Farmland habitat selection of wintering lesser kestrels in a Spanish pseudosteppe: implications for conservation strategies

The lesser kestrel Falco naumanni is a globally threatened species, whose breeding populations seem to have declined due to recent agricultural changes. However, nothing is known about habitat requirements during winter, despite the fact that several populations are overwintering in areas affected by agricultural transformations. We studied population size and habitat selection by wintering lesser kestrels in a Spanish pseudosteppe (Los Monegros), where traditional fallow systems for cereals are rapidly being replaced by intensive and/or irrigated crops. About 15% of the adult population wintered in the study area, as determined by systematic roadside counts compared with accurate censuses made during the breeding season. Wintering lesser kestrels preferred to forage on field margins and stubble, while avoiding abandoned fields, ploughs, scrubland, growing cereals and, mainly, the expanding irrigated crops. This work confirms the need to incorporate the habitat requirements of threatened species over their complete annual cycles; while breeding lesser kestrels scarcely use fallow (ploughed at that time), during the winter, fallow (stubble at that time) is their main foraging habitat. Both fallow land and the present agricultural calendar should be maintained to assure the conservation of wintering lesser kestrel populations.     

Social organization and movement influence the incidence of bovine tuberculosis in an undisturbed high-density badger Meles meles population

1. The culling of European badgers Meles meles has been a central part of attempts to control bovine tuberculosis (TB) in British cattle for many years. Recent results, however, indicate that this approach could in practice enhance disease spread. 2. This paper looks at the relationship between TB incidence and badger ecology in a high-density population in south-west England, which has been the subject of a long-term intensive study. The principal aims were to relate the probability of TB incidence, as detected by culture of clinical samples (i.e. excretion of bacilli), at the level of the individual and of the social group to demographic processes, movement, social organization and disease dynamics. 3. The probability of an individual being an incident case was greater in groups where TB was already present, although this was less influential in groups that were subject to some instability in numbers. Both individuals and groups were more likely to be incident cases where the social group was diminishing in size, although no relationship was observed with group size itself. This suggests that the process of group size reduction rather than group size per se has most influence on disease dynamics. The likelihood that either an individual or a group was an incident case was positively correlated with both individual and group-level movement. When the proportion of females in a social group was high, the positive association between movement and incidence was found to be more pronounced and there was a significantly higher probability of incident cases among males. 4. These relationships highlight the importance of social structure in driving TB transmission dynamics in this stable, high-density badger population. The results support the idea that a stable social structure mitigates against new incident cases of disease, and are consistent with the contention that badger culling may create the social circumstances for enhanced transmission of TB.     

Adaptation and habitat selection in the eco-evolutionary process

The struggle for existence occurs through the vital rates of population growth. This basic fact demonstrates the tight connection between ecology and evolution that defines the emerging field of eco-evolutionary dynamics. An effective synthesis of the interdependencies between ecology and evolution is grounded in six principles. The mechanics of evolution specifies the origin and rules governing traits and evolutionary strategies. Traits and evolutionary strategies achieve their selective value through their functional relationships with fitness. Function depends on the underlying structure of variation and the temporal, spatial and organizational scales of evolution. An understanding of how changes in traits and strategies occur requires conjoining ecological and evolutionary dynamics. Adaptation merges these five pillars to achieve a comprehensive understanding of ecological and evolutionary change. I demonstrate the value of this world-view with reference to the theory and practice of habitat selection. The theory allows us to assess evolutionarily stable strategies and states of habitat selection, and to draw the adaptive landscapes for habitat-selecting species. The landscapes can then be used to forecast future evolution under a variety of climate change and other scenarios.     

内蒙古达赉湖地区赤狐生境选择及生境景观特征分析

近年来,干旱、鼠害及人为对草原的过度开发利用等对达赉湖地区赤狐的数量及分布范围造成了很大影响。借助于主成分分析、Bailey’s判别分析、遥感和地理信息系统对达赉湖自然保护区赤狐的生境选择及生境的景观特征进行了研究。在赤狐家域内采用样线法和样方法,共设置10 m×10 m样方245个(实验样方101个,对照样方144个),并测定样方内的7个生境因子:植被类型、隐蔽级、食物丰富度、雪深、距水源距离、距围栏距离、距居民点距离。对样方内数据进行主成分分析得出,食物和隐蔽性是赤狐生境选择的主要因子,距居民点距离和距围栏距离是赤狐生境选择的次要因子,雪深和距水源距离是赤狐在生境选择中未表现出选择和利用的因子。利用Bailey’s方法和基于赤狐的生境分布图的景观统计得出:赤狐偏好选择柳灌丛和芦苇塘两种生境,这两种生境的总面积约为1093.47 km2,占研究区总面积的14.05%;赤狐随机利用河道、典型草原和草甸草原3种生境类型,这3种生境的总面积约为4721.79 km2,占研究区总面积的60.67%。;回避的生境为冰面和沙化草地,总面积约为1968.09 km2,占研究区总面积的25.29%。基于地理信息系统和Fragstats的景观特征分析得出,赤狐最适宜生境的面积最少,斑块数量最多,平均斑块面积最小,平均形状指数最小,平均斑块距离最大;其次是较适宜生境和不适宜生境;一般适宜生境的面积最多,斑块数量最少,平均斑块面积和平均形状指数最大,平均斑块距离最小。赤狐多分布于斑块较大的适宜其生存的生境或分布于由这些斑块形成的生境斑块镶嵌体中。     

