The distribution and diversity of freshwater snails in Peninsular Malaysia

• Main Author: Hah, Huai En
• Format: Thesis
• Published: 2020
• Subjects: QH Natural history; QL Zoology
• Online Access: http://eprints.sunway.edu.my/2423/

Freshwater snails have important ecological roles in aquatic ecosystems and can significantly impact local and national economies by damaging crops and serving as vectors of disease-causing parasites. The diversity, distribution, and habitat relationships of freshwater gastropods in Peninsular Malaysia is poorly known and of particular concern given the spread of invasive apple snails into many aquatic habitats since the early 1980s. This study was carried out to inventory freshwater snail diversity and distributions, and assess environmental factors associated with gastropod species richness, community structure and heterogeneity among five major types of freshwater habitats. Additionally, I evaluated biotic and abiotic factors influencing the presence of the invasive species Pomacea canaliculata and P. maculata including geospatial characteristics associated with their presence. I surveyed gastropods in 550 sample plots in 108 geographic locations across the peninsula and measured selected biotic and abiotic variables. Using morphological approaches, 22 native and three non-native species were identified from 11 families. Patterns of snail occurrence did not differ markedly across habitat types. Acidification, thermal stress, and nutrient pollution (eutrophication) were the most important factors threatening freshwater snail diversity in Peninsular Malaysia. Species such as Brotia episcopalis and Pila ampullacea displayed distinct habitat requirements which may serve as useful indicators of water quality. Pomacea occurred in 53.7% of the 108 wetlands surveyed and was associated with neutral to slightly alkaline waters with high conductivity (Na+, NO3-), high temperature, low oxygen levels and no vegetation. Surprisingly, Pomacea presence was strongly associated with a diversity of common native gastropods that were habitat generalists. Geospatial analyses revealed that Pomacea was associated with areas containing less forest cover and nearer town centres, reflecting a distribution that was likely human-mediated. The risk map of Pomacea distribution showed areas with the highest risk of Pomacea presence to be in the north, west and north-eastern parts of Peninsular Malaysia. The results of this study provide valuable information for wetland protection and management, by elucidating the types of habitats that support populations, or particular species of freshwater snails.