Investigating yellow dung fly body size evolution in the field: Response to climate change?

Abstract

Uncovering genetic responses to selection in wild populations typically requires tracking individuals over generations and use of animal models. Our group monitored the body size of one Swiss Yellow Dung Fly (Scathophaga stercoraria; Diptera: Scathophagidae) field population over 15 years, including intermittent common-garden rearing in the laboratory to assess body size with minimized environmental and maximized genetic variation. Contrary to expectations based on repeated heritability and phenotypic selection assessments over the years (reported elsewhere), field body sizes declined by >10% and common-garden laboratory sizes by >5% from 1993 to 2009. Our results confirm the temperaturesize rule (smaller when warmer) and, albeit entirely correlational, could be mediated by climate change, as over this period mean temperature at the site increased by 0.5°C, although alternative systematic environmental changes cannot be entirely excluded. Monitoring genetic responses to selection in wild invertebrate populations is thus possible, though indirect, and wild populations may evolve in directions not consistent with strongly positive directional selection favoring large body size.

Empirical evidence for fast temperature-dependent body size evolution in rotifers

“…Our results contribute to the important issue of matching the phenotypic and genetic levels of response to selection for evolutionary inference (Swallow & Garland, 2005;Blanckenhorn, 2015;Merilae & Hendry, 2014). The underlying explanatory factor in evolutionary inference is the adaptive significance of the observed change (Merilae & Hendry, 2014;Teplitsky & Millien, 2014).…”

Decreases in beetle body size linked to climate change and warming temperatures

“…This study adds to a growing body of literature examining patterns in organism body size over time (Babin‐Fenske, Anand, & Alarie, ; Baudron et al., ; Blanckenhorn, ; Caruso, Sears, Adams, & Lips, ; Fenberg, Self, Stewart, Wilson, & Brooks, ; Gardner et al., ; Sheridan & Bickford, ). Some of these studies (and references within) also show decreases in organism body size with increased temperature, but the pattern is not universal.…”

Strong reduction in diapause survival under warm and humid overwintering conditions in a temperate‐zone butterfly

“…Also, the humidity effect on fat content and the other interactions did not reveal conclusive patterns, except that sexes obviously responded differently to environmental conditions which have been shown in several cases before (Bauerfeind & Fischer, ; Fischer & Karl, ; Honěk, ). The significant population and box effects indicate differences among populations and females suggesting heritable variation that can be exploited by natural selection (Blanckenhorn, ; Emlen & Nijhout, ; Zwarts et al, ).…”