Friday, January 6, 2012

[Invertebrate • 2008] Microgeographic Evolution of Snail Shell Shape and Predator Behavior

FIG. 1. The Opisthostoma concinnum complex consists of 16 populations. All are restricted to small limestone outcrops along the lower Kinabatangan River in Sabah, Malaysian Borneo. The populations have been identified with five- or six-letter codes: BATANG (O. concinnum at Batangan), BODTAI (O. concinnum at Bod Tai), GOMcon (O. concinnum at Gomantong), GOMmir (O. mirabile at Gomantong), KAMPUN (O. concinnum at Batu Kampung), KERUAK (O. concinnum at Keruak), MATERI (O. concinnum at Materis), MAWAS (O. concinnum at Mawas), PANGI (O. concinnum at Pangi), QUARRY (O. concinnum at Quarry), TABAco (O. concinnum at Tandu Batu), TABAsi (O. simplex at Tandu Batu), TOMBEE (O. concinnum at the east side of Tomanggong Besar), TOMBEW (O. fraternum at the west side of Tomangong Besar), TOM-2 (O. concinnum at Tomanggong 2), TOMKEC (O. concinnum at Tomanggong Kecil). All populations are allopatric, except those from Gomantong, Tandu Batu, and Tomanggong Besar. (a) Representative individuals for all populations

Genetic divergence in geographically isolated populations is a prerequisite for allopatric speciation, one of the most common modes of speciation. In ecologically equivalent populations existing within a small, environmentally homogeneous area, an important role for environmentally neutral divergence is often found or inferred. We studied a species complex of conspicuously shaped Opisthostoma land snails on scattered limestone outcrops within a small area of lowland rainforest in Borneo. We used shell morphometrics, mitochondrial and nuclear DNA sequences, and marks of predation to study the factors involved in allopatric divergence. We found that a striking geographic divergence exists in shell morphology, which is partly associated with neutral genetic divergence. We also found geographic differentiation in the behavior of the snails’ invertebrate predator and evidence of an evolutionary interaction
between aspects of shell shape and predator behavior. Our study shows that adaptation to biotic aspects of the environment may play a more important role in allopatric speciation than previously suspected, even on a geographically very small scale.

Key words: Adaptation, conchology, Gastropoda, Malaysia, Mollusca, Opisthostoma.

Schilthuizen, M., Van Til A., Salverda M., & et al (2006). Microgeographic evolution of snail shell shape and predator behavior. Evolution. 60, 1851-1858.: