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271.
Size homoplasy and mutational processes of interrupted microsatellites in two bee species, Apis mellifera and Bombus terrestris (Apidae) 总被引:6,自引:0,他引:6
Similar microsatellite electromorphs (PCR products of the same size) can
arise from independent mutational events. Such alleles are not identical by
descent. This phenomenon, termed size homoplasy, was studied by sequencing
electromorphs of two microsatellite loci in which the stretch of basic
repeats is interrupted by different short (1-2 bp) DNA motifs. The number
and position of these interruptions were established for electromorphs from
closely and distantly related populations of honeybees and bumblebees. No
sequence difference was found when electromorphs came from the same
subspecies or from closely related subspecies, suggesting that they were
probably identical by descent. In contrast, sequence differences were often
detected in distantly related subspecies, showing that size homoplasy
frequently occurs at this level of population differentiation. Size
homoplasy is increased by limits to free length variation of alleles, a
phenomenon that seems to act on interrupted microsatellites when comparing
distantly related taxa, that is, honeybee subspecies from different
evolutionary lineages. Electromorph sequences suggest that, within the
scope of these limits, large mutation events have occurred frequently at
both interrupted loci studied. In good agreement with the molecular data,
computations based on the observed heterozygosity and number of
electromorphs and simulation studies showed that neither locus fits the
one-step stepwise mutant model (SMM). We speculate that interrupted
microsatellites in general could be characterized by a higher variance in
repeat number and consequently a lower homoplasy rate than pure ones.
Hence, interrupted microsatellites should be most appropriate for
investigating population differentiation and evolutionary relationship
between relatively distant populations.
相似文献
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274.
The functional feeding groups and diversity of macroinvertebrate communities associated with duckweed mats in the New Years River (two sites) and Bloukrans River (two sites), Eastern Cape province, South Africa, were assessed. Duckweed (Lemnaceae) is a ubiquitous family of floating macrophytes. A total of 41 macroinvertebrate families were collected monthly over a six-month period from February to July 2014. Duckweed biomass in both rivers was highly variable both temporally and spatially. The majority of identified macroinvertebrate taxa were predators and detritivores, with a small percentage of herbivores. An average of approximately 26% of the macroinvertebrate taxa found were from families that include species from more than one functional feeding group. Although overall measures of diversity and ecosystem health (Fisher’s α and Simpson’s index) remained constant over time in the New Years River, significant differences in macroinvertebrate community structure were seen between sites and months on both rivers, with dissimilarity being driven by a larger number of species in the New Years River. This high variability within macroinvertebrate assemblages probably reflects a combination of heterogeneous duckweed distribution, variation in physico-chemistry, opportunistic behaviours of macroinvertebrate predators and/or successional colonisation of duckweed mats. 相似文献
275.
Adam R Burns W Zac Stephens Keaton Stagaman Sandi Wong John F Rawls Karen Guillemin Brendan JM Bohannan 《The ISME journal》2016,10(3):655-664
Despite their importance to host health and development, the communities of microorganisms associated with humans and other animals are characterized by a large degree of unexplained variation across individual hosts. The processes that drive such inter-individual variation are not well understood. To address this, we surveyed the microbial communities associated with the intestine of the zebrafish, Danio rerio, over developmental time. We compared our observations of community composition and distribution across hosts with that predicted by a neutral assembly model, which assumes that community assembly is driven solely by chance and dispersal. We found that as hosts develop from larvae to adults, the fit of the model to observed microbial distributions decreases, suggesting that the relative importance of non-neutral processes, such as microbe-microbe interactions, active dispersal, or selection by the host, increases as hosts mature. We also observed that taxa which depart in their distributions from the neutral prediction form ecologically distinct sub-groups, which are phylogenetically clustered with respect to the full metacommunity. These results demonstrate that neutral processes are sufficient to generate substantial variation in microbiota composition across individual hosts, and suggest that potentially unique or important taxa may be identified by their divergence from neutral distributions. 相似文献
276.
We sampled populations of forest-floor dwelling cave and ground wētā using footprint tracking tunnels and spotlight transect counts in southern beech forest, New Zealand. Samples were compared to estimates of wētā density based on mark–recapture estimates from 25?m2 enclosures. Both activity indices captured variability in cave wētā in time and space, were strongly correlated with each other, and have the potential for monitoring cave wētā activity levels. Comparisons between indices and cave wētā density estimates were equivocal, as recapture rates were too low to calculate high-resolution density estimates. We also found that cave wētā counts had a curved relationship increasing with temperature, and a negative relationship with increasing shrub and woody debris cover. Based on these preliminary results, tracking tunnels could be a viable method of monitoring cave wētā as they appear more efficient than transect counts and are relatively inexpensive. However, further calibration trials are needed to determine if indices mirror robust population density estimates. 相似文献
277.
278.
Marco J Koudijs Marjo J den Broeder Evelyn Groot Fredericus JM van Eeden 《BMC developmental biology》2008,8(1):15
Background
Aberrant activation of the Hedgehog (Hh) signaling pathway in different organisms has shown the importance of this family of morphogens during development. Genetic screens in zebrafish have assigned specific roles for Hh in proliferation, differentiation and patterning, but mainly as a result of a loss of its activity. We attempted to fully activate the Hh pathway by removing both receptors for the Hh proteins, called Patched1 and 2, which are functioning as negative regulators in this pathway. 相似文献279.
280.
The advent of molecular markers has created opportunities for a better understanding of quantitative inheritance and for developing novel strategies for genetic improvement of agricultural species, using information on quantitative trait loci (QTL). A QTL analysis relies on accurate genetic marker maps. At present, most statistical methods used for map construction ignore the fact that molecular data may be read with error. Often, however, there is ambiguity about some marker genotypes. A Bayesian MCMC approach for inferences about a genetic marker map when random miscoding of genotypes occurs is presented, and simulated and real data sets are analyzed. The results suggest that unless there is strong reason to believe that genotypes are ascertained without error, the proposed approach provides more reliable inference on the genetic map. 相似文献