Biology subjects

Bachman, S.

Publications and source records attributed to Bachman, S..

5 recordsLinked to original sources

bioRxiv2026

A framework for measuring national trends in the extinction risk of evolutionarily distinct species using the EDGE Index

The biodiversity crisis is threatening evolutionarily distinct species, those that constitute long periods of unique evolutionary history or that are from highly imperilled lineages. The EDGE (Evolutionarily Distinct and Globally Endangered) index was designed to track the changing extinction risks of these species and is listed as an indicator in the Kunming-Montreal Global Biodiversity Framework. Here, we provide a set of guidelines for calculating the EDGE index at the national level and for addressing data uncertainty. We distinguish two approaches for calculating a country-level EDGE index, either generated directly by using national data or from disaggregated global data. Using two national Red Lists, we show the contrasting state of high evolutionarily distinct nesting birds across French territories, and the elevated threat status of high evolutionarily distinct endemic species for South African vertebrates. Using global extinction risk data, we then reveal the deteriorating state of birds, mammals, and amphibians over time, and we highlight the countries with the highest proportions of threatened evolutionarily distinct species. Application of these guidelines should aid countries in monitoring their evolutionarily irreplaceable species, which in turn can help target local conservation actions, while contributing to global efforts to preserve the tree of life.

evolutionary biology↗

bioRxiv2025

Causal modelling reveals lower coral genetic diversity in more heterogenous reef environments

Conserving genetic diversity is crucial for maintaining species evolutionary potential and resilience to environmental change. Yet, directly measuring genetic diversity across large spatial scales remains resource-intensive and impractical for conservation planning. Identifying reliable, accessible, and cost-effective spatial predictors of genetic diversity would significantly enhance our ability to incorporate genetic diversity into conservation efforts. Caribbean coral reefs represent a compelling system for investigating such predictors, as these ecosystems face unprecedented threats from disease outbreaks and climate change. Here, we investigate the utility of several environmental proxies as surrogates for genetic diversity, which may be useful for conservation planning in resource- or data-poor regions. To achieve this goal, we used reduced-representation genomic sequencing to estimate intraspecific genetic diversity, and in doing so, identified two genetically distinct and sympatric cryptic coral species in the Agaricia tenuifolia species complex. We employed a causal inference approach to assess the relationships between genetic alpha diversity and habitat area and connectivity, habitat heterogeneity, and temperature. Statistical investigations revealed that increased habitat heterogeneity, derived from remotely sensed habitat maps, was associated with lower genetic diversity within coral populations, suggesting that habitat characteristics promoting species diversity may not maintain high genetic diversity within a single species. Habitat area and connectivity, and temperature have predominantly negative effects on genetic diversity with coral habitat area and connectivity showing markedly contrasting responses in two cryptic taxa. Thus, our findings reveal that context matters greatly, as results differ between cryptic species, across variables, and among spatial scales.

evolutionary biology↗

bioRxiv2025

Setting priorities for the acquisition of primary plant occurrence data

AimEffective implementation of the Global Biodiversity Framework and Global Strategy for Plant Conservation depends on accurate species distribution data. Current vascular plant distribution data, while crucial for understanding terrestrial ecosystems, is often sparse and biased and requires significant expansion. This study developed a scalable approach to prioritize areas for plant occurrence data acquisition, adaptable to national priorities and providing a framework for botanical institutions to coordinate efforts and allocate resources. LocationGlobal. MethodsUsing a Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) analysis, we prioritized areas based on: (a) ecosystem service value; (b) floristic value threatened by climate or land-use change; and (c) uncertainty in species richness estimates, stratified by biome and region. Regional prioritization maps for Africa & Madagascar; East, South and Southeast Asia; Siberia and the Russian Far East; South America; and North & Central America were reviewed by botanical experts for validation. Scalability was assessed by comparing regional and global analyses. ResultsData-driven priority maps, divided into tree-dominated and grassland/deforested areas, largely received expert support. High similarity between global and regional maps demonstrated scalability. Main conclusionsOur approach provides a framework for supporting national implementation of the Global Biodiversity Framework. Variables and their weights can be tailored to national or local needs. The methods flexibility and adaptability extend to other taxonomic groups and objectives, such as protected area selection By prioritizing data acquisition, whether field-based or digital, this research promotes the efficient use of resources. A key advantage of this approach is its capacity to systematically translate expert opinion into explicit and quantitative criteria, which in turn facilitates clear communication with policymakers and funders.

plant biology↗

bioRxiv2023

Species abundances often conform to 'abundant-centre' patterns depending on dispersal capabilities

A shared goal within macroecology, biogeography and population ecology research is to understand biodiversity patterns and the processes driving them across spatial and taxonomic scales. A common approach to study macroecological patterns and processes involves developing and testing ecogeographical rules or hypotheses. The much-debated abundant-centre hypothesis posits that species abundances are highest in their range centres and decline towards their range edges. We perform the largest global test of the hypothesis to date, on 3,675 species, using 6,055,549 abundance observations. Using meta-analytical approaches, we summarised species-level abundance-distance correlations exploring the effects of dispersal-related species traits on abundance-distance relationships. Overall, animals did not follow abundant-centre patterns, whereas plants tended to. Larger-bodied mammals were more likely to conform to abundant-centre patterns, as were mammals and freshwater fishes from higher latitudes. Perennial life cycles and large range sizes were significant predictors of abundant-centre patterns in plants. Trees and shrubs with larger seeds showed more support for abundant-centre patterns. Accounting for species dispersal improves models of abundant-centre patterns across geographic space. Assuming abundant-centre patterns represent optimal equilibria within nature, our findings suggest that abundant-centre relationships are not a general ecological phenomenon but tend to manifest only in species with higher dispersal capabilities.

ecology↗

bioRxiv2020

Survival of the salient: Emotion rescues otherwise forgettable memories via neural reactivation and post-encoding hippocampal connectivity

Emotions selective effects on memory go beyond the simple enhancement of threatening or rewarding stimuli. They can also rescue otherwise forgettable memories that share overlapping features. Here, we use functional magnetic resonance imaging (fMRI) to examine the brain mechanisms that support this retrograde memory enhancement. In a two-phase incidental encoding paradigm, participants first view images of neutral tools and animals. During Phase 1, these images are intermixed with neutral scenes, which provides a unique context tag for this specific phase of encoding. A few minutes later, during Phase 2, new pictures from one category are paired with a mild shock (fear-conditioned stimulus; CS+), while pictures from the other category are not shocked. fMRI analyses reveal that, across participants, retroactive memory benefits for Phase 1 CS+ items are associated with greater phasic reinstatement of the prior mental context during Phase 2 CS+ items. We also see that greater VTA/SN activation during Phase 2 CS+ items relates to this retroactive memory enhancement, suggesting that emotion promotes both the encoding and ongoing consolidation of overlapping representations. Additionally, we find that emotional experience-dependent changes in post-encoding hippocampal functional coupling with CS+ category-selective cortex relate to the magnitude of the retroactive memory effect. These hippocampal connectivity patterns also mediate the relationship between dopaminergic emotional encoding effects and across-participant variability in the retroactive memory benefit. Collectively, our findings suggest that an interplay between online and offline brain mechanisms may enable emotion to preserve seemingly mundane memories that become significant in the future.

neuroscience↗