Research
Research Projects	Research Group	Organisms	Collection	DNA Labs
Research Projects My research encompasses a number of fields, but I think the common theme is an interest in biological endemism. I study species and groups of species (particularly land snails) that are restricted to small areas, like individual caves, valleys or hills. This means some of my studies are taxonomic or biogeographic in focus, whereas others deal with the ecology and population genetics of speciation. Besides this there are conservation biological implications to be studied. Below are brief descripions of the main ongoing projects. The corresponding research papers can be found in the list of publications. The evolution of short-range endemics on limestone outcrops in Malaysia Throughout Malaysia, limestone appears at the surface as small, steep-cliffed hills, on average just half a kilometre in diameter, and mostly surrounded by alluvial, non-calcareous soils. In total almost 800 separate hills are known (visit Liz Price's WildAsia site to learn more on Malaysian karst). Many land snails thrive on these calcium-rich, alkaline soils. Certain groups, in particular Diplommatinidae, Streptaxidae, and Vertiginidae, show high degrees of endemism, with strong differentiation in shell shape from one hill to the next and many species that are endemic to just a single hill. Using a combination of population genetics, morphometrics, and field experimentation, we have been trying to understand the factors involved in the evolution of these limestone endemics, in particular within the subgenus Plectostoma of the genus Opisthostoma in Borneo, but also in the vertiginid Gyliotrachela from West-Malaysia. The former group is targeted in a system involving some 15 outcrops along the lower Kinabatangan river valley in eastern Sabah. In addition to evolutionary studies, we study the value of these outcrops in land snail conservation. Funding comes from Universiti Malaysia Sabah, the Treub Foundation, the Clive Marsh Sabah Conservation Fund, and the Royal Netherlands Embassy in Kuala Lumpur. an isolated limestone outcrop in Sarawak.   correlation between genetic and geographic distance among populations of Gyliotrachela hungerfordiana from West-Malaysian limestone hills.   Gyliotrachela hungerfordiana Opisthostoma (Plectostoma) mirabile   Two coiling morphs of A. inversus from West-Malaysia. The maintenance of coil dimorphism in Amphidromus The tropical tree snails of the genus Amphidromus are well-known for their colourful shells and their diversity throughout Southern Asia (see also this website of Conchologists of America for a nice article on this snail genus). One of the subgenera, Amphidromus s. str., is also famous for being one of the few groups of snails in which coil dimorphism is common: in most species, both right-handed and left-handed snails occur together in a population. If, as is the case in most land snails, mating between individuals of opposite coil is hampered, there should always be selection against the rarer morph and the population should quickly evolve towards coiling monomorphism. However, this does not seem to happen. In the Bornean species Amphidromus martensi, for example, all populations show morph frequencies that are close to 50%-50%. This project aims at understanding what maintains the coil polymorphism, by mapping spatial distributions of coiling morphs and by observing copulations in A. martensi and A. inversus. It is funded by Universiti Malaysia Sabah and the Treub Foundation.   The evolution of cave snails Tropical cave snails are good candidates for parapatric speciation across a steep ecotone. For limestone caves in Borneo, the external environment is warm, bright, and ecologically very complex, whereas the cave environment, just a hundred meters from the cave entrance, is cool, dark, and biologically poor. These different conditions may force cave snails to adapt in the face of ongoing gene flow. We study a system of two Georissa snails, a troglobite and its epigean ancestor, in a limestone cave in the interior of Sabah, Malaysian Borneo, using morphometrics and population genetics. The results so far show that the cave snail is indeed descended from the local population of G. saulau that inhabits the cliffs of the hill in which the cave is located. This project is funded by Universiti Malaysia Sabah and the Danish Corporation for Environmental Development.   impressions of the field site at Gua Sanaron, Sabah     Left: the epigean Georissa saulae; right: the (undescribed) descendant cave species; centre: an intermediate form from the cave entrance. A Principal Component Analysis, showing that the epigean G. saulae (OUT-1 and OUT-2) and the cave species living deep in the cave (IN-2) have very different shell shapes. The population that lives in the cave entrance (IN-1) has an intermediate form. a phylogeny based on mtDNA, which shows that the cave species (G. n. sp.) is closely related to the local population of G. saulae.   daybreak over Gunung Kinabalu The evolution of high-altitude endemics on Mount Kinabalu At 4,100 metres high, Mount Kinabalu (click here for UNEP's data sheet on this World Heritage site) is one of the few existing, relatively pristine tall tropical mountains, unique for displaying an uninterrupted series of habitats from lowland tropical rainforest at the foot to subalpine scrub at the summit. The numbers of species endemic to the higher elevations are staggering, especially in taxa like angiosperms, insects and land snails, but even certain bird and mammal species are restricted to Mount Kinabalu and its surrounding peaks. In land snails, many of the high-altitude endemics appear to have existing sister species at the lower elevations. In some cases, several closely related species succeed each other along the elevational gradient. Using detailed mapping of distribution patterns, morphometrics and population genetics, we aim to understand the evolution of endemics on this relatively young (1 million years) mountain. Funding is from Universiti Malaysia Sabah. taking a break from field work at Panar Laban, at 3,500 m altitude.   A selfish symbiont to improve the biocontrol agents of the Cocoa Pod Borer The Malaysian Cocoa Board uses several trichogrammatid egg parasitoids (minute parasitic wasps) to control the Cocoa Pod Borer, a moth that affects cocoa. The wasps are mass-cultured in their labs in Tawau and distributed among cocoa farmers for release. We are attempting to artificially infect these parasitoids with a strain of the endosymbiotic bacterium Wolbachia to produce an all-female, parthenogenetic strain that will be more effective at controlling the pest. This project is funded through the Malaysian government's Intensifying Research Priority Areas programme.