EAGER: Evaluating a drought-driven hypothesis for the origin of obligate apomixis

University Of Minnesota Duluth, Duluth MN

Investigators

Abstract

Obligate apomixis—asexual reproduction by seed, spore, or egg—has evolved repeatedly across the tree of life, in diverse organisms ranging from animals (such as reptiles, insects, and fishes) to angiosperms (flowering plants) and other vascular plants. Despite its many origins, and intriguing ecological and evolutionary parallels among them, little is known regarding the causes and long-term consequences of this heritable reproductive syndrome. Some recent studies have proposed that drought, or periodic water limitation, could be key to driving the repeated evolution of obligate apomixis. This project unites environmental, developmental, and evolutionary data to evaluate the drought hypothesis, leveraging ferns as a model system. Ferns are ideal for this work because observing meiosis (i.e., the specialized cell division that produces spores/gametes) is easy and efficient compared to other organisms. Additionally, this study bridges generational gaps in technical expertise among next-generation researchers for a variety of cutting-edge and classical approaches; it stimulates interdisciplinary undergraduate, graduate, and postdoctoral research, emphasizing the value and relevance of museum specimens for addressing fundamental biological questions; and it expands international scientific collaborations in Mexico and Latin America. Furthermore, because obligate apomixis is highly coveted for, yet recalcitrant to, use in agricultural applications (as a tool for stabilizing optimal genotypes), this study has the potential to yield valuable insights with practical implications for humanity, especially regarding medicine and global food production. This research combines genetic, spatial, environmental, and life history data, across multiple evolutionary and ecological scales, for around 47 species comprising Myriopteris Fée, a well-supported clade in the fern subfamily Cheilanthoideae (Pteridaceae). Preliminary data are integrated with newly-gathered observations of reproductive traits (karyotype, gametophyte development, and spore size/number), climate and microhabitat, and a fully-sampled, time-calibrated phylogeny to rigorously interrogate the relationship between drought and the evolution of obligate apomixis. Specifically, these results are leveraged to address three main questions: Does phylogenetic inertia shape the distribution of obligate apomixis, or associated traits, within the focal clade? Does macroecological niche predict obligate apomixis among deserts of North America, including the Chihuahuan, Sonoran, and Mojave? And, is microhabitat significantly associated with obligate apomixis or its constituent traits across the focal clade? Importantly, this work also serves to resolve complex evolutionary relationships among diverse, previously undescribed, hybrid and polyploid lineages within Myriopteris. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.