Nesting substrate, therefore, has a smaller or negligible effect on bacterial abundance compared to differences among states. Ceratina calcarata foraged from a slightly greater phylogenetic richness of floral genera in New Hampshire than in Georgia. The phylogenetic richness of floral genera in Missouri did not significantly differ from either Georgia or New Hampshire, perhaps because of its mid-lying geographic position and climate. As expected, our reanalysis of the New Hampshire data with 99% ESV matching recovered fewer genera than in McFrederick and Rehan, who found 110 genera compared to this study with 65. We identified the same five genera as being the most abundant , these genera accounting for 92% of the reads . Despite this more conserved estimate of genera, the floral resources used in New Hampshire are still rich compared to those utilized in Georgia. We also found that foraging females in Missouri foraged from more plants to form a single pollen provision mass than those in Georgia . This suggests that suitable floral resources at the time of brood provisioning may not be as diverse in Georgia as more northern areas of Ceratina’s range, or that they were simply not locally abundant in the area around the collected nests. Across its geographic range, C. calcarata encounters a broad variety of possible forage. Diets in Georgia, Missouri and New Hampshire were dominated by pollen from different plant genera . Out of the 96 floral genera found in provisions in this study, only Rubus was found in more than 1% of reads across all three states . All other genera, even if abundant in one or two states, were rare in provisions from the third. For example, grow bucket sumac was a key floral resource in New Hampshire but made up less than 10% of the reads in Georgia and was hardly utilized at all in Missouri .

It is important to note that while read counts have been correlated with microscopy pollen counts in many studies, factors such as pollen morphology can skew the abundance estimate obtained from DNA sequences. Our study uses the marker rbcl, which has shown strong correlation with pollen counts, outperforming trnL and ITS2. With this in mind, comparison of relative abundance between sites shows state-wise differences in diet. Many of these plant genera are common to all three states, so perhaps these dietary variations are due to differences in bee and floral phenologies, as well as possible microhabitat distinctions in floral assemblages in proximity to the bee nest. While we do not have data on floral distributions within each collecting site, our records of nest substrate allow us to determine that foraging was not skewed towards the host plants. Rubus was a common pollen source but even nests formed within Rubus plants did not show a bias in pollen collection. Different pollens vary in nutritional qualities, which may influence foraging decisions. Pollen can also have toxic constituents, and some generalist foragers appear to actively utilize a broad range of floral resources to alleviate the effects these may have on brood development. How these factors influence C. calcarata foraging is unknown but our results suggest that spatial orientation of floral resources alone does not determine foraging preferences. The presence of a consistent core microbial community despite the variation in pollen sources suggests that many of the most common bacterial genera do not have specific floral associations. We identified a number of tentative bacteria–plant correlations, but these were not consistent among states . In the overall analysis, the tupliptree genus Liriodendron was correlated with Lactobacillus, while the same plant genus was correlated with Sphingomonas in Georgia. In Missouri, Wolbachia was correlated with four plant genera: Brunia, Camptotheca, Rhus and Smilax but this bacterium was not correlated with plants in the other states or the overall analysis.

The correlations found in Georgia and Missouri also differ to those previously identified in New Hampshire, following the same methodology. These correlations broadly suggest that plants and bacteria are co-occurring but the variance in results between the overall dataset and the state-level analyses indicates these relationships are facultative or transient. Using read data to identify co-occurrence correlations is statistically challenging and further experiments sampling pollen bacterial communities with and without pollinator visitation, such as the study by McFrederick et al., are needed to directly test for plant–bacteria associations. Whether plants harbor certain microbes over others or not, there are many factors altering microbial floral communities. Long-term artificial warming of grassland plots was found to alter the microbial communities of plant leaves, including microbial groups common to bees. Aydogan et al. found Acinetobacter and Wolbachia increased in frequency, while Sphingomonas frequency decreased, these three bacterial genera being common to C. calcarata pollen provision and adult gut microbiomes. These temperature based microbial changes could translate into changes in insect microbiomes, and indeed climate has been correlated with changes in microbiome composition in some species such as the red palm weevil, the chestnut weevil and a spider mite. Flower visitation by bees can transfer microbes to flowers, but herbivorous insects, other pollinators including thrips and wind are thought to contribute to microbe dispersal as well. Similarly, the presence of potentially predatory or competitive species such as ants can reduce floral visitation and this in turn alters the microbes present on flowers. Any and all of these could be important factors influencing the observed microbiome variation in C. calcarata and are important considerations when concerned with wild bee health generally. Our study shows that the diet of C. calcarata varies widely with geography, with only Rubus found in more than 1% of reads at all three sites, indicating that this generalist bee species is able to utilize different resources as floral communities change. However, it seems that floral preference may not be simply determined by the proximity of the floral resource to the nest.

