Correlates of spatial variation in settlement of two tropical damselfishes

Abstract

Settlement of two planktivorous damselfishes, Dascyllus flavicaudus and D. aruanus, was estimated for ten weeks at 21 localities around the 60 km perimeter of Moorea, French Polynesia. The species displayed distinctly different patterns of settlement. Multiple regressions were used to correlate spatial patterns of settlement with twelve variables representing biological and environmental factors that could influence colonization rates. The models explained >80% of the observed variance in colonization for each species. Two regressors entered positively into the model for D. flavicaudus: near-field current speed at the site and regional abundance (within ~3 km²) of adult conspecifics. Four regressors were included in the model for D. aruanus; one with a positive relationship – regional abundance of adult conspecifics – explained 73% of the variance. The unanticipated correlations of this variable with settlement could reflect local retention of reproductive output within a few kilometres, attraction of larvae to regions of high conspecific abundance perhaps as a response to some water-borne cue, or covariation with other, unmeasured determinants of settlement variation. The findings suggest that patterns of settlement can be shaped by multiple processes that affect differently even closely related species whose larvae are subject to the same hydrodynamic conditions.