Evolutionary pressures on planktonic production of atmospheric sulphur

Abstract

Dimethylsulphide (DMS), produced by marine phytoplankton^1–5, has been proposed as the major source of cloud condensation nuclei (CCN) in the remote marine atmosphere, and as an important factor in global climate¹. Charlson et al.¹ suggested that climate modulation and altruism may have been significant factors in the evolution of DMS production by marine phytoplankton. These proposals have led to a re-examination of the relationship between the Earth's biota and climate^6–11. Calculations of relative evolutionary pressure in models of individual selection¹² and group selection^13–17 suggest that neither climate modulation nor altruism could have been the primary factors in the evolution of mid-ocean DMS production. Although a DMS/climate feedback loop may have a role in modulating fluctuations in the Earth's climate^1,11, the explanation for mid-ocean DMS production can be found primarily in selection based on local interactions, for example, osmoregulation^2,5, and not in evolutionary feedbacks from proposed climate modulation.