SPECIES IDENTIFICATION AND POPULATION GENETIC DIVERSITY OF NON-NATIVE APPLE SNAILS (AMPULLARIIDEA: POMACEA) IN THE WEST LAKE

The exotic apple snails are big freshwater snails that have spread and damaged the West Lake for nearly 10 years. To understand the species and population genetic diversity of apple snails, we explored the distribution of the apple snails in the West Lake. Based on the samples collected in the past six years, identified the species, and analyzed their population genetic diversity. The results showed that the distribution of apple snails was concentrated in west of the Su Causeway, with a high density in the northwest area including Xilihu, Maojiabu, Hangzhou Flowerbed, and Yuehu, and low density in the southwest aera such as Wuguitan and Yuhuwan. We detected 79 variable sites, and defined 6 haplotypes based on mitochondrial COⅠ sequences. Sequences similarity and phylogenetic relationships analysis revealed that the Hap1-Hap5 were Pomacea canaliculata and the Hap6 was P. maculata in the West Lake. The analysis of haplotype diversity, nucleotide diversity, and average number of nucleotide difference indicated that the haplotype diversity (H_d) of P. canaliculata was 0.229—0.600, the nucleotide diversity (π) was 0.011—0.027, the average number of nucleotide difference (k) was 6.797—16.000, and both P. canaliculata and P. maculata in the West Lake have low genetic diversity. There was no significant difference in genetic diversity between 2018—2020 and 2015—2017. In addition, nuclear EF1α sequence analysis demonstrated that the apple snail populations of P. canaliculata in the West Lake included CC (23.08%), CM (23.08%), and CB (53.84%) types. Introgressive hybridization were widely observed in the apple snail populations in the West Lake with a rate over 76.92%. Due to the connectivity of the water diversion project, there is a risk of apple snails spreading to the surrounding wetlands in the West Lake. This study provides some suggestions for the establishment of effective prevention and control strategies of apple snails in the West Lake.