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Breeding biology of the threadstalk milkvetch, Astragalus filipes (Fabaceae), with a review of the genus.

INTRODUCTION

Plants in the legume family (Fabaceae sensu lato Lindl.) are of global economic and ecological significance. The Fabaceae is second only to the grasses in economic importance and is only smaller than the Orchidaceae and Asteraceae in numbers of species. Papilionoid legumes are particularly valuable as ground cover, forage and food crops (Allen and Allen, 1981).

The genus Astragalus L. is the largest of the flowering plant genera (Frodin, 2004). Comprising some 3270 species, Astragalus is most diverse in the Sino-Himalayan region, Russia, the Andes mountains of South America and across western North America (Allen and Allen, 1981; Isely, 1998). Nearly 400 species of Astragalus occur in North America, with 156 species occurring in the Intermountain West alone (Barneby, 1964). Plants in this genus are economically significant as a source of gum tragacanth, as indicators of selenium and uranium and as toxic locoweeds in rangelands (Allen and Allen, 1981). The more widespread and common species can support diverse elements of the region's pollinating bee communities as well (e.g., Green and Bohart, 1975; Clement et al., 2006)

Few Astragalus breeding biologies are known despite the size, geographic extent and prevalence of the genus. A literature search revealed known breeding biologies for only 29 Astragalus species worldwide, accounting for <1% of all Astragalus species (Table 1). These few species have breeding biologies that span the range of self fertility, from self compatible to self incompatible; a few are obligately xenogamous. One annual species (A. cymbicarpos Brot.) is even cleistogamous (Gallardo et al., 1993). This range of breeding biologies within the genus, coupled with a general paucity of knowledge about most species, makes predicting the breeding biology of a given Astragalus species dubious at best.

Our primary objective was to experimentally characterize the breeding biology of Astragalus filipes Torrey ex. A. Gray (threadstalk milkvetch or basalt milkvetch), which is widespread in western North American (Isely, 1998), and compare it with a compilation of other such studies with Astragalus. This species has been evaluated and now propagated for seed to use in future rangeland rehabilitation projects throughout its range (Shaw et al., 2005). Wildland seed production is erratic and susceptible to beetle predation, making it more costly and unpredictable than cultivated seed production (Youtie and Miller, 1986; Cane, 2008a). The first tested germplasm for A. filipes (NBR-1) was recently released for commercial cultivation (Johnson et al., 2008). Knowing a plant's breeding biology informs growers on whether or not they need pollinators for a seed crop, and the importance of outcrossing for consistent and copious seed production. We expect species that are good colonizers, as A. filipes is after fires, to be self-compatible (Kalin Arroyo, 1981; Bhattarai et al., 2008). Conversely, plants like A. filipes with considerable genetic diversity within populations (B.S. Bushman, pers. comm.) often prove to be outcrossers; thus, we speculated that A. filipes might be at least moderately self compatible although likely to benefit from outcrossing. In addition, we report preliminary findings for the composition of the pollinator guild that visits A. filipes in the wild, to discover the kinds of pollinators that might be practical and suitable for this native seed crop.

METHODS

NATURAL HISTORY OF A. FILIPES

Astragalus filipes ranges from the southern Great Basin northward into the Columbia Plateau, with some disjunct populations in southern British Columbia, the San Bernardino mountains of southern California and northern Baja California (Barneby, 1964; Isely, 1998). In some parts of its range A. filipes is "one of the truly common astragali ... often occurring in colonies of great extent, sometimes in such quantity as to color the sagebrush hillsides with a wash of creamy, spicily fragrant blossoms" (Barneby, 1964). Due to its lack of toxins for livestock (Williams and Barneby, 1977) and its extensive ecological and geographic range, A. filipes shows promise for restoration use (Shaw et al., 2005; Bhattarai et al., 2008). The fruits of A. filipes are presented on erect racemes easily accessible for mechanical seed harvest by combine. These factors make A. filipes a good candidate species for cultivated seed production.

PLANT ACQUISITION

Seeds were collected from wild Astragalus filipes populations in fall 2003 by Douglas Johnson and Kevin Connors (USDA-ARS-FRRL). Seed locations used for this experiment represent eight different Omernik Level IV Ecoregions (Omernik, 1987; Table 2). Seeds were germinated, and transplanted into forestry "conetainers" in Jan. 2004. A pair of small experimental arrays was established in a common garden at the USDA-ARS Bee Biology and Systematics Laboratory (BBSL), Logan, UT, USA. The silty clay-loam soil was amended with pea gravel for improved drainage. Seedlings were planted out in May 2004 into holes cut in weed barrier fabric to simplify weed control.

