Seed size variation: magnitude, distribution, and ecological correlates

Abstract

We examined seed-mass variation in 39 species (46 populations) of plants in eastern-central Illinois, USA. The coefficient of variation of seed mass commonly exceeded 20%. Significant variation in mean seed mass occurred among conspecific plants in most species sampled (by hierarchical ANOVA), averaging 38% of total variance. For most species, within-plant variation was the larger component of total variance, averaging 62% of total variance. Variation in seed mass among fruits within crops was significant in most species tested. We conclude that variation in seed mass among and within plants is widespread and common. There was little evidence of trade-offs between number of seeds and mean or variance of seed mass, and little correlational evidence of local competition for maternal resources. No consistent ecological (dispersal mode and growth form) correlates of variance of seed mass were evident.

Environmental and Genetic Sources of Diversification in the Timing of Seed Germination: Implications for the Evolution of Bet Hedging

“…Observed seed germination variance is often explained as a diversification bet-hedging strategy whereby individuals minimize the likelihood of complete reproductive failure by paying a cost in the form of a reduction in expected fitness. Explaining seed trait variance has been, and continues to be, a major concern to those interested in life-history evolution because of the close association between seed traits and fitness (e.g., Cohen 1966;Janzen 1969;Smith and Fretwell 1974;Harper 1977;Marks and Prince 1981;Venable 1985;Kalisz 1986;Michaels et al 1988;Venable and Brown 1988;Westoby et al 1992;Philippi 1993;Rees 1997;Simons and Johnston 2000a;Galloway 2002;Donohue et al 2005;Evans and Dennehy 2005).…”

“…Much seed trait variation also resides within species (Schaal 1980;Stanton 1984;Thompson 1984;Kalisz 1986;Michaels et al 1988;Zammit and Zedler 1990;Biere 1991a;Wolfe 1995;Galloway 2002;Imbert 2002), even in crop plants that have been subjected to artificial selection to control this variance (references in Silvertown 1984). This was neither expected on theoretical grounds (e.g., Smith and Fretwell 1974) nor recognized until the 1980s (Michaels et al 1988;Westoby et al 1992).…”

Variation in Lupinus arboreus alkaloid profiles and relationships with multiple herbivores

“…Environmental maternal effects can influence a variety of plant traits, including emergence time, rates of leaf development and juvenile size (Michaels et al, 1988;Helenurm and Schaal, 1996;Stanton and Galen, 1997). In the wild radish Raphanus raphanistrum, herbivory on maternal plants increased allocation to chemical defense in seedlings (Agrawal et al, 1999), but these effects became less pronounced in older plants, where defenses were more strongly determined by offspring environment (Agrawal, 2001(Agrawal, , 2002.…”

Genetic and environmental determinants of unreduced gamete production in Brassica napus, Sinapis arvensis and their hybrids

“…The combination of low-level baseline unreduced gamete production along with a single high-level producer highlights the variable nature of unreduced gamete production that may be a product of environment, development and genetics (Ramsey and Schemske, 1998). Intensive sampling at other scales, including within individuals, could reveal additional patterns, including the possibility that variation in unreduced gamete production may be greatest at the scale of the flower within an individual, as is the case for seed size (Michaels et al, 1988).…”