Sympatric speciation in the Simulium arcticum s. l. complex (Diptera: Simuliidae): The Rothfels model updated

Abstract

We tested the Rothfels sympatric speciation model for black flies by comparing all available data for sex‐chromosome diversity with the geographic locations of larval collection sites within the Simulium arcticum complex of black flies (Diptera: Simuliidae). Five separate data sets equaling about 20,000 larvae were included from throughout the geographic range of this complex. We record a total of 31 taxa having unique sex chromosomes, all of which demonstrate linkage disequilibrium with most taxa sharing autosomal polymorphisms. All siblings share portions of their distributions with S. negativum , the presumed oldest member of the complex. Twenty‐one of 22 cytotypes have distributions within the ranges of siblings thus supporting the sympatric speciation model of Rothfels. Chromosomally diverse sites may require analysis of as many as 200 larvae to be properly described. There is no effect of any inversions influencing the occurrence of other inversions. Finally, we report a new cytotype, Simulium arcticum IIL‐6, which we originally discovered in Alaska. Aspects of future genomic research are discussed as they relate to the main chromosomal structural/functional tenants of the model. OPEN RESEARCH BADGE This article has earned an Open Data Badge for making publicly available the digitally‐shareable data necessary to reproduce the reported results. The data are available at https://doi.org/10.6084/m9.figshare.7719398

Black flies (Diptera: Simuliidae) of central and northeastern Washington, United States of America, with cytogenetic emphasis on the Simulium arcticum complex

“…Larvae of the S. arcticum complex that had white or grey gill histoblasts were chosen for the chromosome study. It is at these developmental stages, as indicated by the colour, that polytene chromosomes are optimal for analysis (Shields and Procunier 2019). We scored each larvae examined in the chromosome study for all inversions but particularly for inversions in the long arm of chromosome II and for the autosomal inversion, IS-1.…”

“…We scored each larvae examined in the chromosome study for all inversions but particularly for inversions in the long arm of chromosome II and for the autosomal inversion, IS-1. It was possible to detect heterozygotes for this large inversion (Shields and Procunier 2019), but scoring the inversion homozygotes was difficult due to the quality of the chromosomes. As a result, a detailed analysis of the homozygous inverted genotype was not included in this analysis.…”

“…Once complexes are described, biological features of the taxa can be studied further, and some are recognised as good biological species (Adler et al 2004). For example, in the S. arcticum complex, 31 taxa have been described (Shields and Procunier 1982;Adler et al 2004;Shields and Shields 2018;Shields and Hokit 2019;Shields and Procunier 2019), and nine of these have been named as good biological species (Adler et al 2004).…”