基于DNA宏条形码研究四川老君山国家级自然保护区6种同域共存小型哺乳动物的食性

揭示物种共存的发生和维持机制对于群落生态学理论的发展具有重要意义,同时也是生物多样性和保护生物学研究的热点之一。生态位分化是同域分布物种实现共存的重要原因之一。为了解同域分布的多种小型哺乳动物的共存机制,本研究采用DNA宏条形码技术对四川老君山国家级自然保护区内的6种小型哺乳动物胃内容物进行分子食性分析,解析其夏季食物组成特征,并计算和比较种间食物的多样性、生态位宽度和重叠指数。结果表明:(1)鳞翅目(相对丰度:3.76%–42.33%)和双翅目(2.59%–62.63%)是6种小型哺乳动物的主要动物性食物,禾本目(0.02%–45.33%)和豆目(0.19%–38.95%)为其主要植物性食物。6种小型哺乳动物取食主要动植物性食物的相对丰度存在种间差异。(2)黄胸鼠(Rattus tanezumi)和淡灰黑齿鼩鼱(Blarinella griselda)的属水平动物性食物显著重叠(O_jk=0.63);其余物种间的营养生态位存在一定程度重叠,但在主要食物的构成和组成比例上存在明显差异;(3) 6种小型哺乳动物的动物性食物α多样性存在明显种间差异,而植物性食物α多样性...     

神农架一个川金丝猴群的食物分布

食物分布是灵长类行为生态学研究的重要内容之一。国内对川金丝猴(Rhinopithecus roxellana)的食物种类和喜好程度已进行了大量翔实的研究,但在食物的时空分布方面相对薄弱。在2006年8月～2008年7月的两年间,我们对神农架千家坪地区一个川金丝猴群的食物组成做了调查,同时通过样方法(每隔200 m的海拔梯度)研究了该猴群的食物在该地区的分布状况,以及食物分布海拔的季节性变化。结果表明,该猴群的食源植物至少有15种,占食物组成的55.0%,而地衣占食物组成的38.4%;该猴群的食物在某些海拔地带具集中分布趋势,但分布密度总体上不高,重要食源植物(占食物组成的5.0%以上)的乔木胸高断面积和灌木冠部面积所占比例在任何季节分别小于12%和小于14%,约89%的乔木和81%的灌木表面没有地衣覆盖;食物主要分布在海拔1 900～2 500 m之间,可能制约着该猴群的活动海拔范围;植物性食物在海拔上的分布呈现明显的季节性差异,即春季和夏季比秋季和冬季的分布海拔低,这很可能引起该猴群活动海拔的季节性变化。     

荣成天鹅湖湿地越冬大天鹅食性分析

2005年12月～2006年3月以大天鹅(Cygnus cygnus)为对象,研究其越冬期间的食性,利用粪便显微组织分析法定量调查其食物组成。结果表明,大天鹅的越冬食物主要为小麦(Triticum aestivum)、海带(Laminaria japonica)和大叶藻(Zostera marina),其中,小麦的比例最大,分别占冬季食物组成的99.67%和早春的90.17%。对冬季与早春的食物组成的差异进行分析,发现大天鹅在天鹅湖保护区发生了食物替代现象。结合以往资料,认为生态污染和湿地结构性破坏导致大天鹅传统食物减少,致使食物替代现象的发生。     

