Ecophysiology and phylogeny of new terricolous and epiphytic chlorolichens in a fog oasis of the Atacama Desert

Abstract The Atacama Desert is one of the driest and probably oldest deserts on Earth where only a few extremophile organisms are able to survive. This study investigated two terricolous and two epiphytic lichens from the fog oasis “Las Lomitas” within the National Park Pan de Azúcar which represents a refugium for a few vascular desert plants and many lichens that can thrive on fog and dew alone. Ecophysiological measurements and climate records were combined with molecular data of the mycobiont, their green algal photobionts and lichenicolous fungi to gain information about the ecology of lichens within the fog oasis. Phylogenetic and morphological investigations led to the identification and description of the new lichen species Acarospora conafii sp. nov. as well as the lichenicolous fungi that accompanied them and revealed the trebouxioid character of all lichen photobionts. Their photosynthetic responses were compared during natural scenarios such as reactivation by high air humidity and in situ fog events to elucidate the activation strategies of this lichen community. Epiphytic lichens showed photosynthetic activity that was rapidly induced by fog and high relative air humidity whereas terricolous lichens were only activated by fog.

the combination of topography, seasonal wind field and trade inversion height (Borthagaray, Fuentes, & Marquet, 2010;Lehnert, Thies, et al., 2018;Muenchow et al., 2013). The occurrence of fog at Las Lomitas creates a narrow ecological niche for the establishment of at least some vascular plants with a very low coverage which is composed mainly of a few cacti and Euphorbia shrubs. Both length and intensity of fog events is highly variable resulting in a wide range of daily water inputs that can reach up to 16.6 mm precipitation available for lichens on a single day (Lehnert, Thies, et al., 2018). Lichens at Las Lomitas grow epiphytically on cacti and shrubs or as crustose patches on the ground (terricolous) Bernhard et al., 2018).
Lichens represent an obligate mutualistic ectosymbiosis between at least one eukaryotic green algal or cyanobacterial species (photobiont) and one fungal species (mycobiont). Recently, a number of ascomycete macrolichens have been found to consist of more than one mycobiont (Spribille et al., 2016), and for many other lichens, other associations as for example with lichenicolous fungi have been revealed. Although lichenicolous fungi are very common, little is known about their identity or the extent to which they can interact with their hosts (Lawrey & Diederich, 2003;Tuovinen et al., 2019).
The poikilohydric character of lichens plays a crucial role during the survival of long periods of desiccation: lichens are inactive when dry but become rapidly reactivated when water is available (Green & Lange, 1995). Even high relative air humidity (>90%) has been shown to be sufficient for photosynthetic activity in a number of lichens with a green algal photobiont (chlorolichens) (Colesie, Green, Raggio, & Büdel, 2016;Lange, Kilian, & Ziegler, 1986;Raggio et al., 2017).
In addition to high air humidity, epiphytic chlorolichens of the genera Ramalina and Usnea are known to thrive in the Atacama Desert in high abundance due to the capability to capture water from incoming fog. Fog interception should not be confused with condensation (Villegas, Tobón, & Breshears, 2008) as it is comparable to filter feeding by aquatic invertebrates (Larson, 1981;Stanton & Horn, 2013), and seems to be related to lichen growth form (Lange & Redon, 1983;Stanton, 2015). This was demonstrated for lichens from the coastal fog zone of the Namib Desert, where these lichens with the highest surface to volume ratio reached the highest photosynthesis rates and also made most effective use of different water sources (Lange, Meyer, Ullmann, & Zellner, 1991). Fog water capture by epiphytic fruticose lichens is so efficient, that it can result in dripping water, a frequently observed phenomenon in the Atacama Desert, which is known to influence the soil hydrology underneath the cacti (Stanton et al., 2014). However, it remains unclear to which extent terricolous lichens in the Atacama Desert can use different sources of water and how their morpho-anatomical characteristics influence their ecophysiological pattern.
Morphological adaptations on various levels as for example growth form, anatomy but also photobiont diversity determine ecophysiological patterns (e.g. , which have rarely been investigated for lichens from the Atacama Desert (Lange & Redon, 1983). Since terricolous lichens have been recently reported to show a large range of adaptations and rapid responses to their environment (Green, Pintado, Raggio, & Sancho, 2018), the present study aims to compare and describe the ecophysiological patterns of the two most abundant terricolous and epiphytic lichens of an isolated lichen community. Further, the usage of various water sources and how thallus morpho-anatomical and hydrological traits influence photosynthetic activity is investigated. Additionally, the mycobiont and photobiont of the examined lichens, as well as their specific lichenicolous fungi, are sequenced with a multi gene loci approach in order to elucidate their taxonomic identity.

