Dog chromosome-specific paints reveal evolutionary inter- and intrachromosomal rearrangements in the American mink and human

Forty chromosome-specific paint probes of the domestic dog (Canis familiaris, 2n = 78) were used to delineate conserved segments on metaphase chromosomes of the American mink (Mustela vison, 2n = 30) by fluorescence in situ hybridisation. Half of the 38 canine autosomal probes each painted one pair of homologous segments in a diploid mink metaphase, whereas the other 19 dog probes each painted from two to five pairs of discrete segments. In total, 38 canine autosomal paints highlighted 71 pairs of conserved segments in the mink. These painting results allow us to establish a complete comparative chromosome map between the American mink and domestic dog. This map demonstrates that extensive chromosome rearrangements differentiate the karyotypes of the dog and American mink. The 38 dog autosomes could be reconstructed from the 14 autosomes of the American mink through at least 47 fissions, 25 chromosome fusions, and six inversions. Furthermore, comparison of the current dog/mink map with the published human/dog map discloses 23 cryptic intrachromosomal rearrangements in 10 regions of conserved synteny in the human and American mink genomes and thus further refined the human/mink comparative genome map. Copyright (C) 2000 S. Karger AG, Basel.

Identification of native American founder mtDNAs through the analysis of complete mtDNA sequences: Some caveats

In this study, a detailed analysis of both previously published and new data was performed to determine whether complete, or almost complete, mtDNA sequences can resolve the long-debated issue of which Asian mtDNAs were founder sequences for the Native American mtDNA pool. Unfortunately, we now know that coding region data and their analysis are not without problems. To obtain and report reasonably correct sequences does not seem to be a trivial task, and to discriminate between Asian-and Native American mtDNA ancestries may be more complex than previously believed. It is essential to take into account the effects of mutational hot spots in both the control and coding regions, so that the number of apparent Native American mtDNA founder sequences is not erroneously inflated. As we report here, a careful analysis of all available data indicates that there is very little evidence that more than five founder mtDNA sequences entered Beringia before the Last Glacial Maximum and left their traces in the current Native American mtDNA pool.

Molecular evidence for diphyly of the Asian catfish family Amblycipitidae (Teleostei: Siluriformes) and exclusion of the South American Aspredinidae from Sisoroidea

Amblycipitidae Day, 1873 is an Asian family of catfishes (Siluriformes) usually considered to contain 28 species placed in three genera: Amblyceps (14 spp.), Liobagrus (12 spp.) and Xiurenbagrus (2 spp.). Morphology-based systematics has supported the monophyly of this family, with some authors placing Amblycipitidae within a larger group including Akysidae, Sisoridae and Aspredinidae, termed the Sisoroidea. Here we investigate the phylogenetic relationships among four species of Amblyceps, six species of Liobagrus and the two species of Xiurenbagrus with respect to other sisoroid taxa as well as other catfish groups using 6100 aligned base pairs of DNA sequence data from the rag1 and rag2 genes of the nuclear genome and from three regions (cyt b, COL ND4 plus tRNA-His and tRNA-Ser) of the mitochondrial genome. Parsimony and Bayesian analyses of the data indicate strong support for a diphyletic Amblycipitidae in which the genus Amblyceps is the sister group to the Sisoridae and a clade formed by genera Liobagrus and Xiurenbagrus is the sister group to Akysidae. These taxa together form a well supported monophyletic group that assembles all Asian sisoroid taxa, but excludes the South American Aspredinidae. Results for aspredinids are consistent with previous molecular studies that indicate these catfishes are not sisoroids, but the sister group to the South American doradoid catfishes (Auchenipteridae + Doradidae). The redefined sisoroid clade plus Bagridae, Horabagridae and (Ailia + Laides) make up a larger monophyletic group informally termed "Big Asia." Likelihood-based SH tests and Bayes Factor comparisons of the rag and the mitochondrial data partitions considered separately and combined reject both the hypothesis of amblycipitid monophyly and the hypothesis of aspredinid inclusion within Sisoroidea. This result for amblycipitids conflicts with a number of well documented morphological synapomorphies that we briefly review. Possible nomenclatural changes for amblycipitid taxa are noted.

