The Diamesinae (Diptera: Chironomidae) in High-Altitude Andean Streams Using Morphological and Molecular Approaches

Diamesinae is one of the 11 subfamilies of Chironomidae, characterized by its preference for cold waters, typically found in mountainous regions. We aimed to study the biodiversity and distribution of two genera of this subfamily found in high-altitude streams in the Andes (Paraheptagyia Brundin, 1966 and Limaya Brundin, 1966), by combining morphological and molecular analyses. A database with 190 larval specimens of Diamesinae (160 of Paraheptagyia and 22 for Limaya), collected between July and October of 2011 from 20 streams in Colombia, Ecuador, and Peru, at altitudes above 2000 m a.s.l. was used. Paraheptagyia was found in the three countries, whereas Limaya was only found in Ecuador and Peru. Morphological analyses were based on 105 larvae mountings, using several measurements (26 measurements for Limaya and 25 for Paraheptagyia) and specimens for each morphotaxon. As a result, the head capsule width and the antennal ratio (AR) were the most valuable differentiators to distinguish between two morphotypes of Limaya, whereas Paraheptagyia could not be distinguished by using morphological characters. We employed the ABGD, ASAP, and bPTP methods, and supported them with distance matrices and haplotype networks, to delineate operational taxonomic units (OTU) based on 130 molecular sequences (113 for Paraheptagyia and 17 for Limaya). For Limaya, we identified two OTUs with all methods, one from Ecuador and one from Peru. As for Paraheptagyia, we identified between seven and nine OTUs, of which we found the majority in Peru, and two occurred in both Ecuador and Colombia. We hypothesize that the presence of the Huancabamba depression on the border between Ecuador and Peru likely acts as a genetic barrier, limiting gene flow. The difference in branch length between Peruvian and Ecuadorian/Colombian species supports Brundin's (1966) hypothesis of a south-to-north colonization pattern and the Gondwanan origin of both genera.