Heritability of plastic trait changes in drought‐exposed ponderosa pine seedlings

Abstract

AbstractClimate change is imposing new selective pressures on forest tree populations. Evolutionary responses may be important for trees, despite long generation times, since many populations harbor significant genetic variation in environmentally relevant traits. However, the heritability of climate responses (e.g., how much growth differs under drought) has been investigated in only one tree species previously. Here, we quantify heritable variation in environmental response traits of Pinus ponderosa using a greenhouse trial. Five seedlings from each maternal family were exposed to either wet or dry treatments for four months. Traits measured include height and root length, root:shoot mass ratios, and stomatal density and number of rows. Narrow‐sense heritability for all traits was estimated using a half‐sib analysis. Many traits varied by treatment, and some also differed along gradients of “home” climate. Dry treatment root‐to‐shoot dry mass ratio was associated with survival in that treatment. Estimated heritability for drought responsiveness ranged from 0.15 to 0.65, with the highest values occurring in height growth responses. Variation was particularly high for shoot growth under drought conditions. Our results suggest that increasingly arid conditions could result in strong responses to selection.