The maps are work I (DJ) did for a GIS class at the Evergreen State College (TESC). They are based on data obtained from the USDA National Pollinating Insects Database (NPID), current as of 2016.
There has been a lot more sampling of bumble bees, both by scientists and citizen scientists alike, since then. These maps will be refreshed/updated at some point with more current data. The maps are only as accurate as the data points used to generate them.
The maps examined the relationship between bumble bee distributions relative to Level 4 Ecoregions as defined by the US EPA. There are 54 ecoregions located in Washington state. More information on ecoregions can be found on the EPA website at https://www.epa.gov/eco-research/level-iii-and-iv-ecoregions-continental-united-states
If a bee species was detected in an ecoregion, then the ecoregion was associated with that bee species and shown on the map as potential habitat.
Interpreting the results:
What’s the story behind the number?
When one examines the underlying data behind the map and bar chart above a couple of lessons can be learned. A simple one is: without sampling, there is no data. A second one comes from looking at the distribution of the individual bumble records.
In the case of the Western bumble bee, Bombus occidentalis, the map shows that the species was very broadly distributed across the entire state. Gaps may be as much an artifact of a lack of sampling in a particular ecoregion than evidence of no western bumble bee presence. Absence of evidence is not evidence of absence.
In the chart above, Palouse Hills and Central Puget Lowlands jump out as western bumble bee hotspots. What the simple data does not identify is that Washington State University, WSU is located in the Palouse Hills and University of Washington (UW) campus is in the Central Puget Lowlands ecoregion.
Decades of entomology students making and submitting collections of easily spotted and identified bumble bees helps put the numbers in perspective.
Some important caveats about the maps:
Areas that have not been sampled and the data not stored in the NPID will show as unused habitats. This may or may not be true. We have some ecoregions in Washington that have not had bumble bee occurrence data recorded in the database. I am assuming there are some species present in those ecoregions, but the database does not reflect that fact yet.
- One example is the Sitka bumble bee, Bombus sitkensis, the map implies that it does not occur in the NE part of Washington, but Don Rolfs and I sampled there and detected it in 2017.
The maps assume that accurate identification was done when it was collected and cataloged into the database.
- This is less of a problem for the more common species but for rare species it is a concern. There was a single datapoint for Bombus balteatus/kirbiellus I was told at the time I received the data that there was doubt about the accuracy of the record and should not be categorized as reliable.
Locational data (lat/longs) were used as presented, and there is no indication of how precise the lat/long is relative to the actual sampling site. In general, I think the accuracy imprecision does not alter the general distribution results.