Abstract
We test the hypothesis that the biodiversity of the death assemblage of shelled molluscs (gastropods and bivalves) on a single sandflat is representative of the biodiversity of the regional living fauna from the complete spectrum of habitat types, and can therefore be used as a surrogate for the purposes of rapid biodiversity assessment. Two biodiversity indices considered appropriate for such an assessment are average taxonomic distinctness (Δ+) and the variation in taxonomic distinctness (Λ+), which are, respectively, measures of the degree to which the species are taxonomically related to each other (i.e. the average taxonomic spread), and the degree to which taxa are over or under represented (i.e. the evenness of the distribution across the taxonomic tree). In each case, measured values were compared with the regional living species pool using a randomisation test. Collections and identifications of shells were made by both a non-expert in mollusc taxonomy and by taxonomic experts, the latter using microscopic examination of sediment samples as well as simple surface searches for macro-species. In all studies, Δ+ for the gastropods in the death assemblage was fully representative of the regional living fauna, but for bivalves it was significantly lower. This is because most of the bivalves were characteristic of the sandflat habitat, which introduced a bias, whereas post-mortem transport of gastropods, characterising exotic habitats, is more random. For gastropods, in all studies but one, Λ+ was significantly higher than expected from a random sample of the regional species pool, and for bivalves this was the case for all studies, suggesting the over-representation of some taxa and the under-representation of others. For the total shelled molluscan fauna (gastropods + bivalves) all Δ+ values were below, and all Λ+ values above, expectation. Results obtained by experts and a non-expert in mollusc taxonomy did not differ. In general, death assemblages at a single location are only likely to be representative of a wider region if there is randomisation as a result of post-mortem transport processes.
Similar content being viewed by others
References
Clarke KR and Warwick RM (1994) Change in Marine Communities: An Approach to Statistical Analysis and Interpretation. Plymouth Marine Laboratory, Plymouth
Clarke KR and Warwick RM (1998) A taxonomic distinctness index and its statistical properties. Journal of Applied Ecology 35: 523–531
Clarke KR and Warwick RM (1999) A taxonomic distinctness measure of biodiversity: weighting of step lengths between hierarchical levels. Marine Ecology Progress Series 184: 21–29
Clarke KR and Warwick RM (in press) A further biodiversity index applicable to species lists: variation in taxonomic distinctness. Marine Ecology Progress Series
Feral J-P (1999) Indicators of Marine and Coastal Biodiversity of the Mediterranean Sea. United Nations Environment Programme, Tunis, Tunisia
Graham A (1988) Molluscs: Prosobranch and Pyramidellid Gastropods. Synopses of the British Fauna (New Series) No. 2. 2nd Edition. E.J. Brill/Dr W. Backhuys, Leiden, The Netherlands
Hammond PM (1994) Practical approaches to the estimation of the extent of biodiversity in speciose groups. Philosophical Transactions of the Royal Society, Series B 345: 119–136
Harper JL and Hawksworth DL (1994) Biodiversity: measurement and estimation. Philosophical Transactions of the Royal Society, Series B 345: 5–12
Harvey LA (1969) The marine fauna and flora of the Isles of Scilly – the islands and their ecology. Journal of Natural History 3: 3–18
Kidwell SMand Bosence DWJ (1991) Taphonomy and time-averaging of marine shelly faunas. In: Allison PA and Briggs DEG (eds) Taphonomy: Releasing the Data Locked in the Fossil Record, pp 115–209. Plenum Press, New York
Kidwell SMand Flessa KW (1995) The quality of the fossil record: populations, species and communities. Annual Review of Ecology and Systematics 26: 269–299
Kidwell SM (in press) Ecological fidelity of molluscan death assemblages. In: Aller JY, Woodin SA and Aller RC (eds) Organism–Sediment Interactions. University of South Carolina Press, Columbia, South Carolina
Powell EN, Staff GM, Davies DJ and Callender WR (1989) Macrobenthic death assemblages in modern marine environments: formation, interpretation and application. CRC Critical Reviews in Aquatic Sciences 1: 555–589
Rosenzweig ML (1995) Species Diversity in Space and Time. Cambridge University Press, Cambridge Tebble N (1966) British Bivalve Seashells. Her Majesty's Stationary Office, Edinburgh
Turk SM and Seaward DR (1997) The marine fauna and flora of the Isles of Scilly – Mollusca. Journal of Natural History 31: 555–633
Warwick RM and Clarke KR (1991) A comparison of some methods for analysing changes in benthic community structure. Journal of the Marine Biological Association of the United Kingdom 71: 225–244
Warwick RM and Clarke KR (1995) New 'biodiversity' measures reveal a decrease in taxonomic distinctness with increasing stress. Marine Ecology Progress Series 129: 301–305
Warwick RM and Clarke KR (1998) Taxonomic distinctness and environmental assessment. Journal of Applied Ecology 35: 532–543
Wilkinson DM (1999) The disturbing history of intermediate disturbance. Oikos 84: 145–147
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Warwick, R., Light, J. Death assemblages of molluscs on St Martin's Flats, Isles of Scilly: a surrogate for regional biodiversity?. Biodiversity and Conservation 11, 99–112 (2002). https://doi.org/10.1023/A:1014094829984
Issue Date:
DOI: https://doi.org/10.1023/A:1014094829984