[Pollinator] Phylogenetic evidence for a flower size and number trade-off

[Ladadams at aol.com]

American Journal of Botany 2007;94:2059-2062

Phylogenetic evidence for a flower size and number trade-off1
<NOBR>Risa D. S6, , <NOBR>Carol Go7, , <NOBR>Susa8 and  and <NOBR>Ric9  
Department of Integrative Biology, University of California, Berkeley, 
California 94720-3140 USA; Department of Biology, East Carolina University, 
Greenville, North Carolina 27858-4353 USA; Department of Biological Sciences, 
University of Pittsburgh, Pittsburgh, Pennsylvania 15260 USA; Field Museum of Natural 
History, Botany Department, 1400 S. Lake Shore Drive, Chicago, Illinois 60605 
USA  
ABSTRACT  
The size and number of flowers displayed together on an inflorescence (floral 
display) influences pollinator attraction and pollen transfer and receipt, 
and is integral to plant reproductive success and fitness. Life history theory 
predicts that the evolution of floral display is constrained by trade-offs 
between the size and number of flowers and inflorescences. Indeed, a trade-off 
between flower size and flower number is a key assumption of models of 
inflorescence architecture and the evolution of floral display. Surprisingly, however, 
empirical evidence for the trade-off is limited. In particular, there is a lack 
of phylogenetic evidence for a trade-off between flower size and number. 
Analyses of phylogenetic independent contrasts (PICs) of 251 angiosperm species 
spanning 63 families yielded a significant negative correlation between flower 
size and flower number. At smaller phylogenetic scales, analyses of individual 
genera did not always find evidence of a trade-off, a result consistent with 
previous studies that have examined the trade-off for a single species or 
genus. Ours is the first study to support an angiosperm-wide trade-off between 
flower size and number and supports the theory that life history constraints have 
influenced the evolution of floral display.  
Key Words: floral display • flower number • flower size • inflorescence size 
• life history trade-offs • phylogenetic independent contrasts  





Laurie Davies Adams
Executive Director
Coevolution Institute
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