BREEDING BIOLOGIES AND POLLINATORS FOR THREE WESTERN GLOBEMALLOWS
Location: Pollinating Insects-- Biology, Management and Systematics Research
Project Number: 5428-21000-013-15
Start Date: Feb 11, 2008
End Date: Dec 31, 2012
All of the wildflower species that I have thus far studied for Great Basin revegetation benefit from or require pollinators, and in all cases but one, the pollinators are exclusively bees. Experimental studies to reveal any fitness advantages of outcrossing over selfing require manual pollination trials using plants established and blooming in our common garden. We have thus far found gains in seed production or seedling vigor ranging from nil (for the two Cleome species) to more than doubling production of large viable seed and/or seedling vigor (the legumes). The next genus to be thus evaluated is Sphaeralcea (Malvaceae), specifically two Intermountain species, Sphaeralcea grossularifolia (H. & A.) Rydb. and S. munroana (Dougl.) Spach. A species more on the margins to the west of the Intermountain region, S. ambigua, will be added if possible, as it will be of great use in the sister seed increase program for the Mojave. The only study of reproductive biology for the genus, for S. laxa from the Sonoran desert, found that species to be largely self-incompatible, thus requiring outcrossing.
For both (or all 3) Sphaeralcea species, breeding biologies will be studied by comparing fruit and seed sets at caged flowers, openly visited flowers, and manually self- and cross-pollinated flowers in our common garden. We will use these data in combination with flower production and planting density to estimate seed production per hectare as well. Anticipating this need, we started plants from seed a year ago in our greenhouses, transplanting them into our common garden this autumn. From my experience with other globemallows and preliminary visitor surveys at these species, the only floral visitors are bees. Most of the visitors that I have seen in collections from this host have been ground-nesters, but we will survey their bee faunas around the Intermountain West for promising cavity-nesting species to manage. Alternatively, some of the ground-nesting Sphaeralcea specialist bees were abundant in Tom Monaco’s 3-yr-old trial plots here in the valley, despite a lack of nearby globemallows. Hence, it could be that if growers plant Sphaeralcea, the pollinators will come. Our preliminary trials in Monaco’s plots yielded abundant seed from freely-visited flowers (77% capsule set, 5.4 seeds per capsule), but no seeds from bagged racemes, showing that there is no autopollination. This study will define pollination needs for Sphaeralcea grossularifolia and S. munroana, estimate achievable seed yields, and reveal one or more dependable, effective pollinators.
While solving each forb species’ pollination needs for commercial seed growers, we have begun looking at the next step, sustainable restoration of these forbs in wildland plant communities. By “sustainable” I mean self-perpetuation by natural reseeding, which requires extant wild bee communities. Many restoration seedings will be into recently burned habitats. The impact of fire on native bee communities is unknown, although logical predictions are possible (e.g. ground-nesting species may fare better than species nesting above-ground in flammable deadwood). During 2006, I developed and refined an efficient and seemingly effective way to sample bee communities and floral guilds paired in and out of large burns, accompanied by an acceptable method for characterizing salient attributes of the plant community and spatial scales. The field trial with A. filipes growing in and around the 6-yr-old burn nw of Wells NV was successful, but awaits species’ ID. We will expand this survey method in 2007 and subsequent years, likely focusing on bee faunas of globemallows and A. filipes, simply because these are often present and responsive to sagebrush burns. Representative candidate sites include A. filipes at recent burns at Craters of the Moon and globemallows in both this summer’s burns around Elko and 2007 burns planned for research near Tooele Utah. If fire leaves native bee communities largely unscathed, then there would be good hope that restoration seedings will be well-pollinated to replenish their soil seed banks.