The positive effects of an intertidal ecosystem engineer are weaker in its invaded range

HARLEY CDG; SCHWINDT E

Vancouver

Congreso; Eight International Conference on Marine Bioinvasions; 2013

UBC

Invasive species are frequently assumed to have stronger ecological impacts in their invaded ranges, where their specific traits and ecological functions may be novel, than in their native ranges, where they have co-evolved with the rest of the community. Although much attention has been devoted to negative interactions such as competition and predation, less attention has focused on the relative strength of positive interactions between native and invaded ranges. We tested the effects of an important ecosystem engineer, the acorn barnacle Balanus glandula, on high intertidal communities in its native range in British Columbia, Canada, and in its invaded range in Chubut province, Argentina. Both regions support herbivorous limpets (true limpets in BC, pulmonate limpets in Argentina), ephemeral algae, and perennial algae. However, no mid- to high-intertidal barnacle existed in Chubut prior to the introduction of B. glandula. In both regions, B. glandula facilitated ephemeral algae, and limpets were able to reduce ephemeral algal cover in plots with and without barnacles. However, some of the strong positive effects of B. glandula in its native range, such as facilitation of herbivore abundance and perennial algal cover, were neutral in its invaded range. Although there was no identifiable negative effect of B. glandula on the taxa we investigated in Argentina, the overall facilitative effects of B. glandula were weaker in its invaded range, suggesting that the strength of facilitative relationships such as ecosystem engineering may also have some basis in coevolutionary history.