斯氏狸殖吸虫螺类宿主新记录:洪山拟钉螺新种记述

本文报道斯氏狸殖吸虫新的螺类宿主——洪山拟钉螺Tricula hongshanensis sp. nov.的特点:螺壳较宽而短,体螺层较高大,壳口上缘成锐角,触角伸展时较长,收缩吋有环状皱褶,雄性阴茎较粗短,末端钝圆,齿舌公式不同于其它拟钉螺。     

Systematics of a widely distributed western North American springsnail,Pyrgulopsis?micrococcus (Caenogastropoda,Hydrobiidae), with descriptions?of?three new congeners

We describe three new species of springsnails (genus Pyrgulopsis) from the Amargosa River basin, California and Nevada (P. licina sp. n., P. perforata sp. n., P. sanchezi sp. n.), each of which was previously considered to be part of P. micrococcus. We also restrict P. micrococcus to its type locality area (Oasis Valley) and redefine a regional congener, P. turbatrix, to include populations from the central Death Valley region and San Bernardino Mountains that had been previously identified as P. micrococcus. The five species treated herein form genetically distinct lineages that differ from each other by 4.2–12.6% for mtCOI and 5.2–13.6% for mtNDI (based on previously published and newly obtained data), and are diagnosable by shell and/or penial characters. The new molecular data presented herein confirm sympatry of P. licina and P. sanchezi in Ash Meadows (consistent with morphological evidence) and delineate an additional lineage of P. micrococcus (in the broad sense) that we do not treat taxonomically owing to the paucity of morphological material. Conservation measures are needed to ensure the long term persistence of populations of P. micrococcus and a genetically differentiated lineage of P. sanchezi which live in disturbed habitats on private lands.     

Fine scale patterns of migration and gene flow in the endangered mound spring snail, <Emphasis Type="Italic">Fonscochlea accepta</Emphasis> (Mollusca:Hydrobiidae) in arid Australia

Naturally patchy ecosystems are models for other systems currently undergoing anthropogenic habitat fragmentation. Understanding patterns of gene flow in these model systems can help us manage species and ecosystems threatened by human impacts. The mound springs of central Australia represent such a natural model ecosystem, supporting a unique aquatic fauna distributed within an inhospitable arid landscape. Moreover, these springs are being impacted by over extraction of groundwater, providing a unique opportunity to look at dispersal in a patchy habitat that is changing. The present study represents the first fine scale analysis of gene flow under different scenarios of habitat connectivity for the endangered mound spring snail, Fonscochlea accepta. Within a single spring group pairwise estimates of F _ST between springs were very low (ave 0.015) with no association found between genetic distance and a series of geographical distance matrices based on the degree of habitat connectivity among the springs: results implying unstructured dispersal and limited population isolation. However, results from Bayesian assignment tests showed that on average approximately 97% of snails were assigned to their spring of origin. In a preliminary analysis at broader geographic scales (among spring groups) the results from F _ST estimates, Mantel correlation analyses and assignment tests all suggest much stronger and geographically correlated population structuring. While varying results from F-statistics and Bayesian analyses stem from the different information they utilise, together they provide data on contemporary and historical estimates of gene flow and the influence of landscape dynamics on the spatial genetic patterning of the springs.     

Can poorly understood new characters support a poorly understood phylogeny? Shell-structure data in Hydrobiid systematics (Mollusca: Gastropoda: Prosobranchia: Hydrobiidae)

Parsimony-based techniques may help to reconstruct phylogeny based on knowledge of character evolution, and vice versa. Problems arise when one deals with poorly known and poorly understood phylogenies and character behaviour, as in such cases it is not easy to avoid circular logic. This study is concerned with such a case: the poorly understood systematics of the family Hydrobiidae; and with a new character set: shell surface and inner structure as studied by SEM. This is based on previous papers by these authors, describing these structures. A total of 25 binary or multistate characters were chosen, all of unknown transformation series and unclear homologies. The shortest tree was found with the HENNIG86 PC program, and further analysis was carried out with MACCLADE. The evolution of all the characters was analysed. Seven characters were excluded as being uninformative and/or having unknown states in some taxa. MPR was rooted based on the outgroup criterion, resulting in a tree that was two steps longer. The latter was compared with four trees found in the literature. The SEM-based tree supports only the tree based on the classification by Ponder and Warén (1988) and does not support the trees constructed following the systems described by Bernasconi (1992) or Radoman (1983). The shell-structure characters seem to show the same mosaic pattern of evolution as shown by the traditionally used characters, extending the character list. It seems possible to support the ‘traditional’ data set with the ‘new’ one using successive approximations, thus avoiding circular logic.     