| Study site
The National Park Pan de Azúcar is located between 25°53′ and 26°15′S, and 70°29′ and 70°40′W along the Pacific coast in Chile, in the southern part of the Atacama Desert. A narrow pediment close to the coast characterizes the local topography with a steep mountain ridge reaching altitudes up to 850 m a.s.l. that descends slightly towards the inland to altitudes between 700 and 400 m a.s.l. The study site "Las Lomitas" is located in a local fog oasis in the National Park Pan de Azúcar, close to the coastal crest of the first mountain ridge. The annual rainfall is less than 13 mm in average, but totals can be higher due to extreme precipitation events which occur occasionally in El Niño and El Niño-like years when sea surface temperature anomalies off the coast are positive. An average temperature of 13°C during winter (July) and 20°C during summer (January) with daily maxima occasionally exceeding 26°C have been recorded (Rundel et al., 1996;Thompson et al., 2003). Relative air humidity under clear sky conditions is between 80% and 85% with fog affecting the coastal areas. Cacti such as Eulychnia saint-pieana and shrubs of Euphorbia lactiflua dominate the vegetation at parts of Las Lomitas (Bernhard et al., 2018). Here, the cacti are highly occupied by epiphytic lichens (Stanton et al., 2014). Only a few crustose terricolous lichen species occur in this area of the Atacama Desert, forming a socalled biological soil crust (BSC), which also includes cyanobacteria, free living green algae and fungi. They cover between 30% and 40% of the front ridge Lehnert, Jung, Obermeier, Büdel, & Bendix, 2018;Lehnert, Thies, et al., 2018). In August 2017, a high proportion of lichens were found to be associated with lichenicolous fungi, visible by blackish deformations or galls of the lichen thalli.

| Climate stations
Three automatic weather stations were installed in March 2016 at Las Lomitas as described in Lehnert, Thies, et al. (2018). The stations were equipped with standard sensors measuring wind speed, wind direction, surface and air temperatures, relative humidity and precipitation as well as PAR. Fog water fluxes were measured using cylindrical fog collectors ("harp"-type) and a dew balance at the ground level where BSCs (mainly crustose lichens) had been glued on. An analysis regarding fog and dew water fluxes was published in Lehnert, Thies, et al. (2018).
Excess soil was removed with the Petri dish lid. Samples were airdried in the field immediately after collection. The two most abundant epiphytic lichens of the genus Ramalina (fruticose hairlichen) and Everniopsis (fruticose) (Stanton et al., 2014) were picked from cacti and Euphorbia bushes and stored in paper bags. Ten replicates of each lichen species were collected. The dry lichen samples were preserved at −20°C in plastic boxes until further processing. For this study, the samples were slowly defrosted before they were used for the laboratory analyses.

| Isolation of photobionts
The algal partners of all lichen species were isolated from a clean thallus edge by removing small lichen pieces with a razor blade and carefully squeezing them between a microscope slide and cover slip to obtain a green suspension of algal cells and fungal hyphae. Under a binocular stereoscope, a group of algal cells was then transferred with a pipette to a petri dish with solidified Bold's Basal Medium as described for green algae in Baumann et al. (2018). After three to four weeks, visible algal colonies were streaked onto new plates for purification to obtain single-cell based colonies. The isolates were used to capture microscopic images for comparison of the morphological features of the algae with the phylogenetic results.

| Light microscopy
Thin sections of 20-25 µm thickness of the lichen thalli were prepared with a freezing microtome in order to maintain the inner structure of the lichen thalli. The samples were investigated with a light microscope with AxioVision software (Axioskop, Zeiss, Germany) under 630 magnification and oil immersion.
Cultured photobiont colonies were also investigated using light microscopy.

