Sabal palmetto seed size: causes of variation, choices of predators, and consequences for seedlings

Abstract

High variation in seed size, as is common among angiosperms, may be maintained in a plant species when several factors select for seed size. Variation may also result from differences among adult plants, such as nutrient and water availability or the amount of photosynthetic tissue. In a study of Sabal palmetto seed ecology I found high seed size variation both within- and among-palms, and investigated possible factors maintaining this variation. Seed size was positively correlated with the number of leaves on parent palms. Larger seeds produced more vigorous seedlings that had greater leaf length, area, and mass, and greater root mass. Caryobruchus gleditsiae (Bruchidae: Coleoptera), whose larvae develop within palm seeds, preferentially oviposited on larger seeds, which in turn produced larger beetle offspring. By choosing the largest seeds available, ovipositing beetles thus affect both the quantity and the quality of seeds available for recruitment. I conclude that because beetle predation selects against large seeds, while larger seeds promote seedling vigor, the maintenance of seed size variation may be an adaptation of S. palmetto promoting both seed escape from predators and seedling vigor.

Propagule size and predispersal damage by insects affect establishment and early growth of mangrove seedlings

“…In the cases of Avicennia and Rhizophora, these larger seedlings also had more leaves than those that developed from smaller propagules. The latter result, that larger seedlings develop from larger propagules, appears quite general (Howe and Richter 1982;Stanton 1984;Wulff 1986b;Moegenburg 1996;Vaughton and Ramsey 1998;Eriksson 1999). However, the effect of propagule size on seedling establishment is more variable; in some cases there is little or no effect, as in our study (Wulff 1986b;Vaughton and Ramsey 1998;Eriksson 1999), but in others, seedling emergence rates are higher for larger propagules (Stanton 1984;Winn 1988).…”

“…Despite Harper et al's (1970) prediction that seed size should be a canalized trait that varies little within a species, intraspecific variation in seed size, of similar or greater magnitude to that which we observed, has been demonstrated in numerous subsequent studies. Such variation occurs over a wide range of spatial scales: within plants, among plants, and among populations (Wulff 1973(Wulff , 1986aSchaal 1980;Howe and Richter 1982;Stanton 1984;Winn 1988;Moegenburg 1996;Ramsey 1997, 1998;Eriksson 1999).…”

“…Several studies have found that the risk of predation by insects or small mammals increases with seed size (Thompson 1987;Reader 1993;Moegenburg 1996;Brewer 2001; but see Eriksson 1999) However, a recent model of the co-evolution of seed size and seed predation (Geritz 1998) predicts an evolutionary stable strategy consisting of a continuous range of seed sizes, with small seeds tending to be attacked more frequently than large seeds. In our system, we observed little or no correlation between rates of insect attack and propagule size.…”

Seed mass versus seedling performance in Scots pine: a maternally dependent trait

“…In general, it is accepted that, relative to large seeds, small seeds usually have reduced emergence (Zimmerman & Weis, 1983 ;Weller, 1985 ;Winn, 1988 ;Tripathi & Khan, 1990 ;Hendrix & Trapp, 1992 ;Rice et al, 1993 ;Prinzie & Chmielewski, 1994), higher mortality (Schaal, 1980 ;Tripathi & Khan, 1990 ;Bonfil, 1998) and lower seedling growth (Wulff, 1986a ;Hendrix et al, 1991 ;Dawson & Ehleringer, 1991 ;Baker et al, 1994 ;Moegenburg, 1996 ;Weiner et al, 1997 ;Vaughton & Ramsey, 1998 ;Bonfil 1998). However, other studies show no relationship between seed size and seedling performance in some species, as described by Cipollini & Stiles (1991), Rice et al (1993) and Vaughton & Ramsey (1998) for seed germination ; Hendrix & Trapp (1992) for seedling survival ; Dolan (1984) and Marshall (1986) for seedling growth.…”

Seed weight of Xylopia aromatica (Annonaceae): quality evaluation from X-ray and seedling emergence

“…Heavier seeds have more developed endosperm or cotyledons, are richer in the energy reserves necessary for germination (Gonzalez, 1993;Moegenburg, 1996), and can also show a higher hormone level and a larger embryo (Surles et al, 1993). Thus, seedlings from larger seeds emerge faster (Parker et al, 2006), but these characteristics do not necessarily guarantee seedling survival until maturity (Susko and Lovett-Doust, 2000).…”