William P. Kemp

Genomic signatures of evolutionary transitions from solitary to group living

For bees, many roads lead to social harmony Eusociality, where workers sacrifice their reproductive rights to support the colony, has evolved repeatedly and represents the most evolved form of social evolution in insects. Kapheim et al. looked across the genomes of 10 bee species with varying degrees of sociality to determine the underlying genomic contributions. No one genomic path led to eusociality, but similarities across genomes were seen in features such as increases in gene regulation and methylation. It also seems that selection pressures relaxed after the emergence of complex sociality. Science, this issue p. 1139 Social evolution in bees has followed diverse genomic paths but shares genomic patterns. The evolution of eusociality is one of the major transitions in evolution, but the underlying genomic changes are unknown. We compared the genomes of 10 bee species that vary in social complexity, representing multiple independent transitions in social evolution, and report three major findings. First, many important genes show evidence of neutral evolution as a consequence of relaxed selection with increasing social complexity. Second, there is no single road map to eusociality; independent evolutionary transitions in sociality have independent genetic underpinnings. Third, though clearly independent in detail, these transitions do have similar general features, including an increase in constrained protein evolution accompanied by increases in the potential for gene regulation and decreases in diversity and abundance of transposable elements. Eusociality may arise through different mechanisms each time, but would likely always involve an increase in the complexity of gene networks.

Developing and establishing bee species as crop pollinators: the example of Osmia spp. (Hymenoptera: Megachilidae) and fruit trees

The development of a bee species as a new crop pollinator starts with the identification of a pollination-limited crop production deficit and the selection of one or more candidate pollinator species. The process continues with a series of studies on the developmental biology, pollinating efficacy, nesting behaviour, preference for different nesting substrates, and population dynamics of the candidate pollinator. Parallel studies investigate the biology of parasites, predators and pathogens. The information gained in these studies is combined with information on the reproductive biology of the crop to design a management system. Complete management systems should provide guidelines on rearing and releasing methods, bee densities required for adequate pollination, nesting materials, and control against parasites, predators and pathogens. Management systems should also provide methods to ensure a reliable pollinator supply. Pilot tests on a commercial scale are then conducted to test and eventually refine the management system. The process culminates with the delivery of a viable system to manage and sustain the new pollinator on a commercial scale. The process is illustrated by the development of three mason bees, Osmia cornifrons (Radoszkowski), O. lignaria Say and O. cornuta (Latreille) as orchard pollinators in Japan, the USA and Europe, respectively.

Patterns of vegetation and grasshopper community composition

SummaryA study was conducted to evaluate differences in rangeland grasshopper communities over environmental gradients in Gallatin Valley, Montana, USA. The concept of habitat type (Daubenmire 1966) was used as a basis for discriminating between groupings of patches based on vegetation. A total of 39 patches were selected that represented five recognized grassland habitat types (Mueggler and Stewart 1980), as well as two disturbed types (replanting within a known habitat type). Repeated sampling in 1988 of both the insect and plant communities yielded a total of 40 grasshopper (19 664 individuals) and 97 plant species. Detrended Correspondence Analysis (DCA) indicated that patch classifications based on presence and percent cover of plants were appropriate and showed good between-group (habitat type) separation for patches along gradients of precipitation/elevation and plant community complexity. Results from undisturbed habitats showed that plant and grasshopper species composition changed over observed environmental gradients and suggested that habitat type influenced not only species presence, but also relative abundance. Discussion is presented that relates results with patch-use and core and satellite species paradigms.

COMPLEX POPULATION DYNAMICS IN THE REAL WORLD: MODELING THE INFLUENCE OF TIME-VARYING PARAMETERS AND TIME LAGS

We propose a class of complex population dynamic models that combines new time-varying parameters and second-order time lags for describing univariate ecological time series data. The Kalman filter and likelihood function were used to estimate parameters of all models in the class for 31 data sets, and Schwarz’s information criterion (SIC) was used to select the best model for each data set. Using the SIC method, models containing density-dependent processes were selected for 23 of the 31 cases examined, while models containing complex density-dependent processes were selected in 19 of these 23 density dependence cases. The density-dependent models identified by SIC had various linear or nonlinear forms, suggesting variable patterns of population regulation in nature. Population dynamics may combine density-dependent, inversely density-dependent, and density-independent processes, which may operate at different times and under different density ranges. These results suggest that our approach offers an adv...

Development and Emergence of the Orchard Pollinator Osmia lignaria (Hymenoptera: Megachilidae)

Abstract The solitary bee Osmia lignaria Say has been developed as an orchard pollinator in the western United States. Immatures develop through the spring and summer. By late summer, bees become adults and remain in this stage inside their cocoons throughout the winter. In this study, we reared O. lignaria at various temperature regimes in the laboratory and outdoors. Developmental rates increased with temperature: bees reared at 18°C took >120 d to complete development, whereas bees reared at 29°C took half that long. Bees reared outdoors under fluctuating ambient conditions took ≈95 d. At 18°C, some bees were unable to complete prepupal dormancy. Different developmental stages responded differently to the various temperature regimes. Fluctuating temperatures averaging 22°C significantly shortened the dormant prepupal stage, and, as a result, bees developed faster than at the equivalent constant temperatures. Bees that developed faster (29°C and fluctuating temperatures) could be wintered as early as August and incubated for emergence in March, 1 mo ahead of bees exposed to natural conditions. These results can be applied to field populations for pollination of early-blooming crops such as almonds, Prunus amygdalus Batsch.

