Jun Kitaura

Adaptive evolution of sexual systems in pedunculate barnacles

How and why diverse sexual systems evolve are fascinating evolutionary questions, but few empirical studies have dealt with these questions in animals. Pedunculate (gooseneck) barnacles show such diversity, including simultaneous hermaphroditism, coexistence of dwarf males and hermaphrodites (androdioecy), and coexistence of dwarf males and females (dioecy). Here, we report the first phylogenetically controlled test of the hypothesis that the ultimate cause of the diverse sexual systems and presence of dwarf males in this group is limited mating opportunities for non-dwarf individuals, owing to mating in small groups. Within the pedunculate barnacle phylogeny, dwarf males and females have evolved repeatedly. Females are more likely to evolve in androdioecious than hermaphroditic populations, suggesting that evolution of dwarf males has preceded that of females in pedunculates. Both dwarf males and females are associated with a higher proportion of solitary individuals in the population, corroborating the hypothesis that limited mating opportunities have favoured evolution of these diverse sexual systems, which have puzzled biologists since Darwin.

EVOLUTION OF WAVING DISPLAY IN BRACHYURAN CRABS OF THE GENUS ILYOPLAX

Abstract Male waving displays of the species of Ilyoplax (Brachyura: Ocypodidae) have so far been described in I. delsmani, I. gangetica, and I. orientalis. In this study, male waving displays of I. dentata, I. dentimerosa, I. deschampsi, I. formosensis, I. integra, I. ningpoensis, I. pingi, I. pusilla, I. serrata, I. strigicarpa, I. tansuiensis, and Ilyoplax sp. are described for the first time. Waving display of the above 15 species of Ilyoplax can be classified into three patterns; a circular type, vertical type, and asymmetrical type. Asymmetrical wave forms were observed in only two species, I. orientalis and I. tansuiensis, vertical wave forms were seen in four species, I. delsmani, I. dentimerosa, I. pingi, and I. serrata, while most other species exhibited circular wave forms. To understand the evolutionary divergence of these waving forms observed in species of Ilyoplax, a molecular phylogeny was reconstructed based on 1005-bp nucleotide sequences from mitochondrial 16S and 12S rRNA genes of 16 species and two out-group taxa. Phylogenetic analysis of waving forms suggested that circular waves evolved once in the early history of the lineage. Vertical wave forms were suggested to have subsequently evolved three times independently from circular wave forms, and the asymmetrical wave form has also evolved from circular wave form. The evolution of distinct waving forms is considered to be associated with the presence of geographic sympatric species.

Taxonomic re‐examination of the two camptandriid crab species Deiratonotus japonicus (Sakai, 1934) and D. tondensis Sakai, 1983, and genetic differentiation among their local populations

Morphological and genetic characteristics were investigated for two allied brachyuran species, Deiratonotus japonicus (Sakai, 1934) and D. tondensis Sakai, 1983 (family Camptandriidae), occurring in upstream brackish water areas of western Japan. Our observations on over 400 crab specimens from 13 localities, including the types, revealed that there were many specimens that could not be identified morphologically as either species by their diagnostic characters indicated in original descriptions. We grouped specimens into three morphological types of “D. japonicus”, “D. tondensis” and species‐unknown. Specimens of three morphological types were often found even in the same localities. Moreover, there was no correspondence between the morphological types and mitochondrial DNA haplotypes (COI, 540 bp), which was revealed by phylogenetic analyses using maximum likelihood methods and a statistical‐parsimony haplotype network constructed with the TCS computer program. In addition, genetic distance between “D. japonicus” type and “D. tondensis” type (0–1.7%) were in the intraspecific range of Crustacea. Thus, D. japonicus and D. tondensis ought to be treated as the same species and the latter nominal species as a junior synonym of the former. Significant genetic differentiation was recognized among populations with a positive correlation between geographic and genetic distances, suggesting isolation by distance. In consequence, a redescription of the newly defined Deiratonotus japonicus is presented, taking into account the newly recognized morphological variability in this species. Present address: Katsutoshi Watanabe, Graduate School of Science, Kyoto University, Sakyo‐ku, Kyoto, Japan

Genetic relationship among Japanese sentinel crabs (Decapoda: Ocypodidae: genus Macrophthalmus).

Seven species (eight populations) of sentinel crabs (genus Macrophthalmus) from the Japan coast and Uca vocans and Ocypode ceratophthalma, were examined electrophoretically for genetic variations in 13 enzymatic and one non-enzymatic protein comprising 17 loci. Most species were highly differentiated from each other (Neis genetic distance, 0.29-1.63). The least genetic distance was found between M. japonicus and M. banzai, the genetic distinctiveness of the two taxa being supported by three divergent loci with no common allele. The genetic relationships among Macrophthalmus species differed greatly from those inferred from morphological features, with a UPGMA tree suggesting that the sub-genus Macrophthalmus is polyphyletic.

Behavioural and molecular evidence for the systematic position of Macrophthalmus (Hemiplax) hirtipes Hombron & Jacquinot, 1846, with comments on macrophthalmine subgenera (Decapoda, Brachyura, Macrophthalmidae)

The analysis of 16s rRNA data from the New Zealand sentinel crab, Macrophthalmus (Hemiplax) hirtipes (Jacquinot & Hombron, 1846) (Macrophthalminae: Macrophthalmidae) shows that it is the most basal species in the genus Macrophthalmus , and behavioural trait mapping suggests that ancestral behaviours included extended cheliped fighting. Other behaviour found in some sentinel crabs, such as allocleaning and waving displays, were absent in the ancestor and are regarded here as derived traits. It is proposed that the two subgenera Hemiplax and Tasmanoplax be elevated to full generic status. Three subgenera appears to be polyphyletic: Macrophthalmus (26 species), Mareotis (14 species) and Paramareotis (4 species), and to resolve this problem molecular data from the remaining species is added into the analysis. The Australasian fauna contains the four most basal genera of the Macrophthalminae: Tasmanoplax, Hemiplax, Australoplax , and Enigmaplax . The hypothesis is that these were early off-shoots from Tethyan ancestor(s) that colonized Australasia. Keywords:family Macrophthalmidae ; Hemiplax hirtipes ; Hombron; Jacquinot; Macrophthalmus latifrons