Relative Warp Analysis of Shell Shapes of Vivipara Angularis Muller Collected from Four Lakes in Mindanao, Philippines

Studying variation and phenotypic plasticity in the shell shape of Vivipara angularis Muller, a native freshwater species from lakes, has been interesting in order to understand the evolutionary processes in fragile environments. In this study, the population structures of the snails were investigated based on their shell shapes. The snails were collected in Lake Apo in Bukidnon, Lake Wood and Dasay in Zamboanga and Lake Holon, South Cotabato, Philippines. Geometric morphometric tools such as relative warps, superimposition, thin-plate splines and cluster analysis were employed. The results revealed significant variations in shell shapes among V. angularis populations from different lakes. Most variations in the shells were detected in the spire, body whorl and inner lip of the aperture which indicated that the degree of dissimilarity varied from population to population. Meanwhile, Lakes Apo, Dasay and Wood shared the most similarities. Significant differences in shell shapes were observed in lake populations, but what was significant in this study was that the variations could not be attributed to the geographic distances between the lakes but maybe to the ecological and environmental differences between the lakes resulting in the developmental modifications of the shell shapes.

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