Early life-history processes and their implications for the invasion of the barnacle Balanus glandula

ABSTRACT

As invasions become increasingly prevalent, it is important to understand how spread may be moderated by environmental conditions. This study considered the effect of location and changing substratum temperature on the early life-history processes of the alien barnacle Balanus glandula and its native comparator, Chthamalus dentatus, along the South African coast. Using settlement plates of different colours, temperature was manipulated to assess settlement, mortality, recruitment and growth of the two species. These variables were tracked over 10 weeks using repeat photography. Unexpectedly, there was no evidence of an effect of temperature on early life-history processes of either species. Settlement by the two barnacles was spatially segregated, with B. glandula occurring only on the West Coast where it is the dominant intertidal barnacle, while C. dentatus settled only on the South Coast, which has only recently been invaded by the alien. Despite this, it was notable that the relative settlement of B. glandula on rock was higher than that of C. dentatus. However, the lack of mortality of the native resulted in comparable levels of recruitment among the species. Nonetheless, the propensity of B. glandula to settle sporadically, coupled with fast growth, suggests that the invader may still possess the ability to become dominant along the newly invaded South Coast. This study highlights that measurements of early life-history parameters may not adequately predict the future range and impacts of alien species unless interpreted within the broader context of the nature of the recipient region and species-specific traits of the invader.

RESPONSIBLE EDITOR:

• David Thieltges

KEYWORDS:

• Cthamalus dentatus
• invasion
• South Africa
• spread
• survival
• temperature

Acknowledgements

The following people are thanked for help with fieldwork: Koebraa Peters-Abbas, Lona Mjindi, Cherusha Swart, Saachi Sadchatheeswaran, Ben Brooker, Michelle Jooste, Jonathan Jonkers, Jeff, Gala and Chandler Pope, and Dylan Miree. Tracey Weissgerber and colleagues are acknowledged for their freely available template for creating univariate scatterplots which was used for Figure 4. Three anonymous reviewers are thanked for their comments on an earlier version of this paper.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The fieldwork for this project was funded by a core team member grant from the DST–NRF Centre of Excellence for Invasion Biology to T. Robinson. M. Alexander gratefully acknowledges bursary funding from the same source.