Genetic legacy of tertiary climatic change: a case study of two freshwater loaches, Schistura fasciolata and Pseudogastromyzon myersi, in Hong Kong.

The high biodiversity and strong population structure of freshwater fauna has often been attributed to historical geological and climatic alterations. The impact of these historical changes on obligate freshwater species on a small geographical scale has not been well understood due to the lack of fine-scale comparative phylogeographic studies. Strong population structure has been reported in a goby and a caridean shrimp in Hong Kong, a small but highly developed city in South China, but the common drivers of population differentiation in freshwater fauna in this region remain unclear. This study examined the fine-scale phylogeographic patterns of two freshwater loaches, Schistura fasciolata and Pseudogastromyzon myersi in Hong Kong, using sequence data of mitochondrial control region and two nuclear markers (interphotoreceptor retinoid binding protein gene 2 and ribosomal protein S13 gene). Results show that they exhibit pronounced population structure as supported by high and significant ΦST. Phylogenetic analyses based on the control region reveal six and three distinct lineages in S. fasciolata and P. myersi, respectively. Phylogeographic structure of both species generally follows the paleodrainage pattern, though P. myersi shows a shallower structure on the Mainland, perhaps due to their higher mobility. Most of these lineages diverged during the Pliocene and Late Pleistocene, a period with marked sea-level fluctuations. In a broader context, this suggests that sea-level fluctuation played an important role in shaping even the fine-scale population structure of freshwater fish in South China, implying that the genetic diversity of this fauna may be higher than expected.

Molecular evidence for the Southern Hemisphere origin and deep-sea diversification of spiny lobsters (Crustacea: Decapoda: Palinuridae).

Spiny lobsters (family Palinuridae) are economically important marine animals that have been the subject of a considerable amount of research. However, the phylogeny of this group remains disputed. Morphological analyses have not been able to resolve the relationships of the various members of the group, and no agreement has yet been reached on its phylogeny as indicated by the different gene trees reported to date. In the present study, we attempt to reconstruct the phylogeny of Palinuridae and its allies using sequences from three nuclear protein-coding genes (phosphoenolpyruvate carboxykinase, sodium-potassium ATPase alpha-subunit and histone 3). The inferred topology receives strong nodal support for most of the branches. The family Palinuridae is found to be paraphyletic with the polyphyletic Synaxidae nested within it. Stridentes forms a monophyletic assemblage, indicating that the stridulating sound producing organ evolved only once in the spiny lobsters. By contrast, Silentes is paraphyletic, as Palinurellus is more closely related to Stridentes than to other Silentes genera. The three genera restricted to the southern high latitudes (Jasus, Projasus and Sagmariasus) constitute the basal lineages in the spiny lobsters, suggesting a Southern Hemisphere origin for the group. Subsequent diversification appears to have been driven by the closure of the Tethys Sea and the formation of the Antarctic circumpolar current, which isolated the northern and southern taxa. Contrary to an earlier hypothesis that postulated evolution from a deep-sea ancestral stock, the shallow-water genus Panulirus is the basal taxon in Stridentes, while the deep-sea genera Puerulus and Linuparus are found to be derived. This indicates that the spiny lobsters invaded deep-sea habitats from the shallower water rocky reefs and then radiated. Our results suggest that Synaxidae is not a valid family, and should be considered to be synonymous with Palinuridae. We also found that the previously proposed subgenera Sagmariasus and Nupalirus are genetically highly diverged, and both warrant a generic status.

Phylogeny of Decapoda using two nuclear protein-coding genes: origin and evolution of the Reptantia.

