Genetic analyses of Leiognathids and Lutjanus fulviflamma across the coastline of Tanzania

Genetic analyses of Leiognathids and Lutjanus fulviflamma across the coastline of Tanzania.
This study investigated the diversity, morphological variation, phylogenetic relationships of Leiognathidae (ponyfish) in Tanzanian coastal waters, and local adaptation of Lutjanus fulviflamma. Phylogenetic analysis identified ten species within six genera (Gazza, Equulites, Leiognathus, Karalla, Aurigequula, and Deveximentum), revealing well-supported evolutionary clades. Notably, Karalla daura was recorded for the first time in Tanzanian waters, expanding the known species diversity of the region. Morphometric analysis of Leiognathidae species using Principal Component Analysis (PCA) distinguished species based on body shape variation, highlighting adaptations to different ecological niches.
The study further analyzed genetic diversity and local adaptation of Lutjanus fulviflamma populations across Tanzanian coastal waters using mtDNA COI sequences. Genetic diversity metrics revealed low overall haplotype (0.381) and nucleotide (0.19%) diversities. The population exhibited signs of historical bottlenecks followed by expansion, as evidenced by significantly negative overall Tajima’s D (-2.55) and Fu’s Fs (-12.25) values, along with unimodal mismatch distribution and Bayesian skyline plot. Population structure analysis using AMOVA showed high genetic variation within populations (98.78%) and low among populations (1.22%), suggesting substantial gene flow among populations. The low FST value (0.012) and a star like haplotype network further supported the lack of genetic structure, indicating that these populations form a single, genetically similar stock. These findings suggest that L. fulviflamma should be managed as a single conservation unit, aligning with the current fisheries management plan in Tanzania, which does not consider genetic stocks in the fishery management strategy. Given the low genetic diversity, the species is vulnerable to environmental changes and overfishing, thus effective management strategies should include regulating fishing practices such as catch size and quotas limits, protecting critical habitats such as coral reefs and mangrove habitats that serve as important nurseries for juvenile L. fulviflamma.