Search results for "Clade"
showing 10 items of 203 documents
Deep-Time Phylogenetic Clustering of Extinctions in an Evolutionarily Dynamic Clade (Early Jurassic Ammonites)
2012
7 pages; International audience; Conservation biologists and palaeontologists are increasingly investigating the phylogenetic distribution of extinctions and its evolutionary consequences. However, the dearth of palaeontological studies on that subject and the lack of methodological consensus hamper our understanding of that major evolutionary phenomenon. Here we address this issue by (i) reviewing the approaches used to quantify the phylogenetic selectivity of extinctions and extinction risks; (ii) investigating with a high-resolution dataset whether extinctions and survivals were phylogenetically clustered among early Pliensbachian (Early Jurassic) ammonites; (iii) exploring the phylogene…
Gastropod evidence against the Early Triassic Lilliput effect
2010
4 pages; International audience; Size reduction in the aftermath of the Permian-Triassic mass extinction event has repeatedly been described for various marine organisms, including gastropods (the Lilliput effect). A Smithian gastropod assemblage from Utah, USA, reveals numerous large-sized specimens of different genera as high as 70 mm, the largest ever reported from the Early Triassic. Other gastropods reported from Serbia and Italy are also as large as 35 mm. Size frequency distributions of the studied assemblages indicate that they were not unusually small when compared with later Mesozoic and modern faunas. The occurrence of large-sized gastropods less than 2 Ma after the Permian-Trias…
Evolution of Leaf Morphogenesis: Evidence from Developmental and Phylogenetic Data in Papaveraceae
1999
Variation of leaf morphology in Papaveraceae s.l. (including Fumariaceae and Pteridophyllum) has previously been shown to be related to developmental differences in the direction of segmentation and in blade‐petiole differentiation. Based on ontogenetic comparisons, we here distinguish polyternate, acropetal, basipetal‐pedate, basipetal‐pinnate, and divergent modes of dissection. In addition, undissected leaves occur in some taxa. Dissection modes can be grouped in two classes on the basis of blade‐petiole differentiation. Mapping of these morphogenetic traits on an independently obtained phylogenetic reconstruction reveals a high degree of homoplasy, indicating multiple evolutionary parall…
Expression of retinoic acid nuclear receptors in the mouse embryonal carcinoma cell line PCC7-Mz1
1992
Mouse embryonal carcinoma cell line PCC7-Mz1 can serve as a model of mammalian neural development [1989, J. Cell. Biol. 109, 2481-2493]. Upon exposure to all-trans retinoic acid (RA), Mz1 cells differentiate into a stable pattern of neurons, astroglia and fibroblasts whereas variants of the parental cell line either are restricted in their patterns of derivatives or do not respond at all to RA. Using gene probes specific for the alpha 1, alpha 2 and beta 2 isoforms of the retinoic acid nuclear receptor, we have studied by Northern blot analysis the expression of these transcription factors in uninduced and induced cells of clone Mz1 and in variants with different developmental potential. al…
First steps to restructuring the problematic genus Lasiotocus Looss, 1907 (Digenea: Monorchiidae) with the proposal of four new genera
2020
Lasiotocus Looss, 1907 is the largest genus within the Monorchiidae Odhner, 1911, with 52 species currently considered valid. Species belonging to this genus exhibit wide morphological variation and it is likely that many of them belong in other genera; however, testing the validity of the group has been hampered by a lack of molecular sequence data, especially for the type-species. Here, we report the first DNA sequences for Lasiotocus mulli (Stossich, 1883) Odhner, 1911, the type-species of the genus, and only the sixth Lasiotocus species to be sequenced. Sequences were generated for three ribosomal DNA markers, the ITS2, 18S and 28S regions, and for one mitochondrial DNA marker, the cox1…
Phylogeography of the Eurasian Willow Tit (Parus montanus) based on DNA sequences of the mitochondrial cytochrome b gene.
2002
The phylogeographic relationships of the trans-Palearctic Willow Tit assemblage were studied by obtaining sequence data from the mitochondrial cytochrome b gene from 34 specimens representing nine subspecies from across the species range. Four distinct genetic groups were identified: Parus montanus weigoldicus, P. m. affinis, P. m. songarus, and a clade containing six Eurasian subspecies (ssp. baicalensis, borealis, montanus, restrictus, rhenanus, and sachalinensis). P. m. weigoldicus, P. m. affinis, and P. m. songarus were reciprocally monophyletic and separated from each other and other subspecies by uncorrected genetic distances between 1.9 and 5.8%. The remaining six subspecies were clo…
Phylogeographic patterns in Drosophila montana
2006
The Drosophila virilis species group offers valuable opportunities for studying the roles of chromosomal re-arrangements and mating signals in speciation. The 13 species are divided into two subgroups, the montana and virilis 'phylads'. There is greater differentiation among species within the montana phylad in both karyotype and acoustic signals than exists among members of the virilis phylad. Drosophila montana is a divergent species which is included in the montana phylad. Here, we analyse the phylogeography of D. montana to provide a framework for understanding divergence of acoustic signals among populations. We analysed mitochondrial sequences corresponding to the cytochrome oxidase I…
On the transposon origins of mammalian SCAND3 and KRBA2, two zinc-finger genes carrying an integrase/transposase domain
2012
SCAND3 and KRBA2 are two mammalian proteins originally described as “cellular-integrases” due to sharing of a similar DDE-type integrase domain whose origin and relationship with other recombinases remain unclear. Here we perform phylogenetic analyses of 341 integrase/transposase sequences to reveal that the integrase domain of SCAND3 and KRBA2 derives from the same clade of GINGER2, a superfamily of cut-and-paste transposons widely distributed in insects and other protostomes, but seemingly absent or extinct in vertebrates. Finally, we integrate the results of phylogenetic analyses to the taxonomic distribution of SCAND3 and KRBA2 and their transposon relatives to discuss some of the proce…
A Phylogenetic Analysis of Human Syntenies Revealed by Chromosome Painting in Euarchontoglires Orders
2010
To search for cytogenetic signatures that can help to clarify evolutionary affinities among the five orders within the Euarchontoglires clade, we focused on associations of conserved syntenic blocks that have been accumulated in the karyotypes of Primates (Strepsirhini and Haplorhini), five families of Rodentia, Scandentia (Tupaia belangeri), Dermoptera (Galeopterus variegatus) and Lagomorpha (Oryctolagus cuniculus). We examined available chromosome painting data to identify conserved chromosomes and chromosomal segments, and syntenic associations likely to have characterized the ancestral eutherian karyotype. The data set includes 161 characters that have been subjected to a concatenated a…
Genotypic analysis at multiple loci across Kaposi's sarcoma herpesvirus (KSHV) DNA molecules: clustering patterns, novel variants and chimerism
2001
Abstract Background: the genomes of human Kaposi's sarcoma-associated herpesvirus (KSHV) display several levels of DNA sequence heterogeneity and subgrouping that show distinctive clustering patterns in related human populations. The four major subtype patterns for the hypervariable ORF-K1 protein correlate closely with the principal diasporas resulting from the migration of modern humans out of East Africa and suggest that KSHV is an ancient human virus that is transmitted primarily in a familial fashion with consequent very low recombination rates. However, chimeric genomes have also been detected, especially with regard to the presence of P versus M alleles of the ORF-K15 gene. Objective…