Changing Responses to Changing Seasons: Natural Variation in the Plasticity of Flowering Time

Abstract

For plants that live in seasonally changing environments, timing is everything. Matching developmental transitions with the best times of year for growth and reproduction is necessary to maintain high fitness. Consequently, plants employ many mechanisms to sense and integrate multiple predictive seasonal cues to regulate their major developmental shifts. As the annual timing with which the growing season starts and ends changes across the landscape, natural selection has led to the evolution of the mechanisms that regulate the developmental plasticity of flowering among populations or varieties of species and crop plants that inhabit broad geographic ranges. There has been significant recent progress in describing the diversity of this variation in flowering time plasticity and in identifying the specific genetic changes responsible. Such work is an essential step toward understanding the processes that have shaped current and past adaptation, managing genetic diversity and improving crops in the face of climate change, and forecasting how populations may respond plastically and evolutionarily to future environmental challenges. In this Update, I review the findings of recent studies of natural variation in the plasticity of flowering to photoperiod, vernalization, and ambient temperature, and the implications and open questions raised by this work are considered.A fundamental adaptation of plants inhabiting seasonal environments is their ability to match the annual timing of major life history transitions to the local growing season. Most species achieve this synchrony through developmental plasticity. In other words, individuals sense how environmental cues like daylength and temperature change from winter to spring to summer to fall. The information gleaned from these cycles is then integrated molecularly so that germination, flowering, and other key transitions occur during periods favorable for growth, reproduction, and seed set. However, as the climate changes over the 21st century and the relative timing of annual cycles in temperature and precipitation shifts, once adaptive responses will no longer effectively predict the best calendar dates to initiate these essential developmental events (Nicotra et al., 2010;Wilczek et al., 2010). Because natural populations and cultivated landraces of many taxa have evolved to thrive in geographically diverse habitats and climates as their ranges have expanded, they harbor natural variants that may prove instructive in breeding crops and conserving native plant diversity in the face of future environmental challenges. Thus, a critical objective in plant biology is

The soil microbial community alters patterns of selection on flowering time and fitness‐related traits in Ipomoea purpurea

“…Likewise, early flowering is associated with greater susceptibility to damage from herbivory or disease, ultimately leading to lower fitness (Inouye, ). The timing of flowering is itself impacted by various abiotic factors—temperature, drought, photoperiod, soil nutrients, and ambient CO 2 (reviewed by Kazan and Lyons, ; Blackman, ; Cho et al., )—as well as biotic factors such as plant pathogens, herbivory, and soil microbes (Lau and Lennon, , ; Züst et al., ; Panke‐Buisse et al., ; Wagner et al., ; Lyons et al., ). Of these factors, the influence of the soil microbial community on flowering time has come under increasing scrutiny given the recent recognition of the importance of plant–soil feedbacks on fitness (Bever, ; Reynolds et al., ; Geml and Wagner, ).…”

“…Although data show that the presence of microbes leads to larger plant size, which may then lead to higher plant fitness (Lau and Lennon, 2011), whether and how soil microbes influence the optimal transition between growth and flowering has yet to be examined in any species. The life-history switch between growth and flowering is complex and modulated by factors that are intrinsic to the plant-age and hormone levels-and by extrinsic environmental cues such as photoperiod, temperature, light intensity and spectral quality (Kazan and Lyons, 2016;Blackman, 2017;Cho et al, 2017). Given the importance of the transition between growth and flowering and its environmental dependency, selection should favor a transition in life history stage that will optimize fitness in any particular environment.…”

Determining the evolutionary forces shaping G × E

“…An understanding of the evolutionary forces shaping plasticity will have a number of practical applications. For example, the selective pressures that maintain G 9 E will have implications for the prediction of responses to global climate change and other human impacts (Nicotra et al, 2010;Blackman, 2017). In addition, an understanding of the role of selection in shaping G 9 E will be useful for crop breeding.…”

The soil microbial community alters patterns of selection on flowering time and fitness related traits in Ipomoea purpurea

“…Likewise, early flowering is associated with greater susceptibility to damage from herbivory or disease, ultimately leading to lower fitness (Inouye, 2008). The timing of flowering is itself impacted by various abiotic factors – temperature, drought, photoperiod, soil nutrients, and ambient CO 2 ( reviewed in Kazan and Lyons, 2016; Blackman, 2017; Cho et al, 2017) – as well as biotic factors such as plant pathogens, herbivory, and soil microbes (Lau and Lennon, 2011, 2012; Züst et al, 2011; Panke-Buisse et al, 2014; Wagner et al, 2014; Lyons et al, 2015). Of these factors, the influence of the soil microbial community on flowering time has come under increasing scrutiny given the recent recognition of the importance of plant-soil feedbacks on fitness (Bever, 2003; Reynolds et al, 2003; Geml and Wagner, 2018).…”

“…If and how soil microbes influence the optimal transition between growth and flowering, however, has yet to be examined in any species. The life-history switch between growth and flowering is complex and modulated by factors that are intrinsic to the plant – age and hormone levels – as well as extrinsic environmental cues, such as photoperiod, temperature, light intensity and spectral quality (Kazan and Lyons, 2016; Blackman, 2017; Cho et al, 2017). Given the importance of the transition between growth and flowering, and its environmental dependency, selection should favor a transition in life-history stage that will optimize fitness in any particular environment.…”