Pollen grain numbers, ovule numbers and pollen-ovule ratios in Caryophylloideae: correlation with breeding system, pollination, life form, style number, and sexual system

Abstract

Pollen-ovule ratios (P/O) were measured for 79 species of Caryophylloideae (Agrostemma, Dianthus, Saponaria, Silene, and Vaccaria). We analyzed if these features are best correlated with (1) the breeding system (outcrossing or selfing), (2) diurnal or nocturnal pollination, (3) life form (annual versus perennial), (4) style number, (5) the sexual system (hermaphroditism, gynodioecism, dioecism), or (6) the taxonomy of species. According to the classification of Cruden [(1977) Evolution 31:32-46] most species in the subfamily Caryophylloideae are facultative autogamous or facultative xenogamous. Autogamous or cleistogamous species showed significantly lower P/Os than outcrossing species. We found no differences between night-and dayflowering species; thus from our data diurnal and nocturnal flower visitors may be considered as equally efficient in transferring pollen. However, other factors are also important for the interpretation of P/Os. Pollen grain numbers and ovule numbers were found to correlate with style number, life form, and breeding system. The low P/Os of some dioecious, and therefore obligate outcrossing, species are discussed in relation to morphological traits that improve pollen deposition by pollinators on the stigma, and in relation to different flower numbers of male and female plants.

Pollen: ovule ratio and its relationship with other reproductive traits in some <em>Passiflora</em> species (Passifloraceae)

“…The selfcompatible species, with lower P/O ratio, are annuals (the whole plant or the aerial stems) or biannuals (except from P. suberosa, that lives longer) whilst the self-incompatible ones, with higher P/O ratio, render successfully more years. This tendency, discovered by Cruden (1977), was further confirmed in various taxa (Small, 1988;Plitman and Levin, 1990;Galloni & al., 2000;Jürgens & al., 2002;Choteau & al., 2006) with isolated exceptions (López & al., 1999).…”

“…P/O variations were associated to genus but not to tribe in 21 papilionoid Legumes (Etcheverry & al., 2012). Jürgens & al (2002) suggested that taxonomy is indirectly related with P/O as a consequence of the combination of features typical of each taxonomic group. P/O, like other traits related to pollination, are open to selection; as random evolution also takes part in phylogeny, P/O could not necessarily reflect taxonomic affinities, as suggested by Affre and Thompson (1998) and Galloni & al.…”

“…P/O ratio was significantly associated with pollination mechanism in species with unknown breeding system (López & al., 1999) and in 21 xenogamous legumes (Etcheverry & al., 2012). Lower P/O ratios usually coincide with precise or highly specialized pollen transfer mechanisms (Small, 1988;Jürgens & al., 2002;Choteau & al., 2006). This has been exemplified in the Mimosoideae (Cruden, 1977).…”

“…P/O ratio has further been explored in relation to sexual system (Lindsey, 1982;Jürgens & al., 2002;Choteau & al., 2006), pollination system (Plitman and Levin, 1990;Götzenberger & al., 2008), life form (Cruden, 1977;Small, 1988;Jürgens & al., 2002), seed mass (Götzenberger & al., 2006) and floral size (Etcheverry & al., 2012), among other parameters (see Ortega Olivencia & al., 1997). P/O ratio has not been examined in Passiflora L. yet.…”

Insights into the genetic architecture of sexual dimorphism from an interspecific cross between two diverging Silene (Caryophyllaceae) species

“…In this study, we explored the genetic basis of sexual dimorphism in an interspecific cross between two closely related Silene (Caryophyllaceae) species. Silene latifolia and Silene dioica differ in their degree of sexual dimorphism, pollination biology, habitat preferences, and have diverged relatively recently (Desfeux, Maurice, Henry, Lejeune, & Gouyon, 1996;Favre, Widmer, & Karrenberg, 2016;Jürgens, Witt, & Gottsberger, 2002;Waelti, Muhlemann, Widmer, & Schiestl, 2008;Waelti, Page, Widmer, & Schiestl, 2009).…”