Latitudinal and altitudinal clines in body size of a Japanese harvestman, Leiobunum japonicum (Arachnida: Opiliones: Sclerosomatidae)

Abstract

We measured a total of 489 adult specimens of Leiobunum japonicum using 41 populations from various parts of Japan for four characters and found that there are latitudinal clines in the length of legs (femur of the first legs: FIL) in both males and females, that conform to the converse Bergmann’s law. Measurements of a total of 318 adults from 7 sites that differ in elevation on the western and northern slopes of Mt. Daisen (Tottori Prefecture, Honshu) also revealed negative correlation of leg length (FIL) to altitude. Both the trends were not clear, especially in females, in characters that directly pertain to body itself (body length, cephalothorax length), probably due to the influence of feeding or maturation of eggs that considerably alter size of the abdomen. It was suggested that shorter period available for the growth and maturation in northern or higher populations are responsible for the latitudinal and altitudinal clines in the length of legs of the harvestmen having a univoltine life cycle with overwintering as eggs.