洞庭湖区夏季温光条件及被迫迁移对东方田鼠繁殖的影响

在野外 ,从先年的秋初至当年春末被迫迁移前 ,东方田鼠在湖滩上能保持较高的繁殖能力 ;在夏季 ,不论栖息在农田还是岗地 ,都是东方田鼠的繁殖低谷。夏季 (6～ 8月 )在实验室自然温光条件下与人工控制较低温度条件下同时进行观察 ,结果表明 ,前种条件下东方田鼠的繁殖能力明显低于人工降低温度缩短光照条件下的繁殖力 ,此变动趋势与野外观察到的繁殖力季节动态一致 ,可以说明夏季温光条件不利于东方田鼠的繁殖。另一方面 ,东方田鼠的繁殖能力最低的 6月并非全年最热的月份 ,这是因为东方田鼠的被动迁移对体力的消耗加剧了夏季温光对繁殖的影响程度。因此 ,认为洪水引起的东方田鼠被迫迁移和夏季的温光条件共同影响了东方田鼠的繁殖。洞庭湖区东方田鼠主要在冬春季繁殖 ,而分布在高纬度地区的田鼠类动物和分布在高纬度地区的东方田鼠在夏季繁殖 ,在月份上虽不同 ,但其繁殖盛期的气温则相近 ,其实是田鼠类动物喜寒惧热特性的反映 ,乃是对当地的生态环境的适应。     

洞庭湖区东方田鼠迁移的研究

洞庭湖区东方田鼠以湖滩上的芦苇＋荻或薹草沼泽为最适栖息地,枯水季节,多在其上生长、繁殖。汛期,随着湖水上涨,湖滩面积缩小,东方田鼠在拥挤的的压力下或直接被洪水所迫,越过防洪堤迁入垸内。东方田鼠在湖滩及农田间的迁移主要取决于湖水水位及种群密度,无固定的迁移时间。迁入垸内的东方田鼠主要分布于靠近防洪堤一带,其捕获率随着与防洪堤距离的增加而递减。个体较大的东方田鼠迁移距离较远。在迁移期,迁入垸内的东方田鼠的性比在不同的距离上无显著差异。湖水回落时,东方田鼠随湖滩出露而迁回沼泽草地。回迁时,个体较大的雄性首先回迁的比例较高。迁入垸内的东方田鼠,栖息在荒坡地的种群密度大于在农田中的种群密度;东方田鼠不在农田越冬,小部分可在岗地荒坡中越冬,但少有增殖。按迁移动因看,此种迁移乃洪水逼迫所至,而由逼迫外迁和自动回迁构成循环,保证了种群对湖区特殊环境的适应。     

洞庭湖不同退田还湖类型区东方田鼠和黑线姬鼠的繁殖特性

针对洞庭湖区实施的“退田还湖” 重大生态环境恢复工程,以原有“围湖”造的垸田和垸外湖滩为对照,对退田还湖区(含双退与单退两种形式)的啮齿动物群落于2003 ～ 2006 年进行定位观察。采用夹捕法进行采样,于每年的1 月、4 月、7 月、10 月进行。比较洞庭湖不同退田还湖类型区东方田鼠和黑线姬鼠种群的繁殖
指标参数。总体来看,调查期间东方田鼠和黑线姬鼠的繁殖指数要比上世纪80 ～90 年代报道的要高,这与前几年其种群处于年数量低谷有关,是东方田鼠和黑线姬鼠种群负反馈机制的体现。不同类型生境间的比较结果显示,单退垸与原有生境没有明显变化,而双退垸内黑线姬鼠和东方田鼠均有较显著的变化,主要表现在双退垸内夏季东方田鼠保持高的繁殖能力和黑线姬鼠的繁殖力锐减。由于双退垸的高程优势,鼠群在夏季汛期不会迁出垸内,仅迁移集中至较高区域,这种水位变化引导的害鼠种群迁移应该是造成繁殖变化的主要原因。由于黑线姬鼠不适应这种迁移以及集中后与东方田鼠的激烈竞争,迁移到高地后的黑线姬鼠几乎停止繁殖,繁殖指数仅为0.03 (I♀ = 0.05),明显低于当期其它生境。值得注意的是夏季滞留在双退垸内的东方田鼠,繁殖强度却不减,繁殖指数达1.54 (I♀ = 3.36),与春季湖滩种群的相当。说明没有经过长距离迁移的东方田鼠种群,在夏季仍会保持较高的繁殖强度,与夏季被迫远距离迁入农田的东方田鼠种群繁殖力急剧下降形成鲜明对比。由此可知,在初夏如果有适宜的栖息地(如双退垸的高台、原有堤岸等),东方田鼠仍能保持较强繁殖力。本文揭示了双退垸内水位变化引发种群迁移后东方田鼠和黑线姬鼠繁殖能力的这种迥异表现,具体深层次原因有待进一步探讨。     

