Simultaneous Selection on Two Fitness-Related Traits in the Butterfly Bicyclus Anynana

Abstract

Theory about the role of constraints in evolution is abundant, but few empirical data exist to describe the consequences a bias in phenotypic variation has for micro evolution. Responses to natural selection can be severely hampered by a genetic correlation among a suite of traits. Constraints can be studied using antagonistic selection experiments, that is, two-trait selection in opposition to this correlation. The two traits studied here were development time and wing pattern (eyespot size) in the butterfly Bicyclus anynana, both of which have a clear adaptive significance. Rates of response were higher for eyespot size than for development time, but were independent of the concurrent selection (either in the same direction as the correlation or perpendicular to it). Regimes differed in both traits in all directions after 11 generations of selection. The uncoupling lines had higher relative responses than the synergistic lines in development time and equal relative responses in eyespot size. The patterns for eyespot size (reaction norms) were consistent across different rearing temperatures. Differences in lines selected for fast and slow development time were more pronounced at lower temperatures, irrespective of the direction of joint wing pattern selection. Furthermore, correlated responses in pupal weight and growth rate were observed; lines selected for a slower development had higher pupal weights, especially at lower temperatures. The response of the uncoupling lines was not hampered by a lack of selectable genetic variation, and the relative response in the development time was larger than expected based on response in the coupled direction and quantitative genetic predictions. This suggests that the structure of the genetic architecture does not constrain the short-term, independent evolution of both wing pattern and development time.

The genetics of primary and secondary sexual character trade‐offs in a horned beetle

“…One of the best tests of this prediction comes from artificial selection studies that have selected in directions that are for and against the genetic correlation and developmental mechanisms. For example, in the butterfly, Bicyclus anynana , wing pattern and development time (Zijlstra et al. , 2003), and wing area and body size (Frankino et al.…”

“…, 2005) are negatively genetically coupled. Despite these strong internal constraints, artificial selection in directions perpendicular to and in the same direction as the genetic correlations resulted in novel phenotypes, suggesting that genetic architecture does not constrain the short‐term evolution of these traits (Zijlstra et al. , 2003; Frankino et al.…”

Realized correlated responses to artificial selection on pre-adult life-history traits in a butterfly

“…Further, development time is related to wing patterns in B. anynana (Zijlstra et al, 2003(Zijlstra et al, , 2004. Which impact this may have on genetic correlations among other traits is currently unclear.…”

Maternal Body Size as an Evolutionary Constraint on Egg Size in a Butterfly

“…Thus, life histories involve compromises between what selection can achieve (adaptation) and what selection is prevented from achieving (constraints; Barnes and Partridge 2003). Evolutionary constraints may stem from genetic or developmental interrelations among a suite of traits, and have often been invoked to explain patterns of existing morphologies (Yang 2001; Beldade et al 2002a,b; Zijlstra et al 2003; Frankino et al 2005; Brakefield 2006; Griswold 2006). However, to date, empirical data testing evolutionary constraints directly are still scarce (Beldade et al 2002a; Frankino et al 2005; Rose et al 2005; Brakefield 2006).…”