MEPS 610:109-123 (2019)  -  DOI: https://doi.org/10.3354/meps12832

ABSTRACT: Climate may influence biogeography through effects on adult survival and reproductive success. The acorn barnacle Semibalanus balanoides is the most widespread intertidal barnacle in the Northern Hemisphere. At its southernmost European distribution limit in northwestern Iberia (Galicia, northwestern Spain), winter temperatures are close to the thermal limit for penis development, and it is expected that a temperature increase would acutely reduce reproductive success. We studied the effect of temperature on penis development in the laboratory and related the results to field data to estimate fertilization probabilities at different temperatures and population densities. Exposure to colder water temperatures (14 and 17°C) allowed full penis development, but this was inhibited at warmer temperatures (20 and 23°C). Penis annulations and penis length were greater in barnacles exposed to colder water treatments than in those held at warmer temperatures. In the laboratory experiments, fertilization probability was higher at the lowest temperature (~100%). In the field, fertilization probability was higher in the localities with colder temperature as well as those with higher barnacle density. The results support the prediction that rising temperatures will likely reduce reproductive success of S. balanoides at its southernmost distribution limit through failure in fertilization. If similar mechanisms apply in other boreal species, climate change may shrink distribution ranges through large-scale reproductive failures at the southern limits.

KEY WORDS: Climate change · Temperature · Reproduction · Penis development · Fertilization success · Barnacles · Semibalanus balanoides