中国大陆鸟类栖息地选择研究十年

栖息地选择研究一直是鸟类生态学研究的重要内容之一。通过对2001年1月至2010年12月10年期间中国大陆鸟类学家在国内外期刊上发表的鸟类栖息地选择研究的论文进行分析,对我国鸟类栖息地选择研究提出展望。10年间,我国鸟类学家共发表有关鸟类栖息地选择或利用的论文170篇,共涉及到鸟类10目31科73种。在这10年里,中国大陆有关鸟类栖息地选择或利用的文章持续增长。然而,我国鸟类栖息地选择的研究也存在着如下问题:(1)存在栖息地选择和栖息地利用误用的现象,这种现象在10年内并无明显改善;(2)在选择研究方法时,很少考虑个体的可获得性、种群密度及抽样尺度对栖息地选择的影响;(3)大多数的栖息地选择的论文没有对鸟类的栖息地选择行为进行研究,也缺乏对其选择的适合度背景去进行研究。根据这些问题,对我国未来的鸟类栖息地选择研究提出了建议。     

An inter-regional approach to intraspecific variation in habitat association: Rock Buntings Emberiza cia as a case study

The habitat association approach has been increasingly used in ecology to resolve problems in wildlife conservation and management. One problem related to habitat association studies is that they are restricted to small geographical areas within a species' range, and thus they are applicable to only a limited set of environmental conditions utilized by the species. In addition, very few studies address why the preference for specific habitat components may be adaptive for the species in question. The objective of this study was to examine how consideration of populations of a species from two dramatically different environments affects the results of habitat association modelling for a ground-nesting passerine, the Rock Bunting Emberiza cia . At a regional scale, a trend to defending breeding habitat patches with relatively higher stone cover was confined to birds from a temperate region in Slovakia. In contrast, in a semi-arid region in southeastern Spain, Rock Buntings preferred to use breeding habitat patches that had relatively higher grass cover. Combining data from both regions, breeding Rock Buntings showed a general pattern of using habitat patches close to hedges, with low bush cover, high ditch density and a steep slope. Whereas regional habitat association models appear to be sensitive to the particularities of the breeding environment, our study suggests that Rock Bunting breeding habitat association is constrained by the adults' tactics to protect themselves against predators. Although the birds prefer to nest in patches of low vegetation, the better to see nearby predators, these patches are ideally close to taller vegetation that can be used to provide cover when evading predators, and they are also of a rugged profile that helps the birds to approach and leave the nest stealthily.     

Polymorphism in heterogeneous environments,evolution of habitat selection and sympatric speciation: Soft and hard selection models

Summary The adaptation to a variable environment has been studied within soft and hard selection frameworks. It is shown that an epistatically determined habitat preference, following a Markovian process, always leads to the maintenance of an adaptive polymorphism, in a soft selection context. Although local mating does not alter the conditions for polymorphism maintenance, it is shown that, in that case, habitat selection also leads to the evolution of isolated reproductive units within each available habitat. Habitat selection, however, cannot evolve in the total absence of adaptive polymorphism. This represents a theoretical problem for all models assuming habitat selection to be an initially fixed trait, and means that within a soft selection framework, all the available habitats will be exploited, even the less favourable ones.On the other hand, polymorphism cannot be maintained when selection is hard, even when all individuals select their habitat. Here, the evolution of habitat selection does not need any prerequisite polymorphism, and always leads to the exploitation of only one habitat by the most specialized genotype. It appears then that hard selection can account for the existence of empty habitat and for an easier evolution of habitat specialization.     