黄山陈村水库河源溪流鱼类群落的食性

基于2010年11月在黄山陈村水库河源溪流中所采集的鱼类标本,对其中9种优势鱼类的食性特征进行了研究。结果表明:宽鳍鱲(Zacco platypus)、光唇鱼(Acrossocheilus fasciatus)和麦穗鱼(Pseudorasbora parva)等9种鱼类都以有机碎屑、藻类和无脊椎动物为主要食物,属典型的杂食性或无脊椎动物食性鱼类;食物组成的相似性分析结果表明,不同物种间的食物组成差异显著但存在部分重叠(P<0.001)。不同物种间的食物多样性和食性宽度也存在显著性差异(P<0.05),其中底栖型鱼类具有相对较高的饵料来源,而鱼类的食物多样性可能与其小生境选择性有关。根据食物重叠指数,9种优势鱼类之间存在明显的食物重叠(D>0.3),尤其是宽鳍鱲、光唇鱼、麦穗鱼、高体鰟鮍(Rhodeus ocellatus)和稀有花鳅(Cobitis sinensis)间的食物重叠指数超过0.9。陈村水库河源溪流的鱼类群落所表现出的食物组成、食物多样性、食性宽度和种间食物重叠性等特征,可能与其生态系统所具有的营养外源性和物理栖息地周期动荡性等密切相关。     

甘肃民勤治沙站纵纹腹小鸮食性的季节变化

分析民勤治沙站纵纹腹小鸮(Athene noctua)食团405块,共鉴定猎物562只。以个体计,民勤小鸮主要取食昆虫,占64.23%;其次为小型哺乳类,占32.38%;也取食少量爬行类(1.96%)和雀形目鸟类(1.42%)。生物量贡献则以小型哺乳类为主,占93.34%。猎物种类组成存在显著的季节变异:取食小型哺乳类的频率存在显著季节差异,冬季最高94.59%,夏季最低17.75%,食物生物量贡献四季均在90%以上,季节变异不显著;昆虫成分出现在除冬季外的其他季节,且取食频率均在65%以上,季节差异显著;爬行类仅出现于夏季食谱中,仅秋季没有发现鸟类成分。分析秋、冬、春三季哺乳类猎物胫骨的量度发现,小鸮取食哺乳类的胫骨长度平均为16.22mm±4.72mm(n=112),主要取食Ⅰ(10.01mm-15.00mm)和Ⅱ(15.01mm-20.00mm)等级的猎物(分别58.04%和25.00%)。取食猎物的胫骨长度组成存在季节差异,平均长度以春季最大。民勤地区小鸮一年的食物生态位宽度为2.32,季节间存在变异,以冬季最高为2.99,夏季最低为1.64。一年的食物多样性为1.96,季节间存在变异,冬季最高为2.00。食物种类以夏季最多,秋季最少。     

大兴安岭紫貂食物组成分析

在大兴安岭地区, 从1995 年12 月至1996 年11 月在颈环遥测的4 只紫貂活动的范围内共收集紫貂粪样295个, 采用频率法和剩余物相对干重法进行分析, 得出紫貂全年食物组成及比例: 哺乳类(出现率72.09 % , 剩余物干重百分比84.06 %) , 植物浆果及种子(14.51 % , 11.09 %) , 鸟类(7.69 % , 4.24 %) 和昆虫(5.71 % , 0.96 %) 。其中红背　和棕背　构成紫貂食物的主要部分, 其次为松籽、越桔果和花尾榛鸡。紫貂食物组成季节性变化明显, 夏季食物种类丰富, 且比例较均衡; 冬季食物多样性低。文中还对两种粪样分析方法所得结果进行了比较,证明这两种方法在对主要食物种( 出现次数≥5) 的分析评述上是一致的, 无显著差异。     

鄱阳湖越冬白鹤觅食地特征分析

2008年11月至2009年3月,采用样线法、样方法和因子分析法对鄱阳湖国家级自然保护区越冬白鹤(Grus leucogranus)觅食地特征进行了研究。结果表明,白鹤在保护区的分布具有时空动态性,主要受水位和食物的控制;白鹤对不同类型觅食地具有选择性(P0.05),对沉水植物型觅食地,即以苦草(Vallisneria natans)、黑藻(Hydrilla verticillata)、马来眼子菜(Potamogeton malaianus)为主的沉水植物型生境利用度最大;白鹤各型觅食地各因子的方差分析表明,植被因子具有极显著差异(P0.001),基底因子和掘食因子具有显著差异(P0.05);因子分析表明,觅食地选择以取食效率因子为主,其次是基底因子和食物丰富度因子。     