Bee population returns and cherry yields in an orchard pollinated with Osmia lignaria (Hymenoptera: Megachilidae)

During 1998-2003, we used populations of the solitary bee Osmia lignaria Say to pollinate a commercial sweet cherry orchard in northern Utah. Bee densities released each year ranged from 1290 to 1857 females/ha, with approximately twice as many males. Female progeny produced each year were greater than parental populations released, except in 2003, when nesting was poor due to bird predation. Despite poor weather during bloom, and in contrast to most other local producers, the study orchard produced harvestable crops in 1999 (2,964 kg/ha) and 2001 (3,154 kg/ha). In 1998 and 2000, record yields were obtained (10,625 and 12,096 kg/ha, respectively). Including only those years with harvestable crops, average production was 2.2 times higher in 1998-2003 (when O. lignaria populations were used) compared with 1992-1997 (when 10 Apis mellifera hives were used). This is the first study reporting multiyear cherry yields in an orchard pollinated with O. lignaria in North America.

Management of Osmia lignaria (Hymenoptera: Megachilidae) Populations for Almond Pollination: Methods to Advance Bee Emergence

Abstract The objective of this study was to find one or more rearing methods that would allow us to release Osmia lignaria Say populations from natal nests to pollinate February-flowering almonds, Prunus amygdalus Batsch, in California’s Central Valley. We exposed three phenologically distinct O. lignaria populations (early-, mid-, and late-flying) to different temperature treatments through development and wintering for a total of nine rearing treatments. These treatments combined three approaches to obtain early bee emergence: (1) exposing bees to warmer or fluctuating temperatures, or both, during development; (2) exposing bees to warmer wintering temperatures; and (3) using early-flying bee populations from Central Valley California latitudes. Extended periods of high prewintering temperatures resulted in apparent fat body consumption of prewintering adults and reductions in springtime adult longevity. In general, temperature treatments that promoted rapid immature development, and thus longer wintering periods, resulted in earlier spring emergence patterns of bees well timed with bloom period of almonds. Warmer wintering periods also resulted in earlier emergence. In addition to providing good bee-bloom synchrony, several treatments also yielded vigorous emerging populations, rapid establishment and nesting, and population increases. The potential importance of our results to anticipated increases in the demand for pollination services in California’s Central Valley almonds is discussed.

JOINT DENSITY DEPENDENCE

We present a new multivariate model for describing jointly fluctuating, density-dependent populations. The model is a stochastic, multivariate version of a discrete-time logistic model that explicitly accounts for spatial variation of growth rate parameters and covariances of fluctuations between populations. Statistical methods for applying the model to time series data on population abundances are described in detail. We derive formulas for maximum-likelihood estimates of model parameters, and we develop hypothesis tests for various reduced model structures, such as density independence or zero covariance. The applicability of the model to any given data set can be thoroughly evaluated with diagnostic procedures. As examples, we apply the model to two population systems: rangeland grasshoppers (Orthoptera: Acrididae) in three physiographic regions of Montana, USA, and bull trout (Salvelinus confluentus) in four tributaries of the Flathead River in Montana. The model and associated statistical methods have potentially important applications in conservation biology for describing metapopulations and for assessing joint jeopardy of multiple populations.

Effect of Wintering Duration and Temperature on Survival and Emergence Time in Males of the Orchard Pollinator Osmia lignaria (Hymenoptera: Megachilidae)

Abstract We measured winter survival, emergence time following incubation at 20°C, and postemergence longevity in males of the orchard pollinator Osmia lignaria Say exposed to 25 artificial wintering treatments differing in duration (30, 90, 150, 210, and 270 d) and temperature (0, 4, 7, 10, and 13°C). For all temperatures, survival was highest at 90 d of wintering. Temperatures ≥10°C were unsuitable for wintering O. lignaria populations even for short periods. At 7°C, bees showed increased mortality, signs of excessive fat body depletion, and decreased longevity when wintered for >150 d. Wintering durations ≥210 d required temperatures ≤4°C for acceptable survival. Time to emerge following incubation at 20°C decreased with increasing wintering duration and wintering temperature. Many bees emerged before incubation when wintered for long periods at the warmest temperatures. Postemergence longevity was highest when bees were wintered at 0°C for 210 d. Managing the activity of O. lignaria to coincide with fruit tree bloom initiation is much more easily accomplished with the use of populations exhibiting short emergence times. Several wintering treatments that resulted in acceptable survival and longevity (150 d at 0, 4 and 7°C, and 210–270 d at 0 and 4°C), produced mean emergence times ≤5 d. Our results can be used to establish appropriate wintering regimes for O. lignaria populations managed to pollinate orchard crops differing in bloom time (from almonds in February to apples in May), and therefore, allowing for shorter or longer wintering durations.

Exceptional cherry production in an orchard pollinated with blue orchard bees

Poor pollination is a common cause of low fruit set in cherry orchards, and a high population of pollinators is therefore required. Osmia lignaria, the blue orchard bee, has been used successfully in Utah as an alternative to honey bees.