洞庭湖区夏季温光条件及被迫迁移对东方田鼠和繁殖的影响

在野外,从先年的秋初至当年春末被迫迁移前,东方田鼠在湖滩上能保持较高的繁殖能力;在夏季,不论栖息在农田还是岗地,都是东方田鼠的繁殖低谷。夏季（６～８月）在实验室自然温光条件下与人工控制较低温度条件下同时进行观察,结果表明,前种条件下东方田鼠的繁殖能力明显低于人工降低温度缩短光照条件下的繁殖力,此变动真挚势与野外观察到的繁殖力季节动态一致,可以说明夏季温光条件不利于东方田鼠的繁殖。另一方面,东方田鼠     

饥饿和食物单宁酸对东方田鼠(Microtus fortis)食物摄入量和觅食行为的影响

实验室条件下,测定饥饿和食物单宁酸对东方田鼠食物摄入量和觅食行为的影响。结果表明,饥饿使实验个体的食物总摄入量增加,食物摄入率及口量大小随饥饿强度的增大而增加,而觅食频次则无显著改变,实验个体每取食回合的觅食时间呈缓慢增加的趋势,与对照组比较,觅食时间差异不显著。东方田鼠优先选择0%单宁酸食物,次为3%单宁酸食物,而对6%单宁酸食物的摄入量最少。在饥饿条件下,东方田鼠食物摄入率的增加主要源于其口量大小,觅食频次和觅摄食时间对食物摄入量增加的贡献不显著。在饥饿条件下,植食性小哺乳动物并未通过延长觅食时间,降低用于防卫、繁殖活动时间来增加食物摄入量,而是通过增加口量大小,提高其食物摄入率来满足其营养需要。验证了饥饿与植物次生化合物共同作用引起田鼠类动物生理的改变,能影响其食物摄入量及觅食行为的假设。     

饥饿和食物单宁酸对东方田鼠(Microtus fortis)食物摄入量和觅食行为的影响

实验室条件下,测定饥饿和食物单宁酸对东方田鼠食物摄入量和觅食行为的影响。结果表明,饥饿使实验个体的食物总摄入量增加,食物摄入率及口量大小随饥饿强度的增大而增加,而觅食频次则无显著改变,实验个体每取食回合的觅食时间呈缓慢增加的趋势,与对照组比较,觅食时间差异不显著。东方田鼠优先选择0％单宁酸食物,次为3%单宁酸食物,而对6%单宁酸食物的摄入量最少。在饥饿条件下,东方田鼠食物摄入率的增加主要源于其口量大小,觅食频次和觅摄食时间对食物摄入量增加的贡献不显著。在饥饿条件下,植食性小哺乳动物并未通过延长觅食时间,降低用于防卫、繁殖活动时间来增加食物摄入量,而是通过增加口量大小,提高其食物摄入率来满足其营养需要。验证了饥饿与植物次生化合物共同作用引起田鼠类动物生理的改变,能影响其食物摄入量及觅食行为的假设。     

蛋白质,纤维素和单宁酸对东方田鼠摄食的影响

食物选择性是动物对取食生境中现存的食物种类做出的选择,是一个复杂的生态适应过程,与动物自身生理状及环境中食物的可利用量密切相关。单宁酸、蛋白质和纤维素是影响植食性动物食物选择的重要因素。在控制其它营养因子的条件下,设置10%蛋白质+2.25%纤维素+3%单宁酸(食物1)/6%单宁酸(食物2)和20%蛋白质+4.51%纤维素+3%单宁酸(食物3)/6%单宁酸(食物4)4个处理组,通过自助餐式选择笼内的喂养实验,测定单宁酸、蛋白质和纤维素对东方田鼠食物选择的影响。结果表明,东方田鼠对3%单宁酸处理组食物摄食量显著高于对6%单宁酸处理组(P0.001);但东方田鼠对6%单宁酸食物摄食量依蛋白质浓度变化,在20%蛋白质处理组的摄食量显著高于10%蛋白质处理组(P0.05);在含3%单宁酸处理组中,纤维素成为影响东方田鼠摄食的主要因素,而当单宁酸浓度增加到6%时,纤维素和蛋白质对东方田鼠摄食影响差异不显著;总之,单宁酸、蛋白质和纤维素对东方田鼠的摄食都产生重要影响,单宁酸对东方田鼠食物选择的影响程度最大,纤维素次之,蛋白质对东方田鼠摄食的影响会随单宁酸浓度的升高而增大。     