| DNA extraction and amplification
Prior to DNA extraction, lichen fragments that were not affiliated with lichenicolous fungi were carefully washed with distilled water to remove epiphytic algae and adhesive soil under a binocular stereoscope. Specimens that were colonized by lichenicolous fungi were treated in the same way but here only blackish lichenicolous material was picked from the lichen thallus. Sample preparation was followed by DNA extraction using cetrimonium bromide method followed by phenol-chloroform-isoamyl alcohol purification adapted for lichens (Shivji, Rogers, & Stanhope, 1992 (Schoch et al., 2012). After testing several recent primer pairs and PCR conditions (Matheny, Liu, Ammirati, & Hall, 2002;Schmitt et al., 2009;Schoch et al., 2012;Westberg, Millanes, Knudsen, & Wedin, 2015;Williams et al., 2017;Zhao et al., 2017), the following final settings were used for the mycobiont: the primer pair ITS1f and LR3 (ITS) and gRPB1-A and fRPB1-C (RPB1) after Westberg et al. (2015) and Zhao et al. (2017) respectively. The lichenicolous fungi were inseparably connected to the lichen thallus and therefore always mixed with DNA of the mycobiont. Due to a high affinity for lichenicolous DNA the primer pair ITS1f and LR3 (ITS) were chosen to sequence the lichenicolous fungi. All fungal PCRs were conducted in a volume of 25 µl in illustra PuReTaq Ready-To-Go PCR bead tubes (GE Healthcare, UK), because common PCR methods were tested and found to be less successful. The green algal photobiont DNA was amplified with the primer pairs Al1500af (18S rDNA) and LR3 (26S rDNA) and rbcLf and rbcLr (rbcL) both after the conditions described in Williams et al. (2017).
The PCR products were purified with the NucleoSpin ® Gel and PCR Clean-up Kit (Macherey-Nagel GmbH & Co. KG, Düren, Germany) and sent to SeqIT (Kaiserslautern) for Sanger sequencing.
All obtained sequences were submitted to the European Nucleotide Archive (ENA; Appendix Table A2).

| Phylogeny
The sequences were BLASTed against the GenBank data base (http://blast.ncbi.nlm.nih.gov/Blast.cgi) in order to find the most similar sequences which were subsequently incorporated into the alignment. The ClustalW algorithm was applied for all alignments in Mega X (version 10.0.5, Kumar, Stecher, Li, Knyaz, & Tamura, 2018).
One alignment for each gene region was prepared. Ambiguous regions were adjusted or removed manually allowing smaller final blocks and gap positions within the final blocks. Xanthoria parietina KJ027708.1 was included as root for the fungi and Chlorella sorokiniana KX495084.1 was included as root for the green algae trees. A Maximum Likelihood method with 500 bootstrap replications and the Kimura-2-parameter model (Kimura, 1980) was calculated for each alignment with Mega X as well as Bayesian phylogenetic analyses with Mr. Bayes 3.2.1 (Ronquist & Huelsenbeck, 2003). Both used gamma-distributed rates.
The resulting phylogenetic trees were compared and as they did not differ significantly from each other the alignments were concatenated. One phylogenetic tree including two gene regions for the mycobiont, one tree including only the ITS gene region for the lichenicolous fungi and one tree including three gene regions for the photobionts were calculated as mentioned above and visualized using FigTree version 1.4.3. All alignments were deposited at dryad https ://doi.org/10.5061/dryad.jc06126 and the publicly available sequences that were used to create the alignments can be seen in Appendix Tables A3-A5.

