Abstract
Understanding species' responses to environmental change underpins our abilities to make predictions on future biodiversity under any range of scenarios. In spite of the huge biodiversity in most ecosystems, a model species approach is often taken in environmental studies. To date, we still do not know how many species we need to study to input into models and inform on ecosystem‐level responses to change. In this study, we tested current paradigms on factors setting thermal limits by investigating the acute warming response of six Antarctic marine invertebrates: a crustacean Paraceradocus miersi, a brachiopod Liothyrella uva, two bivalve molluscs, Laternula elliptica, Aequiyoldia eightsii, a gastropod mollusc Marseniopsis mollis and an echinoderm Cucumaria georgiana. Each species was warmed at the rate of 1 °C h−1 and taken to the same physiological end point (just prior to heat coma). Their molecular responses were evaluated using complementary metabolomics and transcriptomics approaches with the aim of discovering the underlying mechanisms of their resilience or sensitivity to warming. The responses were species‐specific; only two showed accumulation of anaerobic end products and three exhibited the classical heat shock response with expression of HSP70 transcripts. These diverse cellular measures did not directly correlate with resilience to heat stress and suggested that each species may have a different critical point of failure. Thus, one unifying molecular mechanism underpinning response to warming could not be assigned, and no overarching paradigm was supported. This biodiversity in response makes future ecosystems predictions extremely challenging, as we clearly need to develop a macrophysiology‐type approach to cellular evaluations of the environmental stress response, studying a range of well‐rationalized members from different community levels and of different phylogenetic origins rather than extrapolating from one or two arbitrary model species.
Highlights
Predicting climate change effects at the ecosystem level is complex and fraught with difficulty
The six species used in experimental work (P. miersi, L. uva, L. elliptica, A. eightsii, M. mollis and C. georgiana) were chosen because they demonstrated a wide range of thermal tolerances in their upper lethal temperatures (ULT) at a warming rate of 1 °C hÀ1 (Peck, pers. obs.) (Table 1)
All species were collected from the same site, tested in the same week and subjected to the same ramping of temperature, with each animal being sampled when they were just below the level of being unresponsive and below their ULT, using ULT trials conducted in 2012 as a guideline (Peck, pers. comm.) (Fig. 1)
Summary
Predicting climate change effects at the ecosystem level is complex and fraught with difficulty. Identifying the factors that lie behind the sensitivity or resilience of a range of species to changing conditions enables the extrapolation of those results to other less well-characterized species (i.e. applying a macrophysiological approach) and improves our One approach to this problem is to use experimental manipulation of thermal tolerances using ramping assays. These are proving effective at predicting future thermal tolerances, even though these are very short term relative to the rate of climate change (Peck et al, 2009; Terblanche et al, 2011) They provide an estimate of the relative sensitivities of different species to a particular environmental stress (Peck et al, 2009; Buckley & Kingsolver, 2012). These types of experiments are useful for those species where long-term husbandry is not known, which
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