World Congress of Malacology Antwerp ... - Unitas Malacologica

Sampling micromolluscs on tropical limestone karsts: high sampling efficiencies and novel
biogeographical patterns
Clements, Reuben
Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore
117543, Republic of Singapore,
Email: rclements@nus.edu.sg
Micromolluscs comprise a large proportion of terrestrial malacofaunas on limestone karsts. As such,
sampling protocols for karst molluscs must consider their patchy distributions, high species densities
and minute sizes. As part of a biogeographical study on karst molluscs, sixteen karsts on both sides of
the Titiwangsa Mountain range cutting across Peninsular Malaysia were sampled to: 1) determine
correlates of mollusc endemism from a set of biogeographical factors (i.e., karst area, isolation,
surrounding soil type and geological age); and 2) investigate mollusc species composition trends
across the region. On each karst, systematic sampling methods were employed in lieu of random
sampling to achieve spatial interspersion and reduce bias resulting from possible segregation. Shells
were extracted from soil samples using a combination of floatation and sieving techniques. Sampling
saturation on each karst was assessed using completeness ratios and species accumulation curves.
Generalized linear mixed-effect models (GLMM) were used to determine correlates of endemism,
while non-metric multi-dimensional scaling (NMDS) was used to investigate species compositional
variation. Sampling yielded a total of 198 terrestrial mollusc species, of which about 75% were less
than 5 mm. Based on high completeness ratios and asymptotic species accumulation curves, sampling
on each karst was considered efficient. GLMMs revealed an important contribution of karst area and
surrounding soil type on mollusc endemic richness, while NMDS showed that karst malacofaunas on
either side of the mountain range were distinct from each other. These results have important
conservation implications: planners should take karst area and surrounding soil type into account,
together with the effects of vicariant barriers such as mountains, when designing karst reserves in
order to maximize the protection of invertebrate diversity.
Correlates of endemism and biogeography of terrestrial molluscs on tropical limestone karsts
Clements, Reuben 1 ; Sodhi, Navjot S. 1 ; Ng, Peter K.L. 1 ; Lu, X. X. 2 ; Ambu, Stephen 3 ,
Schilthuizen, Menno 4 ; Bradshaw, Corey J. A. 5
1. Department of Biological Sciences, National University of Singapore, 14 Science Drive 4,
Singapore 117543, Republic of Singapore,
Email: rclements@nus.edu.sg
2. Department of Geography, National University of Singapore, 10 Kent Ridge Crescent, Singapore
119260, Republic of Singapore,
Email: geoluxx@nus.edu.sg
3. Environmental Health Research Centre, Institute for Medical Research, Jalan Pahang, 50588 Kuala
Lumpur, Malaysia,
Email: stephen.ambu@gmail.com
4. National Museum of Natural History 'Naturalis', P.O. Box 9517, 2300 RA Leiden, the Netherlands,
Email: schilthuizen@yahoo.com
5. School for Environmental Research, Institute of Advanced Studies, Charles Darwin University,
Darwin, Northern Territory 0909, Australia,
Email: corey.bradshaw@cdu.edu.au
The main objectives of our study were to identify variables (area, isolation, surrounding soil type and
geological age) hypothesised to correlate with endemic richness of terrestrial molluscs (a majority of
which are micromolluscs) on tropical limestone karsts, and to investigate molluscan species
compositional trends across karsts in two biogeographical regions - Peninsular Malaysia and Sabah,
Malaysian Borneo. Generalized linear mixed-effect models (GLMM) were used to determine
correlates of endemism from the set of biogeographical factors (i.e., karst area, isolation, surrounding
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