5 Algal Diversity and Relationships

Ecologists worldwide are greatly concerned about changes in species diversity arising from global climate change, nutrient pollution of aquatic ecosystems, and other large-scale human disturbances (Chapin et al. 2000). Change in algal species diversity is a concern because many algal species play essential roles in global biogeochemistry, biotic associations, and human technology (see Chapters 2–4). Learning more about these roles and understanding how algal communities respond to environmental change are thus important challenges for phycologists. Another major goal is cataloging species diversity, an activity that has led to the discovery of many new algal species. Many phycologists study the pattern and process of algal evolution by evaluating degrees of relationship among species and their genomes. Measuring levels of genetic variation within algal populations and detecting toxic algal species in natural waters are also active fields of investigation. This chapter provides an overview of algal taxonomy and systematics—the ways in which algal species are identified, named, and grouped by relationship—with an emphasis on the use of molecular methods.