Relationships between coral habitat attributes and associated species richness
Three physical attributes of finger coral habitat structure: coral status (live/dead) (p<0.0001), overhead surface area (p=0.0025) and maximum coral branch length (p=0.0005), predicted the number of species associated with the corals (Table 2). Ordinary Least Squares (OLS) regression analysis indicated that total species richness was positively and linearly related to the top surface area of the colonies, although the significance and strength of these relationships varied between live and dead corals and across time points (Figure 6). Species-area relationships were significant for live corals across all time points (Figure 6, bottom panel), whereas they were only significant for dead corals for the two latter time points (Figure 6, top panel). Surface area also explained a greater proportion of total variation in species richness for live versus dead corals (r2 = 0.26 to r2 = 0.62 versus r2 = 0.15, respectively, Figure 6). The richness of coral-associated macrofauna increased by 14-22 species per a projected 1.0 m2 increase in live coral surface area across time points, and by 18 species per a projected 1.0 m2increase in dead coral surface area (Figure 6). Tighter species-area relationships on live corals were driven by fishes (r2= 0.47 to r2 = 0.58) relative to invertebrates (r2 = 0.19 to r2 = 0.29). For dead corals, richness of associated species was poorly predicted by coral surface area for both fishes (r2 = 0.08 to r2 = 0.14) and invertebrates (r2 = 0.06 to r2 = 0.14) (Figure S4A-B).
Species richness of the associated community was also predicted by the length of live finger coral branches (Figure S5). The richness of coral-associated macrofauna increased in live corals by 8-25 species per a projected 1.0 m increase in coral branch length at three of four time points (r2 = 0.29 to r2 = 0.43). On the other hand, branch length of dead finger corals showed either a weak positive (r2 = 0.21, July 2009) or weak negative (r2 = 0.17, February 2010) relationship with species richness of the associated community (Figure S5 top panel).