Geographic variations in the size and behavior of common earthworms Metaphire peguana (Rosa, 1890) in Penang and neighboring states, Malaysia

Metaphire peguana (Megascolecidae) is a terrestrial earthworm that was found to be widely distributed throughout the whole of Penang state during our field collecting. The differences in the average length and diameter of M. peguana between the island and mainland Penang population were correlated with their behavior and the environmental parameters of the biotope and soil type, pH and moisture content. Principle component analysis of the correlation matrix and dendrogram for M. peguana revealed significant differences in how the types of biotope and environmental factors may affect the size of M. peguana. Morphometric variations in M. peguana did not reflect any genetic difference. Concisely morphometric variation across different types of biotopes, combined with relatively low levels of gene flow, is expected to favor local adaptation of M. peguana.