亚热带城市环境下桑寄生植物的7年扩散动态

Seven-year population dynamics of mistletoes in urban environment in subtropical region,China

【目的】研究2种桑寄生植物寄主种类、寄生感染率和寄生强度的动态,揭示桑寄生植物的种群扩散机制。【方法】以桑寄生植物及其寄主为研究对象,分别于2012和2019年,在成都市区55.4 hm2范围内对寄生植物与寄主植物的种类、数量及其分布进行调查。【结果】研究区域内2012年有寄主植物41种,寄主个体991株;2019年有寄主植物48种,寄主个体1 294株。在2012和2019年,桑寄生植物的寄生强度在寄主植物上的分布格局均呈聚集分布。相比2012年,2019年新增寄主植物13种,减少5种。在2012和2019年,个体数量≥20株的寄主种类均显著多于个体数量<20株寄主的种类(Fisher精确检验,P <0.05),即寄主的树种主要集中于个体数量≥20株的树种上。2019年总体寄生感染率(27.2%)显著大于2012年的总体寄生感染率(18.1%)(P <0.05);其中,15种寄主植物的寄生感染率显著上升(P <0.05),13种寄主植物寄生感染率差异不显著。2019年的总体寄生强度(1 294)显著大于2012年的总体寄生强度(991)(P <0.05);其中,11种寄主植物的寄生强度均显著增加(P <0.05),12种寄主植物的寄生强度变化不显著,仅2种寄主植物的寄生强度显著减少(P <0.05)。【结论】7 a间,桑寄生植物的种群趋于扩张,寄生感染率和寄生强度均显著增大。桑寄生植物潜在寄主植物的多度越大,其越容易成为桑寄生植物的新寄主种类。在桑寄生扩散研究和危害防控方面,需要注意到特定区域内木本植物的种群大小。

【Objective】To reveal the dynamics of host range of two common mistletoe species(Taxillus nigrans and Scurrula parasitica),parasitic prevalence,and parasitic intensity,and the distributions of the two common mistletoes population in urban environment in the sub-tropical region,a seven years’investigation(2012 and 2019)was conducted.【Method】We investigated all the trees and shrubs in a 55.4 hm2 area in Wangjiang campus of Sichuan University in Chengdu,southwest China.The species,abundance and distribution of trees and shrubs in our study area were conducted.We compared the host range,parasitic prevalence,and parasitic intensity,respectively.【Results】There were 991 host individuals from 41 host species in 2012,and 1294 host individuals from 48 species in 2019.The distribution patterns of parasitic intensity of the two mistletoes on host plants were significantly aggregated(P<0.0001)both in 2012 and 2019.Comparing with 2012,13 new host species occurred in 2019,and five host species turned to non-host species.Species with larger sample sizes(≥20)were significantly more likely to be host species than species with smaller sample sizes(<20)(Fisher’s Exact test,P<0.05).The parasitic prevalence of all host species in 2019(27.2%)was significantly higher than that of 2012(18.1%)(P<0.05).From 2012 to 2019,15 host species’parasitic prevalence was significantly increased(P<0.05)and 13 host species’parasitic prevalence showed increasing patterns.The parasitic intensity of all host in 2019(1294)was significantly higher than that of 2012(991)(P<0.05).There were 11 host species parasitic intensity increased significantly(P<0.05),and that of 2 host species decreased significantly,while that of 12 host species was not significant but increased.【Conclusion】From 2012 to 2019,both parasitic prevalence and parasitic intensity of the two mistletoe species showed significantly increasing,indicting the expanding trend of the two mistletoe populations.The host selection of the mistletoes was closely and positively related to the abundance of potential hosts,i.e.,the more abundant of the potential hosts,the higher possibility they could become hosts of the two mistletoe species.Therefore,abundance of the potential host could be the key factor on the research of the dynamics of mistletoe and hazard management.