Chevonne Reynolds

Biological invasions are natural experiments for studying the evolutionary and ecological processes underlying colonization success and range expansion. Using genome-wide data—generated via genotyping-by-sequencing (GBS) from 30 populations spanning Europe and South Africa—we investigated the colonization history and successful spread of the invasive buttonweed Cotula coronopifolia, an annual plant introduced into Europe from South Africa about 300 years ago. Our analyses identified three major lineages in Europe distributed across the continent, often co-occurring without evidence of admixture. Phylogenomic dating revealed that these lineages diverged > 2,000 years ago—well before the earliest European records—suggesting divergence within the native range and either multiple introductions or a single introduction with multiple lineages. Mating-system inference shows that reproduction occurs primarily via self-fertilization (∼70% on average), although outcrossing predominates in some populations, revealing a facultative mating system. This high selfing rate has led to extremely low heterozygosity in most populations and a strong genetic structure. Genetic clustering also revealed admixed individuals resulting from rare inter-lineage outcrossing; comparisons of empirical and simulated data indicate that increased diversity after sporadic admixture events decays rapidly under subsequent selfing. Both the introduction history and long-distance dispersal facilitated by waterbirds likely explain the scattered distribution of lineages across Europe. Altogether, these results illustrate Baker's “ideal weed” concept, highlighting the role of a flexible mating system in providing reproductive assurance during colonization and showing how predominant selfing can shape the genomic landscape of an invasive species.

Biological invasions are natural experiments for studying the evolutionary and ecological processes underlying colonization success and range expansion. Using genome-wide data — generated via genotyping-by-sequencing (GBS) from 30 populations spanning Europe and South Africa— we investigated the colonization history and successful spread of the invasive buttonweed Cotula coronopifolia , an annual plant introduced into Europe from South Africa about 300 years ago. Our analyses identified three major lineages in Europe distributed across the continent, often co-occurring without evidence of admixture. Phylogenomic dating revealed that these lineages diverged > 2,000 years ago —well before the earliest European records— suggesting divergence within the native range and either multiple introductions or a single introduction with multiple lineages. Mating-system inference shows that reproduction occurs primarily via self-fertilization (∼70% on average), although outcrossing predominates in some populations, revealing a facultative mating system. This high selfing rate has led to extremely low heterozygosity in most populations and a strong genetic structure. Genetic clustering also revealed admixed individuals resulting from rare inter-lineage outcrossing; comparisons of empirical and simulated data indicate that increased diversity after sporadic admixture events decays rapidly under subsequent selfing. Both the introduction history and long-distance dispersal facilitated by waterbirds likely explain the scattered distribution of lineages across Europe. Altogether, these results provide an empirical demonstration of Baker’s “ideal weed” concept, highlighting the role of a flexible mating system in providing reproductive assurance during colonization and showing how predominant selfing shapes the genomic landscape of an invasive species. SIGNIFICANCE STATEMENT: Understanding how reproductive strategies influence colonization and spread of alien species is central to invasion biology. By combining population genomics and phylogenomic inference, this study provides key insights into the colonization history and successful invasion of the self-fertilizing plant C. coronopifolia , introduced from South Africa to Europe in the 18 ^th century. We show that the species’ invasion success relies on the introduction of multiple lineages and the predominance of selfing, which has drastically reduced genetic diversity yet contributed to reproductive assurance and spread across diverse habitats. Occasional outcrossing and long-distance dispersal by waterbirds or through horticultural transport have further shaped the species’ genetic landscape. These findings illustrate how self-compatibility and ecological generalism can overcome genetic constraints during range expansion and provide the basis for understanding the evolutionary dynamics of selfing plant invasions.

Insects are the most diverse and functionally important animals on Earth. In at least some regions, terrestrial populations are declining. Despite this, insects are often overlooked in conservation policy, and it is difficult to assess how anthropogenic threats and conservation actions affect insect populations. The Kunming‐Montreal Global Biodiversity Framework (GBF) aims to reduce pressures on biodiversity, increase conservation efforts, and reverse losses. At the International Congress on Conservation Biology in 2023, we convened a round table of specialist scientists and practitioners in insect ecology and conservation to explore how well the GBF addresses insect declines. We discussed and evaluated: (1) how well GBF targets could deliver for insects, and (2) whether the indicators proposed for monitoring progress would detect changes in the status of insects. We found that although the GBF's targets can drive action for insect recovery, almost none of the indicators can effectively measure progress for insects. We propose four principles to enhance the effectiveness of biodiversity policy for insects, and recommend the establishment of a global working group to develop insect‐focused indicators. If implemented effectively, such indicators could provide evidence of whether restoration and conservation actions are putting us on a path to recovery of global biodiversity.

