Seagrasses are flowering plants and, along with mangroves, have greater affinities to terrestrial plants
than other marine macrophytes such as algae. Approximately 55 species of seagrass occur in five
different plant families and represent at least three independent evolutionary lineages. Thus,
seagrasses are not a taxonomically unified group but a ‘biological’ or ‘ecological’ group85,149. The
evolutionary adaptations required for survival in the marine environment have led to convergence
in morphology. Seagrasses evolved under differing ambient CO2 and temperature conditions
so may have different tolerances to changing environmental conditions. A wide range
of tolerances across marine environments exist amongst the extant diversity of seagrasses, reflecting
their substantial adaptive capacity as a group.This is Chapter 8 of Climate change and the Great Barrier Reef: a vulnerability assessment. The entire book can be found at http://hdl.handle.net/11017/13