POLLINATION TREATMENTS

In May 2005, one array of Astragalus filipes plants was covered with a walk-in net field cage (6 x 6 x 2 m) to exclude pollinators and facilitate manual pollinations with minimal handling of the plants. In the caged array, three pollination treatments were assigned to separate tagged racemes on each plant, replicated for 24 plants (Fig. 1). Each flower (Fig. 1) on a raceme received the same pollination treatment. Racemes were chosen before bloom, using those with at least five buds. Number of flowers per raceme varied, and a range of four to 23 flowers were treated per raceme (mean = 12 flowers). The often numerous other racemes were not pollinated. The three manual pollination treatments were: (1) geitonogamy, in which pollen was transferred from flowers of an unmarked raceme to a recipient flower on the same plant; (2) xenogamy, in which flowers of the treatment raceme received pollen from another donor plant from within the same seed accession location as the recipient plant; (3) distant xenogamy, in which flowers of the treatment raceme received pollen from donor plants belonging to a different Ecoregion than that of the recipient flowers (Table 2, Fig. 2). This distantly outcrossed treatment allowed us to examine the possibility of outbreeding depression by transferring pollen between populations too distant for manual pollen transfer in the wild.

All pollen was transferred using the plush dorsal thoraces of dead honeybees as disposable fine brushes, which we first rubbed against the anthers of the donor flower(s) and then immediately pressed against the stigma of a recipient flower. Each honeybee was used to pollinate only a single raceme's open flowers of a given day, then discarded, as crosses were specific to a given plant (geitonogamy) or geographic source (outcrossing). Manual pollination required two persons, one to carefully depress a flower's keel to extend the style and expose the stigma, the other to brush the delicate stigma with the pollen-laden honey bee cadaver. Following pollen transfer, the bright orange pollen was visibly heaped on the tiny stigmas (10x magnification). We also retained one raceme per caged plant as a negative control treatment of autogamy, for which flowers were counted and marked but otherwise left unmanipulated. Each treated flower was marked on the banner petal with indelible ink. Flowers were counted and pollinated every other day at mid-late morning until the racemes produced no new flowers. Plants of the neighboring array were left uncaged as a positive control to evaluate pod and seed set resulting from incidental visits by bees available at BBSL, again mostly visiting mid-late morning. These plants served as our open visitation treatment.

SEED PRODUCTION

Once the fruits (pods) were mature, but just before dehiscence, the racemes were collected and returned to the laboratory. Total number of fruits per raceme was recorded, as well as each pod's content of plump seeds. Aborted ovules were tiny and disregarded. Plump seeds were allowed to dry and mature at 25 C for 2 mo before being placed in cold storage (4 C).

SEED GERMINATION

Seeds were stored dry in envelopes at 4 C for 6 mo. After storage, all plump seeds were poked with an insect pin to perforate the seed coat for better water permeation. Seeds from the same raceme were then placed together in a single well of a tissue culture plate submerged in distilled water imbued with a fungicide to prevent mold. These tissue culture plates were then placed in a dark cold room (4 C) and the seeds were monitored for germination. We recorded if the radicle was protruding from the seed coat and transplanted the germinating seed to a conetainer with a native soil mix.

[FIGURE 1 OMITTED]

SEED COUNTS FROM WILD POPULATIONS

Seeds were collected in 2005 from four different wild Astragalus filipes populations: Pequop Summit, Elko County, NV (2); Big Gulch, Custer County, ID; and King Hill, Elmore County, ID. We counted the seed contents of 100 pods for each population to establish a baseline of wild seed set against which we compared our open visitation seed set at the Logan common garden.

BEE GUILDS FROM WILD POPULATIONS

The fauna of bees that visit Astragalus filipes (and other dominant forbs) are being collected from around the Great Basin and Snake River Plains as part of a larger study dealing with the effects of wildfire on bee communities. We have net collected bees visiting flowers of A. filipes at 24 populations growing in sagebrush basins and dry coniferous forests across five states (California, Idaho, Nevada, Oregon, Utah) during May and June. Identifications to species are ongoing for some genera, notably Osmia.

DATA ANALYSIS

We tested the null hypothesis that frequency of fruit set is independent of manual pollination treatment with an R x C Test of Independence using a C-Test with William's correction (Sokal and Rohlf, 1981). Rows were manual pollination treatments, and columns were counts of pods produced or failed pollinations (no pod). Individual flowers were used as independent replicates, as they arose from separate pollination events (often on different days as bloom proceed along a given raceme). We excluded open visitation data from this analysis, since that used different plants. A significant test for an overall effect of treatment on fruit set was followed by pairwise comparisons with G-Tests (Sokal and Rohlf, 1981). Only flowers setting fruits were used for subsequent seed set analyses.

We compared pollination treatments for the fraction of pods that contained one or more seeds (categorical analysis, CATMOD, SAS Institute, 2004). The linear model compared the proportion of seeded pods of each manual pollination treatments with our distant xenogamy treatment. We used distant xenogamy for comparison, as there was no significant difference in proportion of seeded pods between it and our xenogamy treatment. We made three orthogonal pairwise contrasts: autogamy vs. geitonogamy, geitonogamy vs. outcross and freely-visited vs. outcross.

[FIGURE 2 OMITTED]

We used the Kruskal-Wallis test on ranked seed counts per pod, excluding empty pods, to compare seed counts per pod across pollination treatments (Proc NPARIWAY; SAS Institute, 2004). Germination percentages (transformed to their arcsine values) for seeds from the different pollination treatments were analyzed with General Linear Model (GLM) ANOVA followed by REGWQ a posteriori tests. Seed counts per fruit were also compared using a GLM ANOVA for samples from the four wild populations and our open visitation treatment at the common garden. These data were satisfactorily transformed by adding one to each value, then applying a cube root transformation. Seed count means were compared using REGWQ a posteriori tests.

