Seed size and sex ratio in spinach: application of the Trivers-Willard hypothesis to plants

• Published in: Écoscience (Sainte-Foy) 1994, Vol.1 (1), p.54-63
• Main Authors: Freeman, D.C, Wachocki, B.A, Stender, M.J, Goldschlag, D.E, Michaels, H.J
• Format: Article
• Language: English
• Subjects: Conflit parent-progéniture; Fruits; Germination; Parent-Offspring Conflict; Pericarp; Plants; Pollen; Rapport Des Sexes; reproduction; Seed size; Seeds; sex determination; Sex Ratio; Siblings; Spinacea oleracea; Spinach; Spinacia oleracea; theory; Épinards
• ISSN: 1195-6860; 2376-7626
• DOI: 10.1080/11956860.1994.11682228

Plants germinating from large spinach seeds have a significantly male-biased sex ratio while small seeds yield a female-biased sex ratio, as predicted by the Trivers-Willard hypothesis. This male-biased sex ratio is not due to differential germination or survivorship, nor is it the result of sexual lability. Seeds yielding males are not more likely to occur at lower nodes, or to be the first seed initiated at a node or to have fewer siblings at a node than females. Seeds yielding males acquire a disproportionate share of resources. Interestingly, the gender, but not the size of previously initiated seeds had a profound effect on the size of subsequent seeds and on the likelihood that these seeds would germinate. Males following females were much larger than females following males. If all of the previous seeds initiated at a node were of the same gender, the likelihood that subsequent seeds would fail to germinate was more than four times greater than if the previously initiated seeds were not of the same gender. These results are discussed in relation to maternal resource allocation, selection on males for increased pollen dispersal, parent-offspring conflict and genetic imprinting.