On the need to consider multiphasic sensitivity of marine organisms to climate change: a case study of the Antarctic acorn barnacle

Abstract

Aim Species distribution models (SDMs) are routinely employed to evaluate shifts in the geographic distributions of organisms in response to changing climatic conditions. Many marine invertebrates exhibit a biphasic life cycle: benthic adults and planktonic larvae, which inhabit different environments and may react dissimilarly to anticipated changes in climatological patterns. To date, SDMs applied to benthic species have only considered adult life-history stages. Here, we present the first study in which SDMs have been simultaneously developed for both the larval and adult stages of the same organism. Location The Southern Ocean. Methods Occurrence data for the study species, the Antarctic barnacle Bathylasma corolliforme, were sourced from: (1) benthic geo-referenced records from museum collections and online databases; and (2) observations of planktonic larvae identified with genetic and morphological methods. These records were used to construct two independent SDMs (adult-larvae) with Maxent 3.3.3k; their outputs were then projected to environmental conditions forecast for the year 2050 (IPCC scenario A1B). Results The two different SDMs had high predictive capability and identified preferred environmental conditions of each life-history stage. For the projected 2050 climate change scenario, SDMs predicted that the extent of environmentally suitable areas of both life-history stages was reduced, with planktonic larvae experiencing greater reductions and latitudinal displacement of their suitable areas. Main conclusions For multiphasic species, considering only a single life-history stage while studying distribution shifts may lead to erroneous conclusions for the species as a whole, regardless of the predictive capability of models employed. Ignoring the changes in suitable areas for larval stages can lead to underestimation of habitat reduction, distribution shifts, effects on population connectivity and potential for colonization of newly available habitats.