Maintaining biodiversity is central to the sustainable development agenda ¹ . However, a lack of context-specific biodiversity information at policy-relevant scales has posed major limitations to decision-makers ^2,3 . To address this challenge, we undertook a comprehensive assessment of the biodiversity intactness of sub-Saharan Africa ⁴ using place-based knowledge of 200 African biodiversity experts ⁵ . We estimate that the region has on average lost 24% of its pre-colonial and pre-industrial faunal and floral population abundances, ranging from losses of <20% for disturbance-adapted herbaceous plants to 80% for some large mammals. Rwanda and Nigeria are the least intact (85%). Notably, most remaining organisms occur in unprotected, relatively untransformed rangelands and natural forests. Losses in biodiversity intactness in the worst-affected biomes are driven by land transformation into cropland in grasslands and fynbos (Mediterranean-type ecosystems), by non-agricultural degradation in forests and by a combination of the two drivers in savannas. This assessment provides decision-makers with multifaceted, contextually appropriate and policy-relevant information on the state of biodiversity in an understudied region of the world. Our approach could be used in other regions, including better-studied localities, to integrate contextual, place-based knowledge into multiscale assessments of biodiversity status and impacts.

Urban biodiversity is known to enhance the quality of life of urban dwellers, but its benefits are not equitably shared by the urban population. The positive correlation between urban biodiversity and socio‐economic status within cities (i.e. the Luxury Effect) can thus be considered a measure of environmental injustice. While common, this relationship is not universal, indicating a need to understand its drivers in an attempt to develop more equitable cities. This includes examining how economic and demographic contexts at larger spatial scales are associated with the Luxury Effect. We conducted a meta‐analysis to understand the extent to which wealth, income inequality, human population size and population density at city and national scales were associated with the strength of the Luxury Effect (the degree of correlation between urban biodiversity and socio‐economic status). Importantly, we considered non‐linear effects of these drivers, which are rarely considered in Luxury Effect studies. There was support for the Luxury Effect, with a positive relationship between biodiversity and socio‐economic status within cities. This relationship was generally stronger in poorer cities and countries. There was no support for an association with income inequality and the strength of the Luxury Effect at either city or national scales. We found support for an association between economic development and the strength of the Luxury Effect. Non‐linear effects were generally more supported than linear effects in that the Luxury Effect was strongest in countries with below average wealth, but was lowest in the poorest and wealthiest countries, and in cities with intermediate human population size. However, to adequately test the generality of these relationships, further research is needed in under‐represented countries, which, according to our findings, are those where levels of environmental injustice are likely greatest. Implications . The results suggest that poorer societies do not have the economic resources to confront the environmental injustice represented by the Luxury Effect. Identifying the drivers of the Luxury Effect, while also accounting for broader social challenges such as green gentrification, is fundamental to addressing environmental injustice and may help to prioritise strategies to reduce disparities in terms of gaining biodiversity benefits in cities globally. Read the free Plain Language Summary for this article on the Journal blog.

Invasive species management is often constrained by limited resources and complicated by ecological and socio-economic variability across landscapes, leading to inconsistent outcomes. We use water hyacinth ( Pontederia crassipes ) in South Africa as a case study to demonstrate how combining earth observation (EO) data, species distribution models (SDMs), and explainable artificial intelligence (xAI) can support more spatially explicit and context-sensitive management strategies. Despite decades of control efforts, water hyacinth remains widespread, with its proliferation shaped by ecological and socio-economic contexts in which the weed proliferates. Using SHapley Additive exPlanations (SHAP), we studied the environmental and socio-economic contexts impacting water hyacinth prevalence across multiple spatial scales in South Africa. Consistent patterns emerged with known physiological constraints, such as minimum temperature, while novel spatial trends were revealed—highlighting temperature effects along the coast and the role of vegetation type in inland regions. These insights offer opportunities for targeted fieldwork to investigate emergent non-linear relationships and interaction effects between covariates. The spatially explicit outputs, covering all South African water bodies, provide a low-cost, scalable tool to guide the prioritization of risk, inform monitoring and early detection efforts, and support the selection of locally appropriate management strategies. While focused on water hyacinth, our approach is generalizable to other invasive species, illustrating the value of integrating EO data and xAI to enhance understanding of species-environment dynamics and enable adaptive, data-driven intervention planning.

Context: Urban ecosystems exhibit complex biodiversity patterns influenced by both socio-economic and ecological factors. While the role of ecological factors is widely recognised, the relationships between socio-economic and ecological factors, particularly across various spatial scales and considering both landscape composition and configuration, remains underexplored. This limits our understanding of urban environments as interconnected socio-ecological systems. Objectives: We examine the influence of socio-economic and ecological landscape factors on solitary bee abundance, aiming to elucidate the complex socio-ecological dynamics shaping urban biodiversity across multiple scales. Methods: Data on solitary bee abundance were gathered through a citizen science campaign, supported by 347 participants from Johannesburg, South Africa. We explored the correlations and interactions between solitary bee abundance, socio-economic status (i.e. annual household income) and landscape composition and configuration (i.e. urban green cover and NDVI, and urban vegetation patch density and cohesion), assessing these relationships at 300 m, 2000 m, and 5000 m scales. Results: Annual household income was significantly positively correlated with solitary bee abundance across all spatial scales examined, likely due to increased investment in gardens with diverse floral resources in affluent areas. In contrast, our ecological factors, including both landscape composition and configuration metrics, exhibited negligible effects on solitary bee abundance across all spatial scales. Conclusions: The strong positive relationship between annual household income and bee abundance across scales highlights potential disparities in access to biodiversity and ecosystem services within Johannesburg. Our results indicate the presence of environmental injustice in this African city and reflect the need for integrating socio-economic factors into landscape ecology. Policies on urban greening that consider both socio-economic and ecological factors are essential for equitable, sustainable urban ecosystems.