Spatio-temporal variation of recruitment in sessile intertidal assemblages from northern Chile

In this paper we assessed temporal and spatial variation patterns of recruitment of sessile species during a 14 month period for two similar rocky intertidal assemblages in northern Chile: Chanavayita and Yape (ca. 20 degrees 41' S), which were 4 km appart. A set of experimental quadrants in each site located at three tidal levels within the mid-high intertidal zone were repeatedly denudated every 1.33 months to obtain time-independent recruitment estimates. We recorded a total of 25 and 20 species for Chanavayita and Yape respectively during the study period. Compositional similarity was lower between sites (40 +/- 10%; Jaccard's index) than within sites (more than 55%). Only three species recruited in all periods: the barnacles Jehlius cirratus (Darwin) and Norochtamalus scabrosus (Darwin) and the Chlorophyta Ulva rigida C. Agardh, which are the dominants in the adult assemblage. Community recruitment showed a seasonal pattern both at site and quadrat levels, mainly for algal species, and there was no interaction between time and tidal level. A cross-correlation analysis showed no temporal dependence between sites. At the assemblage level, recruitment decreased from low to high tidal levels, but there were opposite trends among individual species. Spatial and temporal recruitment frequencies were positively correlated in both sites. We discuss the adequacy of traditional concepts such as recruitment schedule and early and late successional species, and some predictions of the supply-side ecology frame.