Fluctuating asymmetry in relation to stress and fitness: Effects of trait type as revealed by meta-analysis

Recently, there has been much controversy over whether fluctuating asymmetry (FA) is related to stress during development, or to fitness of organisms following development. Many tests have found the predicted relations, whereas others have not. To account for these inconsistencies, some researchers have argued that FA of some traits (e.g., sexually selected traits) are more sensitive measures of stress, or are more strongly related to fitness, and that such relations will differ between poikilotherms and homeotherms. Using meta-analysis, we found that FA-stress and FA-fitness relations were nonspurious, despite the large number of relations tested. However, FA-stress and FA-fitness relations were fairly weak and highly heterogenous. Furthermore, our results suggested that trait type was not predictive of the presence or strength of FA-stress or FA-fitness relations and that relations were not stronger for poikilotherms, as one hypothesis suggested.