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71.
72.
73.
DNA hybridization evidence for the principal lineages of hummingbirds (Aves:Trochilidae) 总被引:3,自引:0,他引:3
The spectacular evolutionary radiation of hummingbirds (Trochilidae) has
served as a model system for many biological studies. To begin to provide a
historical context for these investigations, we generated a complete matrix
of DNA hybridization distances among 26 hummingbirds and an outgroup swift
(Chaetura pelagica) to determine the principal hummingbird lineages. FITCH
topologies estimated from symmetrized delta TmH-C values and subjected to
various validation methods (bootstrapping, weighted jackknifing, branch
length significance) indicated a fundamental split between hermit
(Eutoxeres aquila, Threnetes ruckeri; Phaethornithinae) and nonhermit
(Trochilinae) hummingbirds, and provided strong support for six principal
nonhermit clades with the following branching order: (1) a predominantly
lowland group comprising caribs (Eulampis holosericeus) and relatives
(Androdon aequatorialis and Heliothryx barroti) with violet-ears (Colibri
coruscans) and relatives (Doryfera ludovicae); (2) an Andean-associated
clade of highly polytypic taxa (Eriocnemis, Heliodoxa, and Coeligena); (3)
a second endemic Andean clade (Oreotrochilus chimborazo, Aglaiocercus
coelestis, and Lesbia victoriae) paired with thorntails (Popelairia
conversii); (4) emeralds and relatives (Chlorostilbon mellisugus, Amazilia
tzacatl, Thalurania colombica, Orthorhyncus cristatus and Campylopterus
villaviscensio); (5) mountain-gems (Lampornis clemenciae and Eugenes
fulgens); and (6) tiny bee-like forms (Archilochus colubris, Myrtis fanny,
Acestrura mulsant, and Philodice mitchellii). Corresponding analyses on a
matrix of unsymmetrized delta values gave similar support for these
relationships except that the branching order of the two Andean clades (2,
3 above) was unresolved. In general, subsidiary relationships were
consistent and well supported by both matrices, sometimes revealing
surprising associations between forms that differ dramatically in plumage
and bill morphology. Our results also reveal some basic aspects of
hummingbird ecologic and morphologic evolution. For example, most of the
diverse endemic Andean assemblage apparently comprises two genetically
divergent clades, whereas the majority of North American hummingbirds
belong a single third clade. Genetic distances separating some
morphologically distinct genera (Oreotrochilus, Aglaiocercus, Lesbia;
Myrtis, Acestrura, Philodice) were no greater than among congeneric
(Coeligena) species, indicating that, in hummingbirds, morphological
divergence does not necessarily reflect level of genetic divergence.
相似文献
74.
75.
Loss of phylogenetic information in chorion gene families of Bombyx mori gene conversion 总被引:1,自引:0,他引:1
Regier JC; Weigmann BM; Leclerc RF; Friedlander TP 《Molecular biology and evolution》1994,11(1):72-87
The silkmoth chorion has provided a stimulating model for the study of
evolution and developmental regulation of gene families. Previous attempts
at inferring relationships among chorion sequences have been based on
pairwise comparisons of overall similarity, a potentially problematic
approach. To remedy this, we identified the alignable regions of low
sequence variability and then analyzed this restricted database by
parsimony and neighbor-joining methods. At the deepest level, the chorion
sequence tree is split into two branches, called "alpha" and "beta." Within
each branch, early- and late-expressing genes each constitute monophyletic
groups, while the situation with middle-expressing genes remains uncertain.
The HcB gene family appears to be the most basal beta-branch group, but
this conclusion is qualified because the effect of gene conversion on
branching order is unknown. Previous studies by Eickbush and colleagues
have strongly suggested that ErA, HcA, and HcB families undergo gene
conversion within a gene family, whereas the ErB family does not. The
occurrence of conversion correlates with a particular tree structure;
namely, branch lengths are much greater at the base of the family than at
higher internodes and terminal branches. These observations raise the
possibility that chorion gene families are defined by gene conversion
events (reticulate evolution) rather than by descent with modification
(synapomorphy).
相似文献
76.
77.
