Taxonomic delimitation of species using different molecular markers
Research on the mechanisms of montane speciation in neotropical insects is scarce, and we are just now starting to comprehend how they contribute to diversity in neotropical forests Cold-adapted species on mountain peaks can quickly become reproductively isolated during warmer climates due to geographic isolation and niche specialization, though most of their genomes can still be shared due to recent gene flow. Indeed, while A. mantiqueira and A. alalia can be distinguished by a series of distinct morphological characteristics of adults, immature stages, and geographic distribution (Freitas et al., 2018), the COI barcode lacks sufficient interspecific differences to distinguish them. Therefore, based on barcodes, the genetic distance between individuals of these species is virtually zero, that is, there is no ‘barcode gap’ (sensu Hebert et al., 2004) between A. alalia and A. mantiqueira . Furthermore, there is no genetic structure across locations based on COI, and all species delimitation methods evaluated failed to tell the two species apart. Some hypotheses have already been raised to explain this lack of information at the COI level, such as a lower diversification rate compared with other Acraeini species, intrinsically different rates of molecular evolution, or selective sweeps by endosymbionts, as already demonstrated for other Acraeini (Jiggins, 2003; Silva-Brandão et al., 2021), and in fact all mechanisms can contribute to explaining the present pattern for this mitochondrial marker.
In contrast, all analyses performed using genome wide SNPs (genetic distance, phylogenetic hypothesis, clustering analyses, and FST statistics) recovered a clear pattern of two clades, separating individuals of A. alalia from all populations ofA. mantiqueira , validating the taxonomic decision of Freitas et al. (2018). These markers have not been widely used yet in taxonomic studies (but see Bog et al., 2020; Ramírez-Reyes et al., 2020). However, this genomic approach, including markers with a possible faster evolutionary rate, was able to reveal a more detailed and recent history of these populations, confirming their separated evolutionary histories, even though they still share mitochondrial haplotypes.