We demonstrate experimentally that differences in genital characters impose a direct cost of interspecific copulation on two closely related carabid species, Carabus (Ohomopterus) maiyasanus and C. (O.) iwawakianus, that share a narrow hybrid zone. Males of both species attempted copulation indiscriminately between conspecific and heterospecific females. Females experiencing heterospecific mating often suffered mortality due to rupture of their vaginal membranes. Those without fatal injury laid eggs which developed into F adults, but the fertilization rate was much lower than for intraspecific pairs. Males of C. maiyasanus, but not C. iwawakianus, often had broken genital parts (copulatory pieces) following interspecific copulations, which may prevent normal copulation in subsequent matings. Because of female mortality and low fertilization rate, the estimated fitness cost of interspecific mating was very large in terms of the reduction in the number of offspring (hatching larvae) for both sexes and both species. Thus, genital lock-and-key appears to exert significant selection against hybridization in the hybrid zone of these carabid beetles.

We introduce a method to make self-positioned micromachined structures by using the strain in a pair of lattice-mismatched epitaxial layers. This method allows the fabrication of simple and robust hinges for movable parts, and it can be applied to any pair of lattice-mismatched epitaxial layers, in semiconductors or metals. As an application example, a standing mirror was fabricated. A multilayer structure including an AlGaAs/GaAs dielectric mirror and an InGaAs strained layer was grown by molecular-beam epitaxy on a GaAs substrate. After releasing the multilayer structure from the substrate by selective etching, it moved to its final position powered by the strain release in the InGaAs layer.

Geographic variation and interspecific differentiation in body size (body length) were analyzed for 15 species of the carabid subgenus Ohomopterus (genus Carabus; Coleoptera, Carabidae) in Japan. Local species assemblages of this subgenus consist of up to 5 species of different size classes. These beetles exhibited sexual dimorphism in body size where females are larger than males, except Carabus uenoi, in which the male and female sizes were equivalent, possibly because of the exaggerated male genitalia. In 9 of 15 species, there was a positive correlation between mean body size and annual mean temperature of habitat, representing the converse of Bergmann's rule. However, in some cases this correlation does not hold over the range of a species because of regional differences. When allopatric and sympatric populations were compared, allopatric populations of Carabus albrechti and C. japonicus had larger bodies than sympatric populations. These intraspecific differences may have resulted from character displacement. In each local assemblage with 2 or more species, there was little interspecific overlap of body size, although the body size ratio between two species with adjacent body sizes seldom showed strict constancy. The mean size ratio between 2 adjacent species in an assemblage was reduced with the number of species, whereas the size ratio of the largest to smallest species in an assemblage increased with the number of species (i.e., the expansion of body size range). These results indicate that the body size of Ohomopterus species may have evolved in response to both climatic conditions and interspecific interactions. Because each species or species group represents the same size class over the distribution range and similarsized species are parapatric or allopatric, the interspecific segregation in body size in local assemblages may have resulted mainly from a size assortment process during colonization.

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