桂江流域福寿螺种群结构时空分布特征及其驱动机制

Spatio-temporal distribution of population structure of Pomacea canaliculata and driving mechanism in the Guijiang River Basin

福寿螺(Pomacea canaliculata)是我国重点防治的入侵种,对农业生产和淡水生态系统危害严重。而有关福寿螺种群结构及其驱动机制的研究不足。以亚热带桂江流域为例,基于2021—2022年枯平丰的野外调查,系统评估了福寿螺种群结构的时空分布格局,探索福寿螺种群结构变化的关键过程和驱动机制。结果显示:桂江流域福寿螺年均密度((2.21±2.35)个/m^(2)),时空变化不明显;螺重、壳高、壳宽、壳口宽和壳口长时空差异极显著,表现为丰水期>平水期>枯水期和上游>中游>下游的趋势;年龄结构以中螺(壳高30—50 mm)为主,表明桂江流域福寿螺种群处于稳定期;雄雌比0.36±0.40,时空变化不明显。典范对应分析表明:影响福寿螺种群结构的关键环境和空间因子在不同季度间存在差异。pH、海拔、溶氧和盐度等是关键环境因素,PCNM2、PCNM5、PCNM8和PCNM9等是关键空间因素。变差分解显示:环境和空间因子共同决定桂江流域福寿螺种群结构,但两者的相对作用因季度而异。除枯水期外,其它季度的环境因子解释率均大于空间因子。研究结果可为建立有效的福寿螺防控策略提供参考。

Pomacea canaliculata(Lamarck,1819)is a key invasive species in China,which has caused environmental catastrophes,society and ecological security issues across the country.However,our present understanding of the snail's basic biology and ecology is still insufficient,especially in the population structure and underlying driving factors.Here,we first determined the population density,key traits(body weight,shell height and width,aperture length and width)and sex ratio of P.canaliculata population across the Guijiang River Basin,the upper tributary of the Pearl River,based on three seasonal field surveys(dry,normal and wet)in 2021-2022.Then,we explored the size structure and the driving mechanisms that affected population processes.We set up 51 sampling sites in each survey.In each site,we quantitatively collected the snails using one modified sampler(3×3 m^(2) in area)by three replicates within 100 m of each river segment,and simultaneously determined a total of 18 environmental variables with the standard methods.The collected snails were counted,photographed,measured and sexed by the morphology of the opercula and the genital organs.The size-frequency analysis was used to analyze size structure.Based on size-frequency histogram,we sorted the snails into 10 size classes according to shell height:0-20.00,20.00-24.99,25.00-29.99,30.00-34.99,35.00-39.99,40.00-44.99,45.00-49.99,50.00-54.99,55.00-59.99 and>60.00 mm.Snails<30 mm were defined as immatures,whereas snails>30 mm were defined as matures.The local environmental variables measured showed highly longitudinal divergences across the region.A total of 1771 snails were collected,with estimated density of(2.21±2.35)ind./m^(2).There was no significant spatio-temporal difference in density.The body weight,shell height and width,aperture length and width all showed distinctly spatio-temporal differences,with the highest values in the upstream region and during wet season.The size-frequency distribution was distinctly skewed towards the large(adolescent and postadolescent),mature individuals(30-50 mm,54.2%of total individuals),indicating a stable population.The sex ratio(male:female)was 0.36±0.40,but showed no spatio-temporal heterogeneity.Canonical correspondence analysis indicated that local factors(pH,altitude,dissolved oxygen,and salinity)and large-scale spatial factors(PCNM2,PCNM5,PCNM8 and PCNM9)were the key regulators affecting the size structure.Variance partitioning indicated that both the environmental and spatial factors significantly affected the size structure,with environmental filtering generally more important.The study can provide theoretical reference for establishing effective prevention and control strategies of P.canaliculata.