Freshwater Zoogeography of Southeast Asia

The present knowledge of the historical biogeography of aquatic invertebrate groups is reviewed. Most orders of aquatic insects have a fossil record starting in the Early Permian, or Middle Carboniferous (Odonata), making even the break-up of Gondwana (Late Jurassic) relevant to understanding present distributional patterns. The complex geological history of Southeast Asia is summarized, and geological area cladograms presented. Biogeographical studies are seriously hampered by the limited information on subaerial history of the various islands and terranes. The historical biogeography of the Platycnemididae (Odonata), with special reference to the subfamily Calicnemiinae, is presented as one of the first examples of such a study of a widespread group. The species of southeast Asia derived from African Platycnemididae. Malesian Calicnemiinae derived from ancestors on the mainland of Asia, and may have dispersed along the Izu-Bonin Arc (40–50 Ma), or along the Late Cretaceous “Inner Melanesian Arc” sensus Polhemus. A clade of the genera Lieftinckia and Risiocnemis (Solomon Islands and the Philippines) represents a more recent westward dispersal of the Calicnemiinae, via the Caroline and Philippine Arcs during the Oligocene.

Various other more limited phylogenetic reconstructions and biogeographical analyses of other freshwater invertebrates, particularly Odonata and Hemiptera, are discussed. Areas of endemism on New Guinea are generally congruent with geological entities recognized, e.g., the microterranes along the northern margin of New Guinea. Special attention is paid to the fauna of Sulawesi. Area cladistic reconstructions based on distribution patterns and phylogenetic reconstructions of, e.g., Protosticta Selys (Odonata, Platystictidae) and genera and species of Chlorocyphidae (Odonata), show a pattern of (northern arm (southwest arm – central and southeastern arm)), which is a reflection of the geological history of the island.

Biogeographical patterns recognized in freshwater invertebrates of Malesia do not principally differ from those found in strictly terrestrial taxa. The distribution of land and water seems to be the driving force in speciation during the Cenozoicum. It is unresolved whether rafting of biotas on the various island arcs, or congruent patterns in dispersal, are to be considered the underlying principle. The extreme habitat requirements and poor dispersal power of many species involved seem to make a dispersal scenario unlikely. However, recent studies show that such habitat specialization may develop rapidly.