A change in climate causes rapid evolution of multiple life‐history traits and their interactions in an annual plant

Abstract

Climate change is likely to spur rapid evolution, potentially altering integrated suites of life‐history traits. We examined evolutionary change in multiple life‐history traits of the annual plant Brassica rapa collected before and after a recent 5‐year drought in southern California. We used a direct approach to examining evolutionary change by comparing ancestors and descendants. Collections were made from two populations varying in average soil moisture levels, and lines propagated from the collected seeds were grown in a greenhouse and experimentally subjected to conditions simulating either drought (short growing season) or high precipitation (long growing season) years. Comparing ancestors and descendants, we found that the drought caused many changes in life‐history traits, including a shift to earlier flowering, longer duration of flowering, reduced peak flowering and greater skew of the flowering schedule. Descendants had thinner stems and fewer leaf nodes at the time of flowering than ancestors, indicating that the drought selected for plants that flowered at a smaller size and earlier ontogenetic stage rather than selecting for plants to develop more rapidly. Thus, there was not evidence for absolute developmental constraints to flowering time evolution. Common principal component analyses showed substantial differences in the matrix of trait covariances both between short and long growing season treatments and between populations. Although the covariances matrices were generally similar between ancestors and descendants, there was evidence for complex evolutionary changes in the relationships among the traits, and these changes depended on the population and treatment. These results show that a full appreciation of the impacts of global change on phenotypic evolution will entail an understanding of how changes in climatic conditions affect trait values and the structure of relationships among traits.

Heterochrony: the Evolution of Development

“…Studies of evolutionary change in the annual plant Brassica collected in California before and after a five-year drought found that these drought conditions produced many changes in descendant life history traits that relate to changes to timing of development (Franks and Weis 2008). These include a change to earlier flowering time, as well as longer duration of flowering.…”

Toward a synthetic understanding of the role of phenology in ecology and evolution

“…Nevertheless, the age-size compromise may influence the type or magnitude of evolutionary change in phenology that would be expected in response to a warming climate (Etterson & Shaw 2001). In annual plants, for example, there is frequently a positive genetic correlation between age and size at flowering (Mitchell-Olds 1996;Franks & Weis 2008); in insects, many of which are likewise annuals, later metamorphosis to adulthood means more time for growth (Masaki 1967). In both cases, the optimal phenological response to an extended growing season depends on the relative benefits of reaching reproductive maturity earlier in the season or growing larger before reproducing.…”

Ecología evolutiva de la reproducción en dos pinos mediterráneos: Pinus pinaster Ait. y Pinus halepensis Mill.

“…This is even more remarkable if we consider that introduction into non-native ranges usually occurs through strong bottlenecks that narrow genetic diversity (Sakai et al, 2001). There is also mounting evidence on the rapid evolution of flowering time as a consequence of climate change (Franks & Weis, 2008;Munguía-Rosas et al, 2011), highlighting once again the adaptive relevance of reproductive traits. Quantitative genetic and artificial selection experiments have also Introduction Long life cycle of forest trees makes unfeasible for most researchers to accomplish artificial selection experiments and gather results within the duration of a research project.…”

“…On the other hand, populations of annuals or short-lived perennials can undergo genetic changes in shorter periods (Franks & Weis, 2008). Therefore, plasticity might be of greater importance as an adaptive strategy in trees and woody plants compared with short-lived plant species (Willson, 1983) such that long-lived species might exhibit plasticity in both vegetative (Chambel et al, 2005) and reproductive traits like size at reproduction and reproductive investment.…”