Journal Article

Predator satiation and recruitment in a mast fruiting monocarpic forest herb

Zivanai Tsvuura, Megan E. Griffiths, Richard M. Gunton and Michael J. Lawes

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 107, issue 3, pages 379-387
Published in print March 2011 | ISSN: 0305-7364
Published online January 2011 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcq262
Predator satiation and recruitment in a mast fruiting monocarpic forest herb

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  • Ecology and Conservation
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  • Plant Sciences and Forestry

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Background and Aims

Cross-pollination and satiation of seed predators are often invoked to explain synchronous mast reproduction in long-lived plants. However, explanations for the synchronous death of parent plants are elusive. The roles of synchronous seeding and post-reproductive mortality were investigated in a perennial monocarpic herb (Isoglossa woodii) in coastal dune forest in South Africa.

Methods

Pre-dispersal seed predation and seed production were assessed by measuring fruit and seed set of inflorescences sprayed with insecticide or water and with no spray treatments. Seed predation was measured at different densities of I. woodii plants by monitoring removal rates of seed from the forest floor. The influence of adult plants on establishment of I. woodii seedlings was assessed by monitoring growth and survivorship of seedlings in caged and uncaged 1 × 1 m plots in understorey gaps and thickets.

Key Results

Fruit and seed set were similar between spray treatments. An I. woodii stem produced 767·8 ± 160·8 seeds (mean ± s.e.) on dune crests and 1359·0 ± 234·4 seeds on the foredune. Seed rain was greater on the foredune than in other topographic locations. Seed predation rates were 32 and 54 % on dune crests and in dune slacks, respectively, and decreased with seed abundance, number of inflorescences per stem and plant height. Seedling recruitment was greater beneath synchronously dying adult plants than in natural understorey gaps (no I. woodii). However, seedling growth rate beneath I. woodii mid-way through its life-cycle was less than in gaps, although survivorship was similar.

Conclusions

The selective advantage of masting in I. woodii derives from satiation of both pre- and post-dispersal seed predators. In addition, post-seeding mortality of adult plants facilitates seedling establishment. Satiation of seed predators and the benefits of seedling establishment are strong drivers of the evolution of synchronous monocarpy in I. woodii.

Keywords: Synchronous flowering; understorey gaps; Isoglossa woodii; seed predation; seedling establishment; monocarpy

Journal Article.  5656 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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