Relevance of mytilid shell microtopographies for fouling defence - a global comparison

Prevention of epibiosis is of vital importance for most aquatic organisms, which can have consequences for their ability to invade new areas. Surface microtopography of the shell periostracum has been shown to have antifouling properties for mytilid mussels, and the topography shows regional differences. This article examines whether an optimal shell design exists and evaluates the degree to which shell microstructure is matched with the properties of the local fouling community. Biomimics of four mytilid species from different regional provenances were exposed at eight different sites in both northern and southern hemispheres. Tendencies of the microtopography to both inhibit and facilitate fouling were detected after 3 and 6 weeks of immersion. However, on a global scale, all microtopographies failed to prevent fouling in a consistent manner when exposed to various fouling communities and when decoupled from other shell properties. It is therefore suggested that the recently discovered chemical anti-microfouling properties of the periostracum complement the anti-macrofouling defence offered by shell microtopography

The empirics of social capital and economic development: a critical perspective

This paper provides an introduction to the concept of social capital, and carries out a critical review of the empirical literature on social capital and economic development. The survey points out six main weaknesses affecting the empirics of social capital. Identified weaknesses are then used to analyze, in a critical perspective, some prominent empirical studies and new interesting researches published in last two years. The need emerges to acknowledge, also within the empirical research, the multidimensional, context-dependent and dynamic nature of social capital. The survey also underlines that, although it has gained a certain popularity in the empirical research, the use of “indirect” indicators may be misleading. Such measures do not represent social capital’s key components identified by the theoretical literature, and their use causes a considerable confusion about what social capital is, as distinct from its outcomes, and what the relationship between social capital and its outcomes may be. Research reliant upon an outcome of social capital as an indicator of it will necessarily find social capital to be related to that outcome. This paper suggests to focus the empirical research firstly on the “structural” aspects of the concept, therefore excluding by the measurement toolbox all indicators referring to social capital’s supposed outcomes

Cooperative behaviour and prosocial reputation dynamics in a Dominican village

Prosocial reputations play an important role, from the evolution of language to Internet transactions; however, questions remain about their behavioural correlates and dynamics. Formal models assume prosocial reputations correlate with the number of cooperative acts one performs; however, if reputations flow through information networks, then the number of individuals one assists may be a better proxy. Formal models demonstrate indirect experience must track behaviour with the same fidelity as direct experience for reputations to become viable; however, research on corporate reputations suggests performance change does not always affect reputation change. Debate exists over the cognitive mechanisms employed for assessing reputation dynamics. Image scoring suggests reputations fluctuate relative to the number of times one fails to assist others in need, while standing strategy claims reputations fluctuate relative to the number of times one fails to assist others in good standing. This study examines the behavioural correlates of prosocial reputations and their dynamics over a 20-month period in an Afro-Caribbean village. Analyses suggest prosocial reputations: (i) are correlated with the number of individuals one assists in economic production, not the number of cooperative acts; (ii) track cooperative behaviour, but are anchored across time; and (iii) are captured neither by image scoring nor standing strategy-type mechanisms