Data from: Morphological, genetic and chromosomal variation at a small spatial scale within a mosaic hybrid zone of the grasshopper Dichroplus pratensis Bruner (Acrididae)

Hybrid zones are regions where genetically different populations meet and
mate, resulting in offspring of mixed characteristics. In organisms with
limited dispersal, such as melanopline grasshoppers, hybrid zones can
occur at small spatial scales (i. e., < 500 m). We assessed levels
of morphological, chromosomal and molecular variability in adult males of
the grasshopper Dichroplus pratensis Bruner (N = 137) collected at 12
sites within a mosaic hybrid zone in a heterogeneous environment in Sierra
de la Ventana, Argentina. In this hybrid zone, two Robertsonian
chromosomal races, polymorphic for different centric fusions, meet (the
Northern race at low altitudes and the Southern race at higher altitudes),
forming hybrids that show monobrachial homologies during meiosis. High
morphometric variation in six traits was revealed among grasshoppers of
both sexes, with male body size positively and significantly correlated
with increasing altitude. Frequency of Robertsonian fusions characteristic
of the Southern race increased significantly with altitude. Moreover,
fusion frequencies covaried between samples. Considerable genetic
variation was revealed by RAPD markers, with heterozygosity ranging from
0.3477 to 0.3745. Insects from low-altitude and high-altitude populations
showed significant genetic differentiation, as indicated by FST values.
The proposed model for D. pratensis, involving the generation and
maintenance by chromosomal fusions, of gene complexes adaptive in
different environments, could explain the observed clinal patterns within
the contact zone.