Floral nectar of wild mānuka (Leptospermum scoparium) varies more among plants than among sites

Abstract

ABSTRACTUnderstanding of the genetic and environmental controls of floral nectar production by mānuka (Leptospermum scoparium J.R.Forst. et G.Forst.) and other species is limited by high levels of variation. This study partitioned variation in mānuka floral nectar traits between sites, plants, and branches, and tested plant and environmental variables that might contribute to variation. Wild mānuka plants were sampled at five sites across the North Island of New Zealand at the time of flowering for each site. Nectar traits differed significantly between sites, but for most traits plant-to-plant variation within sites was the largest source of variation (40%–70%) identified by linear mixed-effect modelling. Nectar total sugar, dihydroxyacetone (DHA) and hexose and sucrose ratios varied more between plants within sites, than they did between sites or branches within plants. Radiation and night-time temperature accounted for approximately 80% of between-site variation in mean total sugar per flower, and DHA/total sugar, respectively. Nectar total sugar and DHA were correlated across years when nectar was sampled again from the same plants two years later at one site, confirming stable variation between plants over time. Variation in nectar traits between adjacent wild plants suggests interactions between genotype, environment and flowering phenology among plants.