Mechanistic variables can enhance predictive models of endotherm distributions: the American pika under current,past, and future climates

How climate constrains species’ distributions through time and space is an important question in the context of conservation planning for climate change. Despite increasing awareness of the need to incorporate mechanism into species distribution models (SDMs), mechanistic modeling of endotherm distributions remains limited in this literature. Using the American pika (Ochotona princeps) as an example, we present a framework whereby mechanism can be incorporated into endotherm SDMs. Pika distribution has repeatedly been found to be constrained by warm temperatures, so we used Niche Mapper, a mechanistic heat‐balance model, to convert macroclimate data to pika‐specific surface activity time in summer across the western United States. We then explored the difference between using a macroclimate predictor (summer temperature) and using a mechanistic predictor (predicted surface activity time) in SDMs. Both approaches accurately predicted pika presences in current and past climate regimes. However, the activity models predicted 8–19% less habitat loss in response to annual temperature increases of ~3–5 °C predicted in the region by 2070, suggesting that pikas may be able to buffer some climate change effects through behavioral thermoregulation that can be captured by mechanistic modeling. Incorporating mechanism added value to the modeling by providing increased confidence in areas where different modeling approaches agreed and providing a range of outcomes in areas of disagreement. It also provided a more proximate variable relating animal distribution to climate, allowing investigations into how unique habitat characteristics and intraspecific phenotypic variation may allow pikas to exist in areas outside those predicted by generic SDMs. Only a small number of easily obtainable data are required to parameterize this mechanistic model for any endotherm, and its use can improve SDM predictions by explicitly modeling a widely applicable direct physiological effect: climate‐imposed restrictions on activity. This more complete understanding is necessary to inform climate adaptation actions, management strategies, and conservation plans.     

人工饲养条件下高原鼠兔生长和发育的初步研究

本文研究了人工饲养条件下高原鼠兔的生长发育情况,并和其他种鼠兔的生长作了比较。室内高原鼠兔比野外的生长快,人工饲养的阿富汗鼠兔和北美鼠兔生长期短,成熟早。     

高原鼠兔似昼夜活动节律的研究

本文对高原鼠兔活动节律的季节变化,不同光强对高原鼠兔似昼夜活动节律的影响,以及温度效应,饥俄效应等问题进行了研究。同时对昼夜节律研究中长期存在的理论问题,内源性和外源性观点提出探讨。     

高原低氧对高原鼠兔和大白鼠肺泡Ⅱ型细胞及表面活性物质超微结构的影响

本文报道高原低氧(海拔3300米)对高原鼠兔、移居高原大鼠、急进高原大鼠的肺泡Ⅱ型细胞及表面活性物质超微结构的影响。发现高原鼠兔肺占体重的百分比低于移居高原大鼠(P>0.05)和急进高原大鼠(P<0.001)。透射电镜和扫描电镜观察,表明急进高原大鼠肺泡Ⅱ型细胞微绒毛减少,线粒体变性肿胀,板层体排空、合成减少。而高原鼠兔未出现上述超微结构改变。移居高原大鼠的微细结构变化介乎于高原鼠兔与急进高原大鼠之间。     

达乌尔鼠兔和高原鼠兔肝脏线粒体DNA的限制性内切酶图谱的比较研究

达岛尔鼠兔肝细胞线粒体DNA(mtDNA),经限制性内切酶HindI、HindII,EcoRI和BamHI酶切后分别产生5、4、3、2个片段。通过琼脂糖凝肢电泳对这些片段进行测定,并画出其酶切图谱。高原鼠兔肝细胞mtDNA经限制性内切酶EcoR I和BamH 1酶切后,分别产生4、2个片段,对其片段的分子量也进行了测定。测定结果,达乌尔鼠兔肝细胞mtDNA的分子量为10.25MD(兆道尔顿)．大小为16.25kbp(千碱基对);高原鼠兔肝细胞mtDNA的分子量为9.31MD,大小为l5.066kbp。并对两种鼠免的限制性内切酶片段进行了比较讨论。     

低氧对雄性高原鼠兔性腺的影响

在人工模拟低氧环境下（低压舱模拟５０００ｍ和７０００ｍ海拔高度）,低氧暴露２４ｈ和７ｄ,观察低氧对受试动物性腺的影响。结果表明,急性低氧２４ｈ,高原鼠兔血浆雌二醇（Ｅ２）明显升高;低氧暴露７ｄ,高原鼠兔血浆Ｅ２仍维持一较高水平;５０００ｍ低氧暴露７ｄ,其睾丸指数无明显变化,７０００ｍ时却有所降低。同等条件下,大鼠睾丸指数明显增高;５０００ｍ和７０００ｍ低氧暴露７ｄ对高原鼠兔睾丸组织形态无明显影响,然而,大鼠曲细精管间隙增大,且曲细精管内各级细胞排列紊乱。低氧环境下,高原鼠兔雄体血浆Ｅ２增高,可能是其低氧适应的特征之一     

