The distribution of the millipede Ommatoiulus moreleti (Diplopoda, Julida: Julidae) in relation to other Ommatoiulus species on the south-western Iberian Peninsula

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Abstract

Ommatoiuius moreleti(Lucas) occurs naturally in Portugal and Spain, and has been introduced to some Atlantic Islands, South Africa and southern Australia, where it is widespread and numerous.

In southern Portugal and south-west Spain, O. moreleti shares its range with O. oliveirae (Verhoeff), O. cingulatus (Attems) and several undescribed Ommatoiulus spp. In a study area where O. moreleti was confined to deep litter beneath Quercus trees, O. oliveirae predominated in litter of the bushes Cistus spp., while O. cingulatus was most numerous in an area dominated by grasses and herbs, but with little litter. The three species tended to eat different food items, but this probably reflected local availability rather than preference.

Ommatoiulus moreleti has a distinct western boundary which broadly corresponds with changes in the quantity of litter on the ground. The distribution of O. moreleti was related to the availability of deep litter, often provided by Pinus and Quercus trees, but also by dense shrubs and heath, and undisturbed grassland.

In addition to providing food, litter provides a refuge for O. moreleti. Grassland species such as O. cingulutus live where there is little litter, and probably have to dig deep in the soil to avoid summer desiccation and predation of immature stages. It is suggested that soil hardness and litter depth may be important determinants in the distribution of O. moreleti, and relative digging ability may explain the partitioning of the habitat between the three species studied.

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