Genetic and spatial variation in vegetative and floral traits across a hybrid zone

Abstract

Premise Genetic variation influences the potential for evolution to rescue populations from impacts of environmental change. Most studies of genetic variation in fitness‐related traits focus on either vegetative or floral traits, with few on floral scent. How vegetative and floral traits compare in potential for adaptive evolution is poorly understood. Methods We measured variation across source populations, planting sites, and genetic families for vegetative and floral traits in a hybrid zone. Seeds from families of Ipomopsis aggregata, I. tenuituba, and F1 and F2 hybrids of the two species were planted into three common gardens. Measured traits included specific leaf area (SLA), trichomes, water‐use efficiency (WUE), floral morphology, petal color, nectar, and floral volatiles. Results Vegetative traits SLA and WUE varied greatly among planting sites, while showing weak or no genetic variation among source populations. Specific leaf area and trichomes responded plastically to snowmelt date, and SLA exhibited within‐population genetic variation. All aspects of floral morphology varied genetically among source populations, and corolla length, corolla width, and sepal width varied genetically within populations. Heritability was not detected for volatiles due to high environmental variation, although one terpene had high evolvability, and high emission of two terpenes, a class of compounds emitted more strongly from the calyx than the corolla, correlated genetically with sepal width. Environmental variation across sites was weak for floral morphology and stronger for volatiles and vegetative traits. The inheritance of three of four volatiles departed from additive. Conclusions Results indicate stronger genetic potential for evolutionary responses to selection in floral morphology compared with scent and vegetative traits and suggest potentially adaptive plasticity in some vegetative traits.

Chasing the fitness optimum: temporal variation in the genetic and environmental expression of life-history traits for a perennial plant

“…where Var fam is the maternal family variance, Var fam × Var block is the variance attributed to the interaction between family and block, and Var error is the error/residual variance. Heritability calculations from half-sibling analyses typically multiply the numerator, Var fam , by 4 to account for half-sibling relatedness ( Lynch and Walsh, 1998 ; Campbell et al , 2022 ). However, Ahrens et al .…”

What determines the evolutionary trajectories of wild plant species? Approaches to the study of quantitative fitness‐related traits

“…In this issue, common gardens or reciprocal transplants were used to examine a broad array of fitness-related traits, including floral scent (Eisen et al, 2022;Campbell et al, 2022a), SLA, WUE, trichome density, and floral morphology (Campbell, 2022a), germination time (Muir et al, 2022), flowering time (Cheptou et al, 2022), and physiological traits (Volk et al, 2022). Campbell et al (2022a) combined variance component analysis with a common garden experiment comprising multiple generations to detect differentiation between taxa in floral vs. vegetative traits and to compare the current evolutionary potential of these traits in Ipomopsis aggregata (Polemoniaceae), I. tenuituba, and their hybrids raised in three common gardens. Consistent with the high phenotypic plasticity often observed in vegetative traits, SLA and WUE were highly sensitive to garden location and exhibited low genetic differentiation among populations.…”