[Pollinator] Pollinator Digest, Vol 364, Issue 1
Sarina Jepsen
sarina at xerces.org
Fri Feb 6 12:48:52 PST 2009
John Ascher (and pollinator listserve members),
Thank you so much for your comments regarding the discussion of
bumble bee declines, and generally for all of your work on the
conservation of native bees. I think you make a very good point when
you bring up the danger in treating pesticides and habitat loss as
potential causes of the decline in bumble bees in the subgenus
Bombus. The authors of the
<http://www.xerces.org/wp-content/uploads/2008/12/xerces_2008_bombus_status_review.pdf>Status
Review of Three Formerly Common Species of Bumble bee in the subgenus
<http://www.xerces.org/wp-content/uploads/2008/12/xerces_2008_bombus_status_review.pdf>Bombus
strongly favor Dr. Robbin Thorp's hypothesis that disease from
commercially reared bumble bees transmitted to wild populations is
the most likely cause of decline. We favor this hypothesis over
pesticides or habitat for many of the reasons that you presented in
your email, and there is extensive circumstantial evidence for a
disease hypothesis.
Dr. Thorp laid out the strong circumstantial evidence for his disease
hypothesis in an email to the BOMBUS listserve on 12/19/08. I've
copied the most relevant portion of that email below:
* Declines of these once common species occurred recently,
suddenly, and at the same time over much of the known distribution of
each species.
* Other species of bumble bees continue to thrive and populations
of some are increasing in the same areas.
* The species in decline are all closely related to the European
Bombus terrestris, the most widely disseminated species of
commercially produced bumble bees.
* Colonies of B. terrestris imported from Europe to Japan have
been shown to contain Nosema and other pathogenic organisms.
* Pathogen "spillover" from commercial bumble bee colonies in
tomato greenhouses to wild populations in Canada has been
demonstrated in Canada.
* As to the potential source of contamination and route of entry
of exotic diseases from Europe into NA, colonies of B. occidentalis
and B. impatiens were reared from North American queens in production
facilities in Europe and imported to NA from 1992 through 1994 for
commercial distribution.
* In 1997, producers of commercial bumble bee colonies in NA
reported infections of Nosema bombi in their B. occidentalis
populations that they could not clean up.
* Bumble bee species have been shown to differ in susceptibility
to N. bombi. (This may also explain the inability of the commercial
producers to clean up the infection in their B. occidentalis populations).
In summary, the cause of the declines in members of the subgenus
Bombus in NA are quite specific to a group of closely related
species. These bumble bees have overlapping forage resource use and
underground nest location preferences with many species of bumble
bees including many Pyrobombus in NA that are showing population
increases (e.g., B. impatiens and B. bimaculatus in the east, and B.
vosnesenskii and B. bifarius in the west). In addition, other
potential causes such as pesticides, habitat destruction would most
likely show a broader impact over a wider range of bumble bee species.
Tests of my disease hypothesis will be challenging since the
populations of the bees have declined so severely. Fortunately a
group at the University of Illinois is currently developing methods
to test this working hypothesis. Hopefully there will be more to
come in future regarding the validity of the strong supporting
evidence for my disease hypothesis.
****
Best,
Sarina Jepsen
At 12:00 PM 2/6/2009, you wrote:
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>Today's Topics:
>
> 1. Re: Wisconsin Department of Natural Resources to track
> declining bumble bees (John S. Ascher)
>
>
>----------------------------------------------------------------------
>
>Message: 1
>Date: Thu, 5 Feb 2009 15:51:46 -0500 (EST)
>From: "John S. Ascher" <ascher at amnh.org>
>Subject: Re: [Pollinator] Wisconsin Department of Natural Resources to
> track declining bumble bees
>To: pollinator at lists.sonic.net
>Message-ID: <1381.216.73.251.75.1233867106.squirrel at webmail.amnh.org>
>Content-Type: text/plain;charset=iso-8859-1
>
>
>
>Dear all:
>
>I am glad to see this helpful and timely support for bumble bee
>conservation by the Wisconsin DNR.
