Plant life at the dry limit—Spatial patterns of floristic diversity and composition around the hyperarid core of the Atacama Desert

Abstract

Extreme arid conditions in the Atacama Desert in northern Chile have created a unique vegetation almost entirely restricted to the desert margins along the coast of the Pacific Ocean and the Andean range. In this study we provide data on the desert vegetation along elevational gradients at four localities from the western Andean slopes, between 19˚and 21˚S. Additionally, zonation of floristic data was explored. Three altitudinal zones could be classified and described in detail for each locality. Conspicuously divergent floras in the Atacama Desert have been recorded in the coastal 'lomas formations' and in the Andean desert vegetation, separated by a narrow band of absolute desert. In this study, we investigate the floristic relationships between both regions by implementing similarity analyses for 21 localities from the coastal and Andean deserts in northern Chile. Our results show a drastic east-west divergence in pairwise floristic similarity, which is in stark contrast to a weaker north-south divergence. A biotic barrier, preventing plant exchange from east to west and vice versa, imposed by the hyperarid conditions of the absolute desert, is one possible explanation for this finding. Moreover, the coastal and Andean deserts likely represent ecologically divergent habitats, e.g., in rainfall seasonality. Essential differences in factors determining plant life between both regions have probably contributed to a divergent evolution of the floras. Both explanations-ecological divergence and ecogeographical isolation-are not mutually exclusive, but likely complementary. We also combined floristic data from northern Chile and southern Peru. Similarity analyses of this combined dataset provide first floristic evidence for the existence of a biotic north-south corridor along the western slope of the Andes. Sub-Andean distributions of several species are discussed in the light of floristic connectivity between the Peruvian and Chilean Andean floristic clusters.

Quaternary diversification of a columnar cactus in the driest place on earth

“…The onset of hyperarid conditions during the early Pleistocene would have led to habitat fragmentation, promoted speciation, and possibly caused the disjunction of the Peruvian E. ritteri from the Chilean congeners. Despite a reported floristic break along the coast between northern Chile and southern Peru (Ruhm et al, 2020), several studies have reported a similar pattern of disjunct species distribution in other plant groups, such as Malesherbia , Nolana , and Cristaria (Gengler‐Nowak, 2002; Dillon et al, 2009; Böhnert et al, 2019). Although we favor here the contraction–expansion model of populations during climatic oscillations as the ultimate driver for speciation, we do not dismiss the importance of newly emerging pollination syndromes or local adaptation to edaphic factors as other important reasons for Eulychnia diversification.…”

Impacts of Anthropogenic Disturbance on Vegetation Dynamics: A Case Study of Wadi Hagul, Eastern Desert, Egypt

“…Life forms of species depend mainly on adaptation to the environment, particularly climate [ 66 , 67 , 68 , 69 ]. Life forms of desert plants are closely related to precipitation [ 70 , 71 ] and are correlated with both landform and topography [ 72 , 73 , 74 ]. In the present study, the chamaephyte life form was most represented (40%).…”

A Fine-Scale Hotspot at the Edge: Epigean Arthropods from the Atacama Coast (Paposo-Taltal, Antofagasta Region, Chile)

“…It encompasses a wide variety of environments, biotic communities, and species from the southern temperate forests (47 • lat S), to the margin of the Atacama Desert along the coast of Antofagasta to the Mejillones Peninsula, at a latitude close to the Tropic of Capricorn (23 • lat S) (Figure 1). The northern limit of this biodiversity hotspot is the margin of the Antofagasta coastal desert [15,16], which is also part of the Lomas Formation, an area extending from southern Peru to the north of La Serena city, Chile (El Tofo, 29.5 • lat S) [17][18][19] (Figure 1). The Lomas Formation spans tropical and subtropical latitudes and extends into the most arid part of the Atacama Desert as a result of the stable position of the Pacific Anticyclone [19].…”

“…The northern limit of this biodiversity hotspot is the margin of the Antofagasta coastal desert [15,16], which is also part of the Lomas Formation, an area extending from southern Peru to the north of La Serena city, Chile (El Tofo, 29.5 • lat S) [17][18][19] (Figure 1). The Lomas Formation spans tropical and subtropical latitudes and extends into the most arid part of the Atacama Desert as a result of the stable position of the Pacific Anticyclone [19]. The formation has a conspicuous vegetation that is expressed in the so-called 'fog oases', which are dependent on the continuous presence of sea fogs, or camanchacas (Figure 1).…”