Selection and plasticity both account for interannual variation in life‐history phenology in an annual prairie legume

As the environment changes, so too must plant communities and populations if they are to persist. Life‐history transitions and their timing are often the traits that are most responsive to changing environmental conditions. To compare the contributions of plasticity and natural selective response to variation in germination and flowering phenology, we performed a quantitative genetic study of phenotypic selection on Chamaecrista fasciculata (Fabaceae) across two consecutive years in a restored tallgrass prairie. The earliest dates of germination and flowering were recorded for two parental cohorts and one progeny cohort in an experimental garden. Environmental differences between years were the largest contributors to phenological variation in this population. In addition, there was substantial heritability for flowering time and statistically significant selection for advancement of flowering. Comparison between a progeny cohort and its preselection parental cohort indicated a change in mean flowering time consistent with the direction of selection. Selection on germination time was weaker than that on flowering time, while environmental effects on germination time were stronger. The response to selection on flowering time was detectable when accounting for the effect of the environment on phenotypic differences, highlighting the importance of controlling for year‐to‐year environmental variation in quantitative genetic studies.     

Water Scarcity and the Sustainability of a Common Pool Resource Institution in the Urban Andes

The Cochabamba Water War of 2000 was precipitated by Bolivians’ defense of common-pool water resources and institutions against privatization. This article examines the design of a water institution and its sustainability during periods of water scarcity in urban Cochabamba. Based on data collected via participant-observation and panel surveys conducted in 72 randomly selected households, I draw three main conclusions. First, the institution operated according to principles found in sustainable resource management institutions in the rural Andes (Trawick 2001) and across cultures (Ostrom 1990). Second, while the function of the common-pool resource institution was stable over the five study periods, the social structures that supported collective choice and operational rules were sensitive to external events including seasonal water scarcity. Third, while institutions with strong historical precedents for contingencies under resource stress may be sustainable, other forms of social organization on which the institution depends may be more vulnerable to water scarcity.