岩羊(Pseudois nayaur)研究概述

野生动物管理需要生境质量、行为学、种群动态以及种间关系等数据支持。岩羊(Pseudois nayaur)作为我国Ⅱ级保护动物,是雪豹(Panthera uncia)、狼(Canis lupus)、棕熊(Ursus arctos)等珍稀食肉目动物的重要食物来源。20世纪,岩羊作为重要的狩猎物种被大量捕杀贩卖,影响了该物种的种群规模和分布,也影响了雪豹等动物的食物资源。当前,由于缺乏野生动物管理所需数据,岩羊保护与人类利益发生冲突十分常见。岩羊主要分布于青藏高原及周边地区,种群分布及行为学相关研究主要集中在国内的宁夏、甘肃、青海和新疆等省份;在境外地区,印度、尼泊尔等国也有岩羊的反捕食栖息方面研究的报道,而高原中部地区岩羊种群的研究却非常少。当前研究存在主要问题:分类学上对亚种间分化争议较大,栖息地质量评估无法满足岩羊有效管理,网围栏架设等人类活动干扰其生存并间接影响濒危物种雪豹的保护等。此外,有关岩羊动物疫病流行病学、肠道微生物及动物营养学等报道,尚缺乏对岩羊与家畜交叉感染相关案例的深度分析。已有的研究有助于认识物种分化和对环境的适应机制,但对岩羊宏观生态学研究不够系统,仍存在大部分地区种群动态数据不足、亚种分类和地理划分不清等问题。近年来,随着新技术的发展,应用分子识别、计算机识别、无人机技术和红外相机技术等对岩羊进行宏观生态学研究成为热点,建议加大对矮岩羊种群和贺兰山岩羊种群的保护;对保护区内应用新技术构建全面的野生动物及环境监测系统,从而对野生动物的种群分布动态和生存状态能够进行有效监测;增加对区外野生动物的调查频率,及时建立保护区、扩大保护区范围并建立相应的监测站。     

湖南壶瓶山国家级自然保护区两栖 爬行动物多样性的时空格局

本研究利用2013至2016年湖南壶瓶山国家级自然保护区巡护监测数据,评估壶瓶山保护区两栖爬行动物多样性水平。壶瓶山保护区在8个监测站点布设了25条两栖爬行动物调查样线,进行常规监测,其中,日间样线14条,夜间样线11条,日间样线平均长度4 km,夜间样线平均长度0.75 km。每个月,每条样线平均调查3次。4年共调查到62种两栖爬行动物,占湖南省两栖爬行动物总种数的38.04%。逐月计算各监测站点的alpha多样性指数和整个保护区的beta多样性指数,按季节比较不同站点间物种组成的Hellinger距离。结果显示,保护区不同位置间、不同的监测站点间以及年际间的两栖爬行动物多样性没有显著差异,提示保护区环境具有相对稳定性。但是,个别位于实验区或邻近实验区的站点,物种组成有着剧烈的波动,表明人为活动影响了两栖爬行动物的分布。另外,保护区两栖爬行动物的物种组成与多样性有着显著的季节差异,这与两栖爬行动物的生物学特性有关。以上结果说明,壶瓶山保护区两栖爬行动物的多样性结构具有稳定性和敏感性的特点,可以考虑用作保护区生物多样性水平的监测指标。     

