CAREER: At The Convergence of Life Cycles and Reproduction: Insights Into the Diversity of Life

University Of Alabama At Birmingham, Birmingham AL

Investigators

Abstract

This award is funded in part under the American Rescue Plan Act of 2021 (Public Law 117-2). In addition, this project is funded by the Division of Environmental Biology and the Established Program to Stimulate Competitive Research (EPSCoR). All multicellular organisms pass through different stages in their life cycle. These stages may differ in the number of cells, the number of chromosomes per cell, or the arrangement of genetic information on the chromosomes. For example, humans have two life stages: the haploid stage consists of eggs or sperm, and the diploid stage extends from embryo to adult. These alternating stages make a life cycle. Across the natural world, there is an amazing diversity in the duration and complexity of life cycles. This project will expand our understanding of this diversity by linking predictions about life cycles and reproductive variation. Understanding the convergence of these two fundamental organismal traits – the life cycle and reproduction – is crucial for predicting how species are likely to respond to environmental challenges. Common garden experiments and DNA analysis of a widespread seaweed will allow the investigators to explore these connections. The research plan is enhanced by a month-long field course for undergraduates, in which students learn about algae in marine and freshwater ecosystems. Students in this course also collect data for the two main research aims. In addition, research is coordinated with the Alabama Water Watch and the Cahaba River Society. Coordination with these groups increases scientific and environmental literacy in Birmingham and across Alabama. The researchers leverage a widespread seaweed that has become invasive where it has been introduced in the Northern Hemisphere. Upon invasion, the diploid stage predominates. The project investigates how the life cycle of this alga has responded to the process of invasion, thus permitting a test of the connections between life cycles and reproduction. Two sets of experiments address two major questions. The first set of experiments distinguish between predictions of ecological and genetic models. Here, researchers carry out common garden experiments to reveal how different genotypes respond to environmental conditions important to an intertidal alga, such as salinity and temperature. According to ecological predictions, the two life stages should respond differently. The second set of experiments evaluates how the relative length of the diploid and haploid stages affect the reproductive system. To investigate this question, DNA is sampled from natural populations of the seaweed’s native and introduced range. Population genetic analysis determines whether a prolonged haploid stage affects seaweed reproduction. Specifically, it can detect whether the seaweeds mate by outcrossing, self-fertilization or asexual propagation, and whether this reproductive strategy varies depending on the different type of life cycle. Together, the results of these experiments provide unique insight into the ways in which life cycles and reproductive strategies are interdependent. 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.