Water quality and algal populations in the Vaal River Barrage Reservoir have been monitored extensively for many decades, because of its importance as a water source for the most densely populated area in South Africa. Although Aulacoseira granulata (Ehrenberg) Simonsen is frequently found and at it times dominates algal assemblages in the Barrage, Aulacoseira ambigua (F.Meister) Tuji & D.M.Williams has never before been recorded at this locality. During a countrywide proficiency-testing scheme for algae counting, coordinated by Rand Water, spiral-shaped diatom colonies with distinctly curved cells were detected during May 2015. Upon investigation, it was found that the spiral colonies were Aulacoseira ambigua f. japonica, its presence in the fresh waters of South Africa being recorded for the first time. Since their first appearance during May 2015, colonies of Aulacoseira ambigua f. japonica have been constantly present in the surface waters of the Barrage. Their presence at this site can be linked to increasing eutrophication in the Vaal River, because the spiral form is known to prefer eutrophic conditions. Centric diatoms rarely form spiral colonies and there is some confusion in the literature as to the identity of this particular form, therefore in this paper we discuss this taxon, its nomenclature and ecological significance. 相似文献
78.
The bulk of models used to understand the species diversification on Madagascar have been constructed using vertebrate taxa. It is not clear how these models affect less vagile species that may interact at a variety of spatial scales. Several studies on vertebrates have divided Madagascar into east-west bioclimatic regions, suggesting there is a fundamental division between eastern wet-adapted and western dry-adapted taxa. An alternative model of ecogeographic constraints shows a north-south division. We test whether the diversification in a small arthropod with variable degrees of dispersal conform to either model of ecogeographic constraints proposed for vertebrate taxa. We employ a molecular taxonomic dataset using ~2 kilobases nuDNA (Wg, LW Rh, Abd-A, 28s) and 790 basepairs mtDNA (CO1), along with geographic and habitat data, to examine the diversification patterns of the ant genus Mystrium Roger, 1862, (Subfamily Amblyoponinae) from Madagascar. The nuclear and mitochondrial phylogenies were both congruent with morphospecies as indicated in a recent revision of the genus. Species of Mystrium practice different colony reproductive strategies (winged queens vs non-winged queens). Alternate reproductive strategies led to inequalities in female dispersal ability among species, providing an additional layer for examination of the impacts of vagility on divergence, especially when measured using a maternally inherited locus. Mystrium species distribution patterns support these models of ecogeographic constraints. Reproductive strategy effected how Mystrium mtDNA lineages were associated with large-scale habitat distinctions and various topographical features. Furthermore, in some cases we find microgeographic population structure which appears to have been impacted by localized habitat differences (tsingy limestone formations, littoral forest) on a scale much smaller than that found in vertebrates. The current system offers a finer scale look at species diversification on the island, and helps achieve a more universal understanding of the generation of biodiversity on Madagascar. 相似文献
79.
Human embryonic stem cell-derived cells rescue visual function in dystrophic RCS rats 总被引:7,自引:0,他引:7
Lund RD Wang S Klimanskaya I Holmes T Ramos-Kelsey R Lu B Girman S Bischoff N Sauvé Y Lanza R 《Cloning and stem cells》2006,8(3):189-199
Embryonic stem cells promise to provide a well-characterized and reproducible source of replacement tissue for human clinical studies. An early potential application of this technology is the use of retinal pigment epithelium (RPE) for the treatment of retinal degenerative diseases such as macular degeneration. Here we show the reproducible generation of RPE (67 passageable cultures established from 18 different hES cell lines); batches of RPE derived from NIH-approved hES cells (H9) were tested and shown capable of extensive photoreceptor rescue in an animal model of retinal disease, the Royal College of Surgeons (RCS) rat, in which photoreceptor loss is caused by a defect in the adjacent retinal pigment epithelium. Improvement in visual performance was 100% over untreated controls (spatial acuity was approximately 70% that of normal nondystrophic rats) without evidence of untoward pathology. The use of somatic cell nuclear transfer (SCNT) and/or the creation of banks of reduced complexity human leucocyte antigen (HLA) hES-RPE lines could minimize or eliminate the need for immunosuppressive drugs and/or immunomodulatory protocols. 相似文献
80.
JC de Mauroy HR Weiss AG Aulisa L Aulisa JI Brox J Durmala C Fusco TB Grivas J Hermus T Kotwicki G Le Blay A Lebel L Marcotte S Negrini L Neuhaus T Neuhaus P Pizzetti L Revzina B Torres PJM Van Loon E Vasiliadis M Villagrasa M Werkman M Wernicka MS Wong F Zaina 《Scoliosis》2010,5(1):1-15