Biology subjects

Broennimann, O.

Publications and source records attributed to Broennimann, O..

7 recordsLinked to original sources

bioRxiv2026

Widespread but cryptic introgression shapes genetic diversity in natural populations

Introgression following hybridization is increasingly recognized as a major driver of evolution. However, its importance depends on its frequency in nature, which remains to be quantified. To address this, we provide a snapshot of ongoing introgression in a whole species assemblage (4126 ant colonies). 23% of all 82 local species show signs of introgression, which is more than twice previous estimates. Introgression is typically subtle, yet contributes measurably to genetic diversity. Species divergence, rather than classical prezygotic reproductive barriers (mating phenology, ecological niche, fine-scale habitat use) constrains introgression, suggesting that the main reproductive barriers are postzygotic at this stage of divergence. Our results indicate that introgression may be a common but often overlooked feature of natural communities.

evolutionary biology↗

bioRxiv2024

LEVERAGING CITIZEN SCIENCE TO ASSESS RICHNESS, DIVERSITY, AND ABUNDANCE IN ANT COMMUNITIES

AO_SCPLOWBSTRACTC_SCPLOWCitizen science is a key resource in overcoming the logistical challenges of monitoring biodiversity. While datasets collected by groups of volunteers typically have biases, recent methodological and technological advances provide approaches for accounting for such biases, particularly in the context of modelling species distributions and diversity. Specifically, data integration techniques allow for the combination of scientifically collected datasets with haphazardly sampled presence-only datasets created by most citizen science initiatives. Here, we use a hierarchical Bayesian framework to integrate a set of ant presences collected by citizen scientists in the Vaud canton (Switzerland) with ant colony density data collected concurrently in the same region following a scientific sampling design. The community-level Poisson point process model included species-specific responses to the local (1.2 m2) and regional (1 km2) environment, with the presence-only samples incorporated at the regional scale to predict local and regional ant communities. At the regional scale, species richness followed a hump-shaped pattern and peaked near 1000 m while abundance increased with elevation. Low elevation and montane ant communities were composed of distinct species assemblages. At the local scale, the link between elevation and richness, diversity, and abundance was weak. At low elevations, local plots varied both in total abundance and species composition, while at higher elevations, the species composition was less variable. The citizen science dataset showed a general tendency toward under-representation of certain species, and heavy spatial sampling bias. Nonetheless, the inclusion of the citizen science data improved predictions of local communities, and also reduced susceptibility to over-fitting. Additionally, the citizen science dataset included many rare species not detected in the structured abundance dataset. The model described here illustrates a framework for capitalizing on the efforts of citizen scientists to better understand the patterns and distribution of biodiversity.

ecology↗

bioRxiv2023

Implementation of biotic interactions in niche analyses unravels the patterns underneath community composition in clownfishes

Biotic interactions shape the ecology of species and communities, yet their integration into ecological niche modeling methods remains challenging. Despite being a central topic of research for the past decade, the impact of biotic interactions on species distributions and community composition is often overlooked. Mutualistic systems offer ideal case studies for examining the effects of biotic I nteractions on species niches and community dynamics. This study presents a novel approach to incorporating mutualistic interactions into niche modeling, using the clownfish-sea anemone system. By adapting existing niche quantification frameworks, we developed a method to estimate the partial effects of known interactions and refine ecological niche estimates. This approach allows for a more comprehensive understanding of how mutualistic relationships influence species distributions and community assembly patterns. We also used mutualistic information to investigate the resource-use overlap, identitying patterns of competition within clownfish communities. Our results reveal significant deviations in niche estimates when biotic interactions are considered, particularly for specialist species. Host partitioning among clownfish species reduces resource-use overlap, facilitating coexistence in species-rich habitats and highlighting mutualisms role in promoting and maintaining diversity. We uncover complex dynamics in resource-use overlap among clownfish species, influenced by factors such as species richness, ecological niche overlap, and host specialization. Specialist-generalist interactions strike an optimal balance, supporting high species richness while minimizing competition. These insights enhance our understanding of clownfish biodiversity patterns, demonstrating how diverse mutualistic strategies contribute to diversity build-up and mitigate competitive exclusion in saturated communities. The analytical framework presented has broad applications beyond the clownfish-sea anemone system, potentially extending to a broader range of interactions. It enables a more comprehensive understanding of biodiversity maintenance in complex ecosystems and constitutes a valuable tool for conservation planning and ecosystem management.

ecology↗

bioRxiv2023

Conserving genetic diversity during climate change:Niche marginality and discrepant monitoring capacity in Europe

Genetic monitoring of populations currently attracts interest in the context of the Convention on Biological Diversity but needs long-term planning and investments. Genetic diversity has been largely neglected in biodiversity monitoring, and when addressed is treated separately, detached from other conservation issues, such as habitat alteration due to climate change. Genetic monitoring supports the conservation and management of fisheries, game, and threatened populations. It also can contribute to the assessment of predicted and realized impacts of climate change, and their management. We report the first accounting of genetic monitoring efforts among countries in Europe (their genetic monitoring capacity, GMC) to determine where GMC suggests the combination of national infrastructure, political support and resources for continued and expanded monitoring. Overlaying GMC with areas where species ranges approach current and future climate niche limits (i.e., niche marginality) helps identify whether GMC coincides with anticipated climate change effects on biodiversity. Our analysis suggests that country area extent, financial resources, and conservation policy influence GMC, high values of which inconsistently match joint species patterns of climate niche marginality. Populations at niche margins likely hold genetic diversity that is important to adaptation to changing climate, and our results illuminate the need in Europe for expanded genetic monitoring across the climate gradients occupied by species, a need arguably greatest in southeastern European countries.

