AbstractAimDispersal strategies are vital for sessile or passively moving organisms, profoundly influencing the distribution and survival of plant and small-sized animal species. The role of large mammals in dispersal and habitat (re)colonization is recognized, yet their full contribution across propagule taxa, various dispersers, and dispersal modes remains unclear. We assessed the role of common wild mammals in dispersing (semi-aquatic) plants and micro-invertebrates among isolated wetlands, identifying the most effective dispersal agent(s) within a natural assemblage.LocationNortheast Germany.MethodsIn a system of small semi-natural wetlands within an intensive agricultural landscape, we combined non-invasive fecal sampling with opportunistic fur collection from managed and trapped mammals, cultivating plants and micro-invertebrates from these samples to explore dispersal-network structures and quantify taxon richness and propagule abundances, comparing disperser effectiveness.ResultsWe found distinct network topologies for (semi-aquatic) plants and micro-invertebrates, indicating differential contributions and complementary roles of disperser groups and dispersal modes. Roe deer, wild boar, and raccoons were key dispersers, highlighting the broad role of generalist mammals in wetland propagule dispersal. In micro-invertebrates, endozoochorous communities were nested within more diverse epizoochorous communities, with both raccoons and wild boar transporting more diverse taxa through epizoochory. No quantitative differences in endozoochorous dispersal emerged among dispersers. Transported plant communities were dominated by taxa lacking predefined zoochorous syndromes, challenging assumptions about trait-based dispersal constraints.Main conclusionsThe broad spectrum of wild mammals identified as dispersers, supported by quantitative means, offers significant potential for facilitating efficient dispersal of both, plants and micro-invertebrates, consistent with the concept of ‘non-classical zoochory’. Dispersal by abundant and also managed mammals is crucial for ecosystem connectivity and resilience. Altered disperser communities due to population control or habitat changes may affect (re)colonization and local biodiversity, highlighting the need for strategies that preserve dispersal functions across landscapes.

Understanding the environmental impact on the assembly of local communities in relation to their spatial and temporal connectivity is still a challenge in metacommunity ecology. This study aims to unravel underlying metacommunity processes and environmental factors that result in observed zooplankton communities. Unlike most metacommuniy studies, we jointly examine active and dormant communities using a DNA metabarcoding approach to overcome limitations of morphological species identification. We applied two-fragment (COI and 18S) metabarcoding to monitor communities of 24 kettle holes over a two-year period to unravel (I) spatial and temporal connectivity of the communities, (II) environmental factors influencing local communities, and (III) dominant underlying metacommunity processes in this system. We found a strong separation of zooplankton communities from kettle holes of different hydroperiods (degree of permanency) throughout the season, while the community composition within single kettle holes did not differ between years. Species richness was primarily dependent on pH and permanency, while species diversity (Shannon Index) was influenced by kettle hole location. Community composition was impacted by kettle hole size and surrounding field crops. Environmental processes dominated temporal and spatial processes. Sediment communities showed a different composition compared to water samples, but did not differ between ephemeral and permanent kettle holes. Our results suggest that communities are mainly structured by environmental filtering based on pH, kettle hole size, surrounding field crops, and permanency. Environmental filtering based on specific conditions in individual kettle holes seems to be the dominant process in community assembly in the studied zooplankton metacommunity. Understanding the environmental impact on the assembly of local communities in relation to their spatial and temporal connectivity is still a challenge in metacommunity ecology. This study aims to unravel underlying metacommunity processes and environmental factors that result in observed zooplankton communities. Unlike most metacommunity studies, we jointly examine active and dormant zooplankton communities using a DNA metabarcoding approach to overcome limitations of morphological species identification. We applied two-fragment (COI and 18S) metabarcoding to monitor communities of 24 kettle holes over a two-year period to unravel (I) spatial and temporal connectivity of the communities, (II) environmental factors influencing local communities, and (III) dominant underlying metacommunity processes in this system. We found a strong separation of zooplankton communities from kettle holes of different hydroperiods (degree of permanency) throughout the season, while the community composition within single kettle holes did not differ between years. Species richness was primarily dependent on pH and permanency, while species diversity (Shannon Index) was influenced by kettle hole location. Community composition was impacted by kettle hole size and surrounding field crops. Environmental processes dominated temporal and spatial processes. Sediment communities showed a different composition compared to water samples, but did not differ between ephemeral and permanent kettle holes. Our results suggest that communities are mainly structured by environmental filtering based on pH, kettle hole size, surrounding field crops, and permanency. Environmental filtering based on specific conditions in individual kettle holes seems to be the dominant process in community assembly in the studied zooplankton metacommunity.    

Northern range margin populations of the European fire-bellied toad (Bombina bombina) have rapidly declined during recent decades. Extensive agricultural land use has fragmented the landscape, leading to habitat disruption and loss, as well as eutrophication of ponds. In Northern Germany (Schleswig-Holstein) and Southern Sweden, this decline resulted in decreased gene flow from surrounding populations, low genetic diversity, and a putative reduction in adaptive potential, leaving populations vulnerable to future environmental and climatic changes. Previous studies using mitochondrial control region and nuclear transcriptome-wide SNP data detected introgressive hybridization in multiple northern B. bombina populations after presumed illegal release of toads from Austria. Here, we determine the impact of this introgression by comparing the body conditions (as a proxy for fitness) of introgressed and non-introgressed populations, and the genetic consequences in two candidate genes for putative local adaptation (the MHC II gene as part of the adaptive immune system and the stress response gene HSP70 kDa). We detected regional differences in body condition. We observed significantly elevated levels of within individual MHC allele counts in introgressed Swedish populations, associated with a tendency towards higher body weight, relative to regional non-introgressed populations. These differences were not observed among introgressed and non-introgressed German populations. Genetic diversity in both MHC and HSP was generally lower in northern than southern populations. Our study sheds light on the potential benefits of translocations of more distantly related conspecifics as a means to increase adaptive genetic variability and fitness of struggling range margin populations without distortion of local adaptation.