Adaptability and interspecific variability in growth and leaf traits of eucalypt

Abstract

Effective adaptability of plants to new environments can be analysed in terms of survival rate. Analysing the traits that favour adaptation to environmental changes provides a more in-depth understanding of the mechanisms involved. Local adaptation occurs because different environmental factors exert selec-tive pressure across habitats. Understanding the leaf mechanisms underlying plant survival and growth is crucial to determine why local adaptation involves trade-offs. A comparative provenance test on 29 eucalyptus species was con-ducted to improve our understanding of species adaptation strategies on coastal plains of Pointe-Noire, Republic of the Congo. We studied the different functional traits to determine how plants function and to highlight the different species’ adaptive strategies. For each species, survival, growth traits and leaf traits were measured, and the climatic factors of the origin area for each species was taken into account. Cluster analysis was performed on groups of species with a similar growth strategy. The results revealed general trends that explain the physiological mechanisms involved in the species’ local adaptation. Indeed, species have survived to current environmental changes by adjusting their specific leaf area plasticity. The 32 provenances of eucalyptus were sub-divided into four groups by cluster analysis. The first cluster included two species (E. pilularis and E. peltata) that are totally unsuited to the local conditions in Pointe-Noire, with the slowest growth rate and smallest specific leaf area. The second cluster contained species that showed a wide variety of growing strategies, allowing them to adapt to local conditions. The third cluster included a species that is specialised in obtaining large quantities of resources, while investing very little in growth. The fourth cluster included species that acquired and used resources at a slow rate. Leaf anatomy was quite responsive to climatic conditions. We evaluated the different strategies and found that eucalyptus species had very diverse functional traits, which may explain their broad ecological range.