Fig 1.
Location of the 173 honey samples within Australia.
The data used to produce this figure can be found in the S1 Table.
Fig 2.
Percentage pollen diagram illustrating the pollen content of the honey samples.
Samples are arranged in a sequence determined by cluster analysis. Coloured bar indicates whether each sample was produced in eastern (purple) or southwestern (green) regions of Australia, though note that region was not used as a criterion for the cluster analysis; a, the numerically most important taxa; b, minor taxa, arranged according to whether probable source species are primarily indigenous to Australia or primarily introduced/agricultural species.
Fig 3.
Principal component biplots of pollen types.
Upper panel, numerically dominant types, 42% of variance explained by the first two axes; lower panel, numerically minor types, 31% of variance explained by the first two axes.
Fig 4.
Numbers of pollen types and pollen concentrations.
a, Histograms of total number of pollen types per sample, and b, pollen concentration, on a log10 scale, with Maurizio’s groups I-V [7] delineated.
Fig 5.
Myrtaceae pollen diversity observed in the honeys.
36 distinct Myrtaceae morphotypes observed in the 173 honey samples, many unassigned below family level. Morphotypes 1–12, parasyncolporate grains with more or less well developed pore thickenings, broadly consistent with Eucalyptus species; morphotype 15, large grains, weakly oblate, approaching cubic or spheroidal shape, consistent with some Corymbia/Angophora species; morphotype 16, with short colpi not reaching the polar region, consistent with some members of the VACDH clade [52]; morphotype 29, regulate grains possibly consistent with tribe Myrteae; morphotypes 30–32 and 34–35, consistent with tribes Leptospermeae and Chamelaucieae; morphotype 33, very small grain possibly consistent with Tristania. For brief descriptions, see S1 Appendix.
Fig 6.
a-y, Pollen types observed in the honeys. a-y, a representative sample of Proteaceae morphotypes observed in this study; a-n, triporate Proteaceae, the probable plesiomorphic condition for the family [53]; o-y, biporate grains consistent with Banksia. z, small, spheroidal tricolporate grains with reticulate, heterobrochate exine, lumina becoming smaller near the colpi, consistent with Bursaria (Pittosporaceae); aa-bb, spheroidal, finely reticulate diploporate grains (ectocolpi have paired endoapertures), consistent with Myoporeae (in Australia, Myroporum and Eremophila), Scrophulariaceae.
Fig 7.
Myrtaceae morphotype diversity and total percent Myrtaceae pollen.
Linear correlation between number of Myrtaceae morphotypes per honey sample, and percent Myrtaceae pollen (the sum of Eucalyptus, Corymbia/Angophora, Leptospermeae and Myrtaceae undif.) within the sample, is low and statistically insignificant (n = 173, r = -0.015. T-value of -0.193 is less than a critical threshold tcritical = 1.65, testing the hypothesis that the correlation coefficient equals zero. Pink bar indicates approximate region in which Mediterranean-region Eucalyptus honeys would plot, with gradient indicating that Eucalyptus pollen % in Mediterranean honeys can vary from 0 to ~100%, but consistently with only 1–2 Myrtaceae pollen morphotypes. Comparatively few Australian honeys plot in this region.
Fig 8.
East-west comparison of Myrtaceae and Proteaceae morphotypes diversity.
Histograms of number of Myrtaceae (green) and Proteaceae (blue) pollen morphotypes, for eastern (a,b) and southwestern (c,d) Australian honey samples.
Fig 9.
Relationship between percent Eucalyptus pollen and total pollen concentration, in purportedly unifloral Eucalyptus honeys.
Percent Eucalyptus pollen in 76 samples described by Australian beekeepers as derived solely from one or more Eucalyptus species (that is, unifloral, or in some cases bifloral Eucalyptus honeys), vs. total pollen concentration, plotted with a log10 scale. For comparison, pink shading indicates the International Honey Commission’s criteria [32], based on percent Eucalyptus pollen (>83%) and range of total pollen concentration (9000–54,000 pollen grains/g), for acceptance of a honey as a unifloral Eucalyptus honey. Comparatively few Australian Eucalyptus unifloral honeys plot in this region.
Table 1.
Number of Myrtaceae pollen types reported in melissopalynological studies in Mediterranean countries.
Table 2.
Number of Myrtaceae pollen types reported in melissopalynological and pollen foraging studies in South America.