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Title: How does genome size affect the evolution of pollen tube growth rate, a haploid performance trait?
Premise

Male gametophytes of most seed plants deliver sperm to eggs via a pollen tube. Pollen tube growth rates (PTGRs) of angiosperms are exceptionally rapid, a pattern attributed to more effective haploid selection under stronger pollen competition. Paradoxically, whole genome duplication (WGD) has been common in angiosperms but rare in gymnosperms. Pollen tube polyploidy should initially acceleratePTGRbecause increased heterozygosity and gene dosage should increase metabolic rates. However, polyploidy should also independently increase tube cell size, causing more work which should decelerate growth. We asked how genome size changes have affected the evolution of seed plantPTGRs.

Methods

We assembled a phylogenetic tree of 451 species with knownPTGRs. We then used comparative phylogenetic methods to detect effects of neo‐polyploidy (within‐genus origins),DNAcontent, andWGDhistory onPTGR, and correlated evolution ofPTGRandDNAcontent.

Results

Gymnosperms had significantly higherDNAcontent and slowerPTGRoptima than angiosperms, and theirPTGRandDNAcontent were negatively correlated. For angiosperms, 89% of model weight favored Ornstein‐Uhlenbeck models with a fasterPTGRoptimum for neo‐polyploids, whereasPTGRandDNAcontent were not correlated. For within‐genus and intraspecific‐cytotype pairs,PTGRs of neo‐polyploids < paleo‐polyploids.

Conclusions

Genome size increases should negatively affectPTGRwhen genetic consequences ofWGDs are minimized, as found in intra‐specific autopolyploids (low heterosis) and gymnosperms (fewWGDs). But in angiosperms, the higherPTGRoptimum of neo‐polyploids and non‐negativePTGRDNAcontent correlation suggest that recurrentWGDs have caused substantialPTGRevolution in a non‐haploid state.

 
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NSF-PAR ID:
10460304
Author(s) / Creator(s):
 ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
American Journal of Botany
Volume:
106
Issue:
7
ISSN:
0002-9122
Page Range / eLocation ID:
p. 1011-1020
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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