7种荒漠啮齿动物食物组成与消化道长度的比较

对荒漠地带几种啮齿动物在自然环境中夏季主要食物组成以及消化道长度的适应性变化进行了比较。三趾跳鼠(Dipus sagitta)、五趾跳鼠(Allactage sibirica)、子午沙鼠(Meriones meridianus)和红耳鼠兔(Ochotona erythrotis)胃内的主要食物成分为当年生植物嫩茎、叶和部分灌木韧皮部分，灰仓鼠(Cricetulus migratorius)及黑线仓鼠(C．barabensis)食物组成中种子、花和浆果以及昆虫出现较高的频率，小家鼠(Mus musculus)的食物构成以种子类为主，与食物组成相适应，总消化道和各器官长度存在明显的种间差异，而且各器官间盲肠和大肠长度的种间差异明显大于小肠的种间差异，胃和盲肠及其内容物的重量也存在显著的种间差异，但小肠和大肠及其内容物重量的种间差异则不显著。其结果验证了下述假设：栖息于同一生境的植食性小哺乳类具有不同食物资源利用模式，而同域共存物种消化道形态结构的差异是对食物资源利用种间权衡的功能反应[动物学报49(2)：171—178，2003]。     

Interacting effect of wolves and climate on recruitment in a northern mountain caribou population

There is limited research on the influence of Pacific‐based climate in large herbivore populations. Additionally, much of our understanding on the effect of large‐scale climate on ungulate population dynamics has occurred on forage‐limited rather than predator‐limited populations. We compared the influence of the Pacific Decadal Oscillation (PDO), North Pacific Index, and local weather on recruitment in a predator‐limited mountain‐dwelling caribou Rangifer tarandus caribou population in the Yukon Territory, Canada, across a range of wolf Canis lupus densities. A large‐scale wolf removal program allowed us to examine the role of Pacific climate and weather when wolves were reduced to ～15% of their pre‐removal levels. Recruitment was best explained by the interaction of wolf density and April‐PDO, with wolf density explaining the most deviance. Predicted recruitment during good springs was 0.45 (SE = 0.04) during wolf removal and 0.29 (SE = 0.03) with no wolf removal. During poor springs (low PDO, increased snow depth) predicted recruitment was 0.55 (SE = 0.10) during wolf removal and 0.12 (SE = 0.03) with no wolf removal. With non‐altered wolf densities, there was a positive relationship between April‐PDO and recruitment due to reduced snow depth at calving, allowing parturient females to disperse up in elevation away from predators. When wolf densities were substantially reduced there was a slight negative relationship between April‐PDO and recruitment, possibly due to a more rapid vegetation green‐up reducing the temporal availability of highly nutritious forage necessary for lactation and subsequent calf growth. Attempts to find general relationships between climate and ungulate population dynamics have proven difficult due to different ecological mechanisms by which climate affects individuals across populations. Temporally varying factors, such as predator density, may also play an important role in uncovering the mechanistic relationship between climate and population dynamics.     

Fine-scale genetic structure suggests low levels of short-range gene flow in a wolf population of the Italian Apennines

We investigated local gene flow in a high-density wolf (Canis lupus) population of the Italian Apennines, where no effective barrier to wolf dispersal was present. From 1998 to 2004 we examined wolf carcasses and non-invasively collected samples, focusing on three mountain districts, separated by two valleys, where wolf packs showed high spatial stability. Using nine autosomal microsatellites we successfully genotyped 177 samples, achieving the identification of 74 wolves. Genetic relatedness steeply decreased with increasing distance between sampling areas, thus suggesting that short-distance interpack migration is infrequent in this population. In addition, no individual from a central pack under intensive monitoring was sampled in the range of the surrounding packs over a 4-year period. The limited short-distance gene flow resulted in a cryptic genetic structure, which was revealed by Bayesian analysis. A different genetic cluster was found in each of the three mountain areas, and a small proportion of first-generation immigrants was detected. Overall, the present study suggests that local genetic differentiation in Italian wolves might arise from high spatial stability of packs and can be favoured by a combination of long-range dispersal, the attitude to mate between unrelated individuals and a high young mortality rate.     