| Gas exchange
CO 2 gas exchange measurements were conducted under controlled laboratory conditions using two minicuvette systems in parallel (CMS400 and GFS 3,000, Walz Company, Effeltrich, Germany). The CO 2 gas exchange response in the light (net photosynthesis, NP) and in the dark (dark respiration, DR) was determined for five replicates of each terricolous lichen species and for five replicates of each epiphytic lichen species (Appendix Table A1) after Colesie, Green, Haferkamp, and Büdel (2014).
Before investigating the lichens' NP response to different light conditions, the samples were submerged in water for 20 min at room temperature to guarantee water saturation. After removing them from the water they were shaken to remove excess water and placed into the cuvette and exposed to increasing light intensities (0; 15; 25; 50; 75; 100; 150; 300; 500; 1,000; 1,500; 2000 µmol photons m −2 s −1 ) at 17°C with ambient CO 2 concentrations. Each measuring cycle started in the dark and lasted for 45 min until NP under the highest light intensity was reported. These cycles were repeated until the samples were completely dry. The light saturation point (LSP) was defined as the photosynthetic photon flux density at 90% of maximum NP. The light compensation point (LCP) was calculated as that light intensity at which NP compensates respiration.
Photosynthetic reactivation from high relative air humidity alone was tested by placing completely desiccated lichen samples in the gas exchange cuvette, exposed to an air stream of 90% and 95% relative air humidity, respectively at 17°C. The samples were kept in the dark for 45 min during which one measurement point was reported, representing the DR. Afterwards the light was switched on with an intensity of 800 µmol photons m 2 s −1 for 15 min to obtain an NP value at the end of the interval. This light-dark cycle was repeated for 24 hr.
To determine the optimal thallus water content for net photosynthesis, the samples were submerged in water for 20 min at room temperature to guarantee saturation directly after the experiment where they were exposed to 24 hr of high relative air humidity. After this, they were placed back into the cuvette at 800 μmol photons m −2 s −1 , incident light, ambient CO 2 concentrations and 17°C, which represents the realistic conditions found in the Atacama Desert (Bernhard et al., 2018). The CO 2 exchange of the samples was recorded in alternating intervals in the dark to obtain DR values and afterwards during the given light intensity for NP values until the sample was completely desiccated and showed no further response.
After each DR and NP measurement, the samples were weighed to report the weight loss by evaporating water during desiccation.
After the measurement, the lichens were dried at 65°C for 3 days in a drying oven (Heraeus Instruments T6P, Thermo Fisher Scientific Inc.) and weighed to obtain their dry weight. The thallus water content during the measurements could then together with the dry weight of the sample be calculated as equivalent of mm precipitation.
After completion of all experiments the CO 2 exchange of the samples was related to their chlorophyll content, chlorophyll a+b was extracted after the method described by Ronen and Galun (1984).  Table A1) that were growing attached to cacti in close vicinity were measured at intervals of 3-5 min under foggy conditions. In the laboratory, an additional eight replicates of each lichen were submersed in water for 20 min to reach a fully hydrated state in the dark and measured again. Field measurements were calculated to their corresponding yield in a completely hydrated status and are therefore given in percent. Photosynthetic yield values can strongly vary between lichen species and are shown in percent to their maximum yield in order to compare the four lichen species (see Appendix Table A6 for original values). Yield values lower than 0.2 were treated as not active (Leisner, Bilger, & Lange, 1996).

| Chlorophyll fluorescence
Temperature was recorded using the same instruments simultaneously with the PAM measurements.

| Statistics
Statistics for LSP and LCP were calculated using the software Statistica (Version 9.1; StatSoft Inc. 2010). The data were tested for normal distribution using a Shapiro-Wilk test. After all data were found to be normally distributed and homogeneity of variances was verified using Levene test a one-way ANOVA followed by Tukey post hoc test was used to detect differences between groups. Unless otherwise noted, significant differences refer to p ≤ 0.05.

| Protection of human subjects and animals
The protocol and procedures employed were reviewed and approved by an appropriate institutional review committee.

| Climate
Soil surface temperature ( Figure 1a

| Phylogeny
The mycobiont phylogeny revealed that three of the newly generated sequence groups highly support the other Placidium species. Unfortunately, we were not able to assign them to species level because they are polyphyletic (Figure 2a,e). The sequences of the three replicates were identical to each other. The sampled Acarospora species joined an Acarospora clade (Figure 2a

| Morphology
The Acarospora species showed a morphology that did not fit to any of the described species of the genus and contained a photobiont layer that was arranged in vertical algal stacks that were sometimes discontinued by vertical fungal stacks (Figure 5b). Therefore it has been deemed a new species and was named A. conafii which was supported by the phylogenetic placement.  Micrographs of the terricolous Acarospora conafii is given in (b), Everniopsis trulla in (c), Ramalina thrausta in (d) and Placidium sp. in (e). Scale bar for images is 1 cm inside of the pycnidia in a way that makes the parasitized lichen species appear dark and matt.

| Photosynthetic response to water
The two crustose lichens A. conafii and Placidium sp. did not react within 24 hr of exposure to air of 90% and 95% relative humidity (Figure 6a-d; white areas). The epiphytic lichen R. thrausta became active and showed positive net photosynthesis after 5 hr of exposure while E. trulla was reactivated already during the first hour after exposure. Reactivation patterns during an exposure to 95% relative air humidity showed a slightly higher respiration and net photosynthesis for R. thrausta and E. trulla than during 90% of exposure (data not shown).
During activation by liquid water the longest activity amplitude (7 hr of activity) was detected for Placidium sp. (Figure 6d; blue area) while the highest NP (18 nmol CO 2 mg Chl a+b −1 s −1 ) and DR (13 nmol CO 2 mg Chl a+b −1 s −1 ) were recorded for E. trulla ( Figure 6b; blue area).

