The Breeding System and Reproductive Ecology of the Endangered Plant Fagopyrum Dibotrys (d. Don) Hara

Distyly has been confirmed in Fagopyrum dibotrys (D. Don) Hara. The species are dimorphic in style length, anther height, pollen size and number but not in flower diameter, pollen surface ornamentation and stigma papilla cells. In F. dibotrys populations, style-morph ratios vary from isoplethy (1L : 1S) to strongly L-biased, or they more often contain only the L-morph. Moreover, it was found that larger isoplethic populations of F. dibotrys could produce more seeds than smaller single-morph populations. F. dibotrys had a smaller population size, morph-biased populations, and lower seed setting, which could be the reasons for the decrease in its population. Introduction Fagopyrum dibotrys (D. Don) Hara, (Polygonaceae), is an important wild plant resource and has long been used as a regular medicinal herb. Contemporary researches have shown that F. dibotrys has specific anti-cancer effects (Liu et al. 1981). Recently, F. dibotrys was listed as an endangered species in China (first batch) by the State Council of China in 1999. Distyly is a type of heterostyly that is characterized by the presence of two styles, long-styled and short-styled. For a species to be described as distylous, the principal requirement is that stigma and anther heights should differ reciprocally between morphs, i.e., they must show reciprocal herkogamy (Lloyd and Webb 1992). Quantitative morphological data are necessary to compare the positions of stigmas and anthers and recognize morphs in a population. The distylous breeding system of F. dibotrys has never been studied in detail. The aims of the study were to: (1) determine whether the species is typically distylous, (2) identify and understand polymorphism within the species, (3) determine the influence of the breeding systems on reproductive success and adaptation and (4) identify factors that have led to the endangerment of F. dibotrys. Materials and Methods To confirm distyly in F. dibotrys, corolla diameter, stigma and anther height, stigma-anther separation and relative reciprocity of the species were determined. From each of the four studied population (Siheshan = SHS, Tongcheng = TCH, Hongcun = HC, and Datongcun = DTC, Table 1), 30 flowers of each morph long styled (LS) and short styled (SS) were collected and kept in 70% ethanol until measurement. Corolla diameter was measured when the flower was at the full-open stage. Because the five stamens were at about the same height, anther height (AH) was considered as the height of each of the five stamens, up to the midpoint of each anther; the mean height of anthers was then calculated. Stigma height (SH) was measured from just above the ovary to the tip of the stigma. Stigma-anther separation refers to the spatial separation between the anther and * Author for correspondence: .