Inbreeding depression for various traits in two cultured populations of the American bay scallop, Argopecten irradians irradians Lamarck (1819) introduced into China

This paper examines the effect of inbreeding level of population on the magnitude of inbreeding depression expressed by comparing them between two cultured populations (A and B) in the hermaphroditic animal of the bay scallop Argopecten irradians irradians. Population A is expected to have less genetic variations and higher inbreeding level due to longer cultured history (20 generations) and less "ancestral" individuals (26 individuals) than population B due to shorter cultured history (4 generations) and more "ancestral" individuals (406 individuals). Two groups within each population were produced, one using self-fertilization and one using mass-mating within the same population. Selfed offspring (AS and BS) from two populations both had lower fitness components than their mass-mated counterparts (AM and BM) and exhibited inbreeding depression for all examined traits, e.g. lower hatching, less viability and slower growth, indicating that inbreeding depression is a common feature in this animal. Fitness components in all traits of offspring from population A significantly differed those from population B and the magnitude of inbreeding depression for all traits in population A with higher inbreeding level was significantly smaller than that in population B with lower inbreeding level, indicating that both fitness components and magnitude of inbreeding depression were significantly affected by inbreeding level of populations and genetic load harbored in population A may be partially purged through inbreeding. Moreover, the magnitude of inbreeding depression in the two populations both varied among traits and life history stages. The present results support the partial-dominance hypothesis of inbreeding depression. (C) 2008 Elsevier B.V. All rights reserved.

Molecular evidence for the sister relationship of the eastern Asia-North American intercontinental species pair in the Podophyllum group (Berberidaceae)

The presumed pair relationships of intercontinental vicariad species in the Podophyllum group (Sinopodophyllum hexandrum vs. Podophyllum pelatum and Diphylleia grayi vs. D. cymosa) were recently, considered to be paraphyletic. In the present paper, the trnL-F and ITS gene sequences of the representatives were used to examine the sister relationships of these two vicariad species. A heuristic parsimony analysis based on the trnLF data identified Diphylleia as the basal clade of the other three genera, but provided poor resolution of their inter-relationships. High sequence divergence was found in the ITS data. ITS1 region, more variable but parsimonyuninformative. has no phylogenetic value, Sequence divergence of the ITS2 region provided abundant, phylogenetically informative variable characters. Analysis of ITS2 sequences confirmeda sister relationship between the presumable vicariad species, in spite of a low bootstrap support for Sinopodophyllum hexandrum vs. Podophyllum pelatum. The combined ITS2 and trnL-F data enforced a sister relationship between Sinopodophyllum hexandrum and Podophyllum pelatum with an elevated bootstrap support of 100%. Based on molecular phylogeny, the morphological evolution of this group was discussed. The self-pollination might have evolved from cross-fertilization two times in this group. The different pollination and seed dispersal systems of Sinopodophyllum hexandrum and Podophlyllum pelatum resulted from their adaptations to different ecological habitats. The divergence time of Sinopodophyllum hexandrum-Podophyllum pelatum is estimated to be 6.52+/-1.89 myr based on the ITS divergence. The divergence of this species pair predated or co-occurred with the recent uplift of the Himalayas 4-3 myr during the late Miocene and the formation of the alpine habitats. Sinopodophyllum hexandrum developed a host of specialized characters in its subsequent adaptation to the arid alpine surroundings. The present study confirmed the different patterns of species relationship between Asian-North American disjuncts. The isolation of plant elements between North America and eastern Asia must have been a gradual process, resulting in the different phylogenetic patterns and divergence times of the disjuncts.