The same six bacterial genera consistently dominated provisions in all sites but the relative abundance of these fluctuated widely. There are still many unknowns regarding how microbes are acquired, both in the pollen provisions and subsequently the bees themselves. Flowers appear to be general points of bacterial transmission,but so far specific associations have not been identified. The current lack of knowledge on microbial associates is a major hindrance in our ability to maintain diverse wild bee populations.The fresh market berry industry in Santa Cruz and Monterey counties is an excellent example of transformation in the business of agriculture over the last 50 years. Located along the Central Coast of California, the two counties span the fertile Pajaro and Salinas valleys, and are well known for their amenable climate and production conditions, their diverse crop mix and grower demographics, and their developed agricultural infrastructure and support industries. The majority of the berry sector is comprised of strawberries , raspberries and blackberries , with blueberries and other miscellaneous berries produced on a much more limited basis. Substantial research-based literature and historical information is available for Central Coast strawberries; however, despite the area’s move towards greater production of raspberries and blackberries, less information exists for these crops. We seek here to provide a more complete portrayal and historical context for the berry industry in the Santa Cruz and Monterey area, which is the origin of the berry industry in California. While the berry industry has been very successful in recent decades, it now faces new challenges, such as invasive pests and the phaseout of the soil fumigant methyl bromide. This article draws on previous and more recent research to discuss some of the influences that have contributed to the berry industry’s dramatic expansion in Santa Cruz and Monterey counties, including selected innovations in agricultural practices and heightened consumer demand. Berry industry growth During the 1960s and 1970s, dutch bucket for tomatoes the number of acres planted to berries, tons produced and value of production fluctuated. The fluctuations can be partly explained by farm management: in the past growers often rotated berry and vegetable crops to assist with soil and pest management, thereby influencing these statistics. However, annual crop reports from the county agricultural commissioners show that since the 1980s, berries have become increasingly important to each county’s overall value of production, and by 2014 accounted for 64% and 17% of the total value of all agricultural products in Santa Cruz and Monterey counties, respectively . The industry’s growth can be explained by a shift of some acreage out of tree fruits and field crops , among others, into berries, and by additional acreage put into agricultural production.Strawberries are the undisputed leader in the berry sector and in 2014 represented 58% and 94% of the value of all berry production in Santa Cruz and Monterey counties, respectively , and 50% and 93% of all berry acreage . Table 2 documents the remarkable expansion of the strawberry industry over time in both counties with respect to acreage, tons produced and value of production. Between 1960 and 2014, acreage more than tripled and production increased tenfold. The value of production, in real dollars, increased by 424% in Monterey County and by 593% in Santa Cruz County, reaching an astonishing combined value of nearly $1 billion in both 2010 and 2014. The gains in all statistical categories in Monterey County were enabled in part by an expansion of production into the southern reaches of the county where more and larger blocks of farmland are available, and where land rents are lower than in Santa Cruz and northern Monterey counties.

However, from 2010 to 2014 Monterey County’s tonnage and production values declined, possibly because the area has recently experienced a shortage of labor to harvest fresh market crops. Tonnage was also lower in Santa Cruz County, but production values increased. This may be because of the county’s greater emphasis on local agriculture, organic production and direct market sales, which are often associated with higher crop values. For raspberries, the acreage, tons produced and value of production grew steadily and most strikingly in Santa Cruz County , where production conditions for caneberries are optimal. For example, caneberry fields in Santa Cruz County are situated in areas that have well-drained soils and are protected from damaging winds. Also, fields are planted to take advantage of the growth and yield gains associated with southern exposures. Moreover, field-to-cooler travel distances are shorter in Santa Cruz County, which is critical for safeguarding the quality and marketability of these highly perishable crops. By 2014, raspberries represented 33% of the county’s total value of production for all berries. In contrast, Monterey County raspberry production accounted for only 6% of the county’s total berry value. Blackberries have not been consistently reported as a separate category in archived statistical analyses, but instead were often included under the terms “bush- or miscellaneous berries”. Therefore, similar data for blackberry acreage and value of production cannotbe reported here. However, between 1990 and 2010, Santa Cruz County agricultural commissioner crop reports reported an upward trend for the broad category with respect to acreage planted and value of production . In 2010, blackberries were promoted to a position of prominence in the report and shown as a separate statistic; at the same time, the miscellaneous berry category was shown to be very small indeed. Between 2010 and 2014, however, blackberry acreage and value of production leveled off and have shown only modest gains . This may be because there has been less emphasis on production and market research and promotion for blackberries than for strawberries or raspberries. No comparable data are available for Monterey County. The two counties have contributed significantly to California’s total berry sector: in 2014, area strawberry acreage represented 35% of the statewide total, 37% of the total tons produced and 38% of the total value of production . Area raspberry acreage represented 43% of the statewide total, 42% of the total tons produced and 39% of the total value of production. Comparable statewide statistics are not available for blackberries. County agricultural commissioners’ reports show that the majority of all berries produced in the two counties — up to 98% — are sold as fresh market fruit . In years with adverse production conditions or low prices, a higher percentage of the crop may be diverted to the freezer or processed products market. Fresh market fruit is handled and sold primarily through local grower-shippers; a much smaller share is sold directly to consumers through farmers markets, community supported agriculture operations, farm stands and other direct and intermediated market channels such as restaurants, independent grocers and schools.