RESULTS

Overall, we manually pollinated 830 flowers and marked 795 more (372 flowers for autogamy and 423 freely-visited flowers) to track their reproductive fates. Collectively, the 835 pods that resulted contained 1065 seeds.

Cross pollination significantly enhanced fruit and seed set compared with the two self pollination treatments (autogamy and geitonogamy). The likelihood of fruit set differed among pollination treatments ([G.sub.[3.1191]] = 12.38, P < 0.001, Fig. 3). Flowers of autogamous racemes were less likely to set fruit than any of the other pollination treatments ([G.sub.adj] = 107, P < 0.001). The frequencies of seedless pods differed considerably between pollination treatments ([G.sub.G[4,835]] = 255, P < 0.001, Fig. 4). From the orthogonal contrasts, flowers of autogamous racemes produced more seedless pods than geitonogamous flowers (G = 5.1, P = 0.024), which in turn set more seedless pods than xenogamous racemes (G = 11.2, P = 0.001). Open visitation racemes set proportionately more seeded pods than xenogamous racemes (G = 48.2, P < 0.001). Pollination treatments also differed in the counts of seeds per pod, both for all pods ([H.sub.[3.204]] = 10.7, P = 0.014, Fig. 5) as well as for the subset of seeded pods ([H.sub.[3,187]] = 9.9, P = 0.007).

[FIGURE 3 OMITTED]

Percent germinable seed per raceme varied with pollination treatment ([F.sub.[4.59]] = 3.2, P = 0.02, Table 3). Distant xenogamous seeds were significantly less likely to germinate than seeds from geitonogamy, xenogamous and open visitation treatments. Autogamous seeds were not evaluated as so few were produced. Seed germination spanned a 15 wk period, with a pulse of germination in the 10th week for seeds from each treatment group.

Openly pollinated populations differed in seed set per fruit ([F.sub.[4,658]] = 12.9, P < 0.001, Fig. 6). Openly visited plants in our common garden at BBSL set significantly fewer seeds per pod than did Astragalus filipes plants from four wild populations. Samples from the four wild populations had comparable seed counts per fruit.

The floral visitors foraging at flowers of Astragalus filipes are all bees (adult seed weevils are also present, but they are ovipositing in the young pods). Few of the visiting individuals and species of bees foraging at flowers of A. filipes were social bees (bumblebees mainly) and none appears to be a specialist (=oligolege) for the genus Astragalus. Half of the 353 individual bees thus far sampled at A. filipes belong to 34 species of the bee genus Osmia (Megachilidae), with additional species in the genera Anthidium, Bombus, Eucera (Fig. 1) and Hoplitis also regularly found with the guild of bees sampled at A. filipes flowers.

[FIGURE 4 OMITTED]

DISCUSSION

Breeding biologies of papilionoid legumes are diverse, ranging from cleistogamous to obligately xenogamous (Kalin Arroyo, 1981). Though moderately self-compatible, Astragalus filipes and many other papilionoid legumes are bee pollinated (Kalin Arroyo, 1981). They benefit strongly from outcrossing facilitated by bee visitation. This combination of self-compatibility, but with reproduction enhanced considerably by outcrossing, is often classified as a "mixed mating system" (Neal and Anderson, 2005).

The autogamous (unmanipulated) treatment yielded significantly less fruit and seed set than any other treatment, indicating that most Astragalus filipes Seed production does not result from mere autopollination. Cross pollination yielded nine times more seed than autogamy (93 vs. 11 seeds per 100 flowers) and three times more than geitonogamy (32 seeds per 100 flowers). Hence, although a colonizing individual can produce some progeny, even in the absence of pollinators, a substantial fraction of seed from well pollinated plants in a population likely result from cross pollination.

[FIGURE 5 OMITTED]

Openly visited flowers yielded the most seed per fruit, significantly more than the manual pollination treatments. These flowers likely received more frequent pollen deposition than did our manually pollinated flowers, each of which we pollinated only once. We observed bumble bee queens (Bombus huntii Greene, B. fervidus (Fabricius)) and workers (B. huntii) foraging at these uncaged plants frequently throughout the day. Similar to our results, Geer and Tepedino (1993) found that bees were superior pollinators to the experimenters for another Astragalus species. Despite the considerable fruit and seed set conferred by bumble bees in our common garden, our openly visited seed production was still less than that found in wild A. filipes populations (Fig. 6). Perhaps our pollinator guild, which was primarily just Bombus, was less effective than the species-rich guild of bees dominated by diverse Osmia species that we are finding associated with wild A. filipes throughout its range. Additionally, A. filipes plants may perform better in their respective native locations than in our common garden; a large comparison of accessions in a nearby common garden showed a wide range of performance (Bhattarai et al., 2008). Furthermore, most wild plants that we have surveyed were larger and likely older than our young transplants.

