Molecular systematics of the Simuliidae (Diptera: Culicomorpha)

Abstract

Relationships within Simuliidae, or black flies, are inferred from molecular sequences from four nuclear loci -the large ribosomal subunit (28S rDNA), elongation factor one alpha (EF-1α), dopa decarboxylase (DDC), and phosphoenolpyruvate carboxykinase (PEPCK) - and two mitochondrial loci - the small ribosomal subunit (12S rDNA) and subunit two of NADH dehydrogenase (ND2). Analyses of all genes provide varying degrees of support for subfamily and tribal limits within Simuliidae that are completely concordant with those inferred from the most intensive analysis of morphological data. Additionally, 28S and PEPCK suggest thaumaleids are more closely related to simuliids than are chironomids. Relationships within Simuliidae below the level of tribe were inferred from independent and simultaneous analyses of these data. Phylogenetic trees thought to represent best estimates of simuliid relationships were used to trace the evolution of several morphological characters and of natural partitions of these sequences, particularly codon positions in the four protein coding genes. The rather poor performance of these genes at intermediate taxonomic depths within Simuliidae is hypothesized to be the result of explosive diversification, properties of these genes, or a combination of the two. Potential hypotheses for the rather poor performance of these genes are proposed, and two types of genes hypothesized to be more informative in cases of explosive radiation are described.