Genetic and environmental canalization are not associated among altitudinally varying populations of Drosophila melanogaster

Abstract

Organisms are exposed to environmental and mutational effects influencing both mean and variance of phenotypes. Potentially deleterious effects arising from this variation can be reduced by the evolution of buffering (canalizing) mechanisms, ultimately reducing phenotypic variability. There has been interest regarding the conditions enabling the evolution of canalization. Under some models, the circumstances under which genetic canalization evolves are limited despite apparent empirical evidence for it. It has been argued that genetic canalization evolves as a correlated response to environmental canalization (congruence model). Yet, empirical evidence has not consistently supported predictions of a correlation between genetic and environmental canalization. In a recent study, a population of Drosophila adapted to high altitude showed evidence of genetic decanalization relative to those from low altitudes. Using strains derived from these populations, we tested if they varied for multiple aspects of environmental canalization We observed the expected differences in wing size, shape, cell (trichome) density and mutational defects between high‐ and low‐altitude populations. However, we observed little evidence for a relationship between measures of environmental canalization with population or with defect frequency. Our results do not support the predicted association between genetic and environmental canalization.

The influence of adaptation to life at high-altitude on condition dependent sexual shape and size dimorphism in Drosophila melanogaster

“…Consistent with previous observations (Bitner-Mathe and Klaczko, 1999;David et al, 2009;Debat et al, 2003;Pesevski and Dworkin, 2020;Pitchers et al, 2013), an inverse relationship is seen between wing size and temperature (Figure 1B), and an overall increase in SSD with increasing temperature (Figure 3D). We observed evidence of sex-specific temperature plasticity as well as evidence for population-specific plasticity (significant sexby-temperature and population-by-temperature interaction effects, Supplementary table S4, Figure 1B, Figure 3D).…”

“…Patterns of SShD between HA and LA populations were consistent with previous observations (Pitchers et al, 2013;Pesevski and Dworkin, 2020) (Figure 3, Supplementary Tables S5 and S6). We did not observe substantial population-specific difference in SShD, despite evidence for genetic variation in shape and sexual dimorphism among strains within populations (Supplementary Tables S5 and S6).…”

“…Drosophila melanogaster strains used in these experiments are a subset previously used in Lack et al (2016a,b) and Pesevski and Dworkin (2020). Strains from the high altitude (HA) population were collected in Fiche, Ethiopia (3070m asl) in December 2011, while strains from the low altitude (LA) population were collected in Siavonga, Zambia (530m asl) (Supplementary Tables S1 and S2).…”

“…Flies for temperature treatments were raised flies only on high quality food (100%), in incubators at 18°C, 24°C and 28°C with a 12:12 light/dark cycles. Some results of the temperature manipulation were including in a previous study (Pesevski and Dworkin, 2020), but were done concurrently with the food manipulation study. For all temperature and 100% food treatments, 3 replicate vials of 50 eggs each were collected for each strain.…”

“…As is common with small insects adapting to life at high altitudes (reviewed in Hodkinson, 2005), a number of morphological, physiological and life history traits have evolved in the HA population (Pitchers et al, 2013;Pool et al, 2012;Lack et al, 2016a,b;Klepsatel et al, 2014;Fabian et al, 2015;Klepsatel et al, 2013). In particular, body size and wing size (and wing loading) have increased ∼20% relative to the LA counterparts (Pitchers et al, 2013;Pool et al, 2012;Lack et al, 2016a,b;Klepsatel et al, 2014;Fabian et al, 2015;Klepsatel et al, 2013;Pesevski and Dworkin, 2020). Interestingly, there is evidence of concordance between the direction of temperature-induced plasticity and wing shape between lowland and highland populations (Pitchers et al, 2013).…”