[FIGURE 6 OMITTED]

A smaller proportion of distant xenogamous seeds germinated compared with those from geitonogamy, within-population xenogamy or open visitation treatments. This negative effect of pollen transfer among geographically distant accessions on seed germination rates raises concern of possible outbreeding depression (Price and Waser, 1979), wherein locally adapted genotypes are disrupted or even swamped by mixing with other more distant populations. This concern is relevant to situations wherein farmed seed produced from distant germplasm accessions is seeding back into landscapes where conspecific populations persist (Monsen and Shaw, 2001; Hufford and Mazer, 2003; McKay et al., 2005; Becker et al., 2006). However, experimental trends with small sample sizes such as our's may not reasonably represent conditions at a larger scale. According to B.S. Bushman (pers. comm.) most detected genetic variability in Astragalus filipes is within populations, as is expected for a primarily outcrossing species. Outbreeding depression is less likely to be significant for species with genetically diverse populations.

A rich diversity of breeding biologies is represented among even the small sample (29) of Astragalus species that have been thus studied and reported. From our literature review (Table 1), half (15) of the studied species are self compatible. Of these self compatible species, five are widespread and ten have restricted distributions. Four more species are self compatible but benefit from xenogamous pollen transfer. One third (10) of the species are obligate outcrossers: seven are geographically widespread and three are restricted. Most threatened or endangered astragali are self compatible, though one endangered species in Arizona, A. cremnophylax Barneby, varies from inbreeding to self incompatible, dependent on location and subspecies (Allphin et al., 2005). Among the widespread species, five are self-compatible, seven are obligate outcrossers and three benefit from outcrossing. One unusual annual species from Spain and North Africa, A. cymbicarpos Brot., is even cleistogamous in some populations (Gallardo et al., 1993). Predicting the breeding biology of a single Astragalus species, therefore, is speculative, owing to the diversity of breeding biologies, lack of correlates with life history or ecology and our general lack of knowledge about most species within this genus.

As in other papilionoid legumes, bees commonly visit Astragalus flowers for nectar and pollen (Kalin Arroyo, 1981). Among the 1/2 million bees pinned in the collections of the BBSL, 3400 specimens representing 192 bee species are labeled as having been taken at Astragalus. Among these floral hosts are 55 different species of Astragalus. No species of Astragalus is given for one third of the pinned specimens, probably due to the daunting identification challenge. Perhaps for this reason also, no bee in the BBSL collection was recorded from A. filipes until this study.

The remarkable diversity of Osmia bees thus far identified from specimens collected at A. filipes represents 1/4 of the named species of Osmia in all of North America (Cane et al., 2007). Abundant and diverse Osmia have been observed for other Astragalus species at other locations, with Osmia comprising more than 60% of the total flower visitor fauna sampled from three other Astragalus species over 3 y (Geer et al., 1995). As in that study and others (Green and Bohart, 1975; Clement et al., 2006), bees of the genera Anthidium, Bombus, Eucera (Fig. 1) and Hoplitis were also regular members of the guild of bees sampled at A. filipes flowers.

One of the cavity-nesting megachilid bees that forages at Astragalus filipes, Osmia bruneri Ckll., is widespread across the Intermountain West (Frohlich and Tepedino, 1986) where growers have recently begun to plant released germplasm of A. filipes (Johnson et al., 2008). At the Logan lab, JHC is multiplying and evaluating a growing captive population of this species using nesting substrates, shelters and season management protocols developed and successfully implemented for a close relative, O. aglaia Sandhouse (Cane, 2008b). The population is multiplying 2-4-fold annually in straw-lined wooden (and polystyrene) nesting blocks, in agreement with an earlier report of their nesting success in captivity (Frohlich and Tepedino, 1986). Individual females have reproduced successfully when their foraging was confined to a cage over one of our A. filipes plots.

We found that Astragalus filipes has a mixed mating system, as it is self compatible but benefits greatly from outcrossing. Bees of several genera were regularly observed visiting A. filipes at numerous locations. Bees apparently transfer pollen better than manual pollination by researchers. Wild populations of A. filipes set significantly more seed per pod than did our open visitation treatment. Our research adds to the meager body of literature on breeding biologies of Astragalus, the largest genus of flowering plants, and will help guide successful production of this species for seed to be used in wildland restoration projects in the western USA.

Acknowledgments.--Melissa Weber, Joyce Knoblett and Stephanie Miller provided invaluable help with field and lab aspects of this study. Kevin Connors was indispensible in providing and transplanting the array of seedlings used for our experiments. Scott Jensen, Douglas Johnson and Ann DeBolt kindly provided fruit from wild A. filipes populations. Josh Der, E.W. Evans and E.W. Schupp provided valuable feedback on this manuscript. Research funded by Great Basin Native Plant Selection and Increase Project through the USDI-BLM Great Basin Restoration Initiative and the USDA-FS Rocky Mountain Research Station.

SUBMITTED 3 MAY 2010

ACCEPTED 17 SEPTEMBER 2010

LITERATURE CITED

ALLEN, O. N. AND E. K. ALLEN. 1981. The Leguminosae, a Source Book of Characteristics, Uses, and Nodulation. Univ. Wisconsin Press, Madison. 812 p.

