The effect of interplant distance on mating Success in Federally Threatened, Self‐Incompatible <i>Hymenoxys Herbacea = H. Acaulis</i> var. <i>glabra</i> (Asteraceae)

Abstract

We investigated large- and fine-scale effects of interplant distance on compatibility, seed set, and seed germination in a rare, self-incompatible perennial, Lakeside daisy (Hymenoxys herbacea = H. acaulis var. glabra). Plants were collected at the Marblehead Peninsula. Ohio, and transplanted to a greenhouse where they were hand-pollinated. For the large-scale analysis, 110 crosses were classified in three categories: Near crosses (0.75-6.70 m), Far crosses (17-72 m), and Very Far crosses (>900 ml. There was no significant effect of interplant distance on compatibility, seed set, or seed germination in these crosses. For the fine-scale analysis, we made 44 crosses with interplant distances ranging from 0.75 to 10 m. At this scale, interplant distance explained 10.9% of the variance of the seed/floret ratio, suggesting that local genetic structure may result in a modest amount of biparental inbreeding. We found no fine-scale effects of interplant distance on compatibility or percentage of seed germination, but it is possible that biparental inbreeding could affect later stages of the life cycle not included in this study. For all distance classes, >80% of the crosses were compatible, indicating that lack of compatibility between mates is not likely to limit seed production. Apparently, presumed population bottlenecks have not been severe enough for genetic drift to eliminate substantial numbers of self-incompatibility alleles.