Effects of wolf pack size and winter conditions on elk mortality

Elk (Cervus canadensis) are high-profile game animals for many states in the western United States, yet over the past several decades some populations have experienced a persistent and broad-scale decline in recruitment. Over this same period, gray wolves (Canis lupus) have become an integral component of many western landscapes and agencies are increasingly challenged to maximize hunting opportunities of ungulates via predator management while simultaneously ensuring wolf conservation. To better understand the implications of predator management on elk populations, we monitored survival of 1,244 adult female elk and 806 6-month-old calves from 29 populations distributed throughout Idaho, USA, from 2004 to 2016. We developed predictive models of mortality that related mortality risk to wolf pack size, winter conditions, and individual-level characteristics. Annual mortality rates (excluding harvest) for adult females and calves were 0.09 and 0.40, respectively. Calf mortality was predicted best with a model that included additive effects of chest girth at time of capture, mean size of surrounding wolf packs, and snow depth. Adult female mortality was predicted best with a model that included female age, mean size of surrounding wolf packs, and snow depth. Based on a sensitivity analysis, chest girth had the largest effect on risk of mortality for calves followed by pack size and snow depth. Other than the effect of senescence in the oldest (>15 yr) individuals, pack size and snow depth had the largest effect on risk of mortality for adult females. We estimated cause-specific mortality and predation was the dominant cause of known-fate mortalities for adult females (35% mountain lion [Puma concolor] and 32% wolf) and calves (45% mountain lion and 28% wolf), whereas malnutrition accounted for 9% and 10% of adult female and calf mortalities, respectively. Wolves preferentially selected smaller calves and older adult females, whereas mountain lions showed little preference for calf size or age class of adult females. Our study indicates managers can increase elk survival by reducing wolf pack sizes on surrounding winter ranges, especially in areas where, or during years when, snow is deep. Additionally, managers interested in improving over-winter calf survival can implement actions to increase the size of calves entering winter by increasing the nutritional quality of summer and early fall forage resources. Although our study was prompted by management questions related to wolves, mountain lions killed more elk than wolves and differences in selection of individual elk indicate mountain lions may have comparably more of an effect on elk population dynamics. Although we were unable to relate changes in mountain lion populations to elk survival in our study, future research should seek a better understanding of multi-predator systems, including how management of one predator affect others and ultimately how these interactions affect elk survival. © 2019 The Wildlife Society     

Population responses of roe deer to the recolonization of the French Vercors by wolves

In a context of changing carnivore populations worldwide, it is crucial to understand the consequences of these changes for prey populations. The recolonization by wolves of the French Vercors mountain range and the long-term monitoring (2001–2017) of roe deer in this area provided a unique opportunity to assess the effects of wolves on this prey. Roe deer was the main prey of wolves in the west Vercors mountain range during this recolonization. We compared roe deer abundance and fawn body mass in two contrasted areas of a wolf pack territory: a central area (core of the territory characterized by an intense use by wolves) and a peripheral area (used more occasionally). Roe deer population growth rates were lower in the central area between 2001 and 2006, resulting in a decline in roe deer abundance. Roe deer abundance substantially dropped in the two study areas after an extremely severe winter but the abundance of roe deer in the central area facing with wolves was slower to recover and remained at lower abundance levels for 6 years. Fawn body mass was consistently lower in the central area, varied similarly as roe deer abundance, and was not influenced by weather conditions or red deer population abundance. Altogether, the effects of wolves on roe deer in the central area occurred during a 10-year period following the establishment of wolves, through the interplay between wolf predation (before wolves started preying on red deer), harsh winter conditions and possibly naivety of prey to this recolonizing predator.     

