Environmental adaptation in stomatal size independent of the effects of genome size.
Bottom Line: We also compared how genome and stomatal sizes varied at ancient (among genera) and more recent (within genus) levels.Ancient changes in genome size clearly influenced stomatal size in Proteaceae, but adaptation to habitat strongly modified the genome-stomatal size relationship.Direct adaptation to the environment in stomatal size argues that new proxies for past concentrations of atmospheric CO2 that incorporate stomatal size are superior to older models based solely on stomatal frequency.
Affiliation: School of Biological Sciences, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia.Show MeSH
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Mentions: Genome size varied very little within genera, with almost 99% of the variation in 1C size occurring among genera and < 1% occurring among species within genera (Fig.3). When the Persoonioid clade, with its anomalously large genome, was excluded, 93.2% of the variation still occurred among genera, and only 5.5% among species within genera. In contrast to genome size, stomatal size showed high amounts of variation within genera relative to the variation among genera (Fig.3). Thus, 69% of the variation in log of guard cell length occurred among species within genera, 26% occurred among genera and 5% occurred between individuals within species. When the Persoonioid clade was excluded, 55% of the variation occurred among species within genera, 39% among genera and 6% between individuals within species (Fig.3). As a proportion of the variance among genera, the among-species-within-genera variance component for log of guard cell length was significantly greater than for holoploid genome size, both across the whole family and within the Grevilleoid/Proteoid clade (P < 0.01; randomization test based on 9999 replicates of resampling genera with substitution). As expected, the recently evolved triploid, L. tasmanica (excluded from analyses), had slightly larger stomata than its congeners, but the more ancient tetraploid (T. toru) had stomata of similar size to those of its closest relatives, Persoonia species, in spite of having double the genome size.
Affiliation: School of Biological Sciences, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia.