On the Tempo of Genome Size Evolution in Angiosperms

Jeremy M Beaulieu,Stephen A Smith,Ilia J Leitch

doi:10.1155/2010/989152

Jeremy M Beaulieu, Stephen A Smith + Show 1 more

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https://doi.org/10.1155/2010/989152

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Abstract

Broadly sampled phylogenies have uncovered extreme deviations from a molecular clock with the rates of molecular substitution varying dramatically within/among lineages. While growth form, a proxy for life history, is strongly correlated with molecular rate heterogeneity, its influence on trait evolution has yet to be examined. Here, we explore genome size evolution in relation to growth form by combining recent advances in large-scale phylogeny construction with model-based phylogenetic comparative methods. We construct phylogenies for Monocotyledonae (monocots) and Fabaceae (legumes), including all species with genome size information, and assess whether rates of genome size evolution depend on growth form. We found that the rates of genome size evolution for woody lineages were consistently an order of magnitude slower than those of herbaceous lineages. Our findings also suggest that growth form constrains genome size evolution, not through consequences associated with the phenotype, but instead through the influence of life history attributes on the tempo of evolution. Consequences associated with life history now extend to genomic evolution and may shed light on the frequently observed threshold effect of genome size variation on higher phenotypic traits.

Highlights

The concept of a “molecular clock” predicts that nucleotide substitution rates should scale linearly with time and be equal among lineages
The woody species were mostly confined to the clades corresponding to the Cercideae, Mimosoideae, and Caesalpinioideae, with additional occurrences found within the Papilionoideae
Our analyses demonstrated that the tempo of genome size evolution is strongly influenced by growth form

Summary

Introduction

The concept of a “molecular clock” predicts that nucleotide substitution rates should scale linearly with time and be equal among lineages. Generation time, is a strong correlate of among/within lineage rate heterogeneity in both animals and plants [6,7,8]. Generation time may play a role in this pattern as herbaceous species typically have shorter generation times than woody species, and a greater capacity to accumulate nucleotide substitutions per unit time. Implicit in these results is a renewed appreciation for the link between microevolutionary process and macroevolutionary pattern [9]

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