ARE BIOMETRICS USEFUL IN DISCRIMINATING BETWEEN CLOSELY-RELATED RUBUS L. TAXA?

Abstract

Members of the genus Rubus L., including the Brambles and Raspberries, are known as aggressive weeds and also as plants with beneficial traits. Several wild Bramble species have been improved or crossed to produce marketable varieties and some species are considered to be particularly valuable for their nutritional and medicinal properties. However, for the great majority of botanists they remain a taxonomic enigma. Traditionally batologists (Bramble specialists) have separated taxa mainly by morphological descriptions. Breeders and growers of economically important Rubus species use traditional written descriptions including biometric data, to supplement DNA analysis, drawings and photographs. The following study attempts to contribute to this body of knowledge and presents the results of statistical tests on data from first-year stem leaves. Three named species were compared and the means of some characters were found to be statistically significantly different, in agreement with identifications published by specialist writers and recorders. A further, provisionally named, taxon was compared with the group by Principal Component Analysis (PCA) and was statistically separated from it with reasonable confidence. A further PCA included data derived from one of the three grouped species collected from a single site. The outcome was less clear, suggesting that environmental factors could be responsible for or contribute to differentiation. All data were taken from virtual specimens, the majority of which were obtained from major collections. However, there is an information gap. Specimens on which taxonomic reliance has been placed frequently lack sufficient field data, including precise localities, habitat notes and details of flower structure. A methodology is proposed for fieldwork; as more systematic data collection would enable virtual specimens to be investigated with greater clarity. This would also enable information to be more readily shared, both nationally and internationally, with present and future students of the group.