Delineation of two new, highly similar species of Taiwanese Cylindera tiger beetles (Coleoptera, Carabidae, Cicindelinae) based on morphological and molecular evidence

Abstract

Tiger beetles have been recognized primarily based on morphological characters. However, the variations of elytral maculation and coloration sometimes lead to misjudgment in species classification and the overlooking of the existence of cryptic species. Recently, specimens of two endemic species of Taiwanese Cylindera, C. sauteri and C. pseudocylindriformis, exhibit morphologically recognizable forms, indicating that some undescribed species may exist. To clarify their taxonomic status, morphological characteristics including male genitalia were examined and two mitochondrial genes, COI and 16S rDNA, and one nuclear 28S rDNA were analyzed. Molecular phylogenetic inferences indicated that both forms in both species are reciprocally monophyletic. Moreover, molecular dating showed the forms diverged approximately 1.3 million years ago. Two new species, Cylindera ooa sp. nov. and Cylindera autumnalis sp. nov., are thereby described. The main recognizable characteristics separating C. ooa sp. nov. from C. sauteri are the lack of a triangular spot at the middle edge of elytron and the elongated but not rounded subapical spot. For C. autumnalis sp. nov., the apical lunula near the elytral suture is thickened but not linear and slender, and its elytra are more metallic brownish than those of C. pseudocylindriformis. Although their aedeagi characteristics are not distinctive, the body size of the proposed two new species is different. Field observation revealed that niche utilization would be relevant for differentiating these closely related species.