Open AccessHybrids between Chorthippus brunneus and C. jacobsi (Orthoptera: Acrididae) do not show endogenous postzygotic isolation
Author(s) -
SALDAMANDO C. I.,
TATSUTA H.,
BUTLIN R. K.
Publication year - 2005
Publication title -
biological journal of the linnean society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.906
H-Index - 112
eISSN - 1095-8312
pISSN - 0024-4066
DOI - 10.1111/j.1095-8312.2005.000424.x
Subject(s) - reproductive isolation , biology , allopatric speciation , hybrid zone , sympatric speciation , subspecies , sympatry , evolutionary biology , hybrid , orthoptera , acrididae , zoology , gene flow , genetics , genetic variation , population , botany , gene , demography , sociology
Studies of prezygotic and postzygotic isolation in Drosophila have shown in general that species in sympatry tend to evolve prezygotic barriers earlier than do species in allopatry. However, postzygotic barriers tend to evolve at the same evolutionary rate in both sympatric and allopatric species. In contrast to these observations, the grasshoppers Chorthippus parallelus parallelus and C. p. erythropus show complete hybrid male sterility but only limited prezygotic isolation after an estimated 0.5 millions years of divergence. Like their congeners, C. brunneus and C. jacobsi form a hybrid zone where their ranges meet in northern Spain. However, the hybrid zone is mosaic and bimodal and, in contrast to the high levels of postzygotic isolation between C. parallelus subspecies, these two species showed no significant reduction in hybrid fitness in F 1 or backcross generations relative to the parental generations. The level of prezygotic isolation in laboratory tests was comparable to that between C. parallelus subspecies. These results suggest that endogenous postzygotic isolation does not play an important role in the reproductive isolation between C. brunneus and C. jacobsi , or in determining the structure of the hybrid zone. Exogenous postzygotic isolation may be present and should be tested in future studies. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 84 , 195–203.