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

Behavior of queen bumblebee pollinators on Primula sieboldii (Primulaceae) in response to different patch sizes and spacing

“…Rigney et al . 1993; Waser & Price 1994; Moran‐Palma & Snow 1997; Byers 1998), and the benefit of longer flight distances to larger patches may also apply to such species if their pollinators respond to patch size in the same manner.…”

Gene flow and inbreeding depression inferred from fine‐scale genetic structure in an endangered heterostylous perennial,Primula sieboldii

“…For long‐lived and hummingbird‐ and bumblebee‐pollinated Delphinium nelsonii , Waser & Price (1979, 1994) reported about 25% fitness reduction as a result of mating at 1 m compared with mating at 3 m and 10 m, although they also reported outbreeding depression in mating at excessive distance (≥ 30 m). Significant relationships between seed set and mating distance on only a fine spatial scale (0.75–10 m) was found in the lakeside daisy Hymenoxys herbacea (Moran‐Palma & Snow 1997). The expected spatial scale and magnitude of the fitness reduction in P. sieboldii were similar to those of these other species.…”

Effect of cross proximity on progeny fitness in a rare and a common species of Eupatorium (Asteraceae)

“…This interpretation of a decrease in fitness with nearby mating has been criticized since it is indirect (Heywood, 1993). In Hymenoxys herbacea, a rare self-incompatible species, seed set increased from 3 to 10 m but not at greater distances, and there was no effect of crossing distance on seed germination (Morán-Palma and Snow, 1997). This is particularly critical for rare species even if the detailed genetic basis is not known.…”