>
>I have one concern, not about this press release in particular, which is
>excellent, but about discussion of bumble bee declines in general.
>Specifically, I do not think it is helpful to invoke habitat loss and
>pesticide use as an important cause of Bombus (Bombus) declines.
>Mentioning these factors may seem appropriate as a matter of fairness or
>completeness, because they might plausibly contribute to any bee declines,
>but in my opinion the available evidence argues against their relevance in
>this case.
>
>Most significantly, the timing of abrupt continental-scale declines in
>Bombus (Bombus) and of their Bombus (Psithyrus) social parasites (likely
>at least as threatened as their hosts) does not correspond to any
>documented changes in habitat or pesticide use, and the lack of any known
>correspondence with these factors is one of the most salient features of
>these declines. Many and perhaps most bumble bee species belonging to
>other subgenera such as Pyrobombus remain generally abundant, and Bombus
>(Bombus) and their B. (Psithyrus) parasites also remained numerous until
>the mid-late 1990s, despite massive changes in habitat and pesticide use
>across the continent during the 1940s-1990s and before. If a pesticide
>were involved, why should this have differentially harmed Bombus (Bombus)
>and not other related bumble bee subgenera such as Bombus (Pyrobombus)?
>
>Invoking general causes potentially relevant to declines in any bee taxa
>does not help to correctly identify the precise biological and
>sociological reasons why Bombus (Bombus) declined abruptly and drastically
>whereas most other bee taxa remained numerous in the same habitats with
>presumably the same or similar pesticide exposures. Whatever the relevant
>causes, they are definitely particular to Bombus (Bombus) and do not apply
>to other bumble bee subgenera such as Pyrobombus. In addition to being
>taxon-specific, the relevant causes must date precisely to the mid 1990s.
>
>Inclusion of imprecise and irrelevant causes when discussing the Bombus
>(Bombus) and B. (Psithyrus) declines of greatest concern only helps to
>diffuse what should be a sharply focused effort to identify the true
>causes and responsible parties and to prevent future declines of this
>sort.
>
>Loss of nesting habitat and floral resources is plausible as a primary
>cause of large-scale declines in certain bumble bee species such as B.
>pensylvanicus and their parasite B. variabilis, but declines in these
>species seem to have begun long before the mid-1990s and do not correspond
>in timing or extent with those of Bombus (Bombus) and B. (Psithyrus).
>
>In my opinion it is best to discuss events believed to be causally
>unrelated separately, even if this may require us to contend with
>burdensome concepts such as bumble bee subgenera.
>
>John
>
>
>
>
> > Email not displaying correctly? View it in your
> > browser.<http://www.xerces.org/press-releases/wisconsin_bumble_bees.html>
> > <http://www.xerces.org/press-releases/wisconsin_bumble_bees.html>
> > <http://www.xerces.org/press-releases/wisconsin_bumble_bees.html>
> >
> > For Immediate Release
> > February 4, 2009
> >
> > Contacts:
> > *Eric Mader*, National Pollinator Outreach Coordinator, The Xerces Society;
> > (608) 628-4951
> > *Bill Smith*, Natural Heritage Inventory Program Zoologist, WI DNR;
>(608)
> > 266-0924
> >
> > WISCONSIN DEPARTMENT OF NATURAL RESOURCES
> >
> > TO TRACK DECLINING BUMBLE BEES
> >
> > Madison, WI: Two of Wisconsin's bumble bees have been added to the
>Wisconsin
> > Department of Natural Resources' Special Concern List.
> >
> > This action, a response to dramatically declining populations of the
>yellowbanded bumble bee (*Bombus terricola*) and the rusty-patched
>bumble
> > bee (*Bombus affinis*), will result in official monitoring of both
>species
> > through the DNR's Natural Heritage Inventory database. Field biologists
>will
> > now start keeping records of when and where these species are found.
>Over
> > time, this database will provide a picture of the bees' abundance and
>distribution in the state.
