Molecular phylogeny of the Drosophila obscura species group, with emphasis on the Old World species

<p>Abstract</p> <p>Background</p> <p>Species of the <it>Drosophila obscura </it>species group (e.g., <it>D. pseudoobscura</it>, <it>D. subobscura</it>) have served as favorable models in evolutionary studies since the 1930's. Despite numbers of studies conducted with varied types of data, the basal phylogeny in this group is still controversial, presumably owing to not only the hypothetical 'rapid radiation' history of this group, but also limited taxon sampling from the Old World (esp. the Oriental and Afrotropical regions). Here we reconstruct the phylogeny of this group by using sequence data from 6 loci of 21 species (including 16 Old World ones) covering all the 6 subgroups of this group, estimate the divergence times among lineages, and statistically test the 'rapid radiation' hypothesis.</p> <p>Results</p> <p>Phylogenetic analyses indicate that each of the <it>subobscura</it>, <it>sinobscura</it>, <it>affinis</it>, and <it>pseudoobscura </it>subgroups is monophyletic. The <it>subobscura </it>and <it>microlabis </it>subgroups form the basal clade in the <it>obscura </it>group. Partial species of the <it>obscura </it>subgroup (the <it>D. ambigua</it>/<it>D. obscura</it>/<it>D. tristis </it>triad plus the <it>D. subsilvestris</it>/<it>D. dianensis </it>pair) forms a monophyletic group which appears to be most closely related to the <it>sinobscura </it>subgroup. The remaining basal relationships in the <it>obscura </it>group are not resolved by the present study. Divergence times on a ML tree based on mtDNA data are estimated with a calibration of 30–35 Mya for the divergence between the <it>obscura </it>and <it>melanogaster </it>groups. The result suggests that at least half of the current major lineages of the <it>obscura </it>group originated by the mid-Miocene time (~15 Mya), a time of the last developing and fragmentation of the temperate forest in North Hemisphere.</p> <p>Conclusion</p> <p>The <it>obscura </it>group began to diversify rapidly before invading into the New World. The <it>subobscura </it>and <it>microlabis </it>subgroups form the basal clade in this group. The <it>obscura </it>subgroup is paraphyletic. Partial members of this subgroup (<it>D. ambigua</it>, <it>D. obscura</it>, <it>D. tristis</it>, <it>D. subsilvestris</it>, and <it>D. dianensis</it>) form a monophyletic group which appears to be most closely related to the <it>sinobscura </it>subgroup.</p

The evolution of euhermaphroditism in caridean shrimps: a molecular perspective of sexual systems and systematics

<p>Abstract</p> <p>Background</p> <p>The hippolytid genus <it>Lysmata </it>is characterized by simultaneous hermaphroditism, a very rare sexual system among Decapoda. Specialized cleaning behavior is reported in a few pair-living species; these life history traits vary within the genus. Unfortunately, the systematics of <it>Lysmata </it>and the Hippolytidae itself are in contention, making it difficult to examine these taxa for trends in life history traits. A phylogeny of <it>Lysmata </it>and related taxa is needed, to clarify their evolutionary relationships and the origin of their unique sexual pattern. In this study, we present a molecular phylogenetic analysis among species of <it>Lysmata</it>, related genera, and several putative hippolytids. The analysis is based upon DNA sequences of two genes, 16S mtDNA and nuclear 28S rRNA. Phylogenetic trees were estimated using Bayesian Inference, Maximum Likelihood, and Maximum Parsimony.</p> <p>Results</p> <p>Phylogenetic analysis of 29 species of <it>Lysmata</it>, eight genera of Hippolytidae and two genera of Barbouriidae based on a single (16S, 28S) and combined gene approach (16S+28S) indicates that three groups of <it>Lysmata </it>differentiate according to antennular morphology: (1) <it>Lysmata</it>, having a multi-segmented accessory branch, (2) <it>Hippolysmata </it>(prior to Chace 1972), with a one-segmented accessory branch, and (3) a third group of <it>Lysmata </it>outliers, with one-segmented unguiform accessory branch, and close affinity to the genera <it>Exhippolysmata </it>and <it>Lysmatella</it>. The monophyly of the clade bearing a multi-segmented accessory branch is robust. Within the short accessory branch clade, species with specialized cleaning behaviors form a monophyletic clade, however, the integrity of the clade was sensitive to alignment criteria. Other hippolytid and barbouriid genera used in the analysis are basal to these three groups, including one displaying simultaneous hermaphroditism (<it>Parhippolyte</it>). The two barbouriid species occur in a separate clade, but among hippolytid taxa.</p> <p>Conclusions</p> <p>The data support the historical morphological division of <it>Lysmata </it>into clades based on accessory branch morphology. The position of the "cleaner" shrimps, indicates that specialized cleaning behavior is a derived trait. The topologies of the cladograms support the monophyly of the barbouriids, but do not support their elevation to familial status. Taxa ancestral to the genus <it>Lysmata </it>display simultaneous hermaphroditism, suggesting that this life history trait evolved outside the genus <it>Lysmata</it>.</p

Acute Geometric Changes of the Mitral Annulus after Coronary Occlusion: A Real-Time 3D Echocardiographic Study

We performed real-time 3D echocardiography in sixteen sheep to compare acute geometric changes in the mitral annulus after left anterior descending coronary artery (LAD, n=8) ligation and those after left circumflex coronary artery (LCX, n=8) ligation. The mitral regurgitation (MR) was quantified by regurgitant volume (RV) using the proximal isovelocity surface area method. The mitral annulus was reconstructed through the hinge points of the annulus traced on 9 rotational apical planes (angle increment=20°). Mitral annular area (MAA) and the ratio of antero-posterior (AP) to commissure-commissure (CC) dimension of the annulus were calculated. Non-planar angle (NPA) representing non-planarity of the annulus was measured. After LCX occlusion, there were significant increases of the MAA during both early and late systole (p<0.01) with significant MR (RV: 30±14 mL), while there was neither a significant increase of MAA, nor a significant MR (RV: 4±5 mL) after LAD occlusion. AP/CC ratio (p<0.01) and NPA (p<0.01) also significantly increased after LCX occlusion during both early and late systole. The mitral annulus was significantly enlarged in the antero-posterior direction with significant decrease of non-planarity compared to LAD occlusion immediately after LCX occlusion