Genetic and Morphometric Evidence for the Conspecific Status of the Bumble Bees, Bombus melanopygus and Bombus edwardsii

The taxonomic status of closely related bumble bee species is often unclear. The relationship between the two nominate taxa, Bombus melanopygus Nylander (Hymenoptera: Apidae) and Bombus edwardsii Cresson (Hymenoptera: Apidae), was investigated using genetic (enzyme electrophoretic) and morphometric analyses. The taxa differ in the color of the abdominal terga two and three, being ferruginous in B. melanopygus and black in B. edwardsii. B. edwardsii occurs throughout California, while B. melanopygus extends north through Oregon, to Alaska and Canada. They are sympatric only in southern Oregon and northern California. The taxonomic status of these taxa was questioned when Owen and Plowright (1980) reared colonies from queens collected in the area of sympatry, and discovered that pile coloration was due to a single, biallelic Mendelian gene, with the red (R) allele dominant to the black (r). Here it is shown that all the taxa, whether from California, Oregon, or Alberta, have the same electrophoretic profile and cannot be reliably distinguished by wing morphometrics. This strongly supports the conclusion that B. melanopygus and B. edwardsii are conspecific and should be synonymized under the name B. melanopygus. Hence, there is a gene frequency cline running from north to south, where the red allele is completely replaced by the black allele over a distance of about 600 km

FIGURE 4. A B. terricola-like young queen offspring from a B in Discrimination of the bumble bee species Bombus occidentalis Greene and B. terricola Kirby by morphometric, colour and RAPD variation

FIGURE 4. A B. terricola-like young queen offspring from a B. occidentalis colony.Published as part of <i>Owen, Robin E. & Whidden, Troy L., 2013, Discrimination of the bumble bee species Bombus occidentalis Greene and B. terricola Kirby by morphometric, colour and RAPD variation, pp. 328-344 in Zootaxa 3608 (5)</i> on page 332, DOI: 10.11646/zootaxa.3608.5.2, <a href="http://zenodo.org/record/10096983">http://zenodo.org/record/10096983</a&gt

FIGURE 3 in Discrimination of the bumble bee species Bombus occidentalis Greene and B. terricola Kirby by morphometric, colour and RAPD variation

FIGURE 3. Foundress queen (left) and young queen offspring (right) of B. occidentalis.Published as part of <i>Owen, Robin E. & Whidden, Troy L., 2013, Discrimination of the bumble bee species Bombus occidentalis Greene and B. terricola Kirby by morphometric, colour and RAPD variation, pp. 328-344 in Zootaxa 3608 (5)</i> on page 331, DOI: 10.11646/zootaxa.3608.5.2, <a href="http://zenodo.org/record/10096983">http://zenodo.org/record/10096983</a&gt

FIGURE 2 in Discrimination of the bumble bee species Bombus occidentalis Greene and B. terricola Kirby by morphometric, colour and RAPD variation

FIGURE 2. Two variant colour patterns of B. occidentalis found in Alberta. The specimen on the left has faint yellow hair on the abdomen and some additional yellow on the rear of the thorax, while the specimen on the right has a definite yellow band on abdominal tergum IV.Published as part of <i>Owen, Robin E. & Whidden, Troy L., 2013, Discrimination of the bumble bee species Bombus occidentalis Greene and B. terricola Kirby by morphometric, colour and RAPD variation, pp. 328-344 in Zootaxa 3608 (5)</i> on page 330, DOI: 10.11646/zootaxa.3608.5.2, <a href="http://zenodo.org/record/10096983">http://zenodo.org/record/10096983</a&gt

FIGURE 1 in Discrimination of the bumble bee species Bombus occidentalis Greene and B. terricola Kirby by morphometric, colour and RAPD variation

FIGURE 1. Typical pile colour patterns of B. occidentalis (left) and B. terricola (right).Published as part of <i>Owen, Robin E. & Whidden, Troy L., 2013, Discrimination of the bumble bee species Bombus occidentalis Greene and B. terricola Kirby by morphometric, colour and RAPD variation, pp. 328-344 in Zootaxa 3608 (5)</i> on page 329, DOI: 10.11646/zootaxa.3608.5.2, <a href="http://zenodo.org/record/10096983">http://zenodo.org/record/10096983</a&gt

<strong>Discrimination of the bumble bee species <em>Bombus occidentalis</em> Greene and <em>B. terricola</em> Kirby by morphometric, colour and RAPD variation</strong>

Owen, Robin E., Whidden, Troy L. (2013): Discrimination of the bumble bee species Bombus occidentalis Greene and B. terricola Kirby by morphometric, colour and RAPD variation. Zootaxa 3608 (5): 328-344, DOI: 10.11646/zootaxa.3608.5.

FIGURE 7 in Discrimination of the bumble bee species Bombus occidentalis Greene and B. terricola Kirby by morphometric, colour and RAPD variation

FIGURE 7. Plot of the first two Canonical scores for the 1985 and 1986 specimens of B. occidentalis and B. terricola. Yellow squares = occidentalis, 1985; green triangles = occidentalis 1986; red circles = terricola, 1985; blue pentagons = terricola 1986.Published as part of &lt;i&gt;Owen, Robin E. &amp; Whidden, Troy L., 2013, Discrimination of the bumble bee species Bombus occidentalis Greene and B. terricola Kirby by morphometric, colour and RAPD variation, pp. 328-344 in Zootaxa 3608 (5)&lt;/i&gt; on page 335, DOI: 10.11646/zootaxa.3608.5.2, &lt;a href="http://zenodo.org/record/10096983"&gt;http://zenodo.org/record/10096983&lt;/a&gt

FIGURE 6 in Discrimination of the bumble bee species Bombus occidentalis Greene and B. terricola Kirby by morphometric, colour and RAPD variation

FIGURE 6. Right forewing of a Bombus queen. The distance to point E from each of the other 13 points was measured.Published as part of &lt;i&gt;Owen, Robin E. &amp; Whidden, Troy L., 2013, Discrimination of the bumble bee species Bombus occidentalis Greene and B. terricola Kirby by morphometric, colour and RAPD variation, pp. 328-344 in Zootaxa 3608 (5)&lt;/i&gt; on page 334, DOI: 10.11646/zootaxa.3608.5.2, &lt;a href="http://zenodo.org/record/10096983"&gt;http://zenodo.org/record/10096983&lt;/a&gt

FIGURE 5 in Discrimination of the bumble bee species Bombus occidentalis Greene and B. terricola Kirby by morphometric, colour and RAPD variation

FIGURE 5. Bumble bee collection locations in Alberta: 1 = Ya-Ha Tinda Ranch, 2 = Calgary, 3= Sibbald Flats, 4 = Barrier Lake, 5 = Fortress Mountain, 6 = High Level, 7 = Fort McMurray, 8 = Lesser Slave Lake.Published as part of &lt;i&gt;Owen, Robin E. &amp; Whidden, Troy L., 2013, Discrimination of the bumble bee species Bombus occidentalis Greene and B. terricola Kirby by morphometric, colour and RAPD variation, pp. 328-344 in Zootaxa 3608 (5)&lt;/i&gt; on page 333, DOI: 10.11646/zootaxa.3608.5.2, &lt;a href="http://zenodo.org/record/10096983"&gt;http://zenodo.org/record/10096983&lt;/a&gt