Progress 12/01/14 to 09/30/19
Outputs
Target Audience:Garden clubs, Master Gardener groups, and both amateur and academic Lepidopterists. In the past year I did 7 public presentations (Alameda, Sacramento, Yolo, and San Mateo Counties) to a total of about 600 people. I also carried on an extensive e-mail correspondence.Audience Garden clubs, Master Gardener groups, and both amateur and academic Lepidopterists. In the past year I did 7 public presentations (Alameda, Sacramento, Yolo, and San Mateo Counties) to a total of about 600 people. I also carried on an extensive e-mail correspondence. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?None. How have the results been disseminated to communities of interest?By oral presentations to garden clubs, Master Gardeners, and the like, including at the "butterfly summit" held at Annie's Annuals and Perennials in Richmond on 27 April 2019, which was attended by many hundreds of gardeners and butterfly enthusiasts from all over northern California (I was one of the featured speakers). What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
The project was initiated in the expectation that naturalization of the European Paper Wasp, Polistes dominula, would have important impacts on Lepidopteran populations as it is a caterpillar-hunting specialist. The EPW population in the study areas in Yolo, Solano and Sacramento Counties has been monitored biweekly and has fluctuated around a very low level since crashing only a few years after becoming naturalized; in some locations it is so rare as to be only sporadically detectable. The population at 2000' to 5000' on the Sierran west slope in Nevada County has maintained a higher density, but only in association with human settlements. The EPW has hardly at all penetrated wildlands, and most of its nests are found under eaves and in hedgerows adjacent to buildings. Its foraging is concentrated in urban and suburban areas. We have determined that no quantifiable impacts of the EPW on butterfly populations have occurred in the Sacramento Valley and Delta or in the Sierra. Since the end of the drought butterfly populations at most locations have crashed, but with no statistical relationship to EPW.
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Progress 10/01/17 to 09/30/18
Outputs
Target Audience:The project was discussed in oral presentations to four garden clubs and Master Gardener groups and is updated constantly in email reports to research collaborators, including lepidopterists and birders. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?As noted, in oral and email updates to interested parties (stakeholders). What do you plan to do during the next reporting period to accomplish the goals?Continue monitoring of both the European paper wasp and its lepitopteran prey. This is shaping up to be a "classic" study of the failure of an invasive species to establish a permanent role in the invaded ecosystem and may thus have broad implications for invasion biology.
Impacts
What was accomplished under these goals?
Populations of the European paper wasp were monitored from sea leve to 7000' in the Sierra Nevada at biweekly intervals. Populations remained at very low levels at all sites. Their principal prey items, caterpillars, were very scarce at all sites in 2018 for reasons unrelated to the wasp, primarily climatic. In most sites the was is barely at detectable levels at this time and its ecological impacts are absolutely minimal.
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Progress 10/01/16 to 09/30/17
Outputs
Target Audience:The project was described in oral presentations to four garden clubs and Master Gardener groups. It has also been included in regular e-mails to research collaborators and other interested parties, including Lepidopterists, who have been very concerned about potential paper wasp impacts on butterfly and moth populations. Gardeners are interested because the wasps can be perceived as allies against destructive caterpillars, such as cabbageworms, diamondback moth, and cutworms. Some (well-informed) birders are also concerned about wasps as competitors for caterpillars with insectivorous birds. Such competition would be a serious issue if the wasps had remained abundant. Since they didn't, it isn't, at least for now. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?As noted, orally in presentations to Master Gardeners, and by e-mail to various parties. See under "Target Audience." I would like to publish the statistical model developed by my consultant Joshua O'Brien for assessing wasp impacts, but for reasons I do not understand he has not allowed me to do so. What do you plan to do during the next reporting period to accomplish the goals?Continue monitoring wasps and caterpillars. As noted under "Accomplishments," I am especially interested in trying to correlate specific butterfly declines at my 5000' sites with wasps vs. weather. On the west slope, the infestation is limited to the vicinity of one isolated structure. One way to approach this is to examine the microdistribution of declining populations relative to the wasps' foraging range. There are nests on at least two accessible structures on the east slope, but there are many other structures on private property which are inaccessible. Unfortunately, European paper wasp does not come to bait traps as yellowjackets do (if it did, monitoring would be much easier and more rigorous!). I will also try to do quick "eyeball" surveys in Auburn (1200'), Colfax (2300'), and Truckee, as I have done in the past.
Impacts
What was accomplished under these goals?
The CA drought abated with very heavy precipitation in the 2016-17 wet season. Numbers of wasps showed a very slight uptick early in 2017 but then returned to the bare threshold of detectability, indicating that whatever is holding them down was not affected seriously by the change in precipitation. Caterpillar populations remained unaffected by wasps. To my surprise, wasp numbers have remained relatively high at the 5000' level on both the west and east slopes of the Sierra in the I-80 corridor, despite collapsing near sea level. I have permanent monitoring sites at 5000' on both slopes. There have been butterfly declines at both sites which began during the drought. At present it has not been possible to partition these between drought and wasps as potential causes; this will be pursued in the 2018 season, depending in part on the precipitation outcomes. In the Sierra as in the Valley, wasps are closely tied to built structures and seem to forage mostly very near their nests, not ranging deeply into wildlands. In 2017 two nests were, however, found in the open on low vegetation in eastern Sacramento County at least 0.25 mile from the nearest buildings. In Rancho Cordova, Sacramento County, all wasp sightings and nests recorded have been in the residential Gold River neighborhood, with zero penetration of semi-wildlands along the adjacent American River Parkway. In the vicinity of Granite Regional Park, Sacramento, wasps have again been absent from semi-wildlands and confined to the adjacent industrial park at Belvedere Avenue, off power Inn Road, and their numbers there have fallen to the minimum for detectability.
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Progress 10/01/15 to 09/30/16
Outputs
Target Audience:This project is in its early stages; no public presentations (oral or written) have yet been made. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?Only privately, by e-mail. What do you plan to do during the next reporting period to accomplish the goals?Continue monitoring and analyzing the results, figuring in the dramatic change in weather patterns into the analysis.
Impacts
What was accomplished under these goals?
What was accomplished under the major goals of this project? We continue to track populations of the wasps and of two selected indicator prey butterfly species, Pieris rapae and Hylephila phyleus, in the context of tracking entire butterfly faunas at permanent study sites. Wasp populations were near the threshold of detectability at most sites until late summer, when they increased slightly. H.phyleus populations decreased regionally but before the uptick in wasp numbers, so no causal relationship could be inferred. P. rapae populations were essentially constant. This we continue to see no significant adverse impact of the wasp on butterfly populations.
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Progress 12/01/14 to 09/30/15
Outputs
Target Audience:This project is in its early stages; no public presentations (oral or written) have yet been made. Changes/Problems:No problems or changes in approach, but as noted above, populations of the invasive wasp have suddenly crashed; this was not anticipated. I am watching to see if it comes back and perhaps assumes a cyclical population pattern. Causes of the crash are unknown, but it was regional, not merely local. What opportunities for training and professional development has the project provided?None at this time. How have the results been disseminated to communities of interest?I have communicated some findings informally by email. It is too early in the project to publish results. What do you plan to do during the next reporting period to accomplish the goals?Continue monitoring and assessing impacts, if any. The changing drought context needs to be figured into the statistical analysis.
Impacts
What was accomplished under these goals?
Populations of the wasp have been tracked at my permanent sites in parallel with established monitoring of entire butterfly faunas. Unexpectedly, populations of the wasp crashed, falling to barely-detectable levels at all but one of my sites. So far there is no evidence of negative impacts on butterfly faunas.
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