Understanding a complex ecosystem: Tillandsiales in the hyperarid core of the Chilean Atacama Desert

Abstract

Tillandsia landbeckii is a “core species” in the hyper arid parts of the Atacama Desert colonized by few vascular plants only and this species is totally depending on fog occurrence as the most important source of water. Tillandsia landbeckii is a key element of the most prominent vegetation type of the hyperarid Chilean Atacama core. Epiarenic growth, growing on bare sand and lacking any root system, evolved five times independently in the genus Tillandsia during the past 5 my in the Peruvian-Chilean Desert system and lay the ground to build up unique ecosystems, with Tillandsia purpurea representing the Peruvian vicariant species. The onset of this parallel evolution may be considered as a temporal land-mark for the evolution of those fog-dependent ecosystems of the hyperarid core Atacama. Footprints of evolutionary diversification of present-day gene pools of T. landbeckii go back roughly 500,000 years, and present-day biogeographic distribution pattern is mostly shaped due to environmental changes since the last 22,000 years and the Last Glacial Maximum (LGM). The genetic set-up is surprisingly characterized by ancestral gene pools, “frozen” hybrid genotypes and clonal propagation and dispersal. This observation feeds into our hypothesis that phenotypic plasticity - contributing to plant fitness and survival in space and time - is limited on individual level, but a genetic mosaic on population- and landscape level is compensating this by a mixture of different “frozen” geno- and phenotypes, thereby allowing to cope rapidly with environmental change at the extreme limits of plants´ life. A multi-disciplinary approach combining evidence from different disciplines (plant biology, evolutionary biology, microbiology, climatology, geology, geomorphology and remote sensing technology) aims to unravel the complex interplay of biotic and abiotic factors to elaborate on our understanding of life occuring at the limits of growth due to the lack of water. We introduce the complex phylogeographic history of the species in Chile and introduce a mechanistic/biological growth model exploring environmental - biotic and abiotic - parameters. For comparative analysis on metapopulation level three regions have been selected in Chile (North near Arica, Centre near Iquique, South near Caldera) for detailed comparative in-situ and ex-sito analyses.