Li X, Dunley J E
Department of Environmental Science Policy and Management, University of California at Berkeley 94720-3112, USA.
Exp Appl Acarol. 1998 Apr;22(4):233-48. doi: 10.1023/a:1006018432064.
A common method for sampling tick populations is flagging, which is a method of dragging a white cloth over a plant substrate for a fixed distance along a transect. Flagging over rough physical surfaces or using long subtransect lengths could lead to the underestimation of tick densities. Using estimates of the drop-off rates of adult Ixodes pacificus in flag sampling, optimal sampling schemes (the length and number of subtransects) were examined using the relationships between the tick drop-off rates (c), the tick density and distribution patterns and the roughness of the sampled plant substrate. It was found that the optimal number of subtransects and Lmax, the longest subtransect length which did not significantly underestimate the tick density from c, were affected by the tick density, substrate roughness and tick distribution pattern. This study also showed that the density and distribution of I. pacificus and Dermacentor occidentalis varied greatly over time in the populations sampled, while the Dermacentor variabilis densities were low and showed no significant changes over time. Both I. pacificus and D. occidentalis had clumped distributions along trails and these clumps were aggregated. However, the clump sizes (or individual clump areas) changed significantly over time because of density fluctuation or the movement of ticks. Finally, a positive association between the number of I. pacificus and D. occidentalis adults was observed from 2 m subtransect flag collections in March 1995; no relationship was found in 1994.
蜱虫种群抽样的一种常见方法是拖旗法，即沿着样带在植物基质上拖动一块白布固定距离的方法。在粗糙的物理表面上拖旗或使用较长的子样带长度可能会导致蜱虫密度的低估。利用拖旗采样中成年太平洋硬蜱脱落率的估计值，通过蜱虫脱落率（c）、蜱虫密度和分布模式与采样植物基质粗糙度之间的关系，研究了最佳采样方案（子样带的长度和数量）。研究发现，子样带的最佳数量以及Lmax（即不会因c而显著低估蜱虫密度的最长子样带长度）受蜱虫密度、基质粗糙度和蜱虫分布模式的影响。本研究还表明，在采样种群中，太平洋硬蜱和西方革蜱的密度和分布随时间变化很大，而变异革蜱的密度较低且随时间无显著变化。太平洋硬蜱和西方革蜱在小径上均呈聚集分布，且这些聚集区相互聚集。然而，由于密度波动或蜱虫移动，聚集区大小（或单个聚集区面积）随时间变化显著。最后，在1995年3月的2米子样带拖旗采集样本中观察到太平洋硬蜱和西方革蜱成虫数量呈正相关；1994年未发现这种关系。