The phylogeny of Decapoda is contentious and many hypotheses have been proposed based on morphological cladistic analyses. Recent molecular studies, however, yielded contrasting results despite their use of similar data (nuclear and mitochondrial rDNA). Here we present the first application of two nuclear protein-coding genes, phosphoenolpyruvate carboxykinase and sodium-potassium ATPase alpha-subunit, to reconstruct the phylogeny of major infraorders within Decapoda. A total of 64 species representing all infraorders of Pleocyemata were analyzed with five species from Dendrobranchiata as outgroups. Maximum likelihood and Bayesian inference reveal that the Reptantia and all but one infraorder are monophyletic. Thalassinidea, however, is polyphyletic. The nodal support for most of the infraordinal and inter-familial relationships is high. Stenopodidea and Caridea form a clade sister to Reptantia, which comprises two major clades. The first clade, consisting of Astacidea, Achelata, Polychelida and three thalassinidean families (Axiidae, Calocarididae and Eiconaxiidae), corresponds essentially to the old taxon suborder Macrura Reptantia. Polychelida nests within Macrura Reptantia instead of being the most basal reptant as suggested in previous studies. The high level of morphological and genetic divergence of Polychelida from Achelata and Astacidea justifies its infraorder status. The second major reptant clade consists of Anomura, Brachyura and two thalassindean families (Thalassinidae and Upogebiidae). Anomura and Brachyura form Meiura, with moderate support. Notably thalassinidean families are sister to both major reptant clades, suggesting that the stem lineage reptants were thalassinidean-like. Moreover, some families (e.g. Nephropidae, Diogenidae, Paguridae) are paraphyletic, warranting further studies to evaluate their status. The present study ably demonstrates the utility of nuclear protein-coding genes in phylogenetic inference in decapods. The topologies obtained are robust and the two molecular markers are informative across a wide range of taxonomic levels. We propose that nuclear protein-coding genes should constitute core markers for future phylogenetic studies of decapods, especially for higher systematics.

Angiography of primary central nervous system angiitis of childhood: conventional angiography versus magnetic resonance angiography at presentation.

BACKGROUND AND PURPOSE: To systematically analyze conventional angiographic (CA) features of children with primary central nervous system angiitis (cPACNS), to compare and correlate CA and MR angiography (MRA) lesion characteristics, and to define the sensitivity and specificity of MRA with CA as a reference standard. METHODS: A retrospective, single-center cohort study of consecutive patients with cPACNS was performed. Patients with CA and MRA studies at diagnosis were included. Imaging studies were blindly reviewed by 2 neuroradiologists using a standard analysis protocol. CA and MRA studies were compared using nonparametric analysis. RESULTS: Of 45 patients with MRA at diagnosis, there were 25 for whom CA and MRA studies were performed within 1 month of each other. These comprised the study group. The CA distribution of lesions was multifocal (76%) and proximal (86%) (P < .05) with a trend toward unilaterality (P = .06) with anterior circulation involvement (P = .08). The sensitivity and specificity of MRA for CA abnormality was 70% and 98%, respectively. There was no significant difference between MRA and CA for lesion detection or characterization (P = .87), and the modalities showed a fair correlation (kappa = 0.4). CONCLUSION: Angiographic lesions are multifocal and occur proximally and unilaterally within the anterior circulation. There is no significant difference in the ability of MRA to detect and characterize lesions when compared with CA.

MR imaging and angiography of primary CNS vasculitis of childhood.

BACKGROUND AND PURPOSE: Primary angiitis of the central nervous system of childhood (cPACNS) is a rare and ill-defined disease. In the absence of a brain biopsy, the diagnosis is based on typical clinical and imaging abnormalities. The aim of this study was to analyze systematically the MR imaging and MR angiographic (MRA) abnormalities in a large cohort of children with cPACNS. METHODS: We analyzed the MR imaging features of a single pediatric center cohort of 45 cPACNS patients. MR imaging studies were performed for all patients, and both MR imaging and MRA were performed for 42 patients, who formed the cohort for review of the presence and correlation of lesions. Proportions were calculated by using the Fisher exact test, and agreement between MR imaging and MRA was calculated by using the McNemar test. The sensitivity of each diagnostic technique was established. RESULTS: The most-common pattern of parenchymal abnormality was multifocal, unilateral involvement, each in 42/45 patients (93%). The lateral lenticulostriate artery terrritory was affected in 56% of cases, with involvement of a supratentorial deep gray matter structure in 91%. No infratentorial lesion occurred in the absence of supratentorial abnormality. MRA was normal in 12/42 patients (28.6%). Among the abnormal studies, stenosis was detected on MRA in 83% and was "benign" in appearance in 73% of patients and "aggressive" in 16.7%. Involvement was proximal in 83% and distal in 27% of patients. Multiple ipsilateral lesions were seen in 63%. MR imaging was abnormal in every patient where MRA was abnormal. With the assumption of MR imaging as the gold standard, the sensitivity of MRA was 72%. The agreement between MR imaging and MRA for abnormality was significant (P = .04). CONCLUSION: We have illustrated the MR imaging and MRA appearances of cPACNS in the largest cohort to date. Both parenchymal and vascular lesions were predominantly proximal, unilateral, and multifocal within the anterior circulation. There was good agreement between MR imaging and MRA for lesion location. MR imaging findings were abnormal in all cases at diagnosis, and this remains the most sensitive technique to the detection of vasculitis.