> >
> > "This is a very significant step", said Eric Mader, National Pollinator
>Outreach Coordinator for the Xerces Society. "The Department of Natural
>Resources has taken the first step in protecting these species."
> >
> > Both species were once among the most common of state's bumble bees
>prior
> > to
> > the late 1990's. In a 1995 survey, over 90% of all bumble bees collected in
> > the northern part of the state were the yellowbanded bumble bee. Recent
>surveys have found that the yellowbanded and rusty-patched bumble bees
>represent less than 1% of all bumble bees observed in the region.
> >
> > "This is really a very dramatic decline", said Sarina Jepsen, Endangered
>Species Coordinator for the Xerces Society and co-author of a recent
>status
> > review of the species. "The two bumble bees have declined across the
>eastern
> > U.S. and a closely related species, the western bumble bee is
>experiencing
> > similar declines on the west coast."
> >
> > This decline is especially alarming because bumble bees are important
>pollinators of many native plants, as well as some of the state's
>high-value
> > agricultural crops, including cranberries. Several studies have shown
>that
> > on a bee-for-bee basis bumble bees are several times more efficient than
>honey bees for some crops.
> >
> > The exact reason for the decline of these species is unclear. The
>leading
> > theory is that one or more European bumble bee diseases were introduced
>to
> > North America during efforts by a European company to rear American
>bumble
> > bees for managed crop pollination in their European facility. However,
>habitat loss as well as pesticide use are likely contributing factors.
>The
> > decline of these bumble bees does not appear directly related to similar
>highly publicized declines of the non-native European honey bee
> > (*Apis**mellifera
> > *).
> >
> > In 2007 and 2008, isolated populations of the yellowbanded bumble bee
>were
> > found around the towns of Mountain, Manitowish Waters, and Two Rivers in
>northeastern Wisconsin. There is also a 2007 report from the
>UW-Milwaukee
> > Cedarburg Bog Field Station, in Ozaukee Co. These populations represent the
> > only remaining known yellow-banded bumble bees in the Midwest. While the
>rusty-patched bumble bee has not been documented in the state in recent
>years, some individuals have been found in isolated areas of Illinois.
> >
> > The Status Review of Three Formerly Common Species of Bumble Bee in the
>Subgenus
> >
> Bombus<http://www.xerces.org/wp-content/uploads/2008/12/xerces_2008_bombus_status_review.pdf>documents
>the decline of these two species throughout their native ranges in the
>eastern U.S. It also includes information on the decline of the western
> > bumble bee in the western U.S.
> >
> > Download the report or read more about declining bumble
> > bees<http://www.xerces.org/bumblebees/>
> > <http://www.xerces.org/bumblebees/>Read about the rusty-patched
> > bumble bee<http://www.xerces.org/rusty-patched-bumble-bee/>
> > <http://www.xerces.org/bumblebees/>Read about the yellowbanded bumble
> > bee<http://www.xerces.org/yellow-banded-bumble-bee/>
> >
> > PHOTO CREDIT
> > The rusty-patched bumble bee (*Bombus affinis*) by Johanna James-Heinz
> >
> > ###
> >
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>
>
>--
>John S. Ascher, Ph.D.
>Bee Database Project Manager
>Division of Invertebrate Zoology
>American Museum of Natural History
>Central Park West @ 79th St.
>New York, NY 10024-5192
>work phone: 212-496-3447
>mobile phone: 917-407-0378
>
>
>
>
>
>
>------------------------------
>
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>
>End of Pollinator Digest, Vol 364, Issue 1
>******************************************
>
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________________________________________
The Xerces Society for Invertebrate Conservation
The Xerces Society is an international, nonprofit organization that
protects wildlife through the conservation of invertebrates and their
habitat. To join the Society, make a contribution, or read about our
work, please visit <http://www.xerces.org/>www.xerces.org
Sarina Jepsen
Endangered Species Coordinator
4828 SE Hawthorne Blvd. Portland, OR 97215
tel: 503-232-6639 fax: 503-233-6794
email: sarina at xerces.org
________________________________________
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