福寿螺的寄主植物及其对福寿螺体重的影响

为了明确福寿螺对寄主植物的选择性,进一步掌握其可能的危害及入侵暴发机制,对稻田水域及周边的24科43种植物进行了室外取食试验,分别在取食后3、5d对受试样品及成螺称重,比较其无选择条件下的取食偏好性及其对成螺增长率的影响。结果表明:福寿螺对受试的24科43种植物(样品)的根、茎、叶、果实以及块根(茎)均能取食,对水生(湿生)和陆生植物没有偏好性;在取食过程中,优先取食细嫩的植株和部分,硬老部分需经水浸泡软化后才能被取食;辣椒、苦瓜等果实的辣苦味对福寿螺无驱避作用;取食率与体重增长率呈显著正相关,取食越多生长越快;但体重与植物的总酚含量呈负相关。福寿螺的广食性、取食量、植物总酚含量、植物丰盛度等种群和生态系统特征是影响其快速扩散的重要原因,同时可以借助福寿螺对植物的不同利用类型防范其扩散和危害。     

东方田鼠种群扩散及活动对外部因子的反应格局

在野外围栏条件下,采用2×2×2析因实验,测定外部因子食物、捕食,以及同域分布物种黑线姬鼠的种间竞争对东方田鼠扩散和活动距离的独立作用及其交互作用的效应。研究结果表明,在所有的扩散个体中,幼体扩散的比例为71.0%。雄体扩散的比例为80.5%。东方田鼠扩散的趋势与其种群密度及补充量的变动一致。食物对扩散具有显著独立作用;捕食对扩散的作用接近显著;种间竞争对扩散的直接效应不显著;食物、捕食与种间竞争交互作用对扩散的效应亦不显著。在诱捕期内雄性的长距离活动比例及其诱捕期间长距离活动比例均显著大于诱捕期内雌性及其诱捕期间的长距离活动比例。不同处理种群间,仅雄体在诱捕期间的长距离活动比例具有显著差异;食物对雄体的长距离活动具有直接和间接(通过密度)的效应;而预防捕食者和竞争物种对不同处理种群雄体的长距离活动则无一致的效应。     

东方田鼠的游泳行为和能力

东方田鼠(Microtus fortis)是一种栖息于湿地生境的小型哺乳动物,为了解其水生运动适应,作者在实验室内观察和测试了该鼠的游泳行为、皮毛防水性能和长时间游泳能力。结果发现,东方田鼠主要在水面游泳,亦能潜水,游泳姿势是狗刨式,并主要以后肢交替划水提供推进力,速度约为0.37 m/s。在20℃水温条件下,东方田鼠皮毛表现出良好的防水性能,且防水性能与其年龄及体重均存在极显著的负相关关系(P 0.01,R~2=0.805);东方田鼠具有平均约持续5 h以上的长时间游泳能力,且长时间游泳能力与其皮毛防水性能存在极显著的正相关关系(P 0.01,R~2=0.682);上述两项指标性别差异显著。这表明,东方田鼠有较强的水中运动能力和长时间游泳能力,具有水生运动方面的适应性进化,有利于其在沼泽等栖息地的生存。     

洞庭湖区东方田鼠种群动态及其危害预警

洞庭湖区东方田鼠以湖滩沼泽为最适栖息地．秋末洞庭湖水位回落,湖滩出露,东方田鼠从农田迁回到湖滩生活、繁殖,种群数量呈逐月上升趋势．春末夏初,洞庭湖水位上涨,湖滩被淹,东方田鼠被迫越过大堤迁入垸内农田．其种群动态由“水位影响东方田鼠的栖息地变换”主导．每年迁入农田的数量首先取决于东方田鼠在湖滩生活繁殖时期的长短,亦即枯水期的天数;其次3月降雨量对东方田鼠在湖滩上的繁殖有较大的影响．东方田鼠迁入垸内后,种群数量呈逐月下降趋势．在分析影响洞庭湖区东方田鼠种群数量动态的主要因子的基础上,提出了东方田鼠种群迁入垸内农田的迁入量预警模型．经过几年的实际预测,吻合情况良好．     

