Reproductive Status of Cytotypes within the Simulium arcticum Complex at Rock Creek, Missoula Co., MT 3/14/06

Abstract

This two year study was an in depth cytogenetic analysis of the IIL-9 and IIL-19 cytotypes of the Simulium arcticum complex from a March 14, 2006 collection at Rock Creek, Missoula Co., MT to assess reproductive status. In this research, conventional methods of collection, morphological classification, and chromosomal preparation and analysis were used. The reproductive status of the two cytotypes was examined using the autosomal polymorphisms IS-1 (Figure 2) and IL-1 (Figure 3), which occurred in sufficient abundance to estimate equilibrium frequencies within the 3/14/06 sample. I hypothesized that these two divergent cytotypes, IIL-9 and IIL-19 (Figure 1), would exhibit a lesser degree of reproductive isolation than previously established cytospecies. Frequencies of the IS-1 and IL-1 autosomal polymorphisms were calculated for the IIL-9 and IIL-19 cytotypes and were compared to the equilibrium values using a Chi square analysis. The statistical analysis of the material revealed the IIL-9 and IIL-19 cytotypes to be in equilibrium at Rock Creek on 3/14/06. This would suggest that these two cytotypes are indeed not reproductively isolated from one another based on random sharing of autosomal inversions. The limited geographic distribution of the IIL-9 and IIL 19 cytotypes suggests that they may be evolutionarily young. This information coupled with the fact that they are in equilibrium at Rock Creek supports the S. arcticum Geographic Distribution/Taxon Age Continuum of Shields (2006).