ALLPHIN, L., N. BRIAN AND T. MATHESON. 2005. Reproductive success and genetic divergence among varieties of the rare and endangered Astragalus cremnophylax (Fabaceae) from Arizona, USA. Consero. Genet., 6:803-821.

BARNEBY, R. C. 1964. Atlas of North American Astragalus. Part I. The Phacoid and Homaloboid Astragali. Mem. N. Y. Bot. Gard., 13:1-1188.

BASKIN, C. C., J. M. BASIN AND E. QUARTERMAN. 1972. Observations on the ecology of Astragalus tennesseensis. Am. Midl. Nat., 88:167-182.

BECKER, U., T. REINHOLD AND D. MATTHIES. 2006. Effects of pollination distance on reproduction and offspring performance in Hypochoeris radicata: experiments with plants from three European regions. Biol. Conserv., 132:109-118.

BHATTARAI, K., D. A. JOHNSON, T. A. JONES, K. J. CONNORS AND D. R. GARDNER. 2008. Physiological and morphological characterization of Basalt Milkvetch (Astragalus filipes): basis for plant improvement. Range. Ecol. Mngmt., 61:444-455.

BRYCE, S. A., A. J. WOODS, J. D. MOREFIELD, J. M. OMERNIK, T. R. MCKAY, G. K. BRACKLEY, R. K HALL, D. K. HIGGINS, D. C. MCMORRAN, K. E. VARGAS, E. B. PETERSEN, D. C. ZAMUDIO AND J. A. COMSTOCK. 2003. Ecoregions of Nevada (color poster with map, descriptive text, summary tables, and photographs): Reston, Virginia, U.S. Geological Survey (map scale 1:1,350,000).

CANE, J. H., T. GRISWOLD AND F. D. PARKER. 2007. Substrates and materials used for nesting by North American Osmia bees (Hymenoptera: Apitormes: Megachilidae). Ann. Entom. Soc. Am., 100:350-358.

--. 2008a. Pollinating bees crucial to farming wildflower seed for U.S. habitat restoration, p. 48-64. In: James, R. R. and T. Pitts-Singer (eds.). Bees in agricultural ecosystems. Oxford University Press, New York.

--. 2008b. An effective, manageable bee for pollination of Rubus bramble fruits, Osmia aglaia. Acta Horticult., 777:459-464.

CLEMENT, S. L., T. GRISWOLD, R. W. RUST, B. C. HELLIER AND D. M. STOUT. 2006. Bee associates of flowering Astragalus and Onobrychis genebank accessions at a Snake River site in Eastern Washington. J. Kans. Entom. Soc., 79:254-260.

FRODIN, D. G. 2004. History and concepts of big plant genera. Taxon, 53:753-776.

FROHLICH, D. R. AND V. J. TEPEDINO. 1986. Sex ratio, parental investment, and interparent variability in nesting success in a solitary bee. Evolution, 40:142-151.

GALLARDO, R., E. DOMINGUEZ AND J. M. MUNOZ. 1993. The heterochronic origin of the cleistogamous flower in Astragalus cymbicarpos (Fabaceae). Am. J. Bot., 80:814-823.

--,--AND J. M. MUNOZ. 1994. Pollen-ovule ratio, pollen size, and breeding system in Astragalus (Fabaceae) subgenus Epiglottis:. a pollen and seed allocation approach. Am. J. Bot., 81:1611-1619.

GEER, S. M. AND V. J. TEPEDINO. 1993. Breeding systems of the rare Heliotrope milkvetch (Astragalus montii Welsh: Fabaceae) and two common congeners, p. 334-344. In: R. Sivinski and K. Lightfoot (tech. coords.). Proceedings of the Southwestern Rare and Endangered Plant Conference. New Mexico Forestry and Resources Conservation Division, Santa Fe.

--,--, T. L. GRISWOLD AND W. R. BOWLIN. 1995. Pollinator sharing by three sympatric milkvetches, including the endangered species Astragalus montii. Great Basin Nat., 55:19-28.

GREEN, T. W. AND G. E. BOHART. 1975. The pollination ecology of Astragalus cibarius and Astragalus utahensis (Leguminosae). Am. J. Bot., 62:379-386.

HUFFORD, K. M. AND S. J. MAZER. 2003. Plant ecotypes: genetic differentiation in the age of ecological restoration. Trends Ecol. Evol., 18:147-155.

ISELY, D. 1998. Native and naturalized Leguminosae (Fabaceae) of the United States. Brigham Young University Press, Provo. 1007 p.

JOHNSON, D. A., T. A. JONES, K. J. CONNORS, K. BHATTARAI, B. S. BUSHMAN AND K. B. JENSEN. 2008. Notice of release of NBR-1 germplasm Basalt Milkvetch. Native Plants J., 9:127-132.

KALIN ARROYO, M. T. 1981. Breeding systems and pollination biology in Leguminosae, p. 723-769. In: R. M. Polhill and P. H. Raven (eds.). Advances in legume systematics part 2. Royal Botanic Gardens, Kew, UK.

KARRON, J. D. 1987. The pollination ecology of co-occurring geographically restricted and widespread species of Astragalus (Fabaceae). Biol. Conserv., 39:179-193.