Scales and costs of habitat selection in heterogeneous landscapes

Summary Two scales of habitat selection are likely to influence patterns of animal density in heterogeneous landscapes. At one scale, habitat selection is determined by the differential use of foraging locations within a home range. At a larger scale, habitat selection is determined by dispersal and the ability to relocate the home range. The limits of both scales must be known for accurate assessments of habitat selection and its role in effecting spatial patterns in abundance. Isodars, which specify the relationships between population density in two habitats such that the expected reproductive success of an individual is the same in both, allow us to distinguish the two scales of habitat selection because each scale has different costs. In a two-habitat environment, the cost of rejecting one of the habitats within a home range can be expressed as a devaluation of the other, because, for example, fine-grained foragers must travel through both. At the dispersal scale, the cost of accepting a new home range in a different habitat has the opposite effect of inflating the value of the original habitat to compensate for lost evolutionary potential associated with relocating the home range. These costs produce isodars at the foraging scale with a lower intercept and slope than those at the dispersal scale.Empirical data on deer mice occupying prairie and badland habitats in southern Alberta confirm the ability of isodar analysis to differentiate between foraging and dispersal scales. The data suggest a foraging range of approximately 60 m, and an effective dispersal distance near 140 m. The relatively short dispersal distance implies that recent theories may have over-emphasized the role of habitat selection on local population dynamics. But the exchange of individuals between habitats sharing irregular borders may be substantial. Dispersal distance may thus give a false impression of the inability of habitat selection to help regulate population density.     

Genetic evidence that culling increases badger movement: implications for the spread of bovine tuberculosis

The Eurasian badger (Meles meles) has been implicated in the transmission of bovine tuberculosis (TB, caused by Mycobacterium bovis) to cattle. However, evidence suggests that attempts to reduce the spread of TB among cattle in Britain by culling badgers have mixed effects. A large-scale field experiment (the randomized badger culling trial, RBCT) showed that widespread proactive badger culling reduced the incidence of TB in cattle within culled areas but that TB incidence increased in adjoining areas. Additionally, localized reactive badger culling increased the incidence of TB in cattle. It has been suggested that culling-induced perturbation of badger social structure may increase individual movements and elevate the risk of disease transmission between badgers and cattle. Field studies support this hypothesis, by demonstrating increases in badger group ranges and the prevalence of TB infection in badgers following culling. However, more evidence on the effect of culling on badger movements is needed in order to predict the epidemiological consequences of this control strategy. Here, analysis of the genetic signatures of badger populations in the RBCT revealed increased dispersal following culling. While standard tests provided evidence for greater dispersal after culling, a novel method indicated that this was due to medium- and long-distance dispersal, in addition to previously reported increases in home-range size. Our results also indicated that, on average, badgers infected with M. bovis moved significantly farther than did uninfected badgers. A disease control strategy that included culling would need to take account of the potentially negative epidemiological consequences of increased badger dispersal.     

Strong habitat selection and the development of population structure in a mosquito

Summary Remarkably simple and regular patterns of genic variation for two electrophoretically assayed loci are presented against a background of strong habitat selection, population isolation, and population structuring in the pitcher-plant mosquitoWyeomyia smithii. The genic variation assessed thus far comes from 29 local populations, all but one of which lie within the glaciated region of North America. Although the conclusions drawn from these patterns are still quite tentative, it appears that the fact that the same higher frequency electromorphs occurred everywhere for both loci may be due more to selection than drift. Drift or selection, acting alone or in concert may be responsible for the almost complete absence of electromorphs of intermediate frequency. A weak association was found between the two-locus genic variation and the well-studied diapause-development time variation in this species. It is suggested that a Wrightian interaction system and fluctuating-stabilizing selection might account for maintenance of the genic level polymorphism. The observations reported are circumstantially in accord with Wright's shifting balance process of evolution. Future studies in the older parts of the species range will put these hypotheses to a strong test.     

A review of habitat selection by the swamp rat,Rattus lutreolus (Rodentia: Muridae)

Abstract This review clarifies important points on habitat selection by the Swamp Rat Rattus lutreolus (Rodentia: Muridae), a species that has been the subject of much research in Australia and has provided a useful model for understanding ecological and biological processes. It also provides an opportunity to cite important earlier research, not readily available through electronic search engines, thus bringing it into current literature to avoid its disappearance into Internet obscurity. We comment on some papers in the literature to correct errors detected and to emphasize the importance of due care in all aspects of a research project, including its reporting. We show that both floristic and structural components have been reported as important to an understanding of habitat and microhabitat selection by R. lutreolus and conclude that it is vegetation density that is of paramount importance. Female R. lutreolus are clearly dominant in driving microhabitat selection, occupying the ‘best’ or densest habitats with male R. lutreolus occupying the next best and Pseudomys or other species, where present occupying the remainder. This demonstrates the important role that intraspecific and interspecific competition play in determining habitat selection. Direct predation and the perception of predation risk may also play a role in habitat selection, again perceived to be pushing individuals towards denser vegetation, representing ‘better cover’. Whether these effects operate as bottom‐up or top‐down needs careful consideration. Climatic variables, such as ENSO‐affecting productivity, and related variables such as temperature and humidity may also play important roles in habitat selection, as can disturbance effects such as wildfire. The relative importance of all of these potential determining factors may vary from place to place, particularly when climatic clines are involved.     

