Topic
Chalcosoma caucasus
About: Chalcosoma caucasus is a research topic. Over the lifetime, 3 publications have been published within this topic receiving 179 citations.
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TL;DR: The results suggest that allomorphosis of horns and wings is general and widespread among rhinoceros beetles of different phytogenies, and male dimorphism is also common, but its rigidity varies among different phylogenetic groups.
Abstract: In populations of four rhinoceros beetle species ( Chalcosoma Caucasus F. and C. atlas L. from Asia, and Dynastes neptunus Quonsel and D. hercules L. from America), quantitative analyses of intraspecific variations were conducted with emphasis on the allomorphosis of horns and wings. In all female populations, body length was isometric to all other morphological traits measured, indicating that large females are in all aspects magnified versions of small females. Males were larger and more variable than females. In all male populations, head and thorax horns were remarkably and positively allometric, whereas hind wing length and width were negatively allometric to body size. Thus, smaller males had comparatively large wings and rudimentary horns, and larger males had greatly enlarged horns and comparatively small wings. Males of C. Caucasus, C. atlas, and D. neptunus diverged into two clearly distinguishable morphs: minor with comparatively small body and shorter horns, and major with larger body and longer horns; in each morph the body and horn size relationship was subject to a different formula. In D. hercules, divergence of males into two morphs was less clear-cut; yet distinct body and horn size relationships could be detected in the minors and majors. The positive allometry of horns and the negative allometry of wings persisted across as well as within morphs. These results suggest that allomorphosis of horns and wings is general and widespread among rhinoceros beetles of different phytogenies, and male dimorphism is also common, but its rigidity varies among different phylogenetic groups.
87 citations
TL;DR: Male morphology of two closely related rhinoceros beetles species indicates that morphological character displacement in sympatry was most complete in sexual organs, which may account for the process of existing species conserving themselves as integrated units by avoiding interspecific competition and enhancing reproductive isolation.
Abstract: I quantitatively analyzed male morphology of two closely related rhinoceros beetles species (Chalcosoma caucasus F. and Chalcosoma atlas L.) in 12 allopatric and seven sympatric locations throughout Southeast Asia. The qualitative features and the magnitude of intraspecific variation of each species were unaltered between allopatric and sympatric locations. Across allopatric locations, body size, horn size, dimorphic dimension, and genitalia size nearly completely overlapped between C. caucasus and C. atlas. Yet, in all sympatric locations, the differences between the two species in these characters were highly significant. While the enlarged difference between the two species in body size in sympatry could be attributed to habitat differentiation, that in genitalia size far exceeded what was expected from the general body‐size displacement. These results indicate that morphological character displacement in sympatry was most complete in sexual organs. This may account for the process of existin...
71 citations
TL;DR: The results suggest that habitat shift and phenotypic body size displacement in sympatry of these species took place in response to the presence of the other species avoiding interspecific competition without changing intraspecific variability.
Abstract: Body and horn morphology of two rhinoceros beetle species ( Chalcosoma Caucasus F. and C. atlas L.) was observed in six allopatric (one of the two species occurs within the same geographical area) and three sympatric (both of them occur) locations. Across allopatric locations, the ranges of elevational distribution partially overlapped between the two species. In sympatric locations, C. Caucasus occurred at higher elevational range than C. atlas with little overlap of elevational distribution between the two species. Both species showed a clear male dimoiphism in all locations, that is, a minor morph with smaller body and rudimentary horns and the major morph with larger body and disproportionally large horns. Across allopatric locations, the sizes of the corresponding morphs partially overlapped between the two species. In sympatric locations, the sizes of each morph of C. Caucasus were greater than those of its corresponding morph in allopatric locations, whereas those of C. atlas were smaller than those in allopatric locations. Thus, in sympatric locations, the size of each morph of C. Caucasus was distinctly larger than that of the corresponding morph of C. atlas and there were little dimensional overlaps between the corresponding morphs of the two species. It is possible that the two species responded behaviorally to the presence of each other and the resultant elevational habitat shift caused the morphological differences. The magnitudes of intraspecific variation in body size and male dimorphic divergence of the two species did not differ significantly between allopatry and sympatry. These results suggest that habitat shift and phenotypic body size displacement in sympatry of these species took place in response to the presence of the other species avoiding interspecific competition without changing intraspecific variability.
32 citations