HNSE-O3-2. Third-Generation Metrosideros Germination Trials: The Effects of Homozygosity and Inbreeding Depression in Metrosideros polymorpha
Faculty Mentor: Elizabeth Stacy, Ph.D.3
1College of Sciences, Department of Chemistry and Biochemistry
2College of Sciences, Department of Physics and Astronomy
3College of Sciences, School of Life Sciences
Metrosideros polymorpha is a widely dispersed, pioneering tree species endemic to the main islands of Hawaii. The vast variation of the Hawaiian landscape has fostered the phenotypic plasticity of this species to adaptively specialize to thrive within its environmental niches thus producing distinct varieties of form in differing stages of incipient radiation. The geographical isolation of specialized phenotypic forms encourages the use of self-pollination as members of the population no longer need to overcome prezygotic barriers or distance. However, self-pollination has been seen to be detrimental to fitness as it may lead to the expression of deleterious recessive traits resulting in an inbreeding depression within the population. Increased homozygosity has been observed to lead to reduced survival and fertility of the offspring. These concepts are evaluated in a third-generation Metrosideros model through a survey of the effects of inbreeding depression and self pollination within the germinal and embryonic development stages relative to the out-crossed offspring. Each sample cross was plated on water-saturated Whatman filter paper in a petri dish and irradiated under a full-spectrum LED light for 12-hour light cycles during a six-week germination trial period. The number of filled embryonic seeds and germinants grown of each sample was visually assessed using a dissecting microscope. As the underlying driving forces of divergence and speciation amongst tree species are poorly understood, this model seeks to provide insight into the potential postzygotic reproductive isolating barriers and challenges in fitness that offspring may face in development due to increased homozygosity and inbreeding depression.