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abundance are highly seasonal, were adapted to large-scale disturbances such as those
caused by a severe storm. This study has demonstrated that the P. elegans population
on Drum Sands possesses the latter reproductive strategy. Levin (1984a) suggested
that species adapted to large-scale disturbances were able to successfully colonise and
dominate in areas where the timing of the disturbance coincided with periods of peak
larval availability. The two peak periods of larval settlement at Drum Sands occurred
during May and December coinciding with the most probable timings of macroalgal
mat formation, and sediment movement by storms, respectively. If P. elegans larvae
settle and metamorphose more successfully than other species in areas where these
types of disturbances occur, then weed mat development and sediment movement are
perhaps positive structuring forces in population maintenance. The effects of both
artificially-implanted and natural weed mats on adult densities and larval recruitment,
and colonisation of disturbed areas are discussed in Chapters 4, 5 and 6 respectively.
With the absence of both asexual reproduction and the production of benthic larvae,
maintenance of P. elegans's spatial heterogeneity described in Chapter 2 must have
involved either increased larval recruitment or adult migration to established high-
density patches, or increased juvenile survival within them. Larval recruitment to
patch and non-patch azoic and ambient sediments are compared in Chapters 6 and 8
respectively. In Chapter 6, the extent to which adult migration may have been
influential in patch maintenance is also discussed.
This study has indicated that P. elegans on Drum Sands exclusively relied upon
sexual reproduction for population maintenance. Schlotzer-Schrehardt (1987; 1991)
suggested that P. elegans was the only reported spionid species in which direct
spermatophore transfer is used during sexual reproduction. While other species
indirectly transfer their free-floating spermatophores, a special pattern of reproductive
behaviour including active seeking of the females tubes by the males is needed for
spermatophore transfer. This has implications for both the population's reproductive
potential and the micro-scale patterns of P. elegans. The latter will be addressed in
Chapter 7.
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