| Lichen phylogeny
The Acarospora sequences from GenBank utilized in this study represent the largest taxon sampling available with our addition of A. conafii as a new species (Westberg et al., 2015). Identifications within Verrucariaceae can be even more complicated due to a scarcity of discriminating morphological characters as well as a lack of phylogenetic data. These problems have also been highlighted and To date some Ramalina species have been recorded for the coastal Atacama Desert that show a considerable morphological variation (Rundel, 1978;Santiago, Gonçalves, Gómez-Silva, Galetovic, & Rosa, 2018) but this is the first record of R. thrausta for the southern hemisphere. Typical are the filamentous thin branches that are slightly and irregularly swollen, the small hooked shaped terminal soralia, the spotlike to elongate pseudocyphellae and the presence of usnic acid only (Bowler, 1977). Apothecia are very rare in the Northern hemisphere and no information on the spore length is given. However, the specimen investigated here frequently does have apothecia and the spores are 9-16 × 2-4 µm. Interestingly there is a macaronesian species, thrausta, but with apothecia containing spores of 14-17 × 5-6 µm and without hooked shaped soralia (Krog & Osthagen, 1980

| Associated lichenicolous fungi
At Las Lomitas, roughly 20% of the A. conafii population was found to be accompanied by a lichenicolous fungus highly related to P.
subfuscescens (Nyl.) K. Knudsen & Kocourk (Figure 4a,f,g), which is a widely distributed, successful and aggressive parasite. This parasitic fungus invades the host's thalli through the ostioles of the pycnidia or perithecia and grows inside them (Figure 4f,g). It is known to suppress ascomata production of the host, to deplete the algal layer and finally destroy the host (Knudsen & Kocourkova, 2008). Besides Acarospora, Caloplaca species are also considered to be possible hosts. This was observed at the study site for C. santessoniana ad int. (Gaya et al., 2015), where up to 50% of the population was parasitized. Almost no specimens of A. conafii or C. santessoniana ad int.
were found with apothecia, which might be caused by the strong parasitism (Knudsen & Kocourkova, 2008).
In contrast to the parasitic character of P. subfuscescens, a Neonectria species was found to persistently invade the epinecral layer of Placidium sp. (Figure 4a,d,e). According to the saprophytic character of some Neonectria species, the fungi stopped penetrating the lichen thallus at the pigmented layer, which was formed by living lichenized hyphae, spreading only within the epinecral layer composed of dead cells (Figure 4e).

Ramalina thrausta was moderately affiliated with a gall inducing
Tremella sp. (Figure 4a-c) although lichenicolous species are among the most poorly known representatives of this genus (Millanes, Westberg, Wedin, & Diederich, 2012). Tremella species were reported from a wide range of lichen genera (Diederich et al. 2018

| Structural adaptations
Interestingly, the photobiont layer of A. conafii and Placidium sp. is organized in vertical stacks that are separated by vertical channels summer at the sampling site (Figure 1d), which was reflected in high LSP and LCP values of A. conafii and Placidium sp. Furthermore, the feature of fungal and algal stacks was initially thought to extend the period of CO 2 assimilation but could not be supported by the authors nor within this study during gas exchange experiments.
In terms of morphology and ecophysiology the prominent epinecral layer of Placidium sp. may have played a crucial role since it was built from hyaline hyphae surrounded by a gelatinous matrix ( Figure 5a). Hence, we assumed that the epinecral layer of Placidium sp. provided water to the photobiont layer underneath, increasing the duration of activity of the green algal cells. Acclimation of the epinecral layer to increased irradiation within a single species was observed for the cyanolichens Peltigera rufescens (Weiss) Humb. and P. praetextata (Sommerf.) Zopf (Dietz, Büdel, Lange, & Bilger, 2000).
Additionally, the chlorolichen Psora decipiens (Hedw.) Hoffm. which also belongs to Verrucariaceae, shows an adaption towards xeric stress in a similar way to Placidium sp. by increasing the ability to take up water from the environment . Morphological adaptation patterns were also found within the epiphytic lichens. For example, R. thrausta has a relatively thick cortex that was assumed to be a characteristic adaptation of fog zone lichens. A thick cortex may prevent mechanical damage and desiccation by wind, as has been shown especially for Ramalina species (Rundel & Bowler, 1974).

