Biology subjects

Mitchell-Olds, T.

Publications and source records attributed to Mitchell-Olds, T..

4 recordsLinked to original sources

bioRxiv2022

Soil variation among natural habitats alters glucosinolate content in a wild perennial mustard

Baseline levels of glucosinolates--important defensive phytochemicals in Brassicaceous plants--are determined by both genotype and the environment. However, the ecological causes of glucosinolate plasticity are not well characterized. Fertilization is known to alter glucosinolate content of Brassica crops, but the effect of naturally-occurring soil variation on glucosinolate content of wild plants is unknown. Here, we conduct greenhouse experiments using Boechera stricta to ask 1) whether soil variation among natural habitats shapes leaf and root glucosinolate profiles; 2) whether such changes are caused by abiotic soil properties, soil microbes, or both; and 3) whether soil-induced glucosinolate plasticity is genetically variable. Total glucosinolate quantity differed up to two-fold between soils from different natural habitats, while the relative amounts of different compounds was less responsive. This effect was due to physico-chemical soil properties rather than microbial communities. We detected modest genetic variation for glucosinolate plasticity in response to soil. In addition, glucosinolate composition, but not quantity, of field-grown plants could be accurately predicted from measurements from greenhouse-grown plants. In summary, soil alone is sufficient to cause plasticity of baseline glucosinolate levels in natural plant populations, which may have implications for the evolution of this important trait across complex landscapes.

plant biology↗

bioRxiv2020

The evolution of sex is tempered by costly hybridization in Boechera (rock cress)

Even after decades of research, the evolution of sex remains an enigma in evolutionary biology. Typically, research addresses the costs of sex and asexuality to characterize the circumstances in which one reproductive system is more favorable. Yet surprisingly few studies address the influence of common traits that are obligately correlated with asexuality, including hybridization and polyploidy; even though these traits have substantial impacts on selective patterns. In particular, hybridization is well-known to alter trait expression; these alterations may themselves represent a cost of sex. We examined the role of reproductive isolation in the formation of de novo hybrid lineages between two widespread species in the ecological model system Boechera. Of 664 crosses between Boechera stricta and Boechera retrofracta, 17% of crosses produced F1 fruits. This suggests that postmating prezygotic barriers, i.e. pollen-pistil interactions, form the major barrier to hybrid success in this system. These interactions are asymmetrical, with 110 F1 fruits produced when B. stricta was the maternal parent. This asymmetry was confirmed using a chloroplast phylogeny of wild-collected B. stricta, B. retrofracta, and hybrids, which showed that most hybrids have a B. stricta chloroplast haplotype. We next compared fitness of F2 hybrids and selfed parental B. stricta lines, finding that F2 fitness was reduced by substantial hybrid sterility. Our results suggest that multiple reproductively isolating barriers likely influence the formation and fitness of hybrid lineages in the wild, and that these costs of hybridization likely have profound impacts on the costs of sex in the natural environment.

evolutionary biology↗

bioRxiv2019

Identifying the fitness consequences of sex in complex natural environments

In the natural world, sex prevails, despite its costs. While much effort has been dedicated to identifying the intrinsic costs of sex (e.g. the cost of males), few studies have identified the ecological fitness consequences of sex. Furthermore, correlated biological traits that differ between sexuals and asexuals may alter these costs, or even render the typical costs of sex irrelevant. Here we use a large-scale transplant experiment of a North American wildflower to show that sex is associated with reduced lifetime fitness, despite lower herbivory. We separate the effects of sex from hybridity, finding that over-winter survival is elevated in asexuals regardless of hybridity, but herbivores target hybrid asexuals. Survival is lowest in homozygous sexual lineages, implicating inbreeding depression as a cost of sex. Our results show that the consequences of sex are shaped by complex natural environments, correlated traits, and the identity of mates, rather than sex itself.

ecology↗

bioRxiv2017

Plasticity Of Plant Defense And Its Evolutionary Implications In Wild Populations Of Boechera stricta

Phenotypic plasticity is thought to impact evolutionary trajectories by shifting trait values in a direction that is either favored by natural selection (\"adaptive plasticity\") or disfavored (\"nonadaptive\" plasticity). However, it is unclear how commonly each of these types of plasticity occurs in natural populations. To answer this question, we measured glucosinolate defensive chemistry and reproductive fitness in over 1,500 individuals of the wild perennial mustard Boechera stricta, planted in four common gardens across central Idaho, USA. Glucosinolate profiles--including total glucosinolate quantity as well as the relative abundances and overall diversity of different compounds--were strongly plastic both among habitats and within habitats. Patterns of glucosinolate plasticity varied greatly among genotypes. More often than expected by chance, glucosinolate profiles shifted in a direction that matched the direction of natural selection, indicating that plasticity among habitats tended to increase relative fitness. In contrast, we found no evidence for within-habitat selection on glucosinolate reaction norm slopes (i.e., plasticity along a continuous environmental gradient). Together, our results indicate that glucosinolate plasticity may improve the ability of B. stricta populations to persist after migration to new habitats.

evolutionary biology↗