Genetic diversity of populations of the endemic species Coptodon walteri from the Cavally River, Western Côte d’Ivoire

Résumé fourni par la source

Coptodon walteri is a fish species of particular ecological importance due to its endemic status within the Cavally River basin. However, this hydrological basin is experiencing increasing environmental pressures, notably from gold mining, which may alter both the basin and the fish communities inhabiting it. Therefore, the objective of this study was to assess the genetic diversity of C. walteri populations, which to date have not been the subject of any genetic study in this region. A total of 120 individuals (30 per sampling station) were collected through experimental and artisanal fishing using gill nets. DNA from each specimen was extracted from a fragment of the caudal fin following a standard 2% CTAB protocol. To evaluate genetic diversity and population structure, seven microsatellite markers (GM005, UNH142, UNH146, UNH159, UNH174, UNH189, and UNH190) were analyzed. Genetic analyses were conducted using the software GenAlex, MEGA12, and STRUCTURE. The number of alleles per locus ranged from 2 to 9, with an average of 2. A total of 41 alleles were identified, corresponding to a mean polymorphism rate of 54% at a 95% confidence level. Despite this moderate level of polymorphism, the studied populations exhibited a pronounced heterozygote deficit (Ho = 0.01-0.10) and high inbreeding coefficients (Fis = 0.53-0.73), indicating strong genetic depression. High genetic differentiation across all analyzed loci was observed (Fst = 0.93), suggesting an almost complete absence of gene flow (Nm = 0.11) among sampling stations. Phylogenetic and population structure analyses revealed a clear separation of populations into three and four distinct groups, corresponding to their geographic locations. These results highlight severe genetic fragmentation and increased vulnerability in C. walteri, underscoring the urgent need to implement conservation measures.

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