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Morphological rates of angiosperm seed size evolution
1Department of Geoscience, University of Iowa, Iowa City, Iowa, 52242, USA. hallie-sims@uiowa.edu
Evolution; International Journal of Organic Evolution
|April 27, 2013
Summary
Angiosperm seed size evolution shows that lineages near the average seed size evolve faster, both in form and species number. Extreme seed sizes are linked to slower diversification rates.
Area of Science:
- Evolutionary Biology
- Plant Sciences
- Phylogenetics
Background:
- Seed size evolution in angiosperms is key to their ecological diversification.
- Angiosperm seed sizes have expanded beyond Paleozoic boundaries, showing dispersal across phylogeny.
- Phenotypic evolution of seed size is influenced by complex fitness landscapes.
Purpose of the Study:
- To investigate the relationship between seed size evolution rates and diversification rates in angiosperms.
- To determine if seed size evolution is influenced by a lineage's position within the overall seed size distribution.
- To test hypotheses about evolutionary rates in different regions of the seed morphospace.
Main Methods:
- Comparative phylogenetic analysis of seed size evolution across 17,375 angiosperm species in 40 clades.
- Estimation of morphological rates of seed size evolution.
- Analysis of taxonomic diversification rates in relation to seed size distribution.
Main Results:
- Morphological rates of seed size evolution varied significantly among clades (e.g., 0.001 in Garryales to 0.207 in Malvales).
- Higher morphological and taxonomic diversification rates were observed in clades with seed sizes closer to the angiosperm mean.
- Clades with extremely small or large seeds exhibited lower evolutionary rates.
Conclusions:
- Evolutionary rates (morphological and taxonomic) are elevated in densely occupied regions of the seed morphospace.
- Lineages occupying extreme seed size niches show slower diversification.
- Seed size distribution, not absolute size, correlates with evolutionary rates, suggesting niche packing influences diversification.
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