Gypsy Cuckoo Bumble Bee
Bombus bohemicus
Nature serve conservation status 2
Rounded Global Status Rank: GH - Possibly Extinct
Reasons: This recently widespread and fairly common cuckoo bumblebee had not been found since before 2000, despite substantial efforts to find it (Evans et al., 2008) but has turned up in Alaska as recently as 2003 according the Discover Life Website's range map and in Quebec in 2001 (Savard, 2009). Otherwise in the current century, Savard (2009) reports 15 as recently as 2001-2002 in Quebec but zero since then. Notably B. (P.) ashtoni is considered to be possibly extirpated even in Vermont (Rolnick, 2007, Richardson, 2008), despite the fact that Vermont and some other parts of northern New England are among the few places where one of the hosts (Bombus terricola) still turns up with any regularity, even commonly in 2009. However, a nest usurper would obviously be more vulnerable to extirpation or extinction than its hosts, and would be expected to recover more slowly than its hosts. One host, B. terricola, was apparently scarcer in Vermont and other places a few years ago than it is now (2008-2009). It seems unlikely the other definite host, B. affinis, still occurs any place in sufficient numbers to be supporting a nest parasite. Despite documented decline and the near lack of recent records, it is premature to declare Bombus ashtoni extirpated in remote parts of its range, although it is almost certainly extirpated where B. affinis was the main host. In particular, it might reappear in northern New England if B. terricola continues to persist or recover there, and it might still occur in colder remote portions of the Canadian and Alaskan range. For a nest parasite on subgenus Bombus, if the most recent record is as old as 2003 then the possibility that there are no more occurrences has to be considered, which generates a GH from Rank Calculator version 3.1. Bombus declines have not been well documented as far north as Alaska, so one could make a cased for assuming the species probably is still extant, and thus assign GU. There really is no other rank that is appropriate for a recently widespread species that has probably declined by well over 99% in about a decade and has been undetectable anywhere since 2003.
Intrinsic Vulnerability: Highly vulnerable
Comments: An obligate nest parasite that requires substantial populations of bumblebees in the subgenus Bombus.
Environmental Specificity: Broad. Generalist or community with all key requirements common.
Comments: The hosts were widespread and common over a large part of North America and in a variety of habitats into the 1990s. This nest parasite seems to have been likewise.
Threats 3
Degree of Threat: Very high - high
Comments: The only meaningful threat now is the severe decline of the host species: Bombus (Bombus) affinis which may be approaching extinction, or perhaps is holding its own in a small area from northern Illinois to Ontario, and B. (B.) terricola which has also declined severely but is persisting or even beginning to recover in Vermont and is extant as of 2009 from western Massachusetts to Nova Scotia (L. Richardson). See documentation under B. (B.) affinis and B. (B.) terricola.
Sources and Credits
- (c) sydcannings, some rights reserved (CC BY-NC), uploaded by sydcannings
- Adapted by Denis Doucet from a work by (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28926243
- Adapted by Denis Doucet from a work by (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28926248
