Genetic population structure and levels of gene flow in the stream dwelling waterstrider, Aquarius (= Gerris) remigis (Hemiptera: Gerridae)

Abstract

Some 28 Aquarius remigis populations from Quebec, Ontario, New Brunswick, Iowa, North Carolina and California were genetically characterized at 15 loci. Hierarchial F statistics indicated that only sites within streams maintained enough gene flow to prevent differentiation through drift (Nm = 27.5). Above the level of sites within streams gene flow is highly restricted (Nm ≤0.5) and no correlation is found between genetic and geographic distances. This agrees well with direct estimates of gene flow based on mark and recapture data, yielding an Ne of c170 individuals. Previous assignment of subspecific status to Californian A. remigis is not supported by genetic distances between those populations and other populations in North America. Previous suggestion of specific status for south-eastern A. remigis is supported by genetic distances between North Carolina populations and other populations in North America, and a high proportion of regional specific alleles in the North Carolina populations, but because of the high degree of morphological and genetic variability throughout the range of this species, the assignment of specific or subspecific status to parts of the range may be premature. -from Authors