Evolutionary Change in Continuous Reaction Norms

Abstract

Understanding the evolution of reaction norms remains a major challenge in ecology and evolution. Investigating evolutionary divergence in reaction norm shapes between populations and closely related species is one approach to providing insights. Here we use a meta-analytic approach to compare divergence in reaction norms of closely related species or populations of animals and plants across types of traits and environments. We quantified mean-standardized differences in overall trait means (Offset) and reaction norm shape (including both Slope and Curvature). These analyses revealed that differences in shape (Slope and Curvature together) were generally greater than differences in Offset. Additionally, differences in Curvature were generally greater than differences in Slope. The type of taxon contrast (species vs. population), trait, organism, and the type and novelty of environments all contributed to the best-fitting models, especially for Offset, Curvature, and the total differences (Total) between reaction norms. Congeneric species had greater differences in reaction norms than populations, and novel environmental conditions increased the differences in reaction norms between populations or species. These results show that evolutionary divergence of curvature is common and should be considered an important aspect of plasticity, together with slope. Biological details about traits and environments, including cryptic variation expressed in novel environmental conditions, may be critical to understanding how reaction norms evolve in novel and rapidly changing environments.

Predators modify the evolutionary response of prey to temperature change

“…We also observed that Daphnia selected with predators showed faster growth at the higher assay temperature ( figure 2a and table 1). This evolutionary increase in plasticity supports the assertion that biotic interactions may be important drivers of evolutionary changes in reaction norms [25]. A potential mechanism for this result is that the predator treatment created a more heterogeneous environment with regard to spatial or temporal distribution of predation risk than did the temperature treatment, and variable environments have been linked to the evolution of increased plasticity [26].…”

Adaptive responses to cool climate promotes persistence of a non-native lizard

“…Interestingly, there was no, or limited, increase in development rate at 248C and 288C. These responses thus demonstrate adaptive evolution of the slope and curvature of thermal reaction norms, which appears to be common for population divergence in plasticity [48].…”

Phenotypic plasticity and water availability: responses of alpine herb species along an elevation gradient

“…Future investigation into climate change responses within alpine ecosystems should seek to understand how shifts in co-occurring abiotic factors may act synergistically or antagonistically upon fitness, but may also vary as a function of time and space. Moreover, investigations into not only the mean changes in abiotic variables, but also the periodicity and frequency of extreme events, will be of increasing importance [59,60]. Finally, when considering the capacity for adaptive phenotypic plasticity to buffer climate change, it is also important to assess how observed trait changes may translate into population-level responses [61].…”

“…It is also the case that costs and adaptive value of plasticity are not always easy to assess under experimental settings, or on naturally occurring genotypes [15,26,51,[56][57][58]. Finally, plasticity may operate in a non-linear manner and it is possible that our study represents a smaller portion of a much larger and complex reaction norm [59]. Thus, further research to identify the genetic architecture of the observed plastic response to water availability might improve our understanding of its history and adaptive role.…”