The Fitness of Manipulating Phenotypes: Implications for Studies of Fluctuating Asymmetry and Multivariate Selection

Abstract

Abstract.-Phenotypic manipulation (or phenotypic engineering) that alters trait distributions provides a way to increase the statistical power of detecting relationships between traits and fitness. Manipulations relying on plastic responses, however, assume a specific relationship between the perturbation and the alteration of the traits when multiple traits are involved. We measured several traits, including condition measured as fluctuating asymmetry, in the ladybird beetle Harmonia axyridis under six different diets to examine how altered environments affected multiple traits and their distributions. Although diet affected fluctuating asymmetry, we found no consistent relationship between degree of asymmetry and other phenotypic measures. As expected, individual traits were altered by our treatments. Contrary to expectation, relationships among traits were not constant among diets. Our results suggest that assumptions about the relationship between condition and trait values, especially fluctuating asymmetry, cannot be made. Further, studies that use manipulated phenotypes to statistically determine the form of selection must first demonstrate that the pattern of the phenotypic correlation matrix is not itself altered by the manipulation. If the phenotypic correlation matrix is not constant, then experimental estimates of selection coefficients may not reflect selection that occurs in the wild.

Determination of characteristic odorants from Harmonia axyridis beetles using in vivo solid-phase microextraction and multidimensional gas chromatography–mass spectrometry–olfactometry

“…Outside of North America, phenotypic variation is even greater including black morphs with orange to red spots. This aposematic coloration is determined both by genetic factors and the influence of the larval diet [33]. Although the relationship is not clear between color intensity of adult H. axyridis and MP content [34], we separated beetles by apparent color to reduce a possible source of variation.…”

Effect of Propagule Size and Landscape Structure on Morphological Differentiation and Asymmetry in Experimentally Introduced Roesel's Bush‐Crickets

“…This may result from a lower genetic diversity in the original population with less resilience toward stress factors (Saccheri et al 1998; Mpho et al 2002). The correlations I found between fitness indicators such as body weight, body length, and FA have been observed (Bennett & Hoffmann 1998; Uetz & Smith 1999), as have correlations between FA and energy reserves (Blanckenhorn et al 2003) and egg production (Hendrickx et al 2003, but see Preziosi et al 1999). These correlations support the assumption that FA is the result of some bush‐crickets being less able to produce an optimal body, both in size and structure, and validate the measure of FA of tibias as an index of instability in this species.…”