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141.
ABSTRACT Gamebird chick survival is dependent on invertebrate availability, and the ability to access insect prey is an important characteristic defining brood habitat quality. Different mixes of warm-season grasses and forbs were established to improve the habitat quality of fields enrolled in the Conservation Reserve Program (CRP) for gamebirds in the Southern Plains. We analyzed the feeding ecology of human-imprinted, 4- to 10-day-old ring-necked pheasant (Phasianus colchicus) and northern bobwhite (Colinus virginianus) chicks in wheat fields and 4 types of conservation practices (CP) fields enrolled in CRP (CP10, improved CP10, CP2, and CP25) in western Kansas, USA, during June and July, 2004 and 2005. Foraging rates were greatest for bobwhite chicks in improved CP10 and CP25 fields and greatest for pheasant chicks in CP10 and CP25 fields. Vegetation characteristics such as bare ground cover appear to have a significant impact on insect selection, because the diet was more diverse for both species in fields with more bare ground. The CP25 fields provided the best combination of mobility and diet breadth for both species. Although herbicide-treated wheat fields had low feeding rates, we determined non-herbicide-treated fields (i.e., weedy wheat) provided easy mobility and feeding rates similar to CRP fields. We suggest that management of vegetation to benefit gamebirds does not affect species equally. Feeding rates of bobwhite chicks were sensitive to vegetation-influenced mobility. Management of CRP fields for both pheasant and bobwhite chicks can be reconciled by practices that permit more open space at ground level, such as light disking or burning, to permit easier movement for chicks. 相似文献
142.
Aim In order to look for a possible centre of survival for the Norway spruce ( Picea abies Karst.) in the south-western Alps, six natural populations of this area were investigated by means of genetic markers in order to assess the degree and the distribution of genetic diversity within the species.
Location Western and South-western Alps.
Methods Populations were genotyped using seven simple sequence repeat (SSR) markers. Basic population genetics parameters were estimated and the amount of genetic differentiation calculated.
Results A large amount of variability was found (0.59 < He < 0.67); genetic differentiation as measured by F ST was 0.05, close to other similar studies; no isolation by distance was detected by a Mantel test. Analysis of molecular variance confirmed a high degree of variability within populations and a low degree of variability among populations. Finally, the number of populations from which those observed could have arisen was estimated by Bayesian analysis.
Main conclusions The results presented here suggest that the present populations derive their genetic make-up from three inferred clusters. The possible existence in this area of a relict/refuge population during the last glaciation is discussed. 相似文献
Location Western and South-western Alps.
Methods Populations were genotyped using seven simple sequence repeat (SSR) markers. Basic population genetics parameters were estimated and the amount of genetic differentiation calculated.
Results A large amount of variability was found (0.59 < H
Main conclusions The results presented here suggest that the present populations derive their genetic make-up from three inferred clusters. The possible existence in this area of a relict/refuge population during the last glaciation is discussed. 相似文献
143.
Markus Neuhuser 《Biometrical journal. Biometrische Zeitschrift》2003,45(8):974-984
When testing for genetic differentiation the joint null hypothesis that there is no allele frequency difference at any locus is of interest. Common approaches to test this hypothesis are based on the summation of χ2 statistics over loci and on the Bonferroni correction, respectively. Here, we also consider the Simes adjustment and a recently proposed truncated product method (TPM) to combine P‐values. The summation and the TPM (using a relatively large truncation point) are powerful when there are differences in many or all loci. The Simes adjustment, however, is powerful when there are differences regarding one or a few loci only. As a compromise between the different approaches we introduce a combination between the Simes adjustment and the TPM, i.e. the joint null hypothesis is rejected if at least one of the two methods, Simes and TPM, is significant at the α/2‐level. Simulation results indicate that this combination is a robust procedure with high power over the different types of alternatives. 相似文献
144.
The Tasmanian devil (Sarcophilus harrisii) is currently threatened by an emerging wildlife disease, devil facial tumour disease. The disease is decreasing devil numbers dramatically and may lead to the extinction of the species. At present, nothing is known about the immune genes or basic immunology of the devil. In this study, we report the construction of the first genetic library for the Tasmanian devil, a spleen cDNA library, and the isolation of full-length MHC Class I and Class II genes. We describe six unique Class II beta chain sequences from at least three loci, which belong to the marsupial Class II DA gene family. We have isolated 13 unique devil Class I sequences, representing at least seven Class I loci, two of which are most likely non-classical genes. The MHC Class I sequences from the devil have little heterogeneity, indicating recent divergence. The MHC genes described here are most likely involved in antigen presentation and are an important first step for studying MHC diversity and immune response in the devil. 相似文献
145.
In Rosenzweig-MacArthur models of predator-prey dynamics, Allee effects in prey usually destabilize interior equilibria and can suppress or enhance limit cycles typical of the paradox of enrichment. We re-evaluate these conclusions through a complete classification of a wide range of Allee effects in prey and predator's functional response shapes. We show that abrupt and deterministic system collapses not preceded by fluctuating predator-prey dynamics occur for sufficiently steep type III functional responses and strong Allee effects (with unstable lower equilibrium in prey dynamics). This phenomenon arises as type III functional responses greatly reduce cyclic dynamics and strong Allee effects promote deterministic collapses. These collapses occur with decreasing predator mortality and/or increasing susceptibility of the prey to fall below the threshold Allee density (e.g. due to increased carrying capacity or the Allee threshold itself). On the other hand, weak Allee effects (without unstable equilibrium in prey dynamics) enlarge the range of carrying capacities for which the cycles occur if predators exhibit decelerating functional responses. We discuss the results in the light of conservation strategies, eradication of alien species, and successful introduction of biocontrol agents. 相似文献
146.
