Does the seed size/number trade-off model determine plant community structure? an assessment of the model mechanisms and their generality

• Published in: Oikos Vol. 93; no. 2; pp. 294 - 302
• Main Author: Leishman, Michelle R.
• Format: Journal Article
• Language: English
• Published: Copenhagen Munksgaard International Publishers 01.05.2001; Munksgaard International Publishers, Ltd; Blackwell
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Community structure; COMPETICION VEGETAL; COMPETITION VEGETALE; ECOLOGIA; Ecological competition; ECOLOGIE; ECOLOGY; Fundamental and applied biological sciences. Psychology; General aspects. Techniques; GERMINACION; GERMINATION; GRAINE; Grasses; GRASSLANDS; GROSSEUR DES SEMENCES; HERBAGE; Methods and techniques (sampling, tagging, trapping, modelling...); PERENNIALS; PESO DE LAS SEMILLAS; Plant communities; PLANT COMPETITION; Plant ecology; PLANTAS PERENNES; PLANTE PERENNE; Plants; POIDS DES SEMENCES; PRADERAS; REINO UNIDO; ROYAUME UNI; SEED SIZE; SEED WEIGHT; Seedlings; SEEDS; SEMILLA; Synecology; TAMANO DE LA SEMILLA; Terrestrial ecosystems; UNITED KINGDOM; Vegetation; Community structure; Seeds; Plant community; Morphology; Size; Resource allocation; Interspecific competition; Models; Spermatophyta; Density
• ISSN: 0030-1299; 1600-0706
• DOI: 10.1034/j.1600-0706.2001.930212.x

This paper examines four key mechanisms of the seed size/number trade-off (SSNT) models to assess their relevance to a general understanding of plant community structure. Mechanism 1 is that large seeds have a greater probability of winning in competition against smaller seeds. I provide interspecific experimental evidence that there is a competitive hierarchy among seedlings based on seed size. Mechanism 2 is that a trade-off exists between the number and size of seeds produced for a given reproductive allocation. Negative correlations between seed size and number were found consistently across a range of species from a range of habitats, from published literature. Mechanism 3, that seedling-seedling competition is an important influence on species composition, was found to exist potentially in a range of environments, including annual-dominated, post-fire and gap-dynamic communities. However, there is little quantitative evidence available and this is likely to be a restrictive mechanism. Mechanism 4, that small seeds are superior colonists due to their greater number, was tested in a field experiment in a calcareous grassland community. No supporting evidence was found, suggesting that the SSNT is not an important determinant of structure in this community. Thus two of the four mechanisms can be considered to hold true generally, while the third mechanism may be valid in particular environments. The fourth mechanism did not apply in the community tested, but could be tested in a wider range of communities.