Climate change and invasive species are leading drivers of biodiversity loss. Invasive species thrive due to their adaptability to diverse conditions, high reproductive output, and effective dispersal strategies. Climate change amplifies these traits by expanding the environmental tolerances that promote invasiveness. Island ecosystems are particularly susceptible to invasive species due to limited habitable space, small populations, and low ecological redundancy. South Georgia, a remote sub-Antarctic Island, is 170 km long with approximately 30,000 ha of vegetated coastal areas, as snow and ice dominate inland. Human activities on the island have historically introduced non-native species, resulting in 41 introduced vascular plant species compared with only 24 native ones. To address this imbalance, the South Georgia Non-Native Plant Management Strategy was implemented (2016–2020) to control non-native plant populations. We assessed seeds in South Georgia soil samples to identify which plant species were present and which non-natives had likely formed a persistent seed bank requiring continued above-ground control. Using a molecular barcoding approach, we evaluated traditional markers (rbcL and matK) and optimized a high-throughput sequencing method for accurate seedling identification. Soil samples collected from key areas of the island were analysed to identify emerging seedlings, providing insights into the persistence of invasive plant species in the seed bank and the impact of management efforts. This study highlights the importance of molecular tools for identifying invasive species and informing their management. It offers a framework for monitoring and mitigating invasive species under climate change pressures.

TitleConservation implications of the current population structure of Malagasy baobab Adansonia suarezensis (Malvaceae) using genomics and habitat survey data

Kaitalin White1*, Freya Cornwell-Davison2*, Christopher Cockel1, Ted Chapman 1, Efisio Mattana1, Juan Viruel2†

Jungle Ke Liang1,2, Amelia Shepherd-Clowes1, Pablo Tejero Ibarra3,4*, Juan Viruel1*† 1Royal Botanic Gardens, Kew, Richmond, TW9 3DS, England2Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, PO Box 94240, 1090GE, Amsterdam, The Netherlands3Instituto Pirenaico de Ecología (IPE-CSIC), Av. Nuestra Señora de la Victoria 16, 22700 Jaca, Huesca, Spain                 4Aranzadi Zientzia Elkartea, Zorroagagaina 11, 20014 Donostia, Spain * Both authors contributed as senior authors to this publication.† Author for correspondence (j.viruel@kew.org, juanviruel@gmail.com) Jungle Ke Liang: k.liang@kew.orgAmelia Shepherd-Clowes: A.Shepherd-Clowes@kew.orgPablo Tejero Ibarra: ptibarra@aranzadi.eus

Estimating effective population size (Ne) is essential for theoretical and practical applications in evolutionary biology and conservation. Nevertheless, estimates of Ne in organisms with complex life-history traits remain scarce because of the challenges associated with estimation methods. Partially clonal plants capable of vegetative (clonal) growth and sexual reproduction are a common group of organisms in which the discrepancy between the apparent number of individuals (ramets) and the number of genetic individuals (genets) may be striking, and it is unclear how this discrepancy relates to Ne. In this study, we analysed two populations of the orchid Cypripedium calceolus to understand how the rate of clonal vs. sexual reproduction impacted Ne. We sampled and genotyped >1000 ramets at microsatellites and SNPs loci, and estimated contemporary Ne with the linkage disequilibrium method, starting from the theoretical expectation that variance in reproductive success among individuals caused by clonal reproduction and by constraints on sexual reproduction would lower Ne. We considered factors potentially affecting our estimates, including using different molecular markers and sampling strategies, and pseudoreplication in genomic datasets. The magnitude of Ne/Nramets and Ne/Ngenets ratios we provide may be used as reference points for other species with similar life-history traits. Our findings demonstrate that Ne in partially clonal plants cannot be predicted based on the number of genets generated by sexual reproduction because demographic changes over time strongly influence Ne. This is especially relevant in species of conservation concern, in which population declines may not be detected by only ascertaining the number of genets.

Intense research efforts on phylogeography over the last two decades uncovered major biogeographical trends and renewed our understandings of plant domestication in the Mediterranean. We aim to investigate the evolutionary history and the origin of domestication of the carob tree that has been cultivated for millennia for food and fodder. We used >1000 microsatellite genotypes to identify carob evolutionary units (CEUs) based on genetic diversity structure and geography. We investigated genome-wide diversity and evolutionary patterns of the CEUs with 3557 SNPs generated by restriction-site associated DNA sequencing (RADseq). The 56 populations sampled across the Mediterranean basin, classified as natural, semi-natural or cultivated, were examined. Although, RADseq data are consistent with previous studies identifying a strong West-to-East genetic structure and considerable admixture in some geographic parts, we reconstructed a new phylogeographic scenario with two migration routes occurring from a single refugium likely located in South-Western Morocco. Our results do not favour the regionally bound or single origin of domestication. Indeed, our findings support a cultivation model of locally selected wild genotypes, albeit punctuated by long-distance westward dispersals of domesticated varieties by humans, concomitant with major cultural waves by Romans and Arabs in the regions of dispersal. Ex-situ efforts to preserve carob genetic resources should prioritize accessions from both western and eastern populations, with emphasis on the most differentiated CEUs situated in South-Western Morocco, South Spain and Eastern Mediterranean. Our study underscores the relevance of natural and seminatural habitats of Mediterranean forests and their refugia in the conservation efforts of tree crops.

Background and aims. Among the numerous pantropical species of the yam genus, Dioscorea, only a small group occurs in the Mediterranean basin, including two narrow Pyrenean endemics (Borderea clade), and two Mediterranean-wide species (D. communis and D. orientalis, Tamus clade). However, several currently unrecognized species and infraspecific taxa have been described in the Tamus clade due to significant morphological variation associated with D. communis. Our overarching aim was to investigate taxon delimitation in the Tamus clade using an integrative approach combining phylogenomic, spatial and morphological data.Methods. We analysed 76 herbarium samples using Hyb-Seq genomic capture to sequence 260 low-copy nuclear genes and plastomes, together with morphometric and environmental modelling approaches.Key results. Phylogenomic reconstructions confirmed that the two previously accepted species of the Tamus clade, D. communis and D. orientalis, are monophyletic and form sister clades. Three subclades showing distinctive geographic patters were identified within D. communis. These subclades were also identifiable from morphometric and climatic data, and introgression patterns were inferred between subclades in the eastern part of the distribution of D. communis. Conclusions. We propose a taxonomy that maintains D. orientalis, endemic to the eastern Mediterranean region, and splits D. communis sensu lato into three species: D. edulis, endemic to Macaronesia (Canary Islands and Madeira); D. cretica, endemic to the eastern Mediterranean region; and D. communis sensu stricto, widespread across western and central Europe. Introgression inferred between D. communis s.s. and D. cretica is likely to be explained by their relatively recent speciation at the end of the Miocene, disjunct isolation in eastern and western Mediterranean glacial refugia and a subsequent westward recolonization of D. communis s.s. Our study shows that the use of integrated genomic, spatial and morphological approaches allows a more robust definition of species boundaries and the identification of species that previous systematic studies failed to uncover.