Positive effects of larval quality on early barnacle recruitment through adaptive substrate selection

Abstract

Variation in larval supply alone often fails to explain recruitment dynamics in marine benthic populations, suggesting that larval traits may influence settlement success. We tested whether larval quality influences habitat selection and recruitment in the intertidal barnacle Chthamalus bisinuatus. Over a 26-day field sampling, we found no correlation between larval supply and settlement rates on experimental arenas featuring varying microtopographies. Instead, recruitment dynamics tracked changes in larval quality. Early settlement was primarily driven by low-quality larvae, consistent with the "desperate larva hypothesis", whereas later recruitment was characterized by high-quality larvae. Cyprids generally preferred rugose over smooth surfaces, but substrate selectivity depended on larval condition and disappeared after biofilm development. Early benthic performance indicated adaptive habitat selection, with higher survival and larger recruits on rugose surfaces. These findings identify larval quality as a key driver of settlement, shaping recruitment patterns and should be incorporated into ecological models of marine population connectivity.