Vincent J. Tepedino

Spatial patterns of bee captures in North American bowl trapping surveys

Abstract.  1. Bowl and pan traps are now commonly used to capture bees (Hymenoptera: Apiformes) for research and surveys.

SEX RATIO, PARENTAL INVESTMENT, AND INTERPARENT VARIABILITY IN NESTING SUCCESS IN A SOLITARY BEE

Observations of uniquely marked females of the solitary, twig‐nesting bee, Osmia bruneri, were conducted under greenhouse conditions to test several predictions of sex‐ratio and parental‐investment theory. In support of Fishers (1958) theory, we found that the observed sex‐ratio of progeny in this dimorphic species did not differ from that expected on the basis of average male and female weights. Investment patterns also exhibited a seasonal component: female parents produced more female than male offspring early in the nesting season but reversed this pattern later. Interfemale variability was large for all nesting parameters examined. Neither female‐parent size nor the rate at which females completed cells was significantly related to several estimates of parent fitness. Parent‐offspring heritability for size was also low. We found no evidence to support the hypothesis that progeny sex‐ratios are influenced by maternal condition. Variance in progeny sex‐ratios was large, but the population sex‐ratio probably departs frequently from the equilibrium value. The results marginally support Kolmans (1960) prediction of large variance in progeny sex‐ratios in large panmictic populations. We conclude that variability among females in investment patterns and variability in size among progenies are probably maintained by such factors as resource heterogeneity and the shape of the adult survivorship curve.

Might Flowers of Invasive Plants Increase Native Bee Carrying Capacity? Intimations From Capitol Reef National Park, Utah

Abstract We compared the native bees visiting the flowers of three species of invasive plants, saltcedar (Tamarix spp.) and white and yellow sweet clover (Melilotus albus, M. officinalis), with those visiting seven concurrently blooming native plant species in mid-summer at three sites in Capitol Reef National Park, Utah. Overall, as many total species of bees visited the flowers of the three invasive plant species as visited the seven natives. On average, invasive species were visited by twice as many bee species as were natives. With a single exception, visitors of invasives were generalist bees, rather than specialists. Colletes petalostemonis, the only native legume specialist recorded, was an abundant forager on the flowers of both species of Melilotus, demonstrating that at least some specialist bees will move to invasive plants that are closely related to their usual hosts. Species abundant on the flowers of invasives tended to collect both pollen and nectar, suggesting that bees are using pollen of Tamarix and Melilotus to provision their offspring. We argue that invasives with entomophilous flowers are unlikely to either facilitate the reproduction of uncommon native plants or consistently compete with them for pollinators. Rather, they are likely, over time, to selectively increase the carrying capacity and population size of native bees, specifically generalists, and specialists of closely related plant species.

The reproductive biology and effective pollinators of the endangered beardtongue Penstemon penlandii (Scrophulariaceae)

Penlands beardtongue, a rare endemic plant of the Colorado Plateau, displays a mixed breeding system. Plants are partially self-compatible but set more fruits when cross-pollinated than when self-pollinated. Fruit production is significantly increased by pollinators. However, in two years of study there was no indication that fruit set was being limited by inadequate pollinator visitation. Pollinator effectiveness was judged by correlating bee behavior at the flowers with analysis of the pollen carried on bee bodies. The most important pollinators were native megachilid bees, particularly in the genusOsmia. The bees that pollinate Penlands beardtongue are essential to its reproduction and must be preserved along with this rare plant.

Temporal variability in the sex ratio of a non-social bee, Osmia liqnaria propinqua Cresson: Extrinsic determination or the tracking of an optimum?

Six years data on the sex ratio of Osmia lignaria obtained from several sites in northern Utah and southern Idaho, was used to test Fishers theory of an equilibrium sex ratio. The results emphasize that several years of data are necessary to adequately test the predictions of sex-ratio theory. There was considerable variability in the sex ratio for both between-site within-year comparisons and for within-site between-year comparisons. Thus, the sex ratio appeared sensitive to both site-specific factors and to year-year changes in external agents such as climate. Despite this variability, patterns consistent with Fishers theory were evident. The sex ratio at all sites changed from a significant male bias in 1973 to a significant female bias in 1975 and subsequently returned to the area of equilibrium. Data from another study are cited to support the contention that variation in the sex of offspring produced by adult females has a genetic basis. The results are most reasonably interpreted as support for Fishers theory.

