Thibault, Cynthia; Massamba-N'siala, Gloria; Noisette, Fanny; Vermandele, Fanny; Babin, Mathieu; Calosi, Piero (2018): Supplementary material on within- and trans-generational responses to combined global changes in two congeneric species of marine annelids [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.896395

The extent of species' geographical distribution can help us define their sensitivity to environmental challenges. Rare species are expected to have narrower tolerance windows and reduced plasticity compared to their common relatives. Assessing rare species' tolerance and plasticity under environmental changes will thus help predicting future changes in the structure and functions of ecosystems. We examined the level of tolerance and transgenerational responses of life-history and physiological traits in a rare (Ophryotrocha robusta) and common (Ophryptrocha japonica) marine polychaete species exposed over two generations to ocean acidification (OA: pH -0.5) and warming (OW: + 4 °C) in isolation and combined (OAW: + 4 °C, pH -0.5). Life history traits (growth, fecundity and eggs volume) were measured on a four months period, after which metabolomics profiles were analysed to highlight molecular pattern (energetic metabolism) linked to life history traits' changes. In the rare species, warming scenarios (OW and OAW) led to a decrease in energy production together with an increase in energy requirements, which were shortly lethal before viable offspring could be produced at the first generation. Under OA conditions, the rare species was able to reach the second generation, despite showing lower survival and reproductive performance when compared to control conditions. This was accompanied by a marked increase in fecundity and eggs volume in F2 females, suggesting higher capacity for transgenerational plasticity. Differently, the common species thrived under all scenarios across both generations, by maintaining fitness levels via adjusting its metabolic profile. Overall, whilst the rare species shows greater capacity to plastically adjust its life history responses after two generations under OA, it is not able to cope with future warming conditions due to lower tolerance to heat. If our results are to apply more broadly, given that rare species are most represented across taxa, and possess key ecological roles, our results support the idea that global changes will lead to an important loss in both specific and functional diversity in marine ecosystems.