepherding network explained functional connectivity in P. vulgaris and if higher connectivity translated to higher genetic diversity and fitness of populations. We found that population-specific F-st was lowest in populations that had high connectivity within the shepherding network, and that well-connected populations within the network had significantly higher genetic diversity than ungrazed and more isolated grazed populations. Moreover, genetic diversity was significantly positively correlated with both seed set and seed mass. Together our results suggest that the implementation of an ecological shepherding network is an effective management measure to maintain functional connectivity and genetic diversity at the landscape scale for a calcareous grassland specialist. Populations with reduced genetic diversity would likely benefit from inclusion, or better integration into the ecological connectivity network. Our study demonstrates the often postulated but rarely tested sequence of positive associations between connectivity, genetic diversity, and fitness at the landscape scale, and provides a framework for testing the efficacy of ecological connectivity networks for focal species using molecular genetic tools.Peer reviewe

Data from: Directed dispersal by rotational shepherding supports landscape genetic connectivity in a calcareous grassland plant

Directed dispersal by animal vectors has been found to have large effects on the structure and dynamics of plant populations adapted to frugivory. Yet, empirical data are lacking on the potential of directed dispersal by rotational grazing of domestic animals to mediate gene flow across the landscape. Here, we investigated the potential effect of large-flock shepherding on landscape-scale genetic structure in the calcareous grassland plant Dianthus carthusianorum, whose seeds lack morphological adaptations to dispersal to animals or wind. We found a significant pattern of genetic structure differentiating population within grazed patches of three nonoverlapping shepherding systems and populations of ungrazed patches. Among ungrazed patches, we found a strong and significant effect of isolation by distance (r = 0.56). In contrast, genetic distance between grazed patches within the same herding system was unrelated to geographical distance but significantly related to distance along shepherding routes (r = 0.44). This latter effect of connectivity along shepherding routes suggests that gene flow is spatially restricted occurring mostly between adjacent populations. While this study used nuclear markers that integrate gene flow by pollen and seed, the significant difference in the genetic structure between ungrazed patches and patches connected by large-flock shepherding indicates the potential of directed seed dispersal by sheep across the landscape

A functional trait‐based approach to assess the impact of an alien palm invasion on plant and soil communities on a South Pacific island

International audienc

Simulating the spread and establishment of alien species along aquatic and terrestrial transport networks: A multi-pathway and high-resolution approach

The introduction and further spread of many alien species have been a result of trade and transport. Consequently, alien species are often found close to traffic infrastructure and urban areas. To contain and manage the spread of alien species, it is essential to identify and predict major routes of spread, which cannot be obtained by applying common modelling approaches such as species distribution models. Here, we present a new model called CASPIAN to simulate the dispersal of alien species along traffic infrastructure and the establishment of populations along these routes. The model simulates simultaneous spread of species of up to eight different modes of transport along roads, railways and waterways. We calibrated and validated the model using two species that spread within Germany as case studies: the terrestrial plant Senecio inaequidens and the freshwater clam Corbicula fluminea, and performed a shortest path analysis to quantify the relative importance of individual routes for spread. The application of the model yielded detailed predictions of dispersal and establishment for >600,000 segments of the traffic network throughout Germany. Once calibrated, the model captured the general spread dynamics of the two species with higher accuracy for the freshwater environment due to the higher quality of data available for the aquatic species. The quantification of spread routes using the shortest path analysis revealed a clear backbone of major routes of spread, which varied depending on the type of traffic network and the starting points considered. Major routes of spread aligned with high traffic intensities, but high traffic per se did not necessarily result in high spread intensities. Synthesis and application. By simulating the spreading dynamics of alien species along transport networks across multiple pathways, CASPIAN enables the identification of major spread routes along different dispersal pathways and quantification of their relative importance, which helps prioritising pathways of introduction as required by international biodiversity goals such as the CBD Aichi targets.We thank the “BMVI Network of Experts” of the Federal Ministry of Transport and Digital Infrastructure (BMVI) of Germany for funding through the Federal Railway Authority of Germany (project number 2017-U-10-1210). We thank for their valuable input: Marion Leiblein-Wild (Federal Railway Authority, Germany); Katja Broeg, Nicole Heibeck, Mariusz Zabrocki (Federal Maritime and Hydrographic Agency of Germany); Daniel Esser, Andreas Sundermeier (German Federal Institute of Hydrology) and Pia Bartels (Federal Highway Research Institute of Germany). Open access funding enabled and organized by Projekt DEAL

Monitoring global tree mortality patterns and trends. Report from the VW symposium ‘Crossing scales and disciplines to identify global trends of tree mortality as indicators of forest health’

While global forest growth assessments have been carried out, no study has attempted to generate spatially explicit models of global tree mortality, which are necessary to generate a mechanistic understanding and to robustly quantify mortality at a global scale. The current initiative can build upon: (1)an increasing amount of data on forest ecosystems, including national forest inventories and monitoring, as well as an increasing number of research plot networks in all forested biomes; (2) a growing willingness of scientists and governmental agencies to openly share data; and (3) a greater availability of powerful tools for assessing and monitoring forests at broad spatial scales, such as remote-sensing products from satellites or airborne LIDAR. Despite this progress, current monitoring approaches are still incomplete in their spatial extent and data resolution is often inadequate for detecting scattered individual tree mortality and for identifying causal relationships between drivers of change in forest condition