Global patterns and data gaps in avian genetic diversity based on mitochondrial Cyt b and COI sequences

Genetic diversity is a fundamental component of biodiversity, with far-reaching implications for the stability and resilience of ecosystems. Despite the growing recognition of the importance of genetic monitoring in wild species, we still lack a clear understanding of which regions are devoid of genetic diversity data and which lineages remain insufficiently characterized. Although the cost of genome sequencing has declined dramatically, Sanger sequencing still retains practical and economic advantages for applications in conservation biology. To identify global data gaps and facilitate the application of genetic data in future genetic monitoring, this study searched the National Center for Biotechnology Information (NCBI) database for Cytochrome b (Cyt b) and Cytochrome Oxidase subunit I (COI) sequences of all species listed in the Handbook of the Birds of the World (HBW v7.0), and calculated their genetic diversity. The study found that 4052 bird species had at least three available sequences of either Cyt b or COI. These species are mainly distributed in Europe, northern North America, and parts of East Asia, North Asia, and northern Africa, whereas South America, South Africa, South Asia, Southeast Asia, and eastern and northwestern Australia has limited available genetic diversity data. The Cyt b sequence data is entirely absent in groups such as Pterocliformes and Cariamiformes, whereas COI gene data are particularly lacking in Leptosomiformes and Opisthocomiformes. Notably, both genes are completely missing in Musophagiformes and Mesitornithiformes. This uneven distribution of genetic diversity data hinders the development of effective conservation strategies, as such gaps impede the integration of genetic diversity into extinction risk assessments across species. This study highlights priority geographic regions and key evolutionary lineages for future genetic diversity assessments. Despite the inherent limitations of maternally inherited mitochondrial markers, which cannot stand for genome-wide nuclear genetic variation, this study represents the most comprehensive avian genetic diversity dataset currently available. It therefore provides an important baseline for incorporating genetic diversity into extinction risk assessments and for advancing long-term genetic monitoring efforts in birds.