Pollination biology of the endangered Blowout Penstemon (Penstemon haydenii S. Wats.: Scrophulariaceae) in Nebraska1

Abstract We studied the breeding system and pollinators of Nebraska populations of the endangered plant Blowout penstemon, Penstemon haydenii. This species appears to be one of the few known self-incompatible species of Penstemon: few self-pollinated flowers set fruit and few of these produced seeds. We found no indication that sexual reproduction was limited by inadequate pollination or resources. Pollinators were several species of native bees which varied from population to population and from year to year; there did not appear to be a consistent P. haydenii pollinator fauna. Flowers were pollinated mainly by large apid bees in the genera Habropoda and Bombus, by (mostly) smaller halictid bees, and by intermediate sized megachilid bees, particularly in the genus Osmia. One frequent flower-visitor, the presumed Penstemon specialist, Hoplitis pilosifrons (Megachilidae), may be more of a pollen-parasite than a pollinator because it commonly collected pollen into the scopa but carried very little pollen on other body parts. Management plans for conservation of Penstemon haydenii need to recognize its need for pollinators, and that the health of pollinator populations may be site-specific.

Fratricide in Megachile rotundata, a non-social megachilid bee: impartial treatment of sibs and non-sibs

SummaryExperiments simulating spring emergence and partial second generation emergence of the alfalfa leafcutting bee were conducted to determine if emerging bees distinguish full sibs from non-kin and the conditions under which fratricide occurs. Using glass tubes and different incubation treatments, bees were forced to emerge behind sibs or non-sibs whose development had been delayed by 4 or 17 days. Under these conditions, emerging bees had three choices: (1) to destroy their nest mate to exit the tube; (2) to circumvent their nest mate to exit; and (3) to return to their own cells and await the emergence of their nest mate. Emerging bees made no distinction between sibs and non-sibs: non-sibs were not destroyed more often than sibs. This suggests that nest mates are routinely treated as sibs. The emergence behavior of bees was governed by the developmental stage of their nest mates: when development of nest mates was delayed by 4 days, emerging bees most often returned to their cells and waited. Conversely, when development of nest mates was delayed by 17 days, emerging bees either destroyed or circumvented them. Due to their small size, males circumvented nest mates more often than females did. Thus, emerging bees avoided killing their nest mates, except in situations where suicide was the only other option. These results seem consistent with models predicting the conditions under which extreme selfish behavior and kin recognition will occur.

Overestimating Population Sizes of Rare Clonal Plants

In the United States, a petition to list a plant taxon under the Endangered Species Act (ESA) includes preliminary information, usually augmented subsequently, on the status of the taxon (U.S. Fish & Wildlife Service 2009a). Plants with narrow geographic extent and few populations and individuals are considered especially vulnerable because population size is positively related to genetic diversity and fitness (Leimu et al. 2006) and negatively related to the likelihood of extinction. Spielman et al. (2004) report that heterozygosity is 35% lower in rare than in common congeners and conclude that rare plants are less able to adapt to novel challenges and have an elevated extinction risk. Decisions to list rare species that reproduce sexually and vegetatively are complicated because estimates of genetpopulationsizearebasedonstemcounts,butstems

BREEDING BIOLOGY AND FLOWER VISITORS OF THE RARE WHITE RIVER PENSTEMON, PENSTEMON SCARIOSUS VAR. ALBIFLUVIS (SCROPHULARIACEAE)

Abstract We studied the breeding system and flower visitors of White River penstemon, a rare endemic from the Uintah Basin of eastern Utah and western Colorado. Bagging treatments and hand-pollination treatments showed that Penstemon scariosus var. albifluvis has a mixed mating system: while some seeds and fruits are produced through self-pollination (both autogamy and geitonogamy), significantly more are produced when flowers are cross-pollinated. The primary flower visitors, and likely pollinators, were several species of native twig- and ground-nesting bees in the families Apidae, Halictidae, and Megachilidae. We found no differences in fruit or seed production between open-pollinated controls and hand-outcrossed flowers, suggesting that pollinator visits were sufficient to maximize female reproductive success. Management plans to conserve White River penstemon must recognize that full reproductive success of this rare plant taxon relies on a suite of pollinating bees, and that the species richness and abundances of bee visitors should be maintained.

Documenting bee decline or squandering scarce resources.

V. J. Tepedino,∗ ¶ Susan Durham,† Sydney A. Cameron,‡ and Karen Goodell§ ∗Department of Biology, Utah State University, Logan, UT 84322-5305, U.S.A. †Ecology Center, Utah State University, Logan, UT 84322-5205, U.S.A. ‡Department of Entomology and Program in Ecology, Evolution and Conservation (PEEC), University of Illinois, Urbana, IL 61801, U.S.A. §Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Newark, OH 43055, U.S.A.