Updated digital distribution maps were created for each species
based on refinement of existing maps (Green and Short,
2003; UNEP-WCMC, 2010), with bioregions defined by Short
et al. (2007). Each species’ geographic range map was extended
to 100 km from shore for cartographic purposes; range maps
were then overlaid to illustrate species richness. For Data Deficient
species, complete distributional limits were not available;
these species were not included in species richness and population
trends. The population trend for each seagrass species was
calculated based on data from published studies, the Global Seagrass
Trajectories Database (Waycott et al., 2009; NCEAS, 2006)and expert opinion. To examine the relationship between seagrass
species traits and extinction risk, significant differences in
distribution size, maximum depth, depth range and recruitment
rate among seagrass species in threatened (Endangered and Vulnerable),
Near Threatened and Least Concern categories were
determined based on independent t-tests and Kruskall–Wallace
Chi-square tests, or Mann Whitney Wilcoxon tests. In summary,
it was hypothesized that species with smaller distributions,
shallower or more narrow depth ranges, and longer recruitment
rates were more likely meet the criteria for threatened
categories.