Abstract
Taxonomic debates have been carrying on for decades over Formosan stag beetles, which consist of a high proportion of endemic species and subspecies featuring morphological variations associated with local adaptation. With the influence of periodical Pleistocene glaciations and the presence of several mountain ranges, the genetic differentiation and taxonomic recognition, within this medium-size island, of two endemic subspecies for each of four montane stag beetles, i.e. Lucanus ogakii, L. kanoi, Prismognathus davidis, and Neolucanus doro, has been an appealing issue. Based on monophyletic lineages and population structure, possible divergent scenarios have been proposed to clarify the subspecific status for each of the above mentioned stag beetles. Phylogenetic inferences based on COI+16S rDNA+28S rDNA of 240 Formosan lucanids have confirmed most species are monophyletic groups; and the intraspecific (<2%) and interspecific (>2%) genetic distances of the two mitochondrial genes could be applied concordantly for taxonomic identification. On account of Bayesian-based species delimitation, geographic distribution, population structure, and sequence divergences, the subspecific status for L. ogakii, L. kanoi, and Pri. davidis are congruent with their geographic distribution in this island; and the calibration time based on the mitochondrial genes shows the subspecific split events occurred 0.7–1 million years ago. In addition, a more complicated scenario, i.e. genetic differentiation including introgression/hybridization events, might have occurred among L. ogakii, L. kanoi, and L. maculifemoratus. The geological effects of mountain hindrance accompanied by periodical glaciations could have been vital in leading to the geographical subspecific differentiation of these montane stag beetles.
Highlights
The family Lucanidae (Coleoptera, Scarabaeoidea) has received much attention because of their remarkable sexual dimorphism, intraspecific variation, and external morphological allometry in males [1,2,3]
This study revealed the taxonomically debated stag beetles, i.e. L. ogakii, L. kanoi, and Pri. davidis, could have confronted and evolved under similar geological events as proposed for some other organisms on Formosa Island
Morphological variations between populations/subspecies or species in montane stag beetles might be taken as an expression responding to diverse doi:10.1371/journal.pone.0156600.g007
Summary
The family Lucanidae (Coleoptera, Scarabaeoidea) has received much attention because of their remarkable sexual dimorphism, intraspecific variation, and external morphological allometry in males [1,2,3]. Previous studies on stag beetles showed the intraspecific variation within a species or between subspecies could have been related to their local adaptation, such. Genetic Variation of Formosan Stag Beetles as larval consumption of dead wood, mating choice of females, and competition for food resources [2,3,4,5]. With >1,400 species known throughout the world, stag beetles are abundant in Oriental, Sino-Japanese, and the eastern Palearctic regions [6,7,8,9]. Species distributing widely with variable morphological characters are suitable for studying their evolutionary history, especially the genetic differentiation between affinity of subspecies [10, 11]. The affinity subspecies within a species is usually recognized according to their geographic distribution and morphological features. When two subspecies should be recognized, their differentiation processes would be an appealing issue
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