Biology subjects

Pozzi, A. V.

Publications and source records attributed to Pozzi, A. V..

4 recordsLinked to original sources

bioRxiv2026

geoGraph: Connectivity modelling across geographic space with hexagonal discrete global grids

1. Estimating the movement and connectivity of organisms across landscapes is central to research in ecology and evolutionary biology. Although graph-based approaches representing geographic space as weighted networks provide a flexible and computationally efficient framework for such analyses, existing tools either perform their computations only on rectangular raster grids, thus introducing systematic directional and area distortions at global scales, or rely on bespoke pipelines that limit the general applicability of recent hexagonal-grid analyses. 2. To overcome these shortcomings, here we present geoGraph, an R package that brings graph-based spatial modelling to discrete global hexagonal grids. By representing landscapes on an equal-area hexagonal tessellation of the sphere, geoGraph enables global-scale analysis without projection distortion while retaining the flexibility of the graph framework and the performance of the graph and RBGL/Boost libraries. The package integrates both raster- and vector-based GIS data into a single cost surface, supports custom grids at various resolutions, and provides a complete pipeline from raw GIS layers to graph-algorithmic outputs, together with tools for visualising and interactively editing graphs. 3. We illustrate geoGraph by revisiting previous studies of isolation by distance among human populations in the Human Genome Diversity Project panel. At a global scale, restricting movement to land raised the correlation between geographic and genetic distance from r = 0.74 (great-circle) to r = 0.84. On a finer grid within Asia, accounting for terrain ruggedness improved the fit, with the best-fitting models implying reduced movement across the Himalaya and Tibetan Plateau. These analyses demonstrate that geoGraph can model movement and connectivity appropriate to the desired spatial scale and that the level of geographic realism required is itself scale-dependent. 4. By combining discrete global grids with the power of graph algorithms, geoGraph enables seamless connectivity analysis from landscape to global scales. It is broadly applicable across landscape genetics, phylogeography, conservation planning, and studies of human dispersal, and is particularly suited to large-scale problems that rectangular-raster tools cannot address without distortion.

bioinformatics↗

bioRxiv2025

Climate Shaped the Global Population Structure of Leopards and their Extinction in Europe

Environmental change is often invoked as a key force shaping species evolution and demography, but quantifying its role is challenging. Leopards (Panthera pardus), a widely distributed generalist species, provide an ideal case for studying the role of the environment. The population dynamics of African and Asian leopards differ dramatically, with near panmixia in Africa versus a strong structure and eight subspecies in Asia. Fossil records show that a population in Europe disappeared after the Last Glacial Maximum (LGM), further pointing to complex range dynamics in Eurasia. In this study, we explicitly test the role of climate in shaping leopards population dynamics across the continents, by quantitatively combining paleoclimatic, demographic, and genetic simulations over the last 450 thousand years. Using an Approximate Bayesian Computational framework, we show that the genetic structure differences between Africa and Asia can be explained by distinct historical climatic conditions in these two continents: most of sub-Saharan Africa and parts of Southeast Asia exhibited a stable range without geographical barriers, while other areas such as Morocco, Afghanistan and Northeast Asia showed expansion and extinction cycles during glacial and interglacials. We further model population dynamics in Europe and validate it against fossil and radiocarbon dates records. We find that European populations were likely fragile, with extinctions repeatedly predicted over multiple glacial cycles, indicating that climate change possibly led to the extinction of the European subspecies following the LGM. Notably, we found that climate during the Holocene should have allowed a more recent recolonisation that did not happen, indicating other factors such as human presence might have blocked it.

zoology↗

bioRxiv2025

tidygenclust: Clustering for Population Genetics in R

BackgroundPopulation structure analysis is crucial for evolutionary research and medical genomics. Clustering methods, broadly categorized as model-based (e.g. ADMIXTURE) or non-model-based (e.g. SCOPE), differ in their methodology and computational efficiency. Recently, fastmixture, a model-based approach, has improved scalability and performance, while replicate alignment tools, such as Clumppling, extend previous methods by also aligning the modes across K values. However, all the existing tools are standalone and generate numerous untracked text files, as well as offering limited plot customisability. ResultsWe introduce an R package, tidygenclust, which brings the functionalities of the original ADMIXTURE, fastmixture and Clumppling software into R, enabling a streamlined and integrated workflow. By integrating with tidypopgen, a package designed to handle large SNP datasets, these new tools maintain metadata, simplify data handling, and produce results as customisable ggplot2 objects for flexible visualisation. ConclusionsThe R package tidygenclust advances population genetic analysis by combining computational efficiency with reproducible workflows and user-friendly plotting. The source code and instructions can be accessed on https://github.com/EvolEcolGroup/tidygenclust.

bioinformatics↗

bioRxiv2023

High standing diversity masks extreme genetic erosion in a declining snake.

Average heterozygosity is frequently used as a proxy for genetic health, and to compare genetic diversity between species and populations. However, this measurement could be misleading if the distribution of heterozygosity across the genome is highly skewed. We investigated this pitfall in methodology using whole-genome sequencing of the adder (Vipera berus), a species experiencing dramatic declines in the UK. We find that mean heterozygosity in adders is notably high, exceeding that of other vertebrates typically regarded as genetically diverse. Their genome-wide distribution of heterozygosity, however, approximates a negative exponential distribution, with most genome regions showing extremely low heterozygosity. Modelling approaches show that this pattern is likely to have resulted from a recent, severe bottleneck and fragmentation most likely caused by anthropogenic activity in a previously large, interconnected adder population. Our results highlight that high standing diversity may mask severe genetic erosion when declines are recent and rapid. In such situations, whole-genome sequencing may provide the best option for genetic risk assessment and targeted conservation actions.

genomics↗