Dichroplus pratensis and Sorex araneus: two examples of chromosomal hybrid zones in the context of speciation

P. MIROL; J SEARLE

FOLIA ZOOLOGICA

Año: 1994 vol. 43 p. 29 - 36

0139-7893

Different chromosomal races of the South American grasshopper Dichroplus pratensis differ substantially in their complement of metacentric chromosomes. Sometimes the metacentrics in different races show monobrachial homology, presumably due to independent Robertsonian fusions. At least one contact zone between chromosomal races is known, in which individuals forming meiotic quadi- and quinquevalents are observed. There are several characteristics which make this hybrid zone quite different from that of the common shrew (Sorex araneus) in Britain, which likewise occurs at the contact between metacentric races: 1. all populations sampled, wether within or outside the contact area, are polymorphic for the same arm combinations that differ between the races, 2. the frequencies of the metacentric chromosomes are invariable high even within the contact area, and 3. metacentric frequencies vary very abruptly over short distances. A comparison between the chromosomal hybrid zones of D. pratensis and S. araneus is made in relation to current models of raciation and speciation.