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.