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排序方式: 共有92条查询结果,搜索用时 15 毫秒
1.
Jeff A Johnson Heather RL Lerner Pamela C Rasmussen David P Mindell 《BMC evolutionary biology》2006,6(1):65-12
Background
Populations of the Oriental White-backed Vulture (Gyps bengalensis) have declined by over 95% within the past decade. This decline is largely due to incidental consumption of the non-steroidal anti-inflammatory veterinary pharmaceutical diclofenac, commonly used to treat domestic livestock. The conservation status of other Gyps vultures in southern Asia is also of immediate concern, given the lack of knowledge regarding status of their populations and the continuing existence of taxonomic uncertainties. In this study, we assess phylogenetic relationships for all recognized species and the majority of subspecies within the genus Gyps. The continuing veterinary use of diclofenac is an unknown but potential risk to related species with similar feeding habits to Gyps bengalensis. Therefore, an accurate assessment of the phylogenetic relationships among Gyps vultures should aid in their conservation by clarifying taxonomic uncertainties, and enabling inference of their respective relatedness to susceptible G. bengalensis. 相似文献2.
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4.
alpha 1-Proteinase inhibitor (alpha 1-PI), a member of the serine
proteinase inhibitor superfamily, has a primary role in controlling
neutrophil elastase activity within the mammalian circulation. Several
studies have indicated that the reactive center region of alpha 1-PI, the
amino acid sequence of which is critical to recognition of and binding to
target proteinases, is highly divergent within and among species. This
appears to be a consequence of accelerated rates of evolution that may have
been driven by positive Darwinian selection. In order to examine this and
other features of alpha 1-PI evolution in more detail, we have isolated and
sequenced cDNAs representing alpha 1- PI mRNAs of the mouse species Mus
saxicola and Mus minutoides and have compared these with a number of other
mammalian alpha 1-PI mRNAs. Relative to other mammalian mRNAs, the extent
of nonsynonymous substitution is generally high throughout the alpha 1-PI
mRNA molecule, indicating greater overall rates of amino acid substitution.
Within and among mouse species, the 5'-half of the mRNA, but not the
3'-half, has been homogenized by concerted evolution. Finally, the reactive
center is under diversifying or positive Darwinian selection in murid
rodents (rats, mice) and guinea pigs yet is under purifying selection in
primates and artiodactyls. The significance of these findings to alpha 1-PI
function and the possible selective forces driving evolution of serpins in
general are discussed.
相似文献
5.
Mitochondrial DNA polymorphisms in subterranean mole-rats of the Spalax ehrenbergi superspecies in Israel, and its peripheral isolates 总被引:1,自引:0,他引:1
Nevo E; Honeycutt RL; Yonekawa H; Nelson K; Hanzawa N 《Molecular biology and evolution》1993,10(3):590-604
Patterns of mitochondrial DNA (mtDNA) variation were examined in 133
mole-rats constituting all four chromosomal species (2n = 52, 2n = 54, 2n =
58, and 2n = 60) of the Spalax ehrenbergi superspecies in Israel, as well
as the peripheral isolates of 2n = 60. In the main range of the complex, a
total of 28 mtDNA haplotypes were found in 64 mole-rats, with most
haplotypes being unique to either a single chromosomal species or
population. mtDNA divergence increased from low to high diploid number in a
north-to-south direction in Israel. Overall levels of mtDNA diversity were
unexpectedly the highest in the 2n = 60, the youngest species of the
complex. The mtDNA haplotypes can be separated into two major groups, 2n =
52-54 and 2n = 58-60, and a phylogenetic analysis for each group revealed
evidence of a few haplotypes not sorted by diploid number. The overall
patterns of mtDNA divergence seen within and among the four chromosomal
species are consistent with the parapatric mode of speciation as suggested
from previous studies of allozyme and DNA hybridization. In a separate data
set the patterns of mtDNA variation were examined across the main
geographic range and across peripheral semi-isolates and isolates of the 2n
= 60 chromosomal species. Fifteen haplotypes were found in 69 mole-rats.
High levels of mtDNA diversity characterized the main range, semi-isolated,
and even some desert isolated populations. The peripheral isolates contain
much mtDNA diversity, including novel haplotypes.
相似文献
6.
