EVOLUTION OF POSTGONITES IN FRIT FLIES (DIPTERA, CHLOROPIDAE, MEROMYZA)

摘要

Evolution trends of changes in the morphometric characteristics of postgonites (structures important for copulation) and the variability of the mtDNA COI gene region were analyzed for 24 species of the genus Meromyza Mg. The total area, the area and altitude of a protuberance, a correlation between the length of the main part and that of the protuberance align bottom were analyzed for the front process of postgonites. The altitude and way of fixation were analyzed for the posterior process of postgonites. Based on the mtDNA COI locus in Network, eight clusters combined in three groups were distinguished: clusters with a small area of the front process of postgonites and a lateral or caudal way of fixation of the posterior process of postgonites; clusters with a medium area and the same way of fixation of the posterior process of the postgonites; and clusters with a large area and a caudal way of fixation of the posterior process of the postgonites or a P-shaped way of fixation. The evolution trend of size characteristics in male sexual appendages of ancestral forms may have been directed to increasing the area of postgonites within the genus Meromyza, and decreasing the area in relation to the species most similar to a hypothetical ancestor inside the clusters. The features of ancestral forms are a small area, and a short and narrow protuberance of the front process of postgonites. Increasing the area may have resulted in reduction in the statistical significance of differences in the variability of the protuberance of the front process of postgonites and in the appearance of a "volvulus" or projection on its lateral part. The functional value of paramere structures and "edging" are discussed. The investigated morphometric characteristics allowed to include the species M. maculata and M. cognata into the known clusters, although no COI sequence for them were determined.