--. 1989. Breeding systems and levels of inbreeding depression in geographically restricted and widespread species of Astragalus (Fabaceae). Am. J. Bot., 76:331-340.

KAYE, T. N. 1999. From flowering to dispersal: reproductive ecology of an endemic plant, Astragalus australis var. olympicus (Fabaceae). Am. J. Bot., 86:1248-1256.

KUDO, G. AND L. D. HARDER. 2005. Floral and inflorescence effects on variation in pollen removal and seed production among six legume species. Funct. Ecol., 19:245-254.

--AND U. MOLAU. 1999. Variations in reproductive traits at inflorescence and flower levels of an arctic legume, Astragalus alpinus L.: comparisons between a subalpine and an alpine population. Plant Sp. Biol., 14:181-191.

MCKAY, J. K., C. E. CHRISTIAN, S. HARRISON AND K.J. RICE. 2005. "How local is local?"--A review of practical and conceptual issues in the genetics of restoration. Rest. Ecol., 13:432-440.

MCGRATH, C. L., A. J. WOODS, J. M. OMERNIK, S. A. BRYCE, M. EDMONDSON, J. A. NESSER, J. SHELDEN, R. C. CRAWFORD, J. A. COMSTOCK AND M. D. PLOCHER. 2002. Ecoregions of Idaho (color poster with map, descriptive text, summary tables, and photographs): Reston, Virginia, U.S. Geological Survey (map scale 1:1,350,000).

MONSEN, S. B. AND N. L. SHAW. 2001. Development and use of plant resources for western wildlands, p. 47-61. In: E. D. McArthur and D. J. Fairbanks (tech. coords.). Shrubland ecosystem genetics and biodiversity: proceedings. USDA-FS Rocky Mountain Research Station, Ogden, UT.

NEAL, P. R. AND G. J. ANDERSON. 2005. Are 'mating systems' 'breeding systems' of inconsistent and confusing terminology in plant reproductive biology? or is it the other way around? Plant Syst. Evol., 250:173-185.

OMERNIK, J. M. 1987. Ecoregions of the conterminous United States. Ann. Assoc. Am. Geog., 77:118-125.

--AND A. L. GALLANT. 1986. Ecoregions of the Pacific Northwest. EPA/600/3-86/033. U.S. EPA, Environmental Research Laboratory, Corvallis, OR. p. 1-39.

PLATT, W. J., G. R. HILL AND S. CLARK. 1974. Seed production in a prairie legume (Astragalus canadensis L.). Oecologia, 17:55-63.

PRICE, M. V. AND N. M. WASER. 1979. Pollen dispersal and optimal outcrossing in Delphinium nelsoni. Nature, 277:294-297.

RICHARDS, K. W. 1986. Pollination requirements of cicer milkvetch, Astragalus cicer L. J. Range Mngmt., 39:457-459.

SAS INSTITUTE. 2004. SAS/Stat 9.1 User's Guide. SAS Institute, Inc., Cary, NC. 5136 p.

SHAW, N. L., S. M. LAMBERT, A. M. DEBOLT AND M. PELLANT. 2005. Increasing native forb seed supplies for the Great Basin, p. 94-102. In: R. K. Dumroese, L. E. Riley and T. D. Landis (tech. coords.). National proceedings: Forest and Conservation Nursery Associations--2004. USDA-FS Rocky Mountain Research Station, Fort Collins, CO.

SOKAL, R. R. AND F.J. ROHLF. 1981. Biometry. W. H. Freeman and Company, San Francisco. 859 p.

SUGDEN, E. A. 1985. Pollinators of Astragalus monoensis Barneby (Fabaceae): new host records; potential impact of sheep grazing. Great Basin Nat., 45:299-312.

TEPEDINO, V.J. 2005. Final report. Reproduction and pollination of Astragalus from Washington County, southern Utah: A. holmgreniorum and A. ampullarioides, p. 2-16. USDA-ARS Bee Biology & Systematics Laboratory, Department of Biology, Utah State University, Logan.

THORSON, T. D., S. A. BRYCE, D. A. LAMMERS, A. J. WOODS, J. M. OMERNIK, J. KAGAN, D. E. PATER AND J. A. COMSTOCK. 2003. Ecoregions of Oregon (color poster with map, descriptive text, summary tables, and photographs): Reston, Virginia, U.S. Geological Survey (map scale 1:1,500,000).

WILLIAMS, M. C. AND R. C. BARNEBY. 1977. The occurrence of nitro-toxins in North American Astragalus (Fabaceae). Brittonia, 29:310-326.

YOUTIE, B. A. AND R. F. MILLER. 1986. Insect predation on Astragalus filipes and A. purshii seeds. Northwest Sci., 60:42-46.

