Impact of Limited Dispersion Capacity and Natural Barriers on the Population Structure of the Grasshopper Ommexecha virens (Orthoptera: Ommexechidae).

Abstract

The grasshopper Ommexecha virensServille has low dispersion capacity, and it is regarded as a specialist, only being found in sandy, dry environments with high incidence of sunlight. Considering these aspects, we evaluated the diversity and genetic structure of O. virens natural populations using ISSR (Inter Simple Sequence Repeat) markers. The data pointed to low expected heterozygosity for some populations (HE = 0.06-0.09), probably a consequence of positive inbreeding, which is typical of species showing low or null dispersion indices. Moreover, significant genetic differentiation was observed (FST = 0.50 and GST = 0.51), as well as low number of migrants (Nm = 0.47), indicating that the populations are genetically differentiated. This is likely related to the limitation in dispersing and fragmentation of suitable environment localities colonized by O. virens. The populations of O. virens were structured in three genetic groups associated to different landscapes, revealing the presence of a secondary contact zone, possibly arisen from isolation followed by genetic divergence among populations and subsequent gene flow of divergent individuals of O. virens. At last, we found positive isolation by distance (IBD; r: 0.427; P: 0.025) which is an important factor, since it may be adding to the emergence of reproductive barriers among individuals of O. virens that have been experiencing isolation.