Engen S 《Journal of theoretical biology》2007,249(4):791-803
Heterogeneous species abundance models are models in which the dynamics differ between species, described by variation among parameters defining the dynamics. Using a dynamic and heterogeneous species abundance model generating the lognormal species abundance distribution it is first shown that different degrees of heterogeneity may result in equivalent species abundance distributions. An alternative to Preston's canonical lognormal model is defined by assuming that reduction in resources, for example reduction in available area, increases the density regulation of each species. This leads to species-individual curves and species-area curves that are approximately linear in a double logarithmic plot. Preston's canonical parameter gamma varies little along these curves and takes values in the neighborhood of one. Quite remarkably, the curves, which define the sensitivity of the community to area reductions, are independent of the heterogeneity among species for this model. As a consequence, the curves can be estimated from a single sample from the community using the Poisson lognormal distribution. It is shown how to perform sensitivity analysis with respect to over-dispersion in sampling relative to the Poisson distribution as well as sampling intensity, that is, the fraction of the community sampled. The method is exemplified by analyzing three simulated data sets. 相似文献
147.
JAMES R. HERKERT 《The Journal of wildlife management》2007,71(8):2749-2751
ABSTRACT Henslow's sparrow (Ammodramus henslowii) is one of North America's fastest declining songbirds. Population declines combined with a small global population have led to heightened conservation concern. I used data from the North American Breeding Bird Survey to assess the impact that the Conservation Reserve Program (CRP) has had on Henslow's sparrows throughout their United States breeding range. My analysis suggests local Henslow's sparrow population trends are correlated with CRP enrollment, with populations increasing more in areas with relatively high local CRP enrollment, and that CRP appears to be playing a significant role in reversing long-term population declines. 相似文献
148.
基于鸟类特有种亚种分化的保护优先性 总被引:2,自引:0,他引:2
我们以中国鸟类特有种为代表,基于鸟类物种分化程度来探讨多样性保护优先区。本文参照105种中国特有鸟种的分化等级来制作物种地理分布图。依据生物种的概念,给单型种赋值“1”,对具有n各亚种分化的物种赋值“n”。利用GIS叠加与制图功能对物种的分布做图以反映不同区域的物种分化等级。结果发现分布中心赋值很高并以同心圆形式向周边递减,反映了物种在中国西南部横断山区至秦岭高度分化的地理格局,并由此向外递减。作为全球25个生物多样性热点之一的横断山区,可能不仅是物种种级而且是种下级多样性的热点。因此,该地区的多样性保护优先性,不仅要考虑目前物种多样性分布的格局而且要考虑其未来发展 相似文献
149.
Assiminea pecos is an endangered species of amphibious gastropod that occupies four widely separated portions of the Rio Grande region in
the southwestern United States (Pecos River basin) and northeastern Mexico (Cuatro Cienegas basin). Our statistical and discriminant
function analyses of shell variation among the disjunct populations of this species indicate that Mexican specimens differ
in their morphometry from those of the United States and can be diagnosed by several characters. We also analyzed variation
in the mitochondrial genome by sequencing 658 bp of mitochondrial COI from populations of A. pecos, representatives of the other three North American species of Assiminea, and several outgroups. Our results indicated substantial divergence of the Mexican population of A. pecos, which was consistently depicted as a monophyletic unit nested within or sister to the shallowly structured group comprised
of American members of this species. Consistent with our findings, we describe the Mexican population as a new species, which
is provisionally placed in the large, worldwide genus Assiminea pending further study of the phylogentic relationships of the North American assimineids. Our molecular data suggest that
the Rio Grande region assimineids, which are among the few inland members of the otherwise estuarine subfamily Assimineinae,
diverged from coastal progenitors in the late Miocene, with subsequent Pleistocene vicariance of Mexican and American species
perhaps associated with development of the modern, lower course of the Rio Grande.
Handling editor: K. Martens 相似文献
150.
The breeding population of the sandwich tern (Sterna sandvicensis) on the German North Sea coast has undergone substantial fluctuations throughout the last 100 years. Numbers of breeding
birds were fluctuating quite strongly in the first 30 years of the twentieth century. From 1930 to the mid-1950s, a relatively
steady decrease occurred. A minimum was reached in 1965 with 2,243 pairs. Around 1970, numbers increased quite markedly up
to the mid-1990s and reached a centurial maximum with 10,138 pairs in 1996. Most recently, the numbers have dropped to only
5,681 pairs in 2005, the lowest number over the last 30 years. Some colonies have existed over long periods, others only for
short periods, with often substantial and sudden changes. The distribution at sea was studied by transect counts from ships.
During the reproductive period, high totals were found between the mainland coast and the islands, up to 30 km from the outer
coast/island line. The seaward extent of the sandwich tern distribution coincided quite well with the 20-m depth line. Maximum
foraging ranges for single colonies were estimated to be ca. 45 km for Trischen, ca. 35 km for Norderoog and ca. 30 km for
both Scharh?rn/Nigeh?rn and Juist. Overall flight ranges for all colonies were estimated at 33.8 km for 95% of the birds.
Germany has a high international responsibility for the protection of this species. Only a few colonies exist every year,
making this species very vulnerable to anthropogenic disturbance, pollution events and fishing activities.
相似文献
Stefan GartheEmail: |