洞庭湖洲滩及滨湖区鼠类分布格局及其多样性

为全面了解洞庭湖洲滩及滨湖区鼠类分布格局,统计自2003—2013年该湖区15个调查点5种不同生境的鼠类群落调查数据,并对鼠类群落的物种多样性进行分析。结果表明:2003—2013年洞庭湖区捕获鼠类有10种,主要优势种为黑线姬鼠(Apodemus agrarius)和东方田鼠(Microtus fortis);不同生境下的优势种不同,东方田鼠为湖滩生境优势种,黑线姬鼠是滨湖农田和退田还湖洲滩生境优势种,针毛鼠(Niviventer fulvescens)和社鼠(Niviventer confucianus)为滨湖丘岗林地优势种,小家鼠(Mus musculus)及黄胸鼠(Rattus tanzumi)则多出现在农房生境;不同生境的鼠类群落物种多样性不同,滨湖丘岗林地生境受人类活动或洪水干扰程度最低,因此,优势集中性指数最低,而物种多样性Shannon-Wiener指数在干扰较少的滨湖丘岗林地生境物种多样性指数最高。尽管湖滩生境受三峡工程的影响,物种数大量增加,但由于仍受汛期洪涝的干扰,依然具有优势种突出的特征。研究表明,人类社会活动或洪涝等干扰因素降低了鼠类群落物种多样性,致使优势种突出,形成只利于少数几个种群栖息的环境,最终导致种群大暴发。     

Dispersal among habitats varying in fitness: reciprocating migration through ideal habitat selection

Current evolutionary models of dispersal set the ends of a continuum where the number of individuals emigrating from a habitat either equals the number of individuals immigrating (balanced dispersal) or where emigrants flow from a source habitat to a corresponding sink. Theories of habitat selection suggest a more sophisticated conditional strategy where individuals disperse from habitats where they have the greatest impact on fitness to habitats where their per capita impact is lower. Asymmetries between periods of population growth and decline result in a reciprocating dispersal strategy where the direction of migration is reversed as populations wax and wane. Thus, for example, if net migration of individuals flows from high- to low-density habitats during periods of population growth, net migration will flow in the opposite direction during population decline. Stochastic simulations and analytical models of reciprocating dispersal demonstrate that fitness, carrying capacity, stochastic dynamics, and interference from dominants interact to determine whether dispersal is balanced between habitats, or whether one habitat or the other acts as a net donor of dispersing individuals. While the pattern of dispersal may vary, each is consistent with an underlying strategy of density-dependent habitat selection.     

上海郊区红隼(Falco tinnunculus)种群密度及其变化

2002年7月到2004年6月对上海郊区祝桥镇、机场镇和朝阳农场及其附近区域的红隼种群密度进行了计数调查.调查通过固定路线进行,共进行调查53次.结果表明该区域红隼种群密度冬季明显高于夏季,呈现明显的月变化和季节变化,红隼种群的季节变动在一定程度上反映了该区域红隼的迁徙及居留情况,认为红隼在上海地区的居留状况包括留鸟、冬候鸟和过境鸟3种类型.混合农作物生境和芦苇生境中红隼种群密度具有极显著差异（t＝4.6506,P＝0.0000〈0.001）,红隼更加偏好混合农作物生境.通过红隼的种群密度可以反映红隼的居留状况和对生境的选择情况.     

Density and behaviour of Whinchats Saxicola rubetra on African farmland suggest that winter habitat conditions do not limit European breeding populations