KRISTAL M. WATROUS

Department of Biology, Utah State University, Logan 84322

AND

JAMES H. CANE (1)

USDA-ARS Bee Biology and Systematics Laboratory, Utah State University, Logan 84322

(1) Corresponding author: e-mail: Jim.Cane@ars.usda.gov
TABLE 1.--Literature review of Astragalus breeding biologies.
Pollinator genera are included, if known

Astragalus species        Breeding biology          Distribution

A. alpinus L.           obligate outcrosser     widespread,
                                                  circumpolar
                                                  subarctic & arctic
A. americanus (Hook.)   obligate outcrosser     widespread, W.N.Am.
  M.E. Jones
A. ampullarioides       self-compatible         Endangered
  (S.L. Welsh) S.L.                               (restricted),
  Welsh                                           W.N.Am.
A. australis (L.)       moderately              Threatened
  Lam. var. olympicus     self-compatible         (restricted),
  Isely                                           W.N.Am.
A. canadensis L.        obligate outcrosser     widespread, W.N.Am.
A. cibarius Sheldon     outcrossing             widespread, W.N.Am.
                          beneficial
A. cicer L.             outcrossing             widespread crop,
                          beneficial              cosmopolitan
A. cremnaphylax var.    self-compatible         Endangered
  cremnaphylax, North                             (restricted),
  Rim population                                  W.N.Am.
A. cremnaphylax var.    obligate outcrosser     Endangered
  cremnophylax, South                             (restricted),
  Rim population                                  W.N.Am.
A. cremnophylaxvar.     self-compatible         Endangered
  herronii                                        (restricted),
                                                  W.N.Am.
A. cremnophylax var.    outcrossing             Endangered
  myriorraphis            beneficial              (restricted),
                                                  W.N.Am.
A. eymbicarpos Brot.    cleistogamous and       restricted, Iberian
                        chasmogamous are          peninsula & North
                          self-compatible         Africa
A. edulis Durieu ex     self-compatible         widespread, Europe
  Bunge                                           to W. Asia
A. epiglottis L.        self-compatible         widespread, Africa,
  subsp. epiglottis                               Europe & Middle
                                                  East
A. epiglottis L.        self-compatible         restricted, Spain
  subsp. asperulus
  (Dufour) Nyman
A. hamosus L.           self-compatible         widespread, Europe
A. holmgreniorum        self-compatible         restricted, W.N.Am.
  Barneby
A. humillimus A. Gray   self-compatible         Endangered
                                                  (restricted),
                                                  W.N.Am.
A. kentrophyla var.     obligate outcrosser     widespread, W.N.Am.
  tegetarius
  (S. Wars.) Dorn
A. linifolius Osterh.   self-compatible,        restricted, W.N.Am.
                          moderately
                          autogamous
A. lonchocarpus         self-compatible         widespread, W.N.Am.
  Torrey
A. miser var.           obligate outcrosser     widespread, W.N.Am.
  oblongifolius
  (Rydb.) Cron.
A. monoensis Barneby    obligate outcrosser     restricted, W.N.Am.
A. montii Welsh         self-compatible         Endangered
                                                  (restricted),
                                                  W.N.Am.
A. osterhouti M.E.      moderately              restricted, W.N.Am.
  Jones                   self-compatible
A. pectinatus (Hook.)   obligate outcrosser     widespread, W.N.Am.
  G.Don
A. striatus Nutt.       obligate outcrosser     widespread, W.N.Am.
A. tennesseensis        obligate outcrosser     restricted, Midwest
  Chapman                                         U.S.
A. utahensis (Torr.)    outcrossing             widespread, W.N.Am.
  Torr. & A. Gray         beneficial