Difference in habitat selection by different morphs of the land snail Arianta arbustorum

The behaviour of morphs of Arianta arbustorum has been investigated using a new technique involving a paint which fades in daylight. The technique was used to study the response of different morphs to exposure to sunlight at a homogeneous woodland habitat and a heterogeneous open habitat. The yellow morph showed a significantly higher rate of fading than the brown morph. A mark, release and recapture programme was used to analyse the association between frequencies of different morphs recaptured and not recaptured. In both habitats, there was a general tendency for the frequency of recapture to increase with increasing age in both morphs. Habitat selection resulting from different behaviour of different morphs of A. arbustorum is discussed. Morph frequencies can be related to habitat, the brown morphs of A. arbustorum are significantly less frequent in the open habitat. The behavioural responses of Cepaea hortensis , present with A. arbustorum in two other populations, to the exposure of sunshine were also studied. Climatic selection by solar energy associated with different morphs, species and habitat are also discussed.     

Imputation of genotypes from low- to high-density genotyping platforms and implications for genomic selection

The objective of this study was to quantify the accuracy achievable from imputing genotypes from a commercially available low-density marker panel (2730 single nucleotide polymorphisms (SNPs) following edits) to a commercially available higher density marker panel (51 602 SNPs following edits) in Holstein-Friesian cattle using Beagle, a freely available software package. A population of 764 Holstein-Friesian animals born since 2006 were used as the test group to quantify the accuracy of imputation, all of which had genotypes for the high-density panel; only SNPs on the low-density panel were retained with the remaining SNPs to be imputed. The reference population for imputation consisted of 4732 animals born before 2006 also with genotypes on the higher density marker panel. The concordance between the actual and imputed genotypes in the test group of animals did not vary across chromosomes and was on average 95%; the concordance between actual and imputed alleles was, on average, 97% across all SNPs. Genomic predictions were undertaken across a range of production and functional traits for the 764 test group animals using either their real or imputed genotypes. Little or no mean difference in the genomic predictions was evident when comparing direct genomic values (DGVs) using real or imputed genotypes. The average correlation between the DGVs estimated using the real or imputed genotypes for the 15 traits included in the Irish total merit index was 0.97 (range of 0.92 to 0.99), indicating good concordance between proofs from real or imputed genotypes. Results show that a commercially available high-density marker panel can be imputed from a commercially available lower density marker panel, which will also have a lower cost, thereby facilitating a reduction in the cost of genomic selection. Increased available numbers of genotyped and phenotyped animals also has implications for increasing the accuracy of genomic prediction in the entire population and thus genetic gain using genomic selection.     

贵州草海越冬黑颈鹤觅食栖息地选择的初步研究

本文报道了利用Friedman非参数统计方法,研究越冬黑颈鹤(Grus nigricollis)在贵州草海对其觅食栖息地选择的结果。在草海的黑颈鹤越冬觅食栖息地可分为5种——莎草草甸、浅水沼泽、草地、玉米地和蔬菜地。黑颈鹤对莎草草甸的选择性最高,对玉米地的选择性最差,对其余类型栖息地的选择随地点的不同而不同。草海的人为活动很多,是影响黑颈鹤利用和选择栖息地的一个重要因素。本文也对改善黑颈鹤越冬栖息地的管理和保护提出了一些建议。     

Predation-dependent oviposition habitat selection by the mosquito Culiseta longiareolata: a test of competing hypotheses

We investigated the mechanism underlying oviposition habitat selection (OHS) in the mosquito Culiseta longiareolata. The putative outcome of a trade‐off between the risk of predation and detrimental density dependence, OHS in this species presents an opportunity to test two competing alternatives: (1) a polymorphic scenario, in which a fixed proportion of females constantly avoid ‘predator pools’, while the remainder oviposits at random; and (2) a monomorphic scenario, in which all females oviposit in predator pools with a certain probability. We present a conceptual framework that demonstrates how a simple experimental design – whereby predator incidence in artificial pools is alternated between 0.25 and 0.75 – can distinguish between, or refute, the two scenarios. Given the proportional use, by ovipositing females, of predator‐free pools observed under each treatment, and a bootstrap estimate of the ratio of daily oviposition rates, we find the monomorphic scenario twice as likely as the polymorphic.