Artificial selection on flowering time: influence on reproductive phenology across natural light environments

Abstract

Summary1. Flowering time is frequently under selection due to a combination of abiotic, biotic and intrinsic factors. Evolution in response to this selection is likely to have broad effects, altering not only flowering time but reproductive phenology and, potentially, traits throughout the life cycle. We know little about the broader phenotypic changes associated with evolutionary shifts in flowering time, and the extent to which expression of these changes depends on local environmental conditions. 2. After three generations of selection for early-and late-flowering, we grew plants of the herb Campanulastrum americanum in contrasting light environments (light gap and understorey) in its home population. 3. Response to selection on flowering time and correlated responses in reproductive phenology were expressed across light environments with the reproduction of early-flowering lines being over 2 weeks ahead of late-flowering lines. Plants in the understorey delayed initiation of flowering but accelerated flower deployment, fruit maturation and the end of reproduction, resulting in a condensed reproductive period. 4. Timing of seed dispersal influences whether offspring grow as annuals or biennials in C. americanum. Because evolution of flowering time shifted reproductive phenology, it is likely to alter life history frequency. In contrast, understorey habitats both delayed flowering and accelerated reproductive phenology, yielding no expected life history change. 5. Synthesis. Evolution of flowering time altered the phenology of all subsequent reproductive traits and is also likely to affect offspring traits. This ripple effect of changes in flowering time indicates that it is essential to recognize genetic and functional linkages among traits to understand potential life cycle consequences of selection on a single character.

Response to joint selection on germination and flowering phenology depends on the direction of selection

“…Flowering begins in mid‐summer and fruits ripen and dehisce throughout the fall. Seeds disperse when fruits mature (Galloway & Burgess, 2009) and are nondormant at maturity (Baskin & Baskin, 1984), so the reproductive phenology of maternal plants directly influences offspring germination season (Galloway, 2002; Galloway & Burgess, 2009, 2012). Germination and flowering time in C. americana have significant additive genetic variation (Galloway et al., 2009).…”

“…Season of germination is influenced by the seed's genetics as well as by maternal flowering time. Early‐flowering plants disperse seeds early, increasing the potential for fall germination of offspring, while seeds of late‐flowering plants are frequently dispersed in late fall when it is cool and are therefore more likely to germinate the following spring (Galloway, 2002; Galloway & Burgess, 2009, 2012). We predict that there is a genetic correlation between timing of germination and flowering, so they provide a coordinated influence on life history schedule (Peiman & Robinson, 2017).…”

Parental environments and interactions with conspecifics alter salinity tolerance of offspring in the annual Medicago truncatula

“…For example, Stanton, Roy & Thiede (2000) and Stanton, Thiede & Roy (2004) demonstrated that for the annual Sinapsis arvensis, selection favoured earlier reproduction when grown under stressful than under benign environments. An emerging pattern from multiple studies indicates that flowering time can rapidly respond to natural selection (Elzinga et al 2007;Franks, Sim & Weis 2007;Galloway & Burgess 2012), suggesting either ample standing genetic variation for flowering time within populations or ample gene flow between populations with differing phenological set points. The generality of earlier flowering in response to multiple sources of environmental stress suggests that phenology may be an important trait responding to differences in environmental stress, along with growth and competitive ability.…”

Flowering phenology of a herbaceous species (Poa annua) is regulated by soil Collembola

“…A small change in reproductive success or flowering time can affect plant fitness (e.g. Galloway and Burgess, 2012;Weis et al, 2015), and consequently might alter interactions with populations of pollinators, seed dispersers, or floral herbivores. The role of biotic interactions in shaping plant flowering phenology has been demonstrated for pollinators and herbivores (Elzinga et al, 2007).…”