Use of architectural and morphometric analysis to predict the flowering pattern of the invasive Rubus on Réunion island (Indian Ocean)

Abstract

The inability to flower and produce fruit above 1100 m a.s.l. is an important characteristic of Rubus alcei folius Poiret (Rosaceae), an introduced bramble that has invaded large areas of tropical rain forest on Réunion island. Why does R. alceifolius not fruit in the highlands? It is known that a minimal morphological structure and structural maturity level is required for plants to reach the reproductive state. In this study, we explored the threshold of this minimal morphological structure by describing mesotonic and basitonic axes at two different altitudes. All measured axes remained vegetative, except those that fruited in the lowlands. The morphological factors noted in R. alceifolius enabled us to define the minimum structure required for fruiting in lowland areas. Mesotonic axes seem to achieve structural maturity in the highlands, but the reproductive state did not occur. Our results may be helpful for eradication and biocontrol programs that depend strongly on the reproductive strategy of the target invasive plant species.Key words: altitude, metamer, minimum structure, pith, reproductive state, Rubus alceifolius.