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.

Congruence between morphology-based species and Barcode Index Numbers (BINs) in Neotropical Eumaeini (Lycaenidae)

“…The general goal is to quantify the potential usefulness of reference libraries of DNA barcodes for identification and for resolution of taxonomic problems in this group. In previous studies ( e.g ., Prieto et al, 2016 ; Prieto, Nuñez & Hausmann, 2018 ; Faynel, 2019 ) we found that congruence between DNA and morphology varies among genera. We hypothesized that the incidence of congruence among strictly high Andean genera was lower than among lowland genera.…”

“…As noted by Prieto, Nuñez & Hausmann (2018) , the genus Rhamma includes several species presenting both types of discordance, BIN sharing and BIN splitting ( e.g ., R. arria and R. bilix ). Species with a wider geographical distribution in high Andean ecosystems, seem to show a greater number of incongruences.…”

“…We analyzed barcode gaps to evaluate the hypothesis that incongruence between morphological species and BINs increase in high Andean lycaenid genera ( e.g . Prieto, Nuñez & Hausmann, 2018 ; Faynel, 2019 ). The “barcode gap” is a comparison of intraspecific versus interspecific divergence among barcode sequences.…”

“…In contrast with other, better known families, lycaenids lack sufficiently illustrated identification keys, monographs, field guides, or checklists covering regions or countries in a comprehensive and updated manner. The use of DNA barcode sequences and BINs in this group has been limited, but congruence between morphology and barcode sequences is variable ( Prieto, Micó & Galante, 2011 ; Faynel et al, 2011 ; Faynel, Busby & Robbins, 2012 ; Prieto et al, 2016 ; Cong et al, 2016 , 2017 ; Prieto & Lorenc-Brudecka, 2017 ; Busby et al, 2017 ; Prieto, Nuñez & Hausmann, 2018 ; Faynel, 2019 ). In particular, in previous studies it appeared that strictly high Andean genera were more likely, on average, to show incongruence.…”

Parnassius nebrodensis: A threatened but neglected Apollo butterfly species from Southern Europe (Lepidoptera: Papilionidae)

“…These morphologically cryptic white-wood butterfly taxa can reliably be identified by means of either DNA sequences or karyological data (Dincă et al 2011;Lehtonen et al 2017;Talla et al 2019 , 1977), and Rhamma spp. (Lycaenidae) (Lukhtanov et al 2015;Prieto et al 2019;Platania et al 2020b;Hinojosa et al 2021).…”