Mitigating loss of genetic diversity is a major global biodiversity challenge^1–4. To meet recent international commitments to maintain genetic diversity within species^5,6, we need to understand relationships between threats, conservation management and genetic diversity change. Here we conduct a global analysis of genetic diversity change via meta-analysis of all available temporal measures of genetic diversity from more than three decades of research. We show that within-population genetic diversity is being lost over timescales likely to have been impacted by human activities, and that some conservation actions may mitigate this loss. Our dataset includes 628 species (animals, plants, fungi and chromists) across all terrestrial and most marine realms on Earth. Threats impacted two-thirds of the populations that we analysed, and less than half of the populations analysed received conservation management. Genetic diversity loss occurs globally and is a realistic prediction for many species, especially birds and mammals, in the face of threats such as land use change, disease, abiotic natural phenomena and harvesting or harassment. Conservation strategies designed to improve environmental conditions, increase population growth rates and introduce new individuals (for example, restoring connectivity or performing translocations) may maintain or even increase genetic diversity. Our findings underscore the urgent need for active, genetically informed conservation interventions to halt genetic diversity loss.

Genetic monitoring of populations currently attracts interest in the context of the Convention on Biological Diversity but needs long-term planning and investments. However, genetic diversity has been largely neglected in biodiversity monitoring, and when addressed, it is treated separately, detached from other conservation issues, such as habitat alteration due to climate change. We report an accounting of efforts to monitor population genetic diversity in Europe (genetic monitoring effort, GME), the evaluation of which can help guide future capacity building and collaboration towards areas most in need of expanded monitoring. Overlaying GME with areas where the ranges of selected species of conservation interest approach current and future climate niche limits helps identify whether GME coincides with anticipated climate change effects on biodiversity. Our analysis suggests that country area, financial resources and conservation policy influence GME, high values of which only partially match species’ joint patterns of limits to suitable climatic conditions. Populations at trailing climatic niche margins probably hold genetic diversity that is important for adaptation to changing climate. Our results illuminate the need in Europe for expanded investment in genetic monitoring across climate gradients occupied by focal species, a need arguably greatest in southeastern European countries. This need could be met in part by expanding the European Union’s Birds and Habitats Directives to fully address the conservation and monitoring of genetic diversity.

Since their discovery in the 1980s microsatellite or simple sequence repeat (SSR) markers have been widely used in many species to generate relatively dense genetic maps or framework maps on which to anchor more abundant, but anonymous, markers such as amplified fragment length polymorphisms (AFLPs). They are typically highly polymorphic, robust, and often portable, particularly among different mapping populations or crosses and often to related species. They have been useful in species where low levels of genetic diversity limit the use of other markers. Cultivated cotton (Gossypium hirsutum L.) has a history of genetic bottlenecks that have considerably reduced its diversity, with the consequence that most molecular marker genetic linkage studies are done with inter-specific crosses. In this study we evaluated the potential for SSR markers to be used in marker-assisted selection (MAS) breeding in cotton by quantifying the level of polymorphism detected with a set of commercially available SSR markers between and within a collection of cotton cultivars being used in our breeding programs. Although the majority of these markers are polymorphic between the 2 tetraploid species of cotton, G. barbadense and G. hirsutum, they are not highly polymorphic (~5%) either among or within G. hirsutum cultivars. However, 6 of the 8 cultivars studied were found to be segregating for alleles of these SSR markers. This suggests that where polymorphisms exist, heterozygosity within cultivars is maintained by the breeding strategies adopted by many modern cotton breeders. Although SSRs clearly have utility in genetic studies using inter-specific crosses or in the introgression of wild germplasm, they will be more difficult to use for standard cotton breeding until greater numbers are available. The utility of some markers may be reduced in some breeding populations where heterozygosity remains in the parental material.