Predicting the pathway to wind pollination: heritabilities and genetic correlations of inflorescence traits associated with wind pollination in Schiedea salicaria (Caryophyllaceae)

Abstract

The transition from biotic to abiotic pollination was investigated using Schiedea, a genus exhibiting a remarkable diversity of inflorescence architecture associated with pollination biology. Heritabilities and genetic correlations of inflorescence traits were estimated in gynodioecious Schiedea salicaria (Caryophyllaceae), a species that has likely undergone a recent transition to wind‐pollination. Using a partial diallel crossing design, significant narrow‐sense heritabilities were detected for inflorescence condensation (h2 = 0.56 to 0.68 in the two sexes) and other traits related to the extent of wind pollination in Schiedea species. Heritabilities were generally higher in hermaphrodites than in females. Strong genetic correlations may constrain the evolution of some inflorescence traits that facilitate wind pollination, such as simultaneous shortening of inflorescence length and elongation of the subtending internode. The presence of significant narrow‐sense heritabilities for traits associated with wind pollination suggests, however, that selection for more effective wind pollination in the windy, pollinator‐limited environments where S. salicaria grows could lead to the evolution of the highly condensed inflorescences characteristic of other wind‐pollinated species of Schiedea.

Sexual dimorphism and the genetic potential for evolution of sex allocation in the gynodioecious plant, Schiedea salicaria

“…The flower terminating the main axis of the inflorescence is usually the first to open; terminal flowers (distal flowers of the secondary axes) are larger and open before lateral flowers (all other flowers on the secondary or tertiary axes). Inflorescences of S. salicaria have a mean of nine terminal flowers for both sexes, and 42 and 48 lateral flowers for hermaphrodites and females respectively (Weller et al. , 2006).…”

“…Because the plants produce both terminal and lateral flowers that differ in size, we measured biomass allocation separately for these two types of flowers, along with estimates of flower numbers to calculate composite measures of biomass allocation. We included measures of both types of flowers because terminal flowers produced more seeds and pollen than lateral flowers, but changes in lateral flower number may be more important in determining allocation patterns (Weller et al. , 2006, 2007).…”

Evolution of flower shape in Plantago lanceolata

“…Plantago ( internodes (Culley et al 2002;Weller et al 2006;Friedman and Barrett 2008). Two forms of dichogamy exist: protandry (male phase precedes female) and protogyny (female phase precedes male).…”

Phylogenetic evidence for a flower size and number trade‐off

“…For example, a predominantly self-fertilizing mating system can lead to selection for smaller flowers (Wyatt, 1984;Lyons and Antonovics, 1991;Goodwillie, 1999;Goodwillie and Ness, 2005), change in pollination mode is associated with shifts in flower size and number (Proctor et al, 1996;Weller et al, 2005), and male plants of sexually dimorphic species tend to have larger displays with a greater number of smaller flowers than female plants (Delph et al, 2002(Delph et al, , 2004. Selection on fruit size, seed size, and phenology can also influence the relationship (Primack, 1987).…”