Millipede (Diplopoda) distributions: A review

In spite of the basic morphological and ecological monotony, integrity and conservatism expressed through only a small number of morphotypes and life forms in Diplopoda, among which the juloid morphotype and the stratobiont life form are dominant, most of the recent orders constituting this class of terrestrial Arthropoda are in a highly active stage of evolution. This has allowed the colonisation by some millipedes of a number of derivative, often extreme and adverse environments differing from the basic habitat, i.e. the floor of temperate (especially nemoral), subtropical or tropical forests (in particular, humid ones). Such are the marine littoral, freshwater habitats, deserts, zonal tundra, high mountains, caves, deeper soil, epiphytes, the bark of trees, tree canopies, ant, termite and bird nests. Most of such difficult environments are only marginally populated by diplopods, but caves and high altitudes are often full of them. To make the conquest of ecological deviations easier and the distribution ranges usually greater, some millipedes show parthenogenesis, periodomorphosis or morphism. Very few millipede species demonstrate vast natural distributions. Most have highly restricted ranges, frequently being local endemics of a single cave, mountain, valley or island. This contrasts with the remarkable overall diversity of the Diplopoda currently estimated as exceeding 80 000 species, mostly confined to tropical countries. There are few places on the globe where a local diplopod fauna, or faunule, exceeds two dozen species, the world record being a patch of rainforest in central Amazonia where 33 millipede species have been revealed. Such a highly mosaic distribution of the diversity in Diplopoda over the globe is rooted in the group’s general structure, biology, ecology and phylogeny. This particular combination has long made the Diplopoda a group most attractive for biogeographical reconstructions.