A molecular phylogeny of aquatic gastropods provides a new perspective on biogeographic history of the Snake River Region

Mitochondrial DNA sequences of aquatic gastropods of the subgenus Pyrgulopsis (Natricola) were analyzed to test a commonly accepted hypothesis concerning the early history of the Snake River in the northwestern US. Distributions of Natricola and other regional biota were previously used to infer that the Snake River flowed to the Pacific through southeastern Oregon and northern California during the Neogene prior to its capture by the Columbia River in the late Pliocene (2 Ma). A molecular phylogeny based on partial sequences of COI and NDI (1149 bp) indicates that the Natricola clade is restricted to the modern Snake-Columbia River Basin and the Oregon Lakes region whereas northern California populations previously assigned to this subgenus belong to other lineages. The Natricola clade is not deeply subdivided into Oregon Lakes and Snake River Basin units consistent with late Pliocene fragmentation of the hypothesized paleodrainage, but instead is shallowly structured and contains multiple transitions among these two geographic areas. The strongly supported sister relationship between Natricola and a species from northwest Nevada (P. imperialis) is consistent with a recent proposal that the ancestral Snake River did not flow through southeast Oregon but instead flowed south to the Humboldt River. Within the context of this hypothesis, the multiple transitions between the Snake River Basin and the Oregon Lakes region that occurred within Natricola may be attributed to a late Pleistocene connection between these areas that was unrelated to the early course of the Snake River.     

A new species of hydrobiid snails (Mollusca, Gastropoda, Hydrobiidae) from central Greece

Anew minute valvatiform species belonging to the genus Daphniola Radoman, 1973, Daphniola eptalophossp. n., from mountain Parnassos, Greece is described. The new species has a transparent valvatiform-planispiral shell, wide and open umbilicus, grey-black pigmented soft body and head and a black penis with a small colorless outgrowth on the left side near its base. A comparative table of shell dimensions and a key to the species known for this endemic genus for Greece are provided.     

A new species of the Fluviopupa group (Caenogastropoda: Tateidae) from north-east Queensland,Australia

Fluviopupa kessneri n. sp. is described from the Mulgrave River and one of its major tributaries, the Little Mulgrave River, in north-east Queensland. It is the first record of the Fluviopupa group from a continental area, other members of the genus being known only from Fiji, New Guinea and a few other Pacific Islands, including New Caledonia.     

Incipient speciation in aquatic snails in an arid-zone spring complex

The gastropod genus Caldicochlea is endemic to the Dalhousie Springs in the arid north of South Australia. The genus contains two species, or species complexes, Caldicochlea harrisi and C. globosa that overlap morphologically but can be distinguished genetically, principally by allozymes at the Lap, Sordh-1 and Sordh-2 loci. C. harrisi is found in many of the approximately sixty active springs in the 70 km² of the Dalhousie complex, but C. globosa is confined to the northern half where there are larger, hotter springs. The species co-occur in many springs in this area, generally with apparently none, or low levels of hybridization, as judged by the absence of heterozygotes at the Lap and Sordh-2 loci. Introgression is apparendy low and bidirectional. In two springs within the current ranges of both species, Lap genotypes occur in Hardy-Weinberg expected frequencies. Genotypes at other loci suggest that this is unlikely to be due to the independent evolution of Lap polymorphisms in these springs. Reproductive isolation may have broken down or may not have been established in these springs. For the latter to be so, reproductive isolation must have evolved through intra-spring interactions between the species, and independently in different springs. Isolation would not be fully established, if at all, until after secondary contact of their colonizing populations.