西南极南设得兰群岛中新生代火山岩基底沉积学及其大地构造制约

Livingston Island, the second island of South Shetland Island, constains Mesozoic-Cenozoic basement, Mesozoic-Cenozoic volcanic sequences, plutonic intrusions and post-subduction volcanic rocks, which document the history and evolution of an important part of the South Shetland Islands magmatic arc. The sedimentary sequence is named the Miers Bluff Formation (MBF) and is interpreted as turbidite since the first geological study on South Shetland Islands, and is interpreted as turbidite. It base and top are not exposed, but a thickness of more than 3000m has been suggested and seems plausible. The turbidite is overlain by Mid - Cretaceous volcanic rocks and intruded by Eocene tonalites. The age of the Miers Bluff Formation is poorly constrained Late Carboniferous -Early Triassic. Sedimentary Environment, tectonic setting and forming age of sedimentary rocks of the Miers Bluff Formation were discussed by means of the methods of sedimentology, petrography and geochemistry, combinig with the study of trace fossils and microfossil plants. The following conclusions are obstained. A sedimentary geological section of Johnsons Dock is made by outside measuring and watching, and then according the section, the geological map near the Spanish Antarctic station was mapped. Four pebbly mudstone layers are first distinguished, which thickness is about 10m. The pebbly mudstone is the typical rock of debris flow, and the depostional environment of pebbly mudstone may be the channel of mid fan of submarine fan. The sedimentsry structural characteristics and size analysis of sandstones show the typical sedimentary feature of turbidity flow and the Miers Bluff Formation is a deep-water turbidite (include some gravity-flow sediments). The materials of palaeocurrents suggest the continental slope dip to southeast, and indicate the provenance of turbidity sediment in the northwest area. By facies analysis, six main facies which include seven subfacies were recognized, which are formed in mid-fan and lower-fan of submarine, meanwhile, the sedimentary features of each facies and subfacies are summarized. The study of clastic composition, major elements, trace elements and rare earth elements indicates the forming setting of the Miers Bluff Formaton is active continental margin and continental island arc and the provenance is dissected magmatic arc which main composition is felsic gneiss. Many trace fossils of the whole succession were found in the turbidites of the Miers Bluff Formation. All these trace fossils are deep sea ichnofossils. There are fifteen ichnogenus, sixteen ichnospecies. Moreover, a new trace fossil was found and a new ichnogenus and new ichnospecies was proposed - Paleaichnus antarctics ichnogen, et ichnosp, nov.. Except the new ichnogenus and ichnospecies, others had been found in deep-sea flysch turbidites. Some are in mudstone and are preserved in the cast convex of overlying sandstone sole, they formed before turbidity flows occurred and belong to the high-different Graphoglyptida of fiysch mudstone. Others as Fucusopsis and Neonereites are preserved in sandstones and stand for trace assemblages after turbidity sedimentation. These trace fossils are typical members of abyssal "Nereites" ichnofacies, and provide for the depositional environment of the Miers Bluff Formation. Fairly diverse microfossil plants have been recovered from the Miers Bluff Formation, Livingston Island, including spores, pollen, acritarchs, wood fragments and cuticles. Containing a total of about 45 species (forms) of miospores, the palynofiora is quantitatively characterized by the dominance of non-striate bisaccate pollen, but spores of pteridophytes and pollen of gymnosperms are proportionate in diversity. It is somewhat comparable to the subzone C+D of the Alisporites zone of Antarctica, and the upper Craterisporites rotundus zone and the lower Polycingulatisporites crenulatus zone of Australia, suggesting a Late Triassic (possibly Norian-Rhaetian) age, as also evidenced by the sporadic occurrence of Aratrisporites and probable Classopollis as well as the complete absence of bisaccate Striatiti. The parent vegetation and paleoclimate are preliminarily deduced. At last, the paper prooses the provenance of sedimentary rocks of the Miers Bluff Formation locates in the east part to the southern Chile(or Southern South American). In the Triassic period, contrasting with New Zealand, Australia and South American of the Pacific margin of Gondwanaland, the Miers Bluff Formation is deposited in the fore-arc basin or back-arc basin of magmatic arc.