
Honeybee morphometries: linearity of variables with respect to body size and classification tested with European worker bees reared by varying ratios of nurse bees
publication date: Jul 14, 2010
Journal of Apicultural Research   Date   Article Title  Honeybee morphometries: linearity of variables with respect to body size and classification tested with European worker bees reared by varying ratios of nurse bees  Author(s)  Howell V Daly, Robert G Danka, Kim Hoelmer, Thomas E Rinderer, Steven M Buco  Abstract  The effects of nutritional stress on body size of worker honey bees and their morphometries were examined, and morphometries of stressed bees were compared with the morphometries of large reference populations of European and Africanized honey bees. Workers from European queens (4 commercial queens from California plus 2 open stock queens and 2 feral queens from Louisiana) were reared with 4 ratios of nurse bees:eggs: 0.5:1, 1:1,5:1, and 100:1. Measurements of 25 morphometric variables were taken from each of 32 samples of usually ten bees per sample. Raw measurements of stressed bees were analysed separately by analysis of variance and multiple range tests. The treatments resulted in different phenotypes irrespective of the queen or her geographic origin. Workers reared at ratios of 0.5:1, 1:1 and 5:1 were consistently smaller than workers reared at 100:1. Based on the size of the workers reared at 0.5: 1, the initial ratio was apparently altered by the nurse bees, who probably destroyed eggs or larvae, to yield a ratio close to 5:1. This homeostatic behaviour under stress produced adult bees closer to normal size. Principal component analysis showed that 11 of 14 variables involving distance measurements were highly related to the first principal or general size component (PC1) in both stressed and normal bees. Such variables, when standardized, had consistent linear regressions on PC1. Evidence of curvilinear regression among sizerelated variables was inconsistent and limited to three instances, each involving less than 1% of variance. The correlations of sizerelated variables with PC1 for European, Africanized, and stressed bees had a similar pattern but the correlations often differed in magnitude. The slopes of linear regression for most sizerelated variables of European and Africanized bees were the same. Africanized bees, however, were not simply scaled reductions of the larger European bees, but exhibited differences among most sizerelated variables in Y intercepts. The induced variation in morphometries of stressed European bees simulated some features of the covariation observed in normal European and Africanized bees, but differences existed in the magnitudes of correlations, and slopes and Y intercepts of most sizerelated variables with respect to PC1. Despite the small size of some stressed bees, 91assification of the abnormal phenotypes by current methods gave only 2 samples misidentified as Africanized.  Keywords  European honey bees, Africanized honey bees, worker honey bees, nurse honey bees, Apis mellifera, morphometries, size, nutritional stress, principal component analysis, identification  Download  
