Phylogeography of Thorichthys meeki in Southeastern Mexico (Actinopteri: Cichlidae)

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Introduction: The fish fauna in the Yucatan Peninsula exhibit a unique composition, shaped by the region’s complex geological and hydrological history. Thorichthys meeki is a widely distributed cichlid species that has been the subject of morphological, behavioral, and phylogenetic studies. Nevertheless, the historical and biogeographical processes that have shaped its diversification and genetic structure remain unexplored. Objective: The objective of this study was to identify phylogeographic patterns and assess the genetic diversity of T. meeki in southeastern Mexico. Methodology: Genomic DNA was extracted from the muscle tissue of specimens preserved in 90% ethanol. DNA was amplified using a polymerase chain reaction (PCR) and sequences were obtained from two molecular markers: cytochrome oxidase 1 (CO1) and S7 intron 1. Phylogeographic analyses included genetic diversity indices molecular variance analyses to assess population structure and haplotype networks. Results: A total of 60 CO1 and 40 S7 intron 1 sequences were obtained from 26 sampling sites. For CO1, 14 haplotypes were identified, with high haplotype diversity (Hd = 0.84), and low nucleotide diversity (π = 0.0048). For S7 intron 1, 16 haplotypes were recovered with lower haplotype diversity (Hd = 0.543) and π = 0.021. A hierarchical AMOVA (2 groups) showed the greatest variation; 72.3% in CO1 and 79.8% in S7 within population groups with significant ΦST values. Haplotype networks identified three haplogroups for each gene. A single CO1 haplotype was found in 26 sequences from 13 sampling sites. For S7 intron 1, one haplotype was identified in 22 sequences and was shered from all populations. Conclusions: A widely distributed haplotype for CO1 and S7 reflects historical connectivity among hydrological systems. These preliminary results provide an interesting insights into the processesthat have influenced the distribution of T. meeki on the Yucatán Peninsula.

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