Microclimate conditions alter Ixodes scapularis (Acari: Ixodidae) overwinter survival across climate gradients in Maine, United States
Microclimate conditions alter Ixodes scapularis (Acari: Ixodidae) overwinter survival across climate gradients in Maine, United States
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DOI：
10.1016/j.ttbdis.2021.101872
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发表时间：
2022-01-01
影响因子：
3.2
通讯作者：
Gardner, Allison M.
中科院分区：
文献类型：
--
作者：
Volk, Michelle R.;Lubelczyk, Charles B.;Gardner, Allison M.
近几十年来，媒介传播疾病的发病率和地理范围不断扩大，部分原因是全球气候变化。黑腿蜱 (Ixodes scapularis) 是北美多种蜱传病原体的主要媒介，正在迅速蔓延到其历史上的后殖民范围之外，并且被认为主要受到北纬地区冬季温度的限制。我们的研究探讨了冬季气候目前是否会导致若虫越冬死亡，从而限制美国缅因州黑腿蜱的分布及其传播的病原体。我们通过实验测试了蜱在大范围温度和降雪梯度下的越冬存活率，并评估了目前已建立黑腿蜱种群的地区和尚未检测到黑腿蜱的地区导致冬季死亡的因素。我们还测试了这样的假设：尽管环境条件恶劣，蜱虫微栖息地的隔热（即通过落叶和积雪）可以促进黑腿蜱若虫的冬季生存。与缅因州北部沿海和内陆地区相比，南部沿海地区的越冬生存率没有显着差异，这很可能是由于充足的积雪可以防止高纬度地区的低环境温度。积雪和落叶对缅因州南部和北部地区的越冬生存做出了重大贡献。为了进一步评估缅因州黑腿蜱目前的分布是否符合越冬生存模式，我们在该州沿纬度和沿海内陆气候梯度的七个地点系统地搜索和收集了蜱。我们发现缅因州南部沿海地区的黑腿蜱密度（90.2 蜱/1000 m(2)）高于缅因州中部内陆地区（17.8 蜱/1000 m(2)），而缅因州北部内陆地区没有黑腿蜱。我们的结果表明，即使在极冷的环境条件下，越冬生存也不是黑腿蜱分布的唯一限制，其他机制可能会限制蜱继续向北扩张。
The incidence and geographic range of vector-borne diseases have been expanding in recent decades, attributed in part to global climate change. Blacklegged ticks (Ixodes scapularis), the primary vector for multiple tick-borne pathogens in North America, are spreading rapidly beyond their historic post-colonial range and are thought to be constrained mainly by winter temperature at northern latitudes. Our research explored whether winter climate currently limits the distribution of blacklegged ticks and the pathogens they transmit in Maine, U.S.A., by contributing to overwinter mortality of nymphs. We experimentally tested tick overwinter survival across largescale temperature and snowfall gradients and assessed factors contributing to winter mortality in locations where blacklegged tick populations are currently established and locations where the blacklegged tick has not yet been detected. We also tested the hypothesis that insulation in the tick microhabitat (i.e., by leaf litter and snowpack) can facilitate winter survival of blacklegged tick nymphs despite inhospitable ambient conditions. Overwinter survival was not significantly different in coastal southern compared to coastal and inland northern Maine, most likely due to sufficient snowpack that protected against low ambient temperatures at high latitudes. Snow cover and leaf litter contributed significantly to overwinter survival at sites in both southern and northern Maine. To further assess whether the current distribution of blacklegged ticks in Maine aligns with patterns of overwinter survival, we systematically searched for and collected ticks at seven sites along latitudinal and coastal-inland climate gradients across the state. We found higher densities of blacklegged ticks in coastal southern Maine (90.2 ticks/1000 m(2)) than inland central Maine (17.8 ticks/1000 m(2)) and no blacklegged ticks in inland northern Maine. Our results suggest that overwinter survival is not the sole constraint on the blacklegged tick distribution even under extremely cold ambient conditions and additional mechanisms may limit the continued northward expansion of ticks.