The success of assisted colonization and assisted gene flow depends on phenology

Abstract

Global warming will jeopardize the persistence and genetic diversity of many species. Assisted colonization, or the movement of species beyond their current range boundary, is a conservation strategy proposed for species with limited dispersal abilities or adaptive potential. However, species that rely on photoperiodic and thermal cues for development may experience conflicting signals if transported across latitudes. Relocating multiple, distinct populations may remedy this quandary by expanding genetic variation and promoting evolutionary responses in the receiving habitat--a strategy known as assisted gene flow. To better inform these policies, we planted seeds from latitudinally distinct populations of the annual legume, Chamaecrista fasciculata, in a potential future colonization site north of its current range boundary. Plants were exposed to ambient or elevated temperatures via infrared heating. We monitored several life history traits and estimated patterns of natural selection to determine the adaptive value of plastic responses. To assess the feasibility of assisted gene flow between phenologically distinct populations, we counted flowers each day and estimated the degree of temporal isolation between populations. Increased temperatures advanced each successive phenological trait more than the last, resulting in a compressed life cycle for all but the southern-most population. Warming altered patterns of selection on flowering onset and vegetative biomass. Population performance was dependent on latitude of origin, with the northern-most population performing best under ambient conditions and the southern-most performing most poorly, even under elevated temperatures. Among-population differences in flowering phenology limited the potential for genetic exchange among the northern- and southern-most populations. All plastic responses to warming were neutral or adaptive; however, photoperiodic constraints will likely necessitate evolutionary responses for long-term persistence, especially when involving populations from disparate latitudes. With strategic planning, our results suggest that assisted colonization and assisted gene flow may be feasible options for preservation.

Expression of additive genetic variance for fitness in a population of partridge pea in two field sites

“…), and phenological traits (Kelly ; Wadgymar et al. ,b; Wadgymar and Weis ), making it an ideal system for studying capacity for adaptation and G × E . In the fall of 2013, seed pods from 200 maternal plants were collected from a population of C .…”

Identifying targets and agents of selection: innovative methods to evaluate the processes that contribute to local adaptation

“…Provenance trials that manipulate climatic conditions or include sites beyond the current range boundary of a species are valuable for determining the key agents of selection that govern adaptation to climate change and for predicting the evolutionary potential of populations (Griffith & Watson 2006;Wang, O'Neill & Aitken 2010;Wilczek et al 2014;Wadgymar, Cumming & Weis 2015). The manipulative provenance trial approach could also be applied to understand the genetic and environmental basis of local adaptation in agricultural settings to enable researchers to predict which crop varieties will thrive in various locations under climate change and breed regionally adapted varieties.…”

A review and meta‐analysis of intraspecific differences in phenotypic plasticity: Implications to forecast plant responses to climate change

“…Multiple studies have reported significant P × E for a wide suite of plant functional traits, particularly focusing on the adaptive role of plasticity for populations of specific life‐forms or ecoregions (see e.g., Matesanz & Valladares, and references therein; Bansal, Harrington, et al, ; Frei, Ghazoul, & Pluess, ; Wadgymar, Cumming, & Weis, ). Some studies have also discussed the sources of bias in estimates of population differentiation, including the difficulty in distinguishing genetic from plastic components of such differentiation (Merilä & Hendry, ), the effect of the experimental approach (Gibson, Espeland, Wagner, & Nelson, ) and the role of maternal effects (Bischoff & Müller‐Schärer, ).…”