Two Sides of the Same Desert: Floristic Connectivity and Isolation Along the Hyperarid Coast and Precordillera in Peru and Chile

Abstract

In this study we aim at refining our understanding of the floristic connectivity of the loma- and precordillera floras of southern Peru and northern Chile and the parameters determining vegetation cover in this region. We used multivariate analyses to test for floristic- and environmental similarity across 53 precordillera and loma locations in Peru and Chile. We propose the use of predictive modeling in estimating the extent of desert vegetation as a complementary method to remote sensing. We created habitat suitability models for the vegetation on the coast and in the precordillera based on a combination of latent bioclimatic variables and additional environmental predictors using Maxent. We found Peruvian and Chilean lomas to be strongly floristically differentiated, as are the Chilean precordillera and lomas. Conversely, there is clear connectivity between both the Peruvian loma- and precordillera floras on the one hand and the Peruvian and Chilean precordillera floras on the other. Divergent environmental conditions were retrieved as separating the precordillera and lomas, while environmental conditions are not differentiated between Peruvian and Chilean lomas. Peruvian and Chilean precordilleras show a gradual change in environmental conditions. Habitat suitability models of vegetation cover retrieve a gap for the loma vegetation along the coast between Peru and Chile, while a continuous belt of suitable habitats is retrieved along the Andean precordillera. Unsuitable habitat for loma vegetation north and south of the Chilean and Peruvian border likely represents an ecogeographic barrier responsible for the floristic divergence of Chilean and Peruvian lomas. Conversely, environmental parameters change continuously along the precordilleras, explaining the moderate differentiation of the corresponding floras. Our results underscore the idea of the desert core acting as an ecogeographic barrier separating the coast from the precordillera in Chile, while it has a more limited isolating function in Peru. We also find extensive potentially suitable habitats for both loma- and precordillera vegetation so far undetected by methods of remote sensing.

Genome-wide SNP data reveal recent population structure ofHuidobria fruticosa(Loasaceae), a paleo-endemic lineage from the Atacama Desert

“…This finding is congruent with that made for other plant genera such as Eulychnia (Merklinger et al, 2021) or Cristaria (Böhnert et al, 2022), with the difference that those groups seem to have diversified in response to climatic shifts, while in H. fruticosa this does not appear to have been the case. The lack of observable diversification is surprising considering the phylogenetic age of this lineage.…”

“…This has recently been confirmed by molecular clock dating studies, suggesting a divergence between H. fruticosa and the only other species in the genus, H. chilensis, during the early Eocene, around 40-60 Ma (Acuña et al, 2019). Both lineages could thus be classified as paleoendemics (Stebbins & Major, 1965), which contrasts several other Atacama groups studied for this region, the neo-endemics -groups that originated more recently in the Atacama Desert, such as Nolana (Solanaceae, Dillon et al, 2009), Heliotropium (Heliotropiaceae, Luebert et al, 2011), Malesherbia (Malesherbiaceae, Gengler-Nowak, 2002 or Cristaria (Malvaceae, Böhnert et al, 2019Böhnert et al, , 2022. Interestingly, the presence of ancient endemic lineages is rare in the Atacama Desert, where predominantly neo-endemic lineages have been found (Scherson et al, 2017), a feature also documented in other deserts (Thornhill et al, 2016(Thornhill et al, , 2017.…”

“…Despite effective dispersal, however, H. fruticosa has remained an endemic of the extreme north of Chile and has apparently not managed to occupy adjacent regions such as southern Peru, despite similar levels of aridity there. Although there is a floristic break between the coastal floras of southern Peru and northern Chile (Pinto & Luebert, 2009;Ruhm et al, 2022;Rundel et al, 1991), other taxa which have a coastal as well as Andean distribution have migrated across this barrier along the Andean cordillera (Beddows et al, 2017;Dillon et al, 2009;Gengler-Nowak, 2002, Böhnert et al, 2022, which has been proposed to function as a dispersal corridor for taxa (Luebert & Weigend, 2014;Moreno et al, 1994). The absence of Huidobria in southern Peru is thus surprising.…”

“…At the outset of this study, we hypothesized that the population structure of H. fruticosa might reveal the signature of long-term aridity of the Atacama Desert. Phylogenetically, the two species of Huidobria are separate lineages of Eocene origin (Acuna et al, 2019) and thus pre-date most other Atacama Desert lineages for which dated phylogenies are available (e.g., Cristaria, Böhnert et al, 2022;Malesherbia, Gengler-Nowak, 2002;Oxalis, Heibl & Renner, 2012;Heliotropium, Luebert et al, 2012;Nolana, Dillon et al, 2009;Zygophyllaceae, Böhnert et al, 2020). However, our results suggest that the history of the sampled extant populations is rather recent, dating back only to the last ~2 Ma.…”

A new species of Diplostephium (Asteraceae, Astereae) from the Atacama Desert, Chile

“…Reiche, which is narrowly distributed around the Paposo coastal area. Also, several phylogenetic analyses show close relationships of some plant groups in the Atacama Desert to Andean and non-Andean neotropical lineages ( Luebert 2011 ; Ruhm et al 2022 ). Moreover, numerous species have disjunct distributions, being present in the Andes at high altitudes as well as around Paposo; for instance, species like Bidens triplinervia Kunth, Stevia philippiana Hieron., Solanum paposanum Phil., Krameria lappacea (Dombey) Burdet & B.B.…”