Historical assembly of Zygophyllaceae in the Atacama Desert

Tim Böhnert,Dietmar Quandt,Federico Luebert,Felix Merklinger,Maximilian Weigend

doi:10.21425/f5fbg45197

Abstract

The Atacama Desert harbors a unique arid-adapted flora with a high degree of endemism, the origin of which is poorly understood. In the Atacama Desert, Zygophyllaceae is represented by five endemic species: one member of Zygophylloideae: Fagonia chilensis; and four members of Larreoideae: Bulnesia chilensis and Porlieria chilensis, the only representatives in the Atacama Desert of genera with disjunct distributions between Argentina, Peru and Chile; and monotypic endemic genera Metharme lanata and Pintoa chilensis. Zygophyllaceae are thus a particularly suitable group for studying the historical assembly of the Atacama Desert flora as each of these species may represent independent biogeographical events. We made use of published as well as original plastid DNA sequences (rbcL, trnL-trnF & trnS-trnG) to reevaluate the phylogenetic relationships of the Atacama Zygophyllaceae. Bayesian divergence time estimates as implemented in BEAST2 and ancestral area reconstruction with the Dispersal Extinction Cladogenesis approach using BioGeoBEARS were applied to infer ancestral ranges. We compiled the most complete data set of Larreoideae to date with 25 of 28 species. Bulnesia rivas-martinezii from Bolivia forms a clade with Pintoa chilensis from the Atacama Desert, rendering the genus Bulnesia paraphyletic. Most representatives of Zygophyllaceae colonized the Atacama Desert during the Miocene, and only Fagonia dispersed more recently. The colonization history of the Atacama Desert in South America is reflected by three individual distribution patterns or floristic elements. The presence of Bulnesia, Pintoa, and Metharme is best explained by Andean vicariance, while the southern Atacama Desert representative, Porlieria chilensis, has a continuous distribution into central Chile from where it probably dispersed further north. The only South American Fagonia species (F. chilensis) likely colonized the Chilean-Peruvian Coastal Desert via long distance dispersal from North America.

Highlights

Located in northern Chile, the Atacama Desert ranges from 18° S at the border region to Peru and 30° S around La Serena, while it is restricted in the east by the Andean mountain range and the Pacific Ocean to the west
F. chilensis forms a well-supported clade in both analyses, with a crown node age of 4.71 Ma (95% HPD: 1.4–8.6)
Porlieria chilensis is the only species of this clade in the Atacama Desert separated from its sister clade (P. hygrometra Peru + P. microphylla Argentina) in the late Miocene to early Pliocene (6.2 Ma, 95% HPD: 1.7–11.8)

Summary

Introduction

Located in northern Chile, the Atacama Desert ranges from 18° S at the border region to Peru and 30° S around La Serena, while it is restricted in the east by the Andean mountain range and the Pacific Ocean to the west. 18° to 26° S), most species can be found along the coastal range as well as along the Andean foothills, while only few species can survive the harsh conditions of the inner core of the Atacama Desert. The vegetation is more broadly distributed: whereas the conditions are still predominantly arid, Andean and coastal ranges are not separated by a barren zone (Villagrán et al 1983, Rundel et al 1991, Luebert and Pliscoff 2017). We still lack a detailed knowledge of the process, since an understanding of the timing of the onset of aridity remains elusive (Ritter et al 2018), and only few studies have addressed the timing of diversifications of Atacama Desert plant groups (e.g., Luebert and Wen 2008, Dillon et al 2009, Heibl and Renner 2012, Böhnert et al 2019)

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Discussion

Conclusion