高原鼠兔挖掘活动对土壤中氮素含量的影响

本文通过测定不同类型高原鼠兔鼠丘和鼠丘下0 ～ 10 cm 土壤中总氮、铵态氮和硝态氮的含量变化,分析了高原鼠兔挖掘活动对土壤中无机氮含量的影响,并通过测定高原鼠兔鼠丘密度,计算了每只高原鼠兔对氮素循环的贡献。研究结果表明:不同类型鼠丘土壤中总氮含量无明显变化,铵态氮、硝态氮和无机氮含量处理间变化趋势为当年鼠丘>两年鼠丘> 多年鼠丘> 对照。方差分析结果表明,硝态氮含量在5 月时差异显著,当年鼠丘和两年鼠丘显著大于多年鼠丘和对照,无机氮含量在5 月和9 月表现为当年鼠丘显著高于对照。在不同月份,铵态氮含量月间变化趋势为5 ～ 8 月逐渐降低,至9 月略有增加,硝态氮和无机氮含量呈现“高- 低- 高-低- 高”的“W”变化趋势。方差分析结果显示,铵态氮、硝态氮和无机氮含量月间变化显著。不同类型鼠丘下0 ～ 10 cm 土壤中铵态氮、硝态氮和无机氮含量处理间和月份间变化趋势与鼠丘土壤中变化趋势基本一致,但硝态氮和无机氮含量在当年鼠丘中均显著高于对照,且不同月份间铵态氮、硝态氮和无机氮的含量差异显著(P
< 0.05)。每只高原鼠兔挖掘活动所形成的鼠丘土壤中的铵态氮、硝态氮和无机氮分别增加了162.6 mg/ kg、355.1 mg/kg 和497.7 mg/ kg。     

利用无线电技术对达乌尔鼠兔巢区的研究

达乌尔鼠兔是内蒙古草原斑块分布的一种害鼠。它们在斑块间的扩散对其种群调节和进化都有重要意义。文章对两个家族的达乌尔鼠兔进行了无线电遥测研究。它们的巢区面积从3138M²到17062M²,核心区面积从1292M²到7808M²。雄性—雌性巢区重叠面积比雌性—雌性巢区重叠面积大。该鼠的扩散和探索距离可达 200m.从9月开始鼠兔的活动就很活跃,尤其是探索活动和扩散。多数扩散个体在移居点很快消失。     

Characterization of the spatial distribution of plateau pika burrows along an alpine grassland degradation gradient on the Qinghai–Tibet Plateau

Plateau pika burrows are common feature of degraded grassland in the Qinghai–Tibet Plateau (QTP) and serve as an important indicator of pika activity and grassland degradation. However, the current understanding of the spatial pattern changes of pika burrows and their critical thresholds across a degradation gradient in alpine grassland is deficient. In this study, we investigated and quantified changes in the spatial pattern of plateau pika burrows under typical degraded alpine shrub meadows in the northeastern QTP using an unmanned aerial vehicle and landscape pattern metrics. The degradation of the alpine shrub meadow leads to a change in landscape pattern from a two‐layered structure of alpine shrub and alpine meadow to a mosaic of alpine meadow and bare soil, with plateau pika burrows scattered throughout. Moderate degradation is the tipping point for changes in surface landscape patterns, followed by the disappearance of alpine shrub, the retreat of alpine meadows and the encroachment of bare soil, and the increasing density and size of pika burrows. The area characteristics of alpine meadows have influenced changes in the spatial pattern of pika burrow, and maintaining its proportional area is a vital measure to control the threat of pika burrows to pastures. The results of this paper provide a methodological reference and guidance for the sustainable utilization of grassland on the QTP.     

Isolation and characterization of 13 microsatellite loci in the plateau pika (Ochotona curzoniae)

High quality jumping microsatellite libraries of the plateau pika (Ochotona curzoniae) were constructed; 231 out of the 288 clones contained microsatellite repeat motif and 120 pairs of primers were designed accordingly. Polymorphism was assessed for 48 individuals. Only 13 microsatellite loci were polymorphic with high polymorphism information content (PIC) ranging from 0.598 to 0.871, a condition probably resulting from individuals used for assessment being very closely related. This degree of polymorphism, however, is sufficient to conduct parentage analysis. Expected and observed heterozygosities ranged from 0.219 to 0.935 and 0.659 to 0.890, respectively. One locus was in linkage disequilibrium. This information provides efficient tools to allow future parentage studies. Ke-xin Li and Jia-ning Geng contributed equally to this paper.