Biogeography of the ubiquitous marine bacterium Alteromonas macleodii determined by multilocus sequence analysis

Twenty‐three isolates of the widely distributed marine bacteria Alteromonas macleodii have been analysed by multilocus sequence analysis combined with phylogenetic and multivariate statistical analyses. The strains originated from the Pacific Ocean, Mediterranean Sea, English Channel, Black Sea and Thailand. Using the nucleotide sequences of nine loci for each of the 23 isolates, a robust identification was achieved of different clades within the single species. Strains generally clustered with the depth in the water column from which the isolate originated. Strains also showed more recombination with isolates from the same vicinity, suggesting that genetic exchange plays a role in diversification of planktonic marine prokaryotes. This study thus shows for the first time for a large set of isolates of a species of planktonic marine prokaryotes that multilocus sequence analysis overcomes the problems associated with the analysis of individual marker genes or presence of extensive recombination events. It can thus achieve intraspecific identification to the level of genotypes and, by comparison with relevant environmental data, ecotypes.     

Multiple scale patterns of shell and anatomy variability in land snails: the case of the Sicilian Marmorana (Gastropoda: Pulmonata, Helicidae)

Certain major aspects of phenotypic diversity are still largely unexplained. When phenotypic patterns do not relate to habitat variables, fine analysis of morphological patterns and their distribution sheds light on the origin of diversity. Among invertebrates, snails are an ideal model for studying the roles of the neutral processes and selection involved in creating diversity. To understand patterns and processes of variability on different scales (regional: areas; local: sites), morphological variability of two sets of characters (shell and genitalia) was quantified in a group of rock-dwelling land snails of the genus Marmorana (Pulmonata, Helicidae). To analyse shell variability, partitioning of the overall variation into size and shape components was analysed by a principal component-based approach. Shell shape and size variability is not significantly influenced by any environmental pressure. Variability at site scale is mainly attributed to shell size, which is a trait demonstrated to have a high degree of phenotypic plasticity. No sharp changes were observed for genitalia. Moreover, allometries between shell size and genitalia measurements involve a few populations. The observed multiple scale patterns are in line with the hypothesis that genital variance may be selectively controlled to maintain function.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 359–370.     

A molecular perspective on the evolution of microteiid lizards (Squamata, Gymnophthalmidae), and a new classification for the family

A molecular phylogeny was reconstructed for 26 recognized genera of the Gymnophthalmidae using a total of 2379 bp of mitochondrial (12S, 16S and ND4) and nuclear (18S and c-mos) DNA sequences. We performed maximum parsimony (MP) and maximum likelihood (ML) analyses, and data partitions were analysed separately and in combination under MP. ML analyses were carried out only on the combined sequences for computational simplicity. Robustness for the recovered nodes was assessed with bootstrap and partitioned Bremer support (PBS) analyses. The total molecular evidence provided a better-resolved hypothesis than did separate analysis of individual partitions, and the PBS analysis indicates congruence among independent partitions for support of some internal nodes. Based on this hypothesis, a new classification for the family is proposed. Alopoglossus , the sister group of all the other Gymnophthalmidae was allocated to a new subfamily Alopoglossinae, and Rhachisaurus (a new genus for Anotosaura brachylepis) to the new Rhachisaurinae. Two tribes are recognized within the subfamily Gymnophthalminae: Heterodactylini and Gymnophthalmini, and two others within Cercosaurinae (Ecpleopini and Cercosaurini). Some ecological and evolutionary implications of the phylogenetic hypothesis are considered, including the independent occurrence of limb reduction, body elongation, and other characters associated with fossoriality.