Both life history traits and habitat availability play a role.
Earlier this year, I had the opportunity to be part of a large study published in Nature (you can read the story behind the paper here). In this work, we carried out a global meta-analysis of more than three decades of research, compiling all available temporal measures of genetic diversity. Our results revealed a widespread decline in genetic diversity across many species, particularly birds and mammals. The good news is that conservation efforts can make a difference. Actions such as restoring habitats, supporting population growth, or introducing new individuals into populations can help maintain or even increase genetic diversity.
These insights raise an important question: what actually drives genetic diversity in the first place? Understanding this aspect is key to making conservation strategies even more effective. A recent study in the journal Proceedings B sheds light on this question, showing that both extrinsic factors (such as habitat availability) and intrinsic traits (such as body mass and diet) play important roles in shaping patterns of genomic diversity in birds.
Habitat Availability
Anna Brüniche-Olsen, Kenneth Kellner, and their colleagues examined genomic data from 68 bird species to better understand what drives genetic diversity. They focused on two complementary measures: historical effective population size (Ne), which reflects long-term population dynamics, and current heterozygosity (H), a snapshot of present-day genetic variation. Their analyses highlighted the central role of habitat availability. Species with more suitable habitat in the past (estimated through environmental niche modelling) tended to have larger historical effective population sizes. Similarly, species with more suitable habitat today showed higher levels of current heterozygosity.
Life History Traits
These findings point to habitat restoration as a powerful tool for boosting genetic diversity. However, the complete story is more complex. Not all drivers of genetic diversity can be easily addressed with conservation management. Indeed, the researchers found that body mass was negatively correlated with both Ne and H. In other words, larger-bodied species (often with smaller population sizes) tend to harbor less genetic diversity, leaving them especially vulnerable to human disturbance. Diet also played a role: carnivores and scavengers showed the lowest levels of genetic diversity, while herbivores and granivores had the highest. This pattern likely reflects ecological differences: carnivores usually occur at lower population densities, and their specialized food sources are generally less abundant than the more flexible diets of omnivores.
Lessons for Conservation
Taken together, these results highlight both the promise and the limitations of conservation interventions. While protecting and restoring habitats can help safeguard genetic diversity, intrinsic traits also shape the evolutionary resilience of a species. Hence, conservation strategies must not just be tailored to environments, but also to the biology of the species we aim to protect.
References
Brüniche-Olsen, A., Kellner, K. F., Belant, J. L., & DeWoody, J. A. (2021). Life-history traits and habitat availability shape genomic diversity in birds: implications for conservation. Proceedings of the Royal Society B, 288(1961), 20211441.
Shaw, R. E., Farquharson, K. A., Bruford, M. W., Coates, D. J., Elliott, C. P., Mergeay, J., et al. (2025). Global meta-analysis shows action is needed to halt genetic diversity loss. Nature, 638(8051), 704-710.
Featured image: California Condor (Gymnogyps californianus) © Scott Frier Nikon | Wikimedia Commons
Avian Hybrids 