Exploring patterns of population subdivision in the net-winged midge, Elporia barnardi (Diptera: Blephariceridae), in mountain streams of the south-western Cape, South Africa

1. The net-winged midges (Diptera: Blephariceridae) are a highly specialized group whose morphological characteristics and specific habitat requirements suggest a limited potential for dispersal. Levels of genetic variation were examined within streams, between streams in the same range and between mountain ranges in larval populations of Elporia barnardi in the south-western Cape of South Africa. The aim was to examine the hypothesis that population structure would reflect the poor potential for dispersal.
2. Significant deviations from Hardy–Weinberg equilibrium in 17 of the 57 individual comparisons indicate a non-random mating population. Given the swarming behaviour and life history traits, larvae sampled may reflect the product of limited matings.
3. Analysis of population substructuring revealed significant levels of differentiation among geographically proximate populations. Large differences between streams within Table Mountain, similar in magnitude to those between mountain ranges, suggest that movement of individuals out of the stream catchment is rare. Observed F _ST values are more similar to those of fully aquatic species than other lotic insects with winged adult stages.
4. Results suggest that mountain ridges provided effective physical barriers to the dispersal of E. barnardi , with the catchment representing the effective population unit.     

Population Viability, Nature Reserves, and the Outlook for Gray Wolf Conservation in North America

Theoretical work on population viability and extinction probabilities, empirical data from Canis lupus (gray wolf) populations, and expert opinion provide only general and conflicting conclusions about the number of wolves and the size of areas needed for conservation of wolf populations. There is no threshold population size or proven reserve design that guarantees long-term (century or more) survival for a gray wolf population. Most theoretical analyses of population viability have assumed a single, isolated population and lack of management intervention, neither of which is likely for wolves. Data on survival of actual wolf populations suggest greater resiliency than is indicated by theory. In our view, the previous theoretical treatments of population viability have not been appropriate to wolves, have contributed little to their conservation, and have created unnecessary dilemmas for wolf recovery programs by overstating the required population size. Nonetheless, viability as commonly understood may be problematic for small populations at the fringe of or outside the contiguous species range, unless they are part of a metapopulation. The capability of existing nature reserves to support viable wolf populations appears related to a variety of in situ circumstances, including size, shape and topography of the reserve; productivity, numbers, dispersion, and seasonal movement of prey; extent of poaching inside; degree of persecution outside; exposure to enzootica; attitudes of local people; and proximity to other wolf populations. We estimate that a population of 100 or more wolves and a reserve of several thousand square kilometers may be necessary to maintain a viable population in complete isolation, although 3000 km² or even 500–1000 km² may be adequate under favorable circumstances. In most cases, management intervention is probably necessary to assure the viability of relatively small, isolated populations. Because most reserves may be inadequate by themselves to ensure the long-term survival of wolf populations, favorable human attitudes toward the species and its management must be recognized as paramount, and cooperation of neighboring management jurisdictions will be increasingly important.     

A reappraisal of the evidence for regulation of wolf populations

The dogma that gray wolf (Canis lupus) population densities in naturally occurring systems are limited almost solely by available ungulate biomass is based upon studies that fit straight line linear regressions (Type 1 numerical response) to data collected at 32 sites across North America. We fit Type 1, 2, and 3 response functions to the data using linear and nonlinear regression as appropriate and found that the evidence supported wolf population regulation by density-dependence as much as limitation by prey availability. When we excluded 4 of 32 points from the original data set because those points represented exploited or expanding wolf populations the data suggested that wolf populations are self regulated rather than limited by prey biomass by at least a 3:1 margin. In establishing goals for sustainable wolf population levels, managers of wolf reintroductions and species recovery efforts should account for the possibility that some regulatory mechanism plays an important role in wolf population dynamics. © 2011 The Wildlife Society.     

