Parrots (order Psittaciformes) have developed novel cranial morphology. At the same time, they show considerable morphological diversity in the cranial musculoskeletal system, which includes two novel structures: the suborbital arch and the musculus (M.) pseudomasseter. To understand comprehensively the evolutionary pattern and process of novel cranial morphology in parrots, phylogenetic and developmental studies were conducted. Firstly, we undertook phylogenetic analyses based on mitochondrial ribosomal RNA gene sequences to obtain a robust phylogeny among parrots, and secondly we surveyed the cranial morphology of parrots extensively to add new information on the character states. Character mapping onto molecular phylogenies indicated strongly the repeated evolution of both the suborbital arch and the well-developed M. pseudomasseter within parrots. These results also suggested that the direction of evolutionary change is not always identical in the two characters, implying that these characters are relatively independent or decoupled structures behaving as separate modules. Finally, we compared the developmental pattern of jaw muscles among bird species and found a difference in the timing of M. pseudomasseter differentiation between the cockatiel Nymphicus hollandicus (representative of a well-developed condition) and the peach-faced lovebird Agapornis roseicollis (representative of an underdeveloped condition). On the basis of this study, we suggest that in the development of novel traits, modularity and heterochrony facilitate the diversification of parrot cranial morphology.
To infer the differentiation of Japanese Davidius dragonflies, we investigated the genealogies of the mitochondrial cytochrome oxidase subunit I gene (COI) and the nuclear ribosomal RNA gene region encompassing 18S, ITS1, 5.8S, and ITS2 sequences for three species endemic to Japan--Davidius nanus, D. fujiama, and D. moiwanus--as well as D. lunatus from the Korean Peninsula. According to the mitochondrial and nuclear gene genealogies, D. nanus and D. moiwanus are closely related and are sister to the continental species D. lunatus, whereas D. fujiama differentiated from an ancestor of the other three species. Although the mitochondrial DNA data did not resolve the relationships between D. nanus and three D. moiwanus subspecies, the nuclear DNA data indicate the monophyly of D. moiwanus and its subspecies. The nuclear gene genealogy suggests that isolated wetlands used by larval D. moiwanus derive from the ancestral riverine habitats of D. nanus and other Davidius species. The COI sequence divergence among local populations was much greater in D. moiwanus than in D. nanus, which may be the result of differences in the dispersal ranges associated with the habitat types of these species.
Molecular phylogeographical analyses of Anotogaster sieboldii (Selys, 1854) were conducted to reveal the differentiation process of insular populations. The gene genealogy based on 845 bp of the mitochondrial genes (cytochrome oxidase subunit I and subunit II) indicated that A. sieboldii includes two deeply separated lineages. These two major lineages seem to have differentiated in Miocene before the formation of the insular East Asia. One lineage includes three inner clades that correspond to the populations of northern area (the Japanese main islands, Korean Peninsula, Yakushima), Amamioshima and Okinawajima. Populations of Central Ryukyu, including Amamioshima and Okinawajima, might have been divided from the northern populations in early Pleistocene. The other major lineage includes populations of the Yaeyama Group, Taiwan and East China. The former two populations were reconstructed as a reciprocal monophyletic group. Populations of Taiwan and Yaeyama Groups would have been separated from the continental ones in Pleistocene. These two highly divergent lineages should be recognized as distinct species. Furthermore, the mitochondrial lineages revealed six genetically distinct and geographically isolated assemblages: (1) northern populations, (2) Amamioshima, (3) Okinawajima, (4) Yaeyama Group, (5) Taiwan and (6) East China.
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