The causes of selection on flowering time through male fitness in a hermaphroditic annual plant

Abstract

Flowering is a key life-history event whose timing almost certainly affects both male and female fitness, but tests of selection on flowering time through male fitness are few. Such selection may arise from direct effects of flowering time, and indirect effects through covariance between flowering time and the environment experienced during reproduction. To isolate these intrinsically correlated associations, we staggered planting dates of Brassica rapa families with known flowering times, creating populations in which age at flowering (i.e., flowering time genotype) and Julian date of flowering (i.e., flowering time environment) were positively, negatively, or uncorrelated. Genetic paternity analysis revealed that male fitness was not strongly influenced by seasonal environmental changes. Instead, when age and date were uncorrelated, selection through male fitness strongly favored young age at flowering. Strategic sampling offspring for paternity analysis rejected covariance between sire age at flowering and dam quality as the cause of this selection. Results instead suggest a negative association between age at flowering and pollen competitive ability. The manipulation also revealed that, at least in B. rapa, the often-observed correlation between flowering time and flowering duration is environmental, not genetic, in origin.

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

“…Our detection of and G × E for fitness illustrates the power of our experimental quantitative genetic approach coupled with aster analysis. Direct measures of the process of genetic selection are not often undertaken (Austen and Weis ). In contrast with our finding of substantial in two sites, a study of a natural population of the collared flycatcher suggested a negative relationship between the heritability of morphological traits and their association with lifetime reproductive success, and found a heritability of 0 in lifetime reproductive success (Gustafsson ).…”

Estimating selection through male fitness: three complementary methods illuminate the nature and causes of selection on flowering time

“…Strong selection for young AAF when AAF and JDF were uncorrelated rejected this hypothesis [8]. By comparing results of the genetic and mating opportunities methods, we further excluded mating opportunity as the primary driver of selection on AAF.…”

“…We have previously speculated that the unknown factor driving selection for young AAF in the uncorrelated population could be negative covariance between AAF and pollen quality [8]. Such covariance would be masked in the positive and negative populations, because these two treatments affected the date on which pollen of a given AAF was dispersed and deposited on stigmas, but not the identity of competitors: young-AAF pollen competed primarily with young, and old with old [24].…”

Interacting effects of genetic variation for seed dormancy and flowering time on phenology, life history, and fitness of experimental Arabidopsis thaliana populations over multiple generations in the field

“…Both germination and flowering time can experience strong selection within generations to align life history events most favorably with the environment (Kalisz, 1986;VanDijk et al, 1997;Shitaka & Hirose, 1998;Donohue et al, 2000Donohue et al, , 2005aPilson, 2000;Hall & Willis, 2006;Franks et al, 2007;Sandring & Agren, 2009;Munguia-Rosas et al, 2011;Anderson et al, 2012;Colautti & Barrett, 2013;Fournier-Level et al, 2013;Akiyama & Agren, 2014;Austen & Weis, 2016;Postma & Agren, 2016;Colautti et al, 2017), and withingeneration selection on the timing of a life history event may depend upon the timing of earlier events (Forrest & Miller-Rushing, 2010;Mojica & Kelly, 2010;Donohue, 2014;Ehrlen, 2015). For example, there is pervasive evidence of selection for earlier flowering in many species, even when controlling for climate change (Munguia-Rosas et al, 2011;Austen et al, 2017).…”