Astragalus species           Pollinators              Reference

A. alpinus L.           Bombus sp.              Kudo & Molau 1999
A. americanus (Hook.)   Bombus sp.              Kudo & Harder 2005
  M.E. Jones
A. ampullarioides       Anthophora sp.,         Tepedino 2005
  (S.L. Welsh) S.L.       Bombus sp.,
  Welsh                   Dialictus sp.,
                          Osmia sp.
A. australis (L.)       Anthidium sp.,          Kaye 1999
  Lam. var. olympicus     Bombus sp.,
  Isely                   Megachile sp.,
                          Osmia sp.
A. canadensis L.        Bombus sp.              Platt et al. 1974
A. cibarius Sheldon     Anthophora sp.,         Green & Bohart 1975
                          Bombus sp.,
                          Eucera sp.
A. cicer L.             Apis mellifera,         Richards 1986
                          Bombus sp.,
                          Megachile sp.
A. cremnaphylax var.    unknown                 Allphin et al. 2005
  cremnaphylax, North
  Rim population
A. cremnaphylax var.    unknown                 Allphin et al. 2005
  cremnophylax, South
  Rim population
A. cremnophylaxvar.     unknown                 Allphin et al. 2005
  herronii
A. cremnophylax var.    unknown                 Allphin et al. 2005
  myriorraphis
A. eymbicarpos Brot.    unknown                 Gallardo et al. 1993,
                                                  1994
A. edulis Durieu ex     unknown                 Gallardo et al. 1994
  Bunge
A. epiglottis L.        unknown                 Gallardo et al. 1994
  subsp. epiglottis
A. epiglottis L.        unknown                 Gallardo et al. 1994
  subsp. asperulus
  (Dufour) Nyman
A. hamosus L.           unknown                 Gallardo et al. 1994
A. holmgreniorum        Anthophora sp.,         Tepedino 2005
  Barneby                 Apis mellifera
A. humillimus A. Gray   Apis mellifera,         Geer et al.
                          Eucera sp.,             unpublished
                          Osmia sp.
A. kentrophyla var.     Anthidium sp.,          Geer & Tepedino 1993;
  tegetarius              Osmia sp.               Geer et al. 1995
  (S. Wars.) Dorn
A. linifolius Osterh.   Anthophora sp.,         Karron 1987, 1989
                          Apis mellifera,
                          Bombus sp,
                          Osmia sp.
A. lonchocarpus         Anthophora sp.,         Karron 1987, 1989
  Torrey                  Apis mellifera,
                          Bombus sp.,
                          Osmia sp.
A. miser var.           Bombus sp., Osmia sp.   Geer & Tepedino 1993;
  oblongifolius                                   Geer et al. 1995
  (Rydb.) Cron.
A. monoensis Barneby    Anthidium sp.,          Sugden 1985
                          Apis mellifera,
                          Bombus sp.,
                          Hoplitis sp.,
                          Osmia sp.
A. montii Welsh         Anthidium sp.,          Geer & Tepedino 1993;
                          Osmia sp.               Geer et al. 1995
A. osterhouti M.E.      Anthophora sp.,         Karron 1987, 1989
  Jones                   Apis mellifera,
                          Bombus sp.,
                          Osmia sp.
A. pectinatus (Hook.)   Anthophora sp.,         Karron 1989
  G.Don                   Bombus sp.,
                          Osmia sp.
A. striatus Nutt.       Bombus sp.              Kudo & Harder 2005
A. tennesseensis        Apis mellifera,         Baskin et al. 1972
  Chapman                 Bombus sp.,
                          Xylocopa sp.
A. utahensis (Torr.)    Anthophora sp.,         Green & Bohart 1975
  Torr. & A. Gray         Bombus sp.,
                          Eucera sp.

TABLE 2.--Plant accession locations for manual pollination
treatments. Distant xenogamy treatments were applied across different
level IV Ecoregions (Omernik & Gallant, 1986; McGrath et al., 2002;
Bryce et al., 2003; Thorson et al., 2003). Superscript numbers
indicate seed accessions which were crossed in distant xenogamy
treatments and correspond to location numbers in Figure 2

Site name            County, State   Ecoregion IV

Ellensburg (1)       Kittitas, WA    1Og--Yakima Folds
Clarno (1)           Wasco, OR       11a--John Day/Clarno Uplands
Otley Ranche (2)     Harney, OR      80g--High Lava Uplands
Mountain City (2)    Elko, NV        80a--Dissected High Lava Plateau
Warrior Mine (3)     Nye, NV         13v--Tonopah Sagebrush Foothills
Big Gulch (3)        Custer, ID      17e--Barren Mountains
Black Mountain (4)   Owyhee, ID      80f--Owyhee Uplands & Canyons
Champs Flat (4)      Lassen, CA      342Bd--Cottonwood--Skedaddle
                                       Mountains

Site name            Ecoregion III            Latitude N

Ellensburg (1)       Columbia Plateau         46[degrees]56' 15.4"
Clarno (1)           Blue Mountains           44[degrees]55' 07.3"
Otley Ranche (2)     Northern Basin & Range   42[degrees]56' 02.7"
Mountain City (2)    Northern Basin & Range   41[degrees]48' 10.7"
Warrior Mine (3)     Central Basin & Range    38[degrees]36' 37.1"
Big Gulch (3)        Middle Rockies           44[degrees]20' 43.3"
Black Mountain (4)   Northern Basin & Range   43[degrees]08' 07.3"
Champs Flat (4)      Northern Basin & Range   40[degrees]42' 07.7"

Site name            Longitude W              Elev (m)

Ellensburg (1)       120[degrees]15' 22.9"    653
Clarno (1)           120[degrees]31' 09.2"    625
Otley Ranche (2)     118[degrees]36' 48.6"    1502
Mountain City (2)    115[degrees]56' 33.0"    1774
Warrior Mine (3)     117[degrees]50' 08.9"    1888
Big Gulch (3)        113[degrees]31' 01.2"    2201
Black Mountain (4)   116[degrees]43' 27.1"    1700
Champs Flat (4)      120[degrees]53' 32.7"    1711

TABLE 3.--Mean proportion ([+ or -] standard error) for seed
germination per raceme for four pollination treatment. Treatments were
conducted at BBSL in 2005. n = number of plants. Letters following
treatment means indicate statistical difference (P [less than or equal
to] 0.05)

                      N        X [+ or -] [s.sub.x]      Range

Open visitation       22      0.73 (a) [+ or -] 0.33      0-1.0
Geitonogamy           11      0.72 (a) [+ or -] 0.38      0-1.0
Xenogamy              16      0.80 (a) [+ or -] 0.24   0.25-1.0
Distant xenogamy      15      0.43 (b) [+ or -] 0.29      0-1.0
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Author:Watrous, Kristal M.; Cane, James H.
Publication:The American Midland Naturalist
Article Type:Report
Geographic Code:1USA
Date:Apr 1, 2011
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