Environmental variability and population dynamics: do European and North American ducks play by the same rules? 下载免费PDF全文
Hannu Pöysä Jukka Rintala Douglas H. Johnson Esa Lammi Thomas D. Nudds Veli‐Matti Väänänen 《Ecology and evolution》2016,6(19):7004-7014
Density dependence, population regulation, and variability in population size are fundamental population processes, the manifestation and interrelationships of which are affected by environmental variability. However, there are surprisingly few empirical studies that distinguish the effect of environmental variability from the effects of population processes. We took advantage of a unique system, in which populations of the same duck species or close ecological counterparts live in highly variable (north American prairies) and in stable (north European lakes) environments, to distinguish the relative contributions of environmental variability (measured as between‐year fluctuations in wetland numbers) and intraspecific interactions (density dependence) in driving population dynamics. We tested whether populations living in stable environments (in northern Europe) were more strongly governed by density dependence than populations living in variable environments (in North America). We also addressed whether relative population dynamical responses to environmental variability versus density corresponded to differences in life history strategies between dabbling (relatively “fast species” and governed by environmental variability) and diving (relatively “slow species” and governed by density) ducks. As expected, the variance component of population fluctuations caused by changes in breeding environments was greater in North America than in Europe. Contrary to expectations, however, populations in more stable environments were not less variable nor clearly more strongly density dependent than populations in highly variable environments. Also, contrary to expectations, populations of diving ducks were neither more stable nor stronger density dependent than populations of dabbling ducks, and the effect of environmental variability on population dynamics was greater in diving than in dabbling ducks. In general, irrespective of continent and species life history, environmental variability contributed more to variation in species abundances than did density. Our findings underscore the need for more studies on populations of the same species in different environments to verify the generality of current explanations about population dynamics and its association with species life history. 相似文献
7.
Martin Kundrát John Nudds Benjamin P. Kear Junchang Lü Per Ahlberg 《Historical Biology》2019,31(1):3-63
From an initial isolated position as the oldest evolutionary prototype of a bird, Archaeopteryx has, as a result of recent fossil discoveries, become embedded in a rich phylogenetic context of both more and less crownward stem-group birds. This has prompted debate over whether Archaeopteryx is simply a convergently bird-like non-avialan theropod. Here we show, using the first synchrotron microtomographic examination of the genus, that the eighth or Daiting specimen of Archaeopteryx possesses a character suite that robustly constrains it as a basal avialan (primitive bird). The specimen, which comes from the Mörnsheim Formation and is thus younger than the other specimens from the underlying Solnhofen Formation, is distinctive enough to merit designation as a new species, Archaeopteryx albersdoerferi sp. nov., but is recovered in close phylogenetic proximity to Archaeopteryx lithographica. Skeletal innovations of the Daiting specimen, such as fusion and pneumatization of the cranial bones, well vascularized pectoral girdle and wing elements, and a reinforced configuration of carpals and metacarpals, suggest that it may have had more characters seen in flying birds than the older Archaeopteryx lithographica. These innovations appear to be convergent on those of more crownward avialans, suggesting that Bavarian archaeopterygids independently acquired increasingly bird-like traits over time. Such mosaic evolution and iterative exploration of adaptive space may be typical for major functional transitions like the origin of flight. 相似文献
8.
Daily energy expenditure (DEE) of male barn swallows (Hirundo rustica), measured using the doubly labelled water technique, correlated with streamer length. Contrary to predictions derived from previous findings, neither a positive linear nor a u-shaped relationship was found between DEE and streamer length. Instead, an n-shaped curve showed that the highest DEE corresponded to an intermediate streamer length of 119 mm. A model incorporating estimates of resting metabolism and flight energy expenditure from aerodynamics models suggested that variation in individual tail dynamics was the most likely explanation for the observed DEE. We suggest that streamer length is coupled to foraging strategy, because tail dynamics control flight performance, which in turn influences flight behaviour. 相似文献
9.
Phylogenetic utility of the nuclear gene arginine decarboxylase: an example from Brassicaceae 总被引:10,自引:2,他引:8
Arginine decarboxylase (ADC) is an important enzyme in the production of
putrescine and polyamines in plants. It is encoded by a single or low-copy
nuclear gene that lacks introns in sequences studied to date. The rate of
Adc amino acid sequence evolution is similar to that of ndhF for the
angiosperm family studied. Highly conserved regions provide several target
sites for PCR priming and sequencing and aid in nucleotide and amino acid
sequence alignment across a range of taxonomic levels, while a variable
region provides an increased number of potentially informative characters
relative to ndhF for the taxa surveyed. The utility of the Adc gene in
plant molecular systematic studies is demonstrated by analysis of its
partial nucleotide sequences obtained from 13 representatives of
Brassicaceae and 3 outgroup taxa, 2 from the mustard oil clade (order
Capparales) and 1 from the related order Malvales. Two copies of the Adc
gene, Adc1 and Adc2, are found in all members of the Brassicaceae studied
to data except the basal genus Aethionema. The resulting Adc gene tree
provides robust phylogenetic data regarding relationships within the
complex mustard family, as well as independent support for proposed tribal
realignments based on other molecular data sets such as those from
chloroplast DNA.
相似文献
10.