Calculating the ESS level of information transfer in aggressive communication

Summary We present a model of aggressive communication that demonstrates the use of evolutionarily stable ambiguous threat displays. We use stochastic dynamic programming to solve a game in which two contestants of differing fighting ability communicate using cost-free threats. These contestants use communication strategies that supply information of varying reliability to the opponent. The results demonstrate that communication does not need to be either costly or unambiguous to be evolutionarily stable.     

On the estimation of minimum mechanical loss during an in situ biogenic silica dissolution experiment

Maximum dissolution rates of biogenic silica as a function of depth in the ocean were calculated as a function of the variables temperature, pH, dissolved silicon concentration, and the measured surface area of radiolarian skeletons of a single species. These rates when compared with observed weight losses during an in situ dissolution experiment suggest a mechanical weight loss of about 50%. The relationship between mechanical weight loss and total weight loss is linear, suggesting the usefulness of this mathematical approach to dissolution experiments as well as the need for caution in trying to apply such loss data directly to the environment.     

Effects of multiple drivers of ocean global change on the physiology and functional gene expression of the coccolithophore Emiliania huxleyi

Ongoing ocean global change due to anthropogenic activities is causing multiple chemical and physical seawater properties to change simultaneously, which may affect the physiology of marine phytoplankton. The coccolithophore Emiliania huxleyi is a model species often employed in the study of the marine carbon cycle. The effect of ocean acidification (OA) on coccolithophore calcification has been extensively studied; however, physiological responses to multiple environmental drivers are still largely unknown. Here we examined two‐way and multiple driver effects of OA and other key environmental drivers—nitrate, phosphate, irradiance, and temperature—on the growth, photosynthetic, and calcification rates, and the elemental composition of E. huxleyi. In addition, changes in functional gene expression were examined to understand the molecular mechanisms underpinning the physiological responses. The single driver manipulation experiments suggest decreased nitrate supply being the most important driver regulating E. huxleyi physiology, by significantly reducing the growth, photosynthetic, and calcification rates. In addition, the interaction of OA and decreased nitrate supply (projected for year 2100) had more negative synergistic effects on E. huxleyi physiology than all other two‐way factorial manipulations, suggesting a linkage between the single dominant driver (nitrate) effects and interactive effects with other drivers. Simultaneous manipulation of all five environmental drivers to the conditions of the projected year 2100 had the largest negative effects on most of the physiological metrics. Furthermore, functional genes associated with inorganic carbon acquisition (RubisCO, AEL1, and δCA) and calcification (CAX3, AEL1, PATP, and NhaA2) were most downregulated by the multiple driver manipulation, revealing linkages between responses of functional gene expression and associated physiological metrics. These findings together indicate that for more holistic projections of coccolithophore responses to future ocean global change, it is necessary to understand the relative importance of environmental drivers both individually (i.e., mechanistic understanding) and interactively (i.e., cumulative effect) on coccolithophore physiology.     

Formation of cluster roots and mycorrhizal status of Comptonia peregrina and Myrica pensylvanica in Maine, USA

Extent of cluster (proteoid) root formation in the field was examined in relation to availability of P and successional status of the site in two actinorhizal, N₂-fixing shrubs. Comptonia peregrina (L.) Coult. and Myrica pensylvanica Loisel. In C. peregrina cluster roots were present at all 13 sites and comprised between 0.2 and 19% of total fine root dry weight. Cluster root formation was most extensive at recently disturbed sites and was negatively correlated with cover of associated woody species (r =−0.85), litter depth (r =−0.81) and available (extractable) soil P (r =−0.75). In M. pensylvanica cluster roots were present at all 11 sites and comprised between 6 and 20% of total fine root dry weight. On mineral soils (n = 6), extent of cluster root formation was negatively correlated (r =−0.86) with cover of associated woody species and with litter depth (r =−0.78; P = 0.07). Comptonia peregrina and M. pensylvanica lack functional mycorrhizae at these sites because only intracellular infections were found and these lacked arbuscules. None of 22 non-N₂-fixing, dominant woody species associated with C. peregrina and M. pensylvanica formed cluster roots. Cluster roots probably allow C. peregrina and M. pensylvanica to obtain sufficient P from nutrient-poor soils in the absence of functional mycorrhizae. Extensive cluster root formation on disturbed, early successional sites may aid these species in colonizing these sites because they have to form only one symbiosis (with Frankia ) and not two (with Frankia and a mycorrhizal fungus).