Unexplored dimensions of variability in vegetative desiccation tolerance.

Desiccation tolerance has evolved recurrently across diverse land plant lineages as an adaptation for survival in regions where seasonal rainfall drives periodic drying of vegetative tissues. Growing interest in this phenomenon has fueled recent physiological, biochemical, and genomic insights into the mechanistic basis of desiccation tolerance. Although, desiccation tolerance is often viewed as binary and monolithic, substantial variation exists in the phenotype and underlying mechanisms across diverse lineages, heterogeneous populations, and throughout the development of individual plants. Most studies have focused on conserved responses in a subset desiccation-tolerant plants under laboratory conditions. Consequently, the variability and natural diversity of desiccation-tolerant phenotypes remains largely uncharacterized. Here, we discuss the natural variation in desiccation tolerance and argue that leveraging this diversity can improve our mechanistic understanding of desiccation tolerance. We summarize information collected from ~600 desiccation-tolerant land plants and discuss the taxonomic distribution and physiology of desiccation responses. We point out the need to quantify natural diversity of desiccation tolerance on three scales: variation across divergent lineages, intraspecific variation across populations, and variation across tissues and life stages of an individual plant. We conclude that this variability should be accounted for in experimental designs and can be leveraged for deeper insights into the intricacies of desiccation tolerance.

Water stress tolerance tracks environmental exposure and exhibits a fluctuating sexual dimorphism in a tropical liverwort.

Water shortage events negatively impact plant productivity, threaten ecosystem functioning, and are predicted to increase dramatically in the coming years. Consequently, building a detailed understanding of how plants respond to water stress is critical for improving predictions of ecological processes and species range shifts under climate change. Here, we characterized patterns of intraspecific variation in dehydration tolerance (DhT, also dehydration tolerant) across a variable landscape in the tropical plant, Marchantia inflexa. DhT enables tissues to survive substantial drying (below an absolute water content of - 10 MPa) and despite the ecological significance of DhT, many questions remain. We tested if DhT was correlated with an environmental exposure gradient, if male and female plants had contrasting DhT phenotypes, and if variation in DhT had a genetic component. To do so, we collected plants from five populations, spanning an environmental exposure gradient in the forests of northern Trinidad, Republic of Trinidad and Tobago. We measured DhT immediately after collection, and after growing plants for ~ 1 year in a common garden. We found that DhT varied significantly among populations and tracked the characterized exposure gradient. Additionally, we showed that phenotypic differences among populations in DhT were maintained in the common garden, suggesting that underlying genetic differences contribute to DhT variability. Finally, we detected a fluctuating sexual dimorphism where males had lower DhT than females in less exposed sites, but not in more exposed sites. Interestingly, this fluctuating sexual dimorphism in DhT was driven primarily by male variation (females exhibited similar DhT across sites).

The impact of asexual and sexual reproduction in spatial genetic structure within and between populations of the dioecious plant Marchantia inflexa (Marchantiaceae).

Background and Aims: In dioecious plants, sexual reproduction requires close proximity to potential mates, but clonal growth can increase this distance and, therefore, reduce the probability of mating. Reduction in sexual propagules can lead to decreased dispersal and gene flow between populations. Gene flow and clonal growth may be further influenced by the size of the habitat patch. The effects of habitat size and reproductive mode (sexual or asexual reproduction) on spatial genetic structure and segregation of the sexes were tested by quantifying the distributions of genotypes and the sexes using the dioecious liverwort Marchantia inflexa. Methods: Plants were sampled from five pairs of small-large habitat patches to identify within- and among-population spatial genetic structure using 12 microsatellite markers. Spatial distributions were calculated as the likelihood that pairs of individuals were the same sex or genotype, and it was determined how that likelihood was affected by habitat patch size (small/large). Key Results: Asexual reproduction dominates within populations, and asexual dispersal also occurred across populations. Spatial segregation of the sexes was observed within populations; males were more likely to be near individuals of the same sex than were females. Although the likelihood of both sexes being near members of the same sex was similarly greater on small habitat patches, on large habitat patches male genotypes were almost 15 % more likely to be near clonemates than were female genotypes. Conclusions: The results show a sex difference in clonal clumping that was dependent upon habitat size, suggesting differential colonization and/or survival between males and females. The sexes and genotypes being structured differently within and among populations have implications for the persistence of populations and the interactions between them. This study demonstrates that studying only the sexes and not their genotypes (or vice versa) can limit our understanding of the extent to which reproductive modes (sexual or asexual) influence genetic structure both within and between populations.