ecology↗

bioRxiv2022

Microbial landscape ecology: landscape structure better predicts soil protist diversity than local edaphic variables in alpine meadows

ContextHuman-induced changes in landscape structure are among the main causes of biodiversity loss. Despite their important contribution to biodiversity and ecosystem functioning, microbes - and particularly protists - remain spatially understudied. Soil microbiota are most often driven by local soil properties, but the influence of the surrounding landscape is rarely assessed. ObjectivesWe assessed the effect of landscape structure on soil protist alpha and beta diversity in meadows in the western Swiss Alps. MethodsWe sampled 178 plots along an elevation gradient representing a broad range of environmental conditions and land-use. We measured landscape structure around each plot at 5 successive spatial scales (i.e. neighbourhood windows of increasing radius, ranging from 100 to 2000 m around a plot). We investigated the changes of protist alpha and beta diversity as a function of landscape structure, local environmental conditions and geographic distance. ResultsLandscape structures played a key role for protist alpha and beta diversity. The percentage of meadows, forests, or open habitats had the highest influence among all landscape metrics. The importance of landscape structure was comparable to that of environmental conditions and spatial variables, and increased with the size of the neighbourhood window considered. ConclusionsOur results suggest that dispersal from neighbouring habitats is a key driver of protist alpha and beta diversity which highlight the importance of landscape-scale assembly mechanisms for microbial diversity. Landscape structure emerges as a key driver of microbial communities which has profound implications for our understanding of the consequences of land-use change on soil microbial communities and their associated functions.

ecology↗

bioRxiv2020

Beyond range size: drivers of species' geographic range structure in European plants

AimTo assess if and how species range size relates to range structure, if the observed geographic range properties can be retrieved from predicted maps based on species distribution modeling, and whether range properties are predictable from biogeophysical factors. LocationEurope Time periodCurrent Major taxa studied813 vascular plant species endemic to Europe MethodsWe quantified the size and spatial structure of species geographic ranges and compared ranges currently occupied with those predicted by species distribution models (SDMs). SDMs were constructed using complete occurrence data from the Atlas Florae Europaeae and climatic, soil and topographic predictors. We used landscape metrics to characterize range size, range division and patch shape structure, and analysed the phylogenetic, geographic and ecological drivers of species range size and structure using phylogenetic generalized least squares (pGLS). ResultsRange structure metrics were mostly decoupled from species range size. We found large differences in range metrics between observed and predicted ranges, in particular for species with intermediate observed range size and occupied area, and species with low and high observed patch size distribution, geographic range filling, patch shape complexity and geographic range fractality. Elevation heterogeneity, proximity to continental coasts, Southerly or Easterly geographic range positions and narrow ecological niche breadth constrained species observed range size and range structure to different extents. The strength and direction of the relationships differed between observed and predicted ranges. Main conclusionsSeveral range structure metrics, in addition to range size, are needed to adequately describe and understand species ranges. Species range structure can be well explained by geophysical factors and species niche width, albeit not consistently for observed and predicted ranges. As range structure can have important ecological and evolutionary consequences, we highlight the need to develop better predictive models of range structure than provided by current SDMs, and we identify the kinds of species for which this is most necessary.

ecology↗

bioRxiv2019

Soil protist diversity in the Swiss western Alps is better predicted by topo-climatic than by edaphic variables

AimGeneral trends in spatial patterns of macroscopic organisms diversity can be reasonably well predicted from correlative models, using for instance topo-climatic variables for plants and animals allowing inference over large scales. By contrast, soil microorganisms diversity is generally considered as mostly driven by edaphic variables and, therefore, difficult to extrapolate on a large spatial scale based on predictive models. Here, we compared the power of topo-climatic vs. edaphic variables for predicting the diversity of various soil protist groups at the regional scale.\n\nLocationSwiss western Alps.\n\nTaxaFull protist community and nine clades belonging to three functional groups: parasites (Apicomplexa, Oomycota, Phytomyxea), phagotrophs (Sarcomonadea, Tubulinea, Spirotrichea) and phototrophs (Chlorophyta, Trebouxiophyceae, Bacillariophyta).\n\nMethodsWe extracted soil environmental DNA from 178 sites along a wide range of elevations with a random-stratified sampling design. We defined protist Operational Taxonomic Units assemblages by metabarcoding of the V4 region of the ribosomal RNA small sub-unit gene. We assessed and modelled the diversity (Shannon index) patterns of all selected groups as a function of topo-climatic and edaphic variables using Generalized Additive Models.\n\nResultsThe respective significance of topo-climatic and edaphic variables varied among taxonomic and - to a certain extent - functional groups: while many variables explained significantly the diversity of phototrophs this was less the case for parasites. Generally, topo-climatic variables had a better predictive power than edaphic variables, yet predictive power varied among taxonomic and functional groups.\n\nMain conclusionsTopo-climatic variables are, on average, better predictors of protist diversity at the landscape scale than edaphic variables, which opens the way to wide-scale sampling designs avoiding costly and time-consuming laboratory protocols. However, predictors of diversity differ considerably among taxonomic and functional groups; such relationships may be due to direct and/or indirect, e.g. biotic influences. Future prospects include using such spatial models to predict hotspots of diversity or pathogens outbreaks.

ecology↗