| Ecophysiology
Surprisingly, both terricolous lichen species could not be reactivated by exposure to high relative air humidity (90%, Figure 6c,d F I G U R E 6 Ecophysiological measurements of lichens. Gas exchange measurements of the four lichens (a-d) during exposure of the dry thalli to 90% relative air humidity (white section) and after full hydration until they were completely dehydrated (blue section). Water content of the thalli is given in mm H 2 O as equivalent to precipitation for (c) and (d). LSP = light saturation point and LCP = light compensation point are given in μmol photons s −1 m 2 and standard deviation, different letters indicate significant differences between the LSP and LCP of the species, each (n = 5). PAM measurement before, during and after a fog event (e) shows the yield of photosystem II in percent, calculated down to the corresponding 100% yield reached after full hydration of the thalli and the temperature recorded during the measurements. E = Everniopsis trulla; R = Ramalina thrausta; A = Acarospora conafii; P = Placidium sp. (n = 8 for each species) or 95% data not shown) although this was long thought to be a common reactivation pattern in chlorolichens (Lange et al., 1986 (Colesie et al., 2014;Del Prado & Sancho, 2007). High relative air humidity is present at the Coastal Cordillera of the Atacama Desert due to the close vicinity to the Pacific Ocean even under cloud free conditions ranging from 80% to 85% at night and from 60% to 70% during daylight (Rundel et al., 1996).
However, for most chlorolichens' air humidity levels between 90% and 100% were shown to be sufficient to activate photosynthesis. The present levels of air humidity are likely rarely sufficient to activate lichen photosynthesis at Las Lomitas. Even a lower humidity is probably present at ground level due to higher soil surface temperatures and thus terricolous lichens of this environment could lack an adaptation mechanism allowing for reactivation by water vapor. In contrast, Del Prado and Sancho (2007) showed that T. lacunosus did not show photosynthetic activity although it was frequently exposed to relative air humidity ranging between 85% and 100% even at the pediment. They concluded that this is a long-term effect within soil crust lichens from very dry environments where high atmospheric humidity and frequent maritime fogs are extremely favorable for lichen growth.
In contrast to the terricolous lichens, both epiphytes were able to be reactivated by high air humidity. This is especially interesting since the epiphytic R. thrausta and the terricolous A. conafii shared green algal photobionts that were highly similar to T. arboricola. This demonstrates that the ability to use high air humidity for photosynthetic activity may be mainly controlled by the mycobiont.  (Veste, Littmann, Friedrich, & Breckle, 2001). During fog events Placidium sp. did not exceed 33% of its maximum activity as detected by PAM measurements (Figure 6e), suggesting that short fog events and water vapor are not sufficient to saturate the thallus of this lichen and its epinecral layer. This could be caused by a hydrophobic character of the thick epinecral layer as reported previously for various lichens (Lakatos, Rascher, & Büdel, 2006). On the other site, during gas exchange measurements Placidium sp. showed a longer duration of photosynthesis compared to A. conafii (Figure 6), which was probably caused by the increased water holding capacity of the well-developed epinecral layer. Liquid water of more than 0.6 mm even caused photosynthetic depression of NP during the gas exchange measurements (Figure 6d).
In addition, Placidium sp. had an optimum water content of 0.3-0.6 mm which was more than twice as high as for A. conafii (0.2 mm), probably caused by the epinecral layer. This is comparable to a study conducted by Büdel, Vivas, and Lange (2013) Poelt from arid lands of Utah (Lange et al. 1997) or two morphospecies of the epiphytic Ramalina menziesii Taylor from a coastal and an inland habitat in central California (Matthes-Sears, Nash, & Larson, 1987).
The epiphytic species R. thrausta was found to be efficient in fog water interception leading to dripping water and thus might improve host plant water use by microenvironmental modification as it has been demonstrated for Ramalina species from the same study site (Stanton et al., 2014). their adaptions towards arid conditions. They could also demonstrate that high amounts of water vapor at Fray Jorge were found to saturate the lichen thalli during night, leading to efficient NP during the early morning hours (Lange & Redon, 1983). LE903/14-1).

CO N FLI C T O F I NTE R E S T S
The authors declare that they have no conflict of interest.

AUTH O R CO NTR I B UTI O N S
PJ designed the study, conducted measurements and prepared the manuscript, DE sequenced the mycobiont, photobiont and parasites, MS prepared the micrographs, KB conducted field measurements, LW and CC analyzed the gas exchange patterns, LL, JB and SA recorded and analyzed the climatic data, PC helped during the identification of the lichens, LBW guided this work and BB designed the study and guided this work. All authors commented on the manuscript.

E TH I C S S TATEM ENT
The protocol and procedures employed were reviewed and approved by an appropriate institutional review committee in collaboration with the Chilean collaboration partners of the Corporación Nacional Forestal (CONAF).