| Summary: | 碩士 === 國立臺灣大學 === 漁業科學研究所 === 96 === Terrestrial hermit crabs are represented by the Coenobitidae, which includes only two genera, Birgus and Coenobita. Coconut crabs (Birgus) are among the world’s largest terrestrial arthropods, having a crab-like morphology and a strongly calcified exoskeleton. The shell-carrying terrestrial hermit crabs (Coenobita), in contrast, have depended on gastropod shells for protection and as an aid in respiration. The asymmetrical pleons of terrestrial hermit crabs have been considered an evidence of marine hermit crab ancestry. Shell-carrying has constrained the morphological evolution of hermit crabs by requiring a decalcified asymmetrical pleon capable of coiling into gastropod shells. The target purpose of this work is to explore the species identification, phylogenetic relationships and evolutionary processes of terrestrial hermit crabs based on the morphological and molecular information. Comparative analysis of morphological characters and molecular sequences in a phylogenetic effort efficiently improves the sensitivity and accuracy of evolutionary inference, producing more precise results than single dataset analyses can provide. The partial sequences from the mtDNA COI and 16S rDNA genes of Coenobita species, nine of which are presented here for the first time (C. brevimanus, C. cavipes, C. clypeatus, C. hilgendorfi, C. perlatus, C. pseudorugosus, C. purpureus, C. rugosus, C. violascens), demonstrate how morphological patterns can illuminate the processes of evolutionary transition at the genus scale. Besides, there have been several taxonomic ambiguities among these Coenobita species. We reexamined and reidentified reliable morphological characters for species identification by referring to the patristic distances between each species. And, most important of all, we present evidences of molecular and morphological studies that the evolutionary route of terrestrial adaptation in the Coenobita phylogeny was from the inland to the shore, and not, as some carcinologists would have believed, gradually from the shore to the inland.
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