|What is Sundaland?
compiled by Wolfgang A. Nässig — References see below
A short compilation and explanation about zoogeographcal
terms regarding Sundaland and its subdivisions was published by
Nässig & Treadaway (1998: 231) within the monography “The
Saturniidae of the Philippines” and is repeated here with a few minor
corrections or changes; later supplements are indicated as such (below):
information (of 2007/2008):
The evidently first use of the term “Sundaland” (at least the earliest reference which I have discovered so far ...) was by MELL (1930: 459), 34 years before JOHNSON. MELL used the term to describe the distribution areas of eupterotid moths.
The islands along the SW coast of Sumatra (Simeuluë, Nias, Pulau Pulau Batu, Kepulauan Mentawai, Enggano, etc.) show some degree of endemicity, but in general should best be included into Sundaland. This small area constitutes a subregion called Paramalaya (Toxopeus 1926). Toxopeus also included the Nicobar — but not the Andaman — Islands into Paramalaya, which may be questionable; we do not have any information about the saturniid fauna of the Nicobar Islands to comment further upon this question, but, for example, Ripley & Beehler (1989) grouped the Nicobar and Andaman Islands together in a separate subregion closely associated to Burma with respect to their ornithofauna.
Another subdivision of Sundaland is Neomalaya; this term was already introduced by Moulton (1915 a, 1915 b) and comprises the northern corelands of Sundaland, which have the closest faunistic relationships: Sumatra, West Malaysia, and Borneo only, excluding Java, Bali and Palawan as well as Paramalaya.
During most of the glaciation periods, Sundaland was above the sea and formed one more or less united land mass, while in warmer times large areas were submerged. Species inhabiting swampy lowland forests and mangroves were principally able to disperse from one present-day land to the next during these times of lower sea level, while species inhabiting mountain biotopes most likely were not, except the mobile species. On the other hand, at times even the isthmus was submerged (Eliot 1992: 19–23). Today the natural northern borderline of the zoogeographical unit Sundaland on the Asian continent for many species appears to be the climate divide between the perhumid equatorial tropical climate and the monsoonal (seasonal tropical to subtropical) climate in the northern part of West Malaysia and in South Thailand. Many species were able to cross that borderline, and we think there are still dispersal processes going on along the Malayan Peninsula in both directions. One example may be Antheraea larissa, which appears to slowly invade the Indochinese Peninsula north of the narrow Malayan Peninsula today.
Although there was no narrow isthmus as today during the glaciations (even Cambodia and the southern parts of Vietnam were at some times directly connected with Malaya and North Borneo: Tjia 1980, Whitten et al. 1987), probably there have been other barriers (e.g., big rivers — see Tjia 1980: 415 — or drastic climatical borderlines, see MacKinnon et al. 1997: 20) in the northeastern part of the Sunda shelf, because today there appear to be more differences in the faunal composition between Vietnam and Sundaland than between Thailand/Burma and Sundaland.
Recent research (e.g., U. & L.H. Paukstadt 1999, U. Paukstadt et al. 2000a, 2000b) delivered support that the fauna of the Saturniidae and Brahmaeidae of Java and Bali appears to be much more distinct from the Neomalayan fauna than expected by earlier authors (e.g., Nässig et al. 1996). However, the differences between Javanese and Neomalayan Antheraea larissa were demonstrated only very weakly by U. Paukstadt et al. (2000c).
As there was at least in the most recent glaciations no long time difference between the split-off from Sundaland of Java and Bali on one side and Borneo and Sumatra on the other side (the time span for the world-wide post-glacial increase of the sea-level was probably only a few centuries or even decades!), the difference in faunal composition between Java/Bali and Neomalaya must be explained in a different way. One important difference is the climate; Java and Bali show a distinguished seasonal climate, while Neomalaya is more of a perhumid tropical climate without distinctive seasons. Therefore, at least present-day evolutionary pressure on Java/Bali is different from that on Neomalaya. The genetic exchange for less mobile bombycoid species (such as Saturniidae, Brahmaeidae etc.) would be interrupted by the sea level rising for only some thousand years now (mobile species probably still do have genetic interchange within Sundaland!); all these present-day islands became separated by sea only about 8000–10,000 years ago. This time span is probably too short for the evolution of species-specific differences in Saturniidae. Thus, there must have been isolation mechanisms established much earlier than the end of the last glaciation preventing gene-flow between Javanese/Balinese species and Neomalayan species, e.g., possibly by large rivers and swamps between Neomalaya and Java/Bali, surely in combination with the differences in climate.
The model of the “peripherical isolates” (stressed, e.g., by Nässig & Treadaway 1997, 1998 or U. & L.H. Paukstadt 1999) should, therefore, better be seen against the background of longer time spans than only ten thousand years (at least it was definitively seen in this way by myself in 1997/1998). — It should be assessed whether morphological differences between present-day insular populations of closely related “subspecies” or “species” might be explained by climate-dependant modification alone or by genetically fixed differences, and further, if there are any relevant genome differences, they should be studied into more detail (best using alloenzymes or DNA analyses) to find a time-scale for the separation of the different populations and assess the extend of the genetical separation.
The climatical differences
are gradual and clinal; the seasonality is already developed in southern
Sumatra (especially in the provinces of Bengkulu and Lampung, see map)
and becomes much more expressed across Java and Bali from the West to the
East. Differences which are considered as being of species-specific or
subspecific quality should therefore be studied into more detail along
this distance from S. Sumatra to Bali on basis of larger material from
several localities each.
2000–2008 by W. A. Nässig for the internet version (© 1998
for the printed version by Ent.
Verein Apollo e.V./NEVA)
Compiled & published 26. January 2000, last changes 27. March 2000, 18. January 2002, 5. August 2004, 19. III. 2008, 9. VII. 2008