Divergent Selection on Flowering Time Contributes to Local Adaptation in Mimulus Guttatus Populations

Abstract

The timing of when to initiate reproduction is an important transition in any organism's life cycle. There is much variation in flowering time among populations, but we do not know to what degree this variation contributes to local adaptation. Here we use a reciprocal transplant experiment to examine the presence of divergent natural selection for flowering time and local adaptation between two distinct populations of Mimulus guttatus. We plant both parents and hybrids (to tease apart differences in suites of associated parental traits) between these two populations into each of the two native environments and measure floral, vegetative, life-history, and fitness characters to assess which traits are under selection at each site. Analysis of fitness components indicates that each of these plant populations is locally adapted. We obtain striking evidence for divergent natural selection on date of first flower production at these two sites. Early flowering is favored at the montane site, which is inhabited by annual plants and characterized by dry soils in midsummer, whereas intermediate (though later) flowering dates are selectively favored at the temperate coastal site, which is inhabited by perennial plants and is almost continually moist. Divergent selection on flowering time contributes to local adaptation between these two populations of M. guttatus, suggesting that genetic differentiation in the timing of reproduction may also serve as a partial reproductive isolating barrier to gene flow among populations.

Extraordinarily rapid life-history divergence between Cryptasterina sea star species

“…Testing this hypothesis will require several types of new evidence, especially reciprocal transplants or common garden experiments that reveal fitness differences between Cryptasterina species associated with specific environmental differences between their habitats [15], and hybridization experiments that reveal whether pre-or post-zygotic reproductive incompatibility is associated with the recent localized evolution of life-history differences. Evidence for differential fitness in common gardens or in the field, and of gamete compatibility and hybrid viability, would bolster our argument for life-history traits as the targets of selection (and ecological speciation) in the origin of Cryptasterina and other asterinid species.…”

Long prereproductive selection and divergence by depth in a Caribbean candelabrum coral

“…As for flowering plants segregated by altitude (41,55), marine broadcasters segregated by depth often differ in their time of spawning, decreasing the probability of cross-fertilization between depth-segregated colonies (16,29). Before spawning events, colonies in deep areas of E. flexuosa lack mature eggs compared with shallow ones (22).…”

Introduction beyond a species range: a relationship between population origin, adaptive potential and plant performance

“…Increasing aridity leads to shortening of growing season, and populations from arid habitats were found to flower earlier than in more mesic sites in many annual and perennial species (Aronson et al, 1992;Bennington and McGraw, 1995;Del Pozo et al, 2002;Eckhart et al, 2004;Franke et al, 2006;Hall and Willis, 2006;Volis, 2007). Selection for advance of flowering was found in several studies with experimentally induced drought stress (Stanton et al, 2000;Volis et al, 2004;Franks et al, 2007) and in a reciprocal transplant experiment with one desert and one Mediterranean site (Volis et al, .…”