Plasticity, genetic diversity, natural selection, and physiology of polyploid Solidago altissima (Asteraceae) under simulated climate change

Abstract

Although plant response to climate change has been observed in many systems, it is unknown whether populations or subpopulations, such as different ploidy levels, within species respond similarly. Ploidy levels may differ in their ability to adapt immediately to changed conditions through phenotypic plasticity. In the longer term, polyploids may evolve faster in response to natural selection than diploids if they harbor greater genetic diversity. The goals of this research were to compare plasticity, genetic diversity, and patterns of selection between diploid and tetraploid genotypes of a native polyploid, Solidago altissima grown under conditions simulating climate change (+1.9 ° C, -13% soil moisture). Physiological, morphological, life history traits, and fitness correlates were measured throughout the growing season. Differences in phenology, morphology and physiology suggest that diploids are better adapted to drought than tetraploids. Both ploidy levels had stronger plastic responses to water availability than temperature. For traits that differed between ploidy levels in plasticity under drought, diploids grew taller and developed more rhizomes and thicker leaves, whereas tetraploids flowered earlier, grew taller, and increased stomatal density on the lower leaf surface. Significant selection and heritability were detected for earlier flowering in both ploidy levels. More traits were targets of selection in a hot, dry environment for tetraploids than diploids, whereas more traits were targets of selection in a wet, ambient temperature environment for diploids. Tetraploids may be at a disadvantage in their long-term ability to respond to climate change through evolution due to a lack of heritability.