title: Reproductive isolation between 2 karyotypes in natural populations of the leaf beetle Chrysolina aurichalcea.
abstract: Japanese populations of the leaf beetle, Chrysolina aurichalcea, have 2 main karyotypes, Type 31 and Type 41, which greatly differ in chromosome number and form. We examined their geographical distribution and reproductive isolation in southern Hokkaido, northern Japan. Type 41 was widely distributed in the survey area, whereas Type 31 was restricted to a narrow portion. A transect across each karyotypic habitat revealed that both karyotypes co-occurred in a approximately 5 km wide zone, with few hybrids or hybrid derivatives. Assessment of the fine scale distribution showed that the 2 karyotypes do not occupy separate microhabitats within the sympatric zone. Karyotype combinations of copulating pairs in the sympatric zone showed no evidence of assortative mating according to karyotype. These findings suggest that postmating isolation between the 2 karyotypes is strong, whereas premating isolation is weak. It does not agree with results from previous studies, which reported a substantial degree of both post- and premating isolation between the karyotypes. Possible causes of the discrepancy in premating isolation are discussed.
authors.affiliation: Department of Biological Sciences, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minamiohsawa, Hachioji, Tokyo 192-0397, Japan. nkitamur@gmail.com
authors.forename: Norikazu
authors.initials: N
authors.lastname: Kitamura
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Fujiyama
authors.forename: Haruo
authors.initials: H
authors.lastname: Katakura
authors.forename: Tadashi
authors.initials: T
authors.lastname: Aotsuka
mesh_terms: D000818:Animals; D002678:Chimera / Q000235:genetics; D001517:Coleoptera / Q000235:genetics*; D003307:Copulation; D005260:Female; D014644:Genetic Variation; D007564:Japan; D007621:Karyotyping; D008297:Male; D012098:Reproduction / Q000235:genetics