Coexistence of wolves and humans in a densely populated region (Lower Saxony,Germany)

Since the first sporadic occurrences of grey wolves (Canis lupus) west of the Polish border in 1996, wolves have shown a rapid population recovery in Germany. Wolves are known to avoid people and wolf attacks on humans are very rare worldwide. However, the subjectively perceived threat is considerable, especially as food-conditioned habituation to humans occurs sporadically. Lower Saxony (Germany) has an exceedingly higher human population density than most other regions with territorial wolves; thus, the potential for human–wolf conflicts is higher. Using hunters’ wildlife survey data from 455 municipalities and two years (2014–2015) and data from the official wolf monitoring (557 confirmed wolf presences and 500 background points) collected between 2012–2015, grey wolf habitat selection was modelled using generalized additive models with respect to human population density, road density, forest cover and roe deer density. Moreover, we tested whether habitat use changed in response to human population and road density between 2012/2013 and 2014/2015.Wolves showed a preference for areas of low road density. Human population density was less important as a covariate in the model of the survey data. Areas with higher prey abundance (5–10 roe deer/km²) and areas with >20% forest cover were preferred wolf habitats. Wolves were mostly restricted to areas with the lowest road and human population densities. However, between the two time periods, avoidance of human density decreased significantly.Recolonization of Germany is still in its early stages and it is unclear where this process will halt. To-date authorities mainly concentrate on monitoring measures. However, to avoid conflict, recolonization will require more stringent management of wolf populations and an improved information strategy for rural populations.     

Spatial variability in wolf diet and prey selection in Galicia (NW Spain)

We studied wolf (Canis lupus) diet for three different landscapes in the north-western Iberian Peninsula, differing in land uses and availability of food for wolves. We examined 2740 scats, collected over a period of 4 years, in order to describe wolf diet, its geographic variation, and trophic preferences. The most consumed species were wild pony, roe deer and cattle. We observed differences in wolf diet among the three study sites, related to the availability and accessibility of food resources in each habitat. For the two study sites in northern and central Galicia, wolves showed similar diet, with high occurrence of wild pony (37 vs. 34%) and cattle (20 vs. 23%), but differing in the consumption of wild ungulates (16 vs. 8%) and carrion (7 vs. 14%). Wolf diet in eastern Galicia’s mountain ranges was entirely different, due to the higher consumption of wild ungulates (70%). Wolves showed clear prey selection patterns. Between wild ponies and livestock, wolves positively selected ponies. Among wild ungulates, wolves positively selected roe deer. Wild pony and roe deer are key species for wolf feeding in Galicia. In the Galician wild pony range, ponies are the main food for wolves. Given that the availability of wild ponies may contribute to the decrease in wolf predation on cattle, it is essential to develop innovative administrative decisions in such areas to preserve this traditional equid population. In the same way, the population of roe deer should be strengthened in the livestock areas outside the range of wild pony.     

Population structure of Columbia spotted frogs (Rana luteiventris) is strongly affected by the landscape

Landscape features such as mountains, rivers, and ecological gradients may strongly affect patterns of dispersal and gene flow among populations and thereby shape population dynamics and evolutionary trajectories. The landscape may have a particularly strong effect on patterns of dispersal and gene flow in amphibians because amphibians are thought to have poor dispersal abilities. We examined genetic variation at six microsatellite loci in Columbia spotted frogs (Rana luteiventris) from 28 breeding ponds in western Montana and Idaho, USA, in order to investigate the effects of landscape structure on patterns of gene flow. We were particularly interested in addressing three questions: (i) do ridges act as barriers to gene flow? (ii) is gene flow restricted between low and high elevation ponds? (iii) does a pond equal a ‘randomly mating population’ (a deme)? We found that mountain ridges and elevational differences were associated with increased genetic differentiation among sites, suggesting that gene flow is restricted by ridges and elevation in this species. We also found that populations of Columbia spotted frogs generally include more than a single pond except for very isolated ponds. There was also evidence for surprisingly high levels of gene flow among low elevation sites separated by large distances. Moreover, genetic variation within populations was strongly negatively correlated with elevation, suggesting effective population sizes are much smaller at high elevation than at low elevation. Our results show that landscape features have a profound effect on patterns of genetic variation in Columbia spotted frogs.