Associate Professor
Email: aksakai@uci.edu

My research interests are in plant population biology (particularly in the evolution of plant breeding systems), and in conservation biology. Most plants are hermaphroditic, and I am interested in what factors might cause the evolution of separate sexes (dioecy) to arise independently so many times. In collaboration with Stephen G. Weller (UC-Irvine), I am using a multi-disciplinary approach to study the Hawaiian endemic Alsinoideae (Schiedea and Alsinidendron; Caryophyllaceae) as a model system in the evolution of plant breeding systems. This group is a monophyletic lineage with 33 species that have undergone spectacular radiation, with rainforest vines, dry shrubland shrubs, and coastal as well as subalpine herbs. This lineage also exhibits a range of breeding systems, and many of these breeding systems appear to be unstable and in the process of evolving new breeding systems. Investigators in our lab have estimated inbreeding depression levels, measured selfing rates using allozymes as genetic markers, taken phenotypic measures of resource allocation, and conducted field work on habitat partitioning and pollinator shifts to identify factors important in the evolution of dioecy. Using a phylogeny based on morphological and molecular characters, our studies suggest that high levels of inbreeding depression in combination with high selfing rates have been important in the evolution of dioecy. We are continuing collaborative work with Todd Dawson (UC-Berkeley) to conduct field and lab studies of physiological changes in Schiedea with habitat and gender shifts, analyzing data in a phylogenetic context. A major emphasis in our lab is now a quantitative genetics study in collaboration with Diane Campbell (UC-Irvine) investigating the genetic potential for gender shifts through artificial selection experiments. For more detailed information, please see selected references.

A second line of research interests is in conservation biology, particularly the biology of invasive species.   Using a database of ecological traits, Warren L. Wagner (Smithsonian Institution) and I are examining ecological correlates of taxa at risk in the native flowering plants of Hawaii for use in conservation and management of this unique flora. Stephen Weller and I are also involved in conservation and restoration efforts of several endangered Schiedea species.  We have organized the Collaboratory on the Population Biology of Invasive Species, a working group funded by the National Science Foundation to facilitate integration of concepts from population biology with the more applied needs of managers. Undergraduates and graduate students in the combined Sakai-Weller lab have worked on evolution of plant breeding systems of Hawaiian Schiedea and California natives (Fragaria, and Nemophila) as well as aspects of conservation biology, including the population biology of invasive species in California.