A NUMERICAL TAXONOMIC ANALYSIS OF THE EVOLUTIONARY RELATIONSHIPS OF BOMBUS AND PSITHYRUS (APIDAE: HYMENOPTERA)

Abstract

Can. Ent. 105: 733-743 (1973)The question of whether the evolutionary origin of the parasitic bumble bees (Psithyrus Lep.) was monophyletic or polyphyletic has not been convincingly resolved by conventional systematics. In this study numerical taxonomic (NT) analysis was applied to data on wing venation from a set of 13 species of Psirhyrus and 60 species of nonparasitic bumble bees (Bombus Latr.), representing 16 of the subgeneric divisions recognized by Richards. The resultant cluster analysis gave an almost perfect grouping of the constituent Bombus species into their 'correct' subgenera. This was taken as evidence that the NT procedure had yielded discriminant criteria of evolutionary significance. Sin= the same criteria also produced a single grouping of the Psithyrus species, the results support a monophyletic origin for Psithyrus.

Applications of Morphometrics to the Hymenoptera, Particularly Bumble Bees (Bombus, Apidae)

“…They also used multiple discriminant analysis (canonical variates analysis) to visualize the groupings (Hintze, 1996). Again Psithyrus was clearly separated from the Bombus subgenera on the plot of the first two canonical variates (Plowright & Stephen, 1973).…”

“…As will be described later, there are numerous taxonomic problems in the genus Bombus concerning the exact relationship of closely related species. Plowright & Pallett (1978) applied the same measurement techniques as used by Plowright & Stephen (1973) and discriminant analysis to re-investigate the taxonomic status of B. sandersoni Fkln. They measured previously identified museum specimens, and found a non-overlapping separation between B. sandersoni, and B. frigidus F.…”

“…An early application of traditional morphometrics and numerical taxonomy to bumble bees was the study of Plowright & Stephen (1973) on the evolutionary relationship of Bombus and their social parasites, Psithyrus. They measured the coordinates of 19 points using point 19 as the origin and the line from 19-4 as the horizontal axis (Fig.…”

“…The measurements were standardized by dividing them by the length 19-4 to give variables independent of size (Plowright & Stephen, 1973). The generalized Mahalanobis distance, D 2 , was calculated for each species pair (Sneath & Sokal, 1973) and each distance was subtracted from the largest distance to give a measure of similarity (Plowright & Stephen, 1973). Plowright & Stephen (1973) then used weighted-pair-group cluster analysis (Sneath & Sokal, 1973) to produce a phenogram.…”

“…The generalized Mahalanobis distance, D 2 , was calculated for each species pair (Sneath & Sokal, 1973) and each distance was subtracted from the largest distance to give a measure of similarity (Plowright & Stephen, 1973). Plowright & Stephen (1973) then used weighted-pair-group cluster analysis (Sneath & Sokal, 1973) to produce a phenogram. The 13 species of Psithyrus were clearly separated from the 60 Bombus species.…”