Variation in ovule and seed size and associated size-number trade-offs in angiosperms

Unlike pollen and seed size, the extent and causes of variation in ovule size remain unexplored. Based on 45 angiosperm species, we assessed whether intra- and interspecific variation in ovule size is consistent with cost minimization during ovule production or allows maternal plants to dominate con...

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Published inAmerican journal of botany Vol. 94; no. 5; pp. 840 - 846
Main Authors Greenway, Carly A, Harder, Lawrence D
Format Journal Article
LanguageEnglish
Published United States Botanical Society of America 01.05.2007
Botanical Soc America
Subjects
Angiospermae
Angiosperms
Evolution
Flowers
Fruits
integument
nucellus
ovule
Ovules
parent–offspring conflict
Phylogeny
Placentation
Plants
pollen
Regression coefficients
Reproductive Biology
resource allocation
seed
Seed size
seeds
size–number trade‐off
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Summary:Unlike pollen and seed size, the extent and causes of variation in ovule size remain unexplored. Based on 45 angiosperm species, we assessed whether intra- and interspecific variation in ovule size is consistent with cost minimization during ovule production or allows maternal plants to dominate conflict with their seeds concerning resource investment. Despite considerable intraspecific variation in ovule volume (mean CV = 0.356), ovule production by few species was subject to a size-number trade-off. Among the sampled species, ovule volume varied two orders of magnitude, whereas seed volume varied four orders of magnitude. Ovule volume varied positively among species with flower mass and negatively with ovule number. Tenuinucellate ovules were generally larger that crassinucellate ovules, and species with apical placentation (which mostly have uniovulate ovaries) had smaller ovules than those with other placentation types. Seed volume varied positively among species with fruit mass and seed development time, but negatively with seed number. Seeds grew a median 93-fold larger than the ovules from which they originated. Our results provide equivocal evidence that selection minimizes ovule size to allow efficient resource allocation after fertilization, but stronger evidence that ovule size affords maternal plants an advantage in parent-offspring conflict.
Bibliography:http://www.amjbot.org/
Present address: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9
The authors thank B. Smith for taxonomic assistance and M. L. Reid and M. B. Routley for comments on the manuscript. A Discovery Grant (LDH) from the Natural Sciences and Engineering Research Council of Canada provided partial funding for this research.
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ISSN:0002-9122
1537-2197
DOI:10.3732/ajb.94.5.840