Fig 1.
Percentage of plots where the grazer E. niger and the brown algae L. spicata and D. antarctica were recorded at four sites present in northern Chile.
Sites: LIMA: Limarí (30°45’S-71°42’W); PTAL: Punta Talca (30°55’S-71°40’W); POSC: Puerto Oscuro (31°25’S-71°36’W); HUEN: Huentelauquén (31°38’S-71°33’W).
Fig 2.
Average density (± SEM) of juvenile (small recruits from 3.0 to 25 cm frond length) and adult plants (longer than 25–30 cm) of (a) Lessonia spicata (b), Durvillaea antarctica and of the grazer (c) Enoplochiton niger, recorded through the study in the experimental platform (un-manipulated areas) at Punta Talca.
Table 1.
Summary of Moran´s I autocorrelation at lag 1 (0–120 cm) (a) of E. niger, juvenile and adult individuals of D. antarctica and L. spicata, ephemeral and crustose algae during summer and winter and (b) Pearson spatial correlation (r) between densities of E. niger and algae functional groups recorded in the experimental platform.
Modified t-tests were performed to determine significant differences in the herbivore-alga spatial correlation. Degrees of freedom and P-values were adjusted by presence of spatial autocorrelation in the data set (Dutilleul`s correction). Significance is indicated as P < 0.05*, P < 0.01** after random permutation test (1000 permutations).
Fig 3.
Monthly mean cover (±SE) of (a) bare rock; (b) ephemeral/opportunistic algae (i.e. Ulva rigida, U. compressa, Pyropia sp, Hincskia sp. Polysiphonia sp, ceramials) (c) Lessonia spicata and (d) crustose algae (i.e. encrusting coralline algae, Hildenbrandia lecanelleri) found inside experimental plots at Punta Talca.
Fig 4.
Strength of the interaction between the grazer E. niger and algae measured as the grazer capacity to influence the recruitment of algae and bare rock production during early succession.
Average per capita (a and b) and population (c and d) effect of Enoplochiton niger, on mean (a and c) and variance (considered as ‘effect size’) (b and d) of percent cover of bare rock, and ephemeral and crustose algae at the study site in Punta Talca. Bars are 95% confidence intervals estimated through a bootstrapping procedure. Inserts in b and d correspond to per capita effects on mean and variance cover, respectively, of E. niger on D. antarctica plantlets fronds growth and total biomass evaluated with plantlets transplant in the field experiments 2. Hatched bars in b) correspond to the collective effect of grazers measured in control treatment on variance of algae.
Fig 5.
Temporal variation of the interaction between the grazer E. niger and algae and bare rock production recorded in the field experiments.
Per capita effects of E. niger on spatial variance of bare rock, ephemeral and crustose algae recorded at different times of the experiment 1 (see text for details). Collective effects of all herbviores present in the study sites (recorded in open areas) are also presented (crossed black diamonds). Bars are 95% confidence intervals estimated through a bootstrapping procedure.
Fig 6.
Expected population-level effect of E. niger on spatial variation (effect size) of bare space distribution across different sites where the grazer and algae species overlap.
Local densities of E. niger and per capita effects recorded in field experiments in Punta Talca were used to calculate populational effects (see text for details).