Abundance of Tesseropora rosea at the margins of its biogeographic range is closely linked to recruitment, but not fecundity

摘要

For benthic marine invertebrates with planktonic larvae, adult abundance at the species' range limit may depend on local fecundity, and recruitment from central, source populations. We tested the importance of these processes using a hierarchical design at multiple spatial scales (from tens to hundreds of kilometres) to assess relationships between patterns of adult abundance, fecundity and recruitment in the rocky intertidal barnacle Tesseropora rosea, approaching its geographical range limit on the southeast coast of Australia. Across the 600 km region, adult abundance, recruitment and fecundity all declined towards the range limit, but only adult abundance and recruitment were positively correlated, suggesting that recruitment is negatively affected at the range limit and that recruitment plays a significant role in setting the geographical patterns of abundance of T. rosea. In contrast, at smaller spatial scales within this region, adult abundance and recruitment varied by up to 15- and 100-fold, respectively, among some locations only tens of kilometres apart, and no obvious patterns in adult-recruit relationships were revealed towards the range limit. Local patterns of abundance and life-cycle relationships do not, therefore, translate to biogeographic scales, but investigation at this multitude of spatial scales helps to identify the defining processes that account for spatial variation and determine population structure towards the range limits of benthic marine invertebrates.