No abstract

Strains of pink-pigmented facultative methylotrophs which were isolated previously from various environments and assigned tentatively to the genus Methylobacterium were characterized in comparison with authentic strains of previously known species of this genus. Most of the isolates derived from chlorinated water supplies exhibited resistance to chlorine, whereas 29 to 40% of the isolates from air, natural aquatic environments, and clinical materials were chlorine resistant. None of the tested authentic strains of Methylobacterium species obtained from culture collections exhibited chlorine resistance. Numerical analysis of phenotypic profiles showed that the test organisms could be divided into 19 clusters at a similarity level of 80%, at which all established Methylobacterium species tested were separated from each other except M. organophilum and M. rhodesianum. The chlorine-resistant isolates were randomly distributed among all clusters. The 16S ribosomal DNA (rDNA) sequence-based phylogenetic analyses showed that representatives of the isolates together with known Methylobacterium species formed a line of descent distinct from that of members of related genera in the alpha-2 subclass of the Proteobacteria and were divided into three subclusters within the Methylobacterium group. These results demonstrate that there is phenotypic and genetic diversity among chlorine-resistant Methylobacterium strains within the genus.

No abstract

We assessed potential adult longevity and male choice for a mate in two populations of Asteralobia sasakii associated with Ilex crenata and I. integra to test the hypothesis that interbreeding between these populations is prevented by the difference in emergence timing in the field. A previous study showed that the last day of adult emergence on I. integra and the first day of adult emergence on I. crenata were separated by six to 11 days. When adults were maintained in the laboratory with restricted flying, mating and oviposition, adults from both populations survived for four to five days, suggesting that the period when adults were active did not overlap between the two populations in the field. The mate choice test showed that males clearly approached females of the same host origin. These results suggest that the two populations have little chance of interbreeding even when they occur sympatrically. Other life history parameters such as the number of eggs in the ovary, daily emergence pattern, sex ratio and the duration of copulation also varied between the two populations. Our overall results strongly suggest that the two populations on different host plants can be referred to as distinct species.

No abstract