RESUMEN
Full-subsets information theoretic approaches are becoming an increasingly popular tool for exploring predictive power and variable importance where a wide range of candidate predictors are being considered. Here, we describe a simple function in the statistical programming language R that can be used to construct, fit, and compare a complete model set of possible ecological or environmental predictors, given a response variable of interest and a starting generalized additive (mixed) model fit. Main advantages include not requiring a complete model to be fit as the starting point for candidate model set construction (meaning that a greater number of predictors can potentially be explored than might be available through functions such as dredge); model sets that include interactions between factors and continuous nonlinear predictors; and automatic removal of models with correlated predictors (based on a user defined criterion for exclusion). The function takes continuous predictors, which are fitted using smoothers via either gam, gamm (mgcv) or gamm4, as well as factor variables which are included on their own or as two-level interaction terms within the gam smooth (via use of the "by" argument), or with themselves. The function allows any model to be constructed and used as a null model, and takes a range of arguments that allow control over the model set being constructed, including specifying cyclic and linear continuous predictors, specification of the smoothing algorithm used, and the maximum complexity allowed for smooth terms. The use of the function is demonstrated via case studies that highlight how appropriate model sets can be easily constructed and the broader utility of the approach for exploratory ecology.
RESUMEN
The early post-settlement stage is the most sensitive during the life history of reef building corals. However, few studies have examined the factors that influence coral mortality during this period. Here, the impact of fouling on the survival of newly settled coral spat of Acropora millepora was investigated by manipulating the extent of fouling cover on settlement tiles using non-toxic, wax antifouling coatings. Survival of spat on coated tiles was double that on control tiles. Moreover, there was a significant negative correlation between percentage cover of fouling and spat survival across all tiles types, suggesting that fouling in direct proximity to settled corals has detrimental effects on early post-settlement survival. While previous studies have shown that increased fouling negatively affects coral larval settlement and health of juvenile and adult corals, to the best of our knowledge, this is the first study to show a direct relationship between fouling and early post-settlement survival for a broadcast spawning scleractinian coral. The negative effects of fouling on this sensitive life history stage may become more pronounced in the future as coastal eutrophication increases. Our results further suggest that targeted seeding of coral spat on artificial surfaces in combination with fouling control could prove useful to improve the efficiency of sexual reproduction-based coral propagation for reef rehabilitation.