Unveiling the complexity and ecological function of aquatic macrophyte-animal networks in coastal ecosystems

Network theory offers innovative tools to explore the complex ecological mechanisms regulating species associations and interactions. Although interest in ecological networks has grown steadily during the last two decades, the application of network approaches has been unequally distributed across different study systems: while some kinds of interactions (e.g. plant–pollinator and host–parasite) have been extensively investigated, others remain relatively unexplored. Among the latter, aquatic macrophyte–animal associations in coastal environments have been largely neglected, despite their major role in littoral ecosystems. The ubiquity of macrophyte systems, their accessibility and multi-faceted ecological, economical and societal importance make macrophyte–animal systems an ideal subject for ecological network science. In fact, macrophyte–animal networks offer an aquatic counterpart to terrestrial plant–animal networks. In this review, we show how the application of network analysis to aquatic macrophyte–animal associations has the potential to broaden our understanding of how coastal ecosystems function. Network analysis can also provide a key to understanding how such ecosystems will respond to on-going and future threats from anthropogenic disturbance and environmental change. For this, we: (i) identify key issues that have limited the application of network theory and modelling to aquatic animal– macrophyte associations; (ii) illustrate through examples based on empirical data how network analysis can offer new insights on the complexity and functioning of coastal ecosystems; and (iii) provide suggestions for how to design future studies and establish this new research line into network ecology.Peer reviewe

Variation in disgust response provides different social information for predators : implications for the evolution of prey defences

Prey defend themselves from predators using a range of tactics, including evolving distasteful compounds and advertising their unprofitability with aposematic warning signals. Therefore, before attacking a potential prey, predators need to assess whether it is palatable and profitable to consume. Previous studies have demonstrated that predators can rely on personal experience (personal information) and/or observe the foraging behaviour of others (social information) to assess prey profitability. ‘Social avoidance learning’, where predators observe a negative foraging experience associated with beak wiping, has been suggested to be important to explain how novel warning signals evolve. However, in previous studies observers saw a very strong “disgust response” of the demonstrators, when in fact there is variation in how strongly birds respond to unpalatable food. Therefore, to understand how social avoidance learning can work in nature I investigated how blue tits (Cyanistes caeruleus) use social information from demonstrators that show a weaker response to unpalatable food. I provided social information to observers using video playback of a demonstrator bird consuming a novel conspicuous prey item and showing: (1) a strong disgust response (65-95 beak wipes) as in previous studies, (2) a weak disgust response (12-25 beak wipes), or (3) no disgust response (control, no beak wiping). Next, I investigated birds’ foraging choices using a miniature novel world protocol where birds encountered novel aposematic (conspicuous and unpalatable) and cryptic (camouflaged and palatable) prey. Tested individuals consumed fewer aposematic prey after seeing a strong response but seeing a weak response did not influence their foraging choices. My results, therefore, suggest that information about novel aposematic prey may be less likely to spread socially than previously thought. However, more work is needed to determine both the availability and salience of graded social information