巽他大陆的西部（马来西亚半岛和苏门答腊岛）和东部（婆罗洲）生物地理格局具有显著差异。这些差异一直是研究的热点。有人认为这是由于冰川时期干燥热带稀树草原走廊形成的扩散屏障所造成的。然而这些热带稀树草原条件持续时间短，可能不是这些生物地理格局差异的唯一原因。另一种解释可能与巽他大陆中央的沙质土壤有关。
中科院西双版纳热带植物园植物地理创新研究组Ferry Slik研究员等人基于马来西亚半岛、苏门答腊岛和婆罗洲的111个树木物种目录对植物区系进行聚类分析，从而验证这两个假说。然后，他们把那些在巽他大陆中央和周边都有分布的指示属以及仅在某些区域的属进行区分，用这些属来检验它们对干旱和沙质土壤的耐受性的差异。最终他们发现11个不同区系聚类，婆罗洲有10个，苏门答腊有5个，马来西亚半岛有3个。那些跨越巽他大陆分布的指示分类群比只分布在巽他大陆东部、西部或者中央的分类群具有显著高的沙质土壤的耐受性。而对干旱耐受性的检测，则没有发现这种格局的存在。基于这些结果，他们推断巽他大陆中央的沙质海床土壤是扩散屏障。不过，他们无法证实热带稀树草原走廊的存在。
这一发现解释了巽他大陆植物和动物分布生物地理格局的成因，包括早期人类可能的迁移路线在内的一系列问题都需要重新评估。这也是世界上首次提出土壤是造成巽他大陆不同地区生物地理格局差异的原因。
相关研究成果已经发表在国际著名杂志美国《国家科学院院刊》（PNAS）上。(生物谷 Bioon.com)
doi:10.1073/pnas.1103353108
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Soils on exposed Sunda Shelf shaped biogeographic patterns in the equatorial forests of Southeast Asia
Slik, J. W. Ferry; Aiba, Shin-Ichiro; Bastian, Meredith; Brearley, Francis Q.; Cannon, Charles H.; Eichhorn, Karl A. O.; Fredriksson, Gabriella; Kartawinata, Kuswata; Laumonier, Yves; Mansor, Asyraf; Marjokorpi, Antti; Meijaard, Erik; Morley, Robert J.; Nagamasu, Hidetoshi; Nilus, Reuben; Nurtjahya, Eddy; Payne, John; Permana, Andrea; Poulsen, Axel D.; Raes, Niels; Riswan, Soedarsono; van Schaik, Carel P.; Sheil, Douglas; Sidiyasa, Kade; Suzuki, Eizi; van Valkenburg, Johan L. C. H.; Webb, Campbe
The marked biogeographic difference between western (Malay Peninsula and Sumatra) and eastern (Borneo) Sundaland is surprisinggiven the long time that these areas have formed a single landmass. A dispersal barrier in the form of a dry savanna corridorduring glacial maxima has been proposed to explain this disparity. However, the short duration of these dry savanna conditionsmake it an unlikely sole cause for the biogeographic pattern. An additional explanation might be related to the coarse sandysoils of central Sundaland. To test these two nonexclusive hypotheses, we performed a floristic cluster analysis based on111 tree inventories from Peninsular Malaysia, Sumatra, and Borneo. We then identified the indicator genera for clusters thatcrossed the central Sundaland biogeographic boundary and those that did not cross and tested whether drought and coarse-soiltolerance of the indicator genera differed between them. We found 11 terminal floristic clusters, 10 occurring in Borneo,5 in Sumatra, and 3 in Peninsular Malaysia. Indicator taxa of clusters that occurred across Sundaland had significantly highercoarse-soil tolerance than did those from clusters that occurred east or west of central Sundaland. For drought tolerance,no such pattern was detected. These results strongly suggest that exposed sandy sea-bed soils acted as a dispersal barrierin central Sundaland. However, we could not confirm the presence of a savanna corridor. This finding makes it clear that proposedbiogeographic explanations for plant and animal distributions within Sundaland, including possible migration routes for earlyhumans, need to be reevaluated.