The Whinchat Saxicola rubetra is an Afro‐Palaearctic migrant undergoing widespread population decline. Whinchats winter in West Africa but there are almost no data on their habitat use and behaviour there that may help to explain the cause of this decline. We measured the density of Whinchats, the habitat characteristics associated with their occurrence on farmland, and the relationships between behavioural and habitat variation on farmland around Jos, central Nigeria, over three winters. Whinchats occurred in many fields harvested in the dry season, the density at three sites varying from 0.03 to 0.43 birds/ha, but they were absent at a fourth site. Whinchats were less likely to be found in farmland without particular crops (e.g. structural stem crops such as maize and millet), with more trees, lower amounts of short vegetation (grass, weeds, crops and crop stubble less than 10 cm in height), and higher amounts of medium vegetation (coverage of vegetation 10–100 cm in height) and litter (dead, unburned, vegetation on the ground). Whinchat abundance in areas of farmland where they were present was independent of most variables considered, but density was higher where there was more short vegetation cover. Foraging behaviour did not vary significantly between farmland habitats. All predictors were consistent between season, years and across sites. The presence/absence model was very poor at predicting presence and there were no strong predictors of abundance or foraging variation. This is consistent with a species well below carrying capacity within its environment so that many suitable areas do not have birds present and there is little aggregation at better sites. Overall, Whinchats were abundant and appeared to have plentiful habitat; densities have probably increased alongside the intensification of agriculture (presence of fallow farmland, short vegetation and structural crops). The results suggest that West African farmland in the dry season can support large numbers of Whinchats and that recent population declines in Europe are unlikely to be caused primarily by lack of suitable wintering habitat.     

Aedes polynesiensis in the Society Islands: environmental correlates of isoenzyme differentiation

Abstract Isoenzyme genetic differentiation of Aedes polynesiensis mosquitoes in Raiatea island, French Polynesia, was evaluated by two models of population structure based on seven gene-enzyme systems: Ak, Est, Got, Gpi, Hk, Mdh and Pgm. The ecological model tested whether genetic differentiation is congruent with habitat differences. The isolation model evaluated whether genetic differentiation is proportional to geographical distribution. The ecological model found no significant differentiation between populations of Ae.polynesiensis from beach and forest ecotopes, whereas the isolation model was consistent with the data. However, incipient speciation is opposed by the source-sink system of population dynamics in such small neighbouring islands, where Ae.polynensiensis extinction is readily followed by reinvasion causing considerable gene flow between island populations.     

钦州湾越冬鸻鹬类对不同生境利用分析

2008年12月至2009年1月及2011年12月至2012年1月先后两次对钦州湾的越冬鸻鹬类进行了调查,对越冬鸻鹬类退潮后在各类型生境的分布情况和原因进行了分析,以期为制定有效保护越冬鸟类及其生境的措施提供科学依据。结果表明,在不同的天气情况下退潮后各生境内记录到的鸻鹬类物种数和种群数量均不同,钦州湾不同生境鸻鹬类结构特征随天气变化改变。相似性比较显示,晴天各生境中鸻鹬类相似性指数最高的是盐田-养殖塘生境和农田生境,相似性指数为0.96;鸻鹬类相似性指数最低的是红树林滩涂生境和光滩生境,相似性指数为0.49。阴冷天气各生境中鸻鹬类相似性指数最高的是光滩生境和盐田-养殖塘生境,相似性指数为0.79;最低是红树林滩涂生境和光滩生境,相似性指数为0.52。分析表明人类活动的干扰对越冬鸻鹬类生境选择的影响较大。     

Inland flights of young red‐eyed vireos Vireo olivaceus in relation to survival and habitat in a coastal stopover landscape

Inland dispersal of migrating land birds away from the coast, often opposite to the direction of migration, occurs frequently. Many of these movements may involve migrants seeking improved stopover conditions farther inland, but direct study of inland flights and of the ecological factors influencing their occurrence is limited. We used an automated telemetry array and ground‐tracking to assess flight behaviours, survival, and habitat use of young red‐eyed vireos Vireo olivaceus during fall migration at a coastal island and an inland stopover site in southwest Nova Scotia. We recorded inland flights for 41% (11/27) of individuals that departed the island. At least 25% of 16 individuals tagged at the inland site also relocated within the landscape prior to continuing migration, but due to the higher proportion of ambiguous flights at the inland site (44%) compared to the island (15%), we could not be sure if actual proportions of relocations differed between sites. Mortality on the island (at least 10 of 39 individuals) was significantly higher than at the inland site (0 of 16 individuals). At mainland sites near the coast where we found 6 of 11 individuals after they relocated away from the island, mortality remained high (2/6). Lack of deciduous canopy cover may have contributed to the high mortality on the island, but coastal mainland sites had a relatively high amount of deciduous canopy cover, similar to at the inland site where there was no mortality. Although coastal stopover sites may be important for migrating songbirds, especially before or after making a large water crossing, our results show that mortality can be much higher, and habitat poorer, at the coast compared to farther inland. Therefore, relocating inland may be an adaptive strategy for individuals that initially settle at the coast and that need to rest and refuel before they continue migration.