Molecular species delimitation in the genus Rhamma Johnson, 1992 (Lepidoptera: Lycaenidae, Theclinae)

Abstract

In this work, we used mtDNA data as a tool to delimit species and we compared the resulting molecular operational taxonomic units (barcode index number, BIN) with morphology-based identifications in the Colombian species of Rhamma Johnson, 1992 exploring the usefulness of DNA barcodes for taxonomy, species identification and delimitation. We obtained cytochrome oxidase I (COI) sequences for 134 morphologically identified specimens, representing 12 species of Rhamma from Colombia. Ten of these species have not been previously barcoded. DNA barcodes suggested the potential for eight additional cryptic species in Colombia but we were readily able to morphologically diagnose just one of these linages as a new species which recently was described in a separate paper as Rhamma dawkinsi Prieto & Lorenc-Brudecka, 2017. The morphological species were separated into three categories: species showing a perfect match between morphological species and BINs (33%, four species); species sharing a BIN completely or partly (single specimens) with another morphological species (42%, five species placed in three BINs); and morphological species splitting up into more than one BIN (25%, three species placed in 10 BINs). The high percentages of incongruence between morphology-based identification and species delineation through BINs, could be explained as a consequence of high rates of introgressive hybridization. However, DNA barcodes can be considered diagnostic even in cases where specimens of a species were assigned to two or more distinct BINs and in species showing a low but constant divergence causing their assignment to a single BIN, which is often the case in young, allopatric species. We retain 10 of the 12 species (83%) to be diagnostic in molecular identification.