Ecological and functional differentiation in a plant species with disjunct distribution: Morphology, niche and role of Acacia caven at west and east of the Andes

Disjunct distributions in species lead to questions about population separation events and their consequences, affecting traits and functions depending on the disjunction time. While niche and morphology are essential, research on functional differences in disjunct populations is limited.
Acacia caven, found in South America, has a disjunct distribution between Central Chile (west) and the South American Gran Chaco (east of Andes). Chapter 1 explores its origin, supporting a human-mediated dispersal from Argentina to Chile in the early Holocene.
Chapter 2 examines morphological variability in Acacia caven, comparing traits divergence between western and eastern populations, confirming varieties' validity and identifying identification challenges. Of six varieties growing in the eastern range, only one has a closer affinity to the western populations, agreeing with an introduction event.
Chapter 3 uses climatic niche modelling to study Acacia caven's distribution, revealing significant overlap in climatic spaces, supporting niche conservatism. A common area of occupancy is suggested in southern Bolivia and northwest Argentina since the late Pleistocene.
Lastly, chapter 4 investigates Acacia caven's ecological effects as a nurse plant at a continental scale. Geographical differences in its impacts on neighbouring plant communities are emphasized, showing large-scale context dependence but suggesting substantial positive effects on both ranges.
These studies provide insights into Acacia caven's origin, dispersal, morphology, ecological role, and distribution patterns in South America, contributing to its ecological significance in diverse ecosystems.