Recolonization of the Krakataus by Hymenoptera and Isoptera (Insecta)

Abstract

The aculeate and isopteran fauna was surveyed in 1982 on the Krakatau islands, all the biota of which had been exterminated by the great eruption in 1883.The pattern of colonization of these insects (wasps, bees and termites) and the present state of their faunas are discussed based upon our 1982 survey and those made earlier. Species numbers varied only slightly between the four islands in spite of their differing sizes. This may be because the islands are situated close to each other and most of the aculeates prefer open sites rather than forests.The species/time curve for the Aculeata as a whole was still rising in 1982. However, in some groups flattening of the curve had occurred, and a comparison of species number in social wasps and bees, for example, between Java, Krakatau and Sumatra suggested the occurrence of"supersaturation". Cumulative species number was distinctly larger than actual number in the three most recent surveys showing that several species must have become extinct in each intersurvey period. Species turnover associated with habitat changes may have occurred for the whole island group and on particular islands.Analysis of the colour pattern of the Krakatau populations of certain species with different geographical races on Java and Sumatra showed that the Javan elements have a slight preponderance over the Sumatran ones on the Krakataus. Some examples of faunal disharmony were found; the most remarkable was the almost complete lack of species of swarm-founding social wasps and bees, and of ground-nesting termites probably reflecting their poor dispersal ability across the sea barrier.

How important were stepping stones in the colonization of Krakatau?

“…Yamane, a specialist in aculeate hymenoptera collected on Krakatau with Yukawa for 48 man‐days from October to December 1982, finding 86 species. Sumatran and Javan subspecies of the wasp Delta flavopictum (Zimmerman) are distinguishable, and intermediate specimens found on Krakatau by Dammerman and by Yamane and Yukawa were thought to be possible hybrids by Yamane, Abe & Yukawa . (1992), although the Javan subspecies has never been encountered on Krakatau, where the Sumatran one is common.…”

“…By contrast, although both Javan and Sumatran subspecies of the wasp Sphex sericeus Fabricius were recorded from Rakata in 1928 (van der Vecht & Krombein, 1955), in 1982 only the Javan subspecies was found. Yamane et al . (1992) identified three other Krakatau wasps as being of Javan, and one of Sumatran, origin (Table 8).…”

Relative occurrence of the family Kalotermitidae (Isoptera) under different termite sampling methods

“…For example, our expert survey results revealed that the island of Jamaica has 10 endemic kalotermitid species compared to 4 non-kalotermitids, while Panama yielded 23 kalotermitids compared to 53 nonkalotermitids, and the Peruvian Amazon produced only 12 kalotermitid species compared to 95 non-kalotermitids (Scheffrahn et al unpublished). Because of their overwater dispersal abilities (Yamane et al, 1992, Scheffrahn & Postle, 2013, islands become filters for Kalotermitidae. Littoral zones support tree species that are tolerant to tidal exposure and sandy soil.…”

The recolonization of the Krakatau islands by termites (Isoptera), and their biogeographical origins

“…At the generic level, all of the termites of Krakatau are found in at least five biogeographical regions (C?yptotemes Banks is found in eight regions) and at the specific level, most of the Krakatau termites are found throughout South-East Asia, particularly in coastal areas (Thapa, 1981;Abe, 1984Abe, , 1987Tho, 1992;Yamane, Abe & Yukawa, 1992;Eggleton et al, 1997). These species are probably preadapted for dispersal over sea, being salt tolerant wood nesters.…”