Effects of Distance Between Pollen Donor and Pollen Recipient on Fitness Components in Espeletia Schultzii

Abstract

The effect of flowering time and of distance between pollen donor and pollen recipient on the proportion of filled achenes, aborted seeds, and seedling survivorship was studied in populations of Espeletia schultzii in the Venezuelan Andes. Hand-pollinations were performed in two different years and at different times during the flowering season. Pollinations within-population included crosses between plants within a few meters to a maximum of 500 m apart and between-population pollinations included crosses between plants more than 10 km and up to 78 km away. Late in the flowering season, plants suffered a reduction in the proportion of filled achenes and an increase in aborted seeds. The proportion of filled achenes and aborted seeds did not vary significantly between the distances between pollen and ovules in crosses done early in the flowering season. However, the proportion of filled achenes in crosses between individuals within 30 m distance were very variable, either very successful or not successful. Beyond 30 m, for some of the populations, the frequency of unsuccessful crosses was almost 0. This pattern was observed at three elevation sites in two consecutive years. When crosses were done late in the flowering season, the proportion of filled achenes was lower in crosses between close individuals and between very distant ones. Seedling survivorship varied significantly between the crossing distances at the higher elevation only. The results show that a clear effect of the incompatibility alleles on the crossing success of the plants is present in the different populations examined, while they suggest that the effect of inbreeding or outcrossing depression is less clear but might still be present only under certain conditions. Late in the season, when plants might have fewer resources available for reproduction and at the high and intermediate site where cold and dry environmental conditions are less favorable for the plants, the discrimination among distances was stronger.

Pollination biology of Grindelia covasii (Asteraceae), a potential crop for arid lands

“…No observations of the pollen-stigma interactions were made in G. covasii, but the presence of sporophytic self-incompatibility (Sims, 1993) has been established in the closely related G. chiloensis (Roitman, 1995). The presence of obligate xenogamy has also been reported in other species of the genus (Shuck & McLaughlin, 1986) and in other genera of the Asteraceae, for example Bidens (Sun & Ganders, 1988), Senecio (Abott & Irwin, 1988), Espeletia (Sobrevila, 1988), and Cirsium (Michaux, 1989). Grindelia covasii flowers present a typical mellitophilous syndrome (Faegri & van der Pijl, 1966), offering visitors both nectar and pollen.…”

Influence of local floral density and sex ratio on pollen receipt and seed output: empirical and experimental results in dichogamous Alstroemeria aurea (Alstroemeriaceae)

“…Means that share the same lowercase letter do not dier signi®cantly (Ryan's Q test, P < 0.05) pressed as reduced seed output, was found in A. aurea (Aizen and Basilio 1995). Clonality and limited seed dispersal in A. aurea are expected to produce strong genetic structuring of populations, so that mating between two neighboring¯owering ramets likely results in reduced seed output (e.g., Coles and Fowler 1976;Park and Fowler 1982;Levin 1984;Sobrevila 1988;Waser and Price 1991). The compound result of genetically structured neighborhoods plus the occurrence of inbreeding depression is that the sexual identity of¯oral neighborhoods might greatly in¯uence average pollen ow distances and thus pollination quality.…”

Gene Flow by Pollen: Implications for Plant Conservation Genetics

“…The proposed mechanism for this fitness reduction is the breakdown of co-adaptation to local conditions in the hybrids or segregants (Templeton 1986, Waser andPrice 1989). Outbreeding depression for interplant matings at a spatial scale as short as 100 m has been well documented for Ipomopsis aggregate and Delphinium nelsoni (Price and Waser 1979, Waser and Price 1983 and occurs in many other species (reviewed by Sobrevila 1988, Waser 1991. The fitness decline can be substantial.…”