Adaptive Shifts in the Regulation System of Seed Yield in Japanese Species of Epimedium (Berberidaceae)

概要

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Total seed yield per plant in one season was differentiated neither between Epimedium diphyllum and the E. grandiflorum complex (E. grandiflorum and E. sempervirens), nor between these two groups and one of their hybrid derived species, E. trifoliatobinatum. Total ovules per plant and seed-set rate per capsule (SR) did not vary greatly between these species, and seed weight (SW) was almost the same between them. The number of flowers per inflorescence (F) was also constant. However, the remaining reproductive component characters, ovule number per ovary (O) and inflorescence number per plant (I), were differentiated between the three taxa. These two characters were negatively correlated and a trade-off relationship occurred under the constant total seed yield (=O×F×I×SR×SW). Ovule number per ovary was highly correlated with spur length of the flower. During the course of the hybrid speciation of E. trifoliatobinatum, selection pressure by pollinators on intermediate spur length seems to have favored plants with an intermediate ovule number. On the other hand, this selection pressure counteracted the increase of the inflorescence number under the trade-off. The resultant seed yield of E. trifoliatobinatum did not differ from that of the parental species, but the pattern of ovule allocation to ovaries (capsules) was altered.
種生物学会の論文