Life on a block of limestone: Evolutionary, ecological and geological dynamics of isolated malacofaunas on tropical karst M. Schilthuizen Schilthuizen, M. Life on a block of limestone: Evolutionary, ecological, and geological dynamics of iso- lated malacofaunas on tropical karst. Scripta Geologica, 143: 27, Leiden, May 2011. Menno Schilthuizen, Department of Terrestrial Zoology, NCB Naturalis, Postbus 9517, NL-2300 RA Lei- den, The Netherlands (Menno.Schilthuizen@ncbnaturalis.nl) and Institute for Tropical Biology and Conservation, Universiti Malaysia Sabah, Locked Bag 2073, 88999 Kota Kinabalu, Malaysia. The karst formations of southeast Asia are a wonderful evolutionary and ecological experiment, and a sad example of observable extinction (Clements et al., 2006). In this paper, I shall focus on those in Malaysia and, in particular, on the land snail faunas that they support. Limestone in Malaysia comes in the form of around 800 discrete units, most of them karst towers of, on average, a few hundred metres diameter (Price, 2001). Ecologically, and oten also geologically (many are lenticular), these hills oten show a considerable degree of isolation. In invertebrates with high calcium requirements, like terrestrial gastropods, this situation has led to the evolution of locks of endemic species, many occurring on a single outcrop and nowhere else on earth. In some instances, we have a good insight into the evolutionary processes responsi- ble for this insular endemism. Many species of the bizarrely-shaped subgenus Plecto- stoma, for example, appear to engage in an evolutionary arms race with their slug preda- tors, leading to site-speciic evolutionary trajectories of ever-changing morphological defense and behavioural ofense (Schilthuizen et al., 2006). Studies of fossil deposits combined with molecular phylogenetics allow parts of these trajectories to be retraced. Ecologically, the dense and diverse land snail communities living on limestone provide good opportunities for testing macroecological models of niche-based and dispersal- based community assembly. The geological characteristics of these karst habitats also prove to be their undoing. Easily accessible carbonate formations as they are, they are prone to quarrying by the cement industry (Clements et al., 2006). Also, land clearing in the surrounding area of- ten leads to ires which sweep up the dry karst vegetation. Sadly, extinctions of en- demic species have already been documented and, based on successive satellite images of quarried hills, it is possible to predict future ones (Schilthuizen & Clements, 2008). References Clements, R., Sodhi, N.S., Schilthuizen, M. & Ng, P.K.L. 2006. Limestone karsts of southeast Asia: imper- iled arks of biodiversity. Bioscience, 56: 733-742. Price, L. 2001. Caves and Karst of Peninsular Malaysia. A Register. Gua Publications, Kuala Lumpur, Ma- laysia: 98 pp. Schilthuizen, M. & Clements, R. 2008. Tracking extinction from space. Tentacle, 17: 8-9. Schilthuizen, M., van Til, A., Salverda, M., Liew, T.-S., James, S.S., Elahan, B. & Vermeulen, J.J. 2006. Micro-allopatric divergence in a snail associated with behavioural diferences in its predator. Evolu- tion, 60: 1851-1858.