Resource allocation, demography and the radiation of life histories in rough periwinkles (Gastopoda)
- 80 Downloads
Applicability of life-history theory to higher levels of comparison (from populations, through ecotypes to sibling species) was investigated in rough periwinkles, whose life histories have diversified since colonization of the North Atlantic by an oviparous ancestor in the upper Pliocene. Comparisons were made among populations of the ovoviviparous Littorina saxatilis, between L. saxatilis and its ecotype, L. neglecta (with an annual life history) and between the sibling species L. saxatilis and L. arcana, the latter of which retains the ancestral oviparity.
Resource-allocation priority, reproductive effort and related trade offs were compared between the ecotypes and the sibling species by measuring changes in flesh mass and reproductive output in snails subjected to different degrees of food deprivation, and by measuring mortality rate of snails stressed by desiccation, high temperature and low salinity. Body size had a marked effect on all parameters, but after statistically removing this effect there remained no significant differences in allocation among ecotypes or species.
Published demographical data were reviewed for correlations between habitat, mortality regime and life-history characteristics. Populations of L. saxatilis varied principally in size at birth and in adult size. Theoretical premises based on density-dependent versus density-independent mortality regimes could not explain these trends. Instead, size at birth may have reflected the mechanical, physiological or biological nature of mortality risk rather than its density dependence or independence. Adult size reflected the available sizes of crevices used for shelter and perhaps also the quality of feeding conditions.
Radiation of life histories within the rough periwinkles is interpreted as a series of adaptations to a progressively wider range of habitats. The transition from oviparity to ovoviviparity allows colonization of estuaries, saltmarshes and pebble beaches too hazardous for naked egg masses. The transition from a perennial to an annual life history in barnacle ecotypes follows from allometric re-scaling of morphological and physiological parameters, enabling reproduction and brooding to occur at the small body size necessary for life within empty barnacle tests. This suite of adaptations allows exploitation of a relatively benign microhabitat that occurs almost ubiquitously on exposed rocky shores of the temperate North Atlantic. The persistence of oviparous forms, presumably in the face of competition from sympatric ovoviviparous forms, remains unexplained.
Key wordsallocation trade offs oviparity/brooding body size niche diversification
Unable to display preview. Download preview PDF.
- Brody, S. J., 1945. Bioenergetics and growth. Reinhold, New York, 1023 pp.Google Scholar
- Cannon, J. P. & R. N. Hughes, 1992. Resistance to environmental Stressors in Littorina saxatilis (Olivi) and L. neglecta Bean. In J. Grahame, P. J. Mill & D. G. Reid (eds), Proceedings of the 3rd International Symposium on Littorinid Biology. The Malacolog-ical Society of London, London: 61–68.Google Scholar
- Fish, J. D. & L. Sharp, 1985. The ecology of the periwinkle, Littorina neglecta Bean. In P. G. Moore & R. Seed (eds), The ecology of rocky coasts. Hodder & Stoughton, Lond.: 143–156.Google Scholar
- Grahame, J. & P. J. Mill, 1992. Local and regional variation in shell shape of rough periwinkles in southern Britain. In J. Grahame, P. J. Mill & D. Reid (eds), Proceedings of the 3rd International Symposium on Littorinid Biology. The Malacological Society of London, London: 99–106.Google Scholar
- Hannaford Ellis, C. J., 1979. Morphology of the oviparous rough periwinkle, Littorina arcana Hannaford Ellis, 1978, with notes on the taxonomy of the L. saxatilis species complex (Prosobranchia: Littorinidae). J. Conch. 30: 43–56.Google Scholar
- Hannaford Ellis, C. J., 1983. Patterns of reproduction in four Littorina species. J. moll. Stud. 49: 98–106.Google Scholar
- Hughes, R. N. 1986. A functional biology of marine gastropods. Croom-Helm, London and Sydney, 245 pp.Google Scholar
- Mill, P. J. & J. Grahame, 1992. Distribution of the rough periwinkles in Great Britain. In J. Grahame, P. J. Mill & D. G. Reid (eds), Proceedings of the 3rd International Symposium on Littorinid Biology. The Malacological Society of London, London: 305–307.Google Scholar
- Naylor, R. & M. Begon, 1982. Variations within and between populations of Littorina nigrolineata Gray on Holy Island, Anglesey. J. Conch. 31: 17–30.Google Scholar
- Palmer, A. R., 1982. Growth in marine gastropods: a nondestructive technique for independently measuring shell and body weight. Malacologia 23: 63–73.Google Scholar
- Raffaelli, D. G., 1976. The Determinants of Zonation of Littorina neritoides and Littorina saxatilis species-complex. Ph.D. thesis, University of Wales, Bangor, 177 pp.Google Scholar
- Raffaelli, D. G. 1978. Factors affecting the population structure of Littorina neglecta Bean. J. moll. Stud. 44: 223–230.Google Scholar
- Raffaelli, D. G. 1982. Recent ecological research on some European species of Littorina. J. moll. Stud. 48: 241–342.Google Scholar
- Reid, D. G. 1990. Trans-Arctic migration and speciation induced by climatic change: the biogeography of Littorina (Mollusca: Gastropoda). Bull. mar. Sci. 47: 35–49.Google Scholar
- Roberts, D. J. 1979. Reproductive strategies of Littorina neritoides and the Littorina saxatilis species complex. Ph.D. thesis, University of Wales, Bangor, pp. 160.Google Scholar
- Ryan, B. F., B. L. Joiner & T. Ryan, 1985. Minitab Handbook. Duxbury Press, Boston.Google Scholar
- Sibly, R. M. & P. Calow, 1986. Physiological ecology of animals: an evolutionary approach. Blackwell Scientific Publications, Oxford, 179 pp.Google Scholar
- Stearns, S. C, 1992. The evolution of life histories. Oxford University Press, Oxford, 179 pp.Google Scholar
- Warwick, T., 1983. A method of maintaining and breeding members of the Littorina saxatilis (Olivi) species complex. J. moll. Stud. 48: 368–370.Google Scholar