Genomic data identify genetic structure in Enoploctenus cyclothorax (Araneae: Ctenidae), revealing two distinct taxonomic units in the southern region of the Brazilian Atlantic Forest

Abstract

Habitat fragmentation is among the greatest threats to arachnids present in the forests, especially to Enoploctenus cyclothorax (Ctenidae), which is widely distributed in the Atlantic Forest of southern and southeastern Brazil. Fragmented populations, whether due to anthropic or stochastic factors, tend to be more susceptible to extinction, since genetic diversity is reduced in small and isolated populations. Considering this, the current work aimed to understand how the genetic variability is distributed in six populations of E. cyclothorax (120 individuals sampled), sampled in fragments of the Atlantic Forest in Paraná (Brazil), based on Single Nucleotide Polymorphism (SNP) genotyping. The results obtained support the separation of E. cyclothorax into two distinct genetic groups in the state, based mainly on analyses of genetic structure and connectivity. A strong and significant genetic structure was observed in the species, supported by the k = 3 estimated using Bayesian analysis, by the high values of F_ST genetic differentiation, and by the low gene flow identified between the genetic groups. Corroborating these results, isolation by distance and the presence of a genetic barrier in the evaluated populations were evidenced. Population genomic analysis also revealed non-homogeneous genetic diversity in E. cyclothorax (H_E = 0.14 to 0.31). The hypothesis that population fragmentation could possibly impact the genetic variability of E. cyclothorax throughout the state was confirmed by the inferred data, which point to phytophysiognomy, geographical distance, and forest fragmentation as factors that shaped the current genetic structure identified in the evaluated populations.