Lichens and animal camouflage : some observations from central Asian ecoregions

Camouflage is a fitness-relevant trait that supports survival and fosters evolutionary adaptation by which animals match their body pattern to a background setting. Lichens are among the most common of these backgrounds that several animal species use for camouflage. Lichens are omnipresent and grow in wide arrays of colorations and compositions. Their composition and phenotypic diversity might facilitate cryptic coloration and habitat matching by various animal species. Here, we describe the role of lichens in providing camouflage to various animal species in central Asian and Caucasus mountain ecoregions, which are categorized as global biodiversity hotspots. Despite multiple ecological studies, no information is available on the role of this regions‘ lichen diversity in providing animal camouflage. Casual field observations of lichen camouflage are reported for four (one mammal and three reptile) species: the Persian Leopard’s Panthera pardus saxicolor body coat seems to closely match the colors and patterns of saxicolous lichens (Acarospora sp. and Circinaria sp.) in their habitat. A similar background matching pattern was observed in both morphs of the Caucasian Rock Agama Paralaudakia caucasia upon crustose lichens: Caloplaca spp., Circinaria spp., and the Radde’s Rock Lizard Darevskia raddei to the crustose lichens Acarospora sp. and Caloplaca sp. Likewise, the Horny-scaled Agama’s Trapelus ruderatus grey matches with the color of multiple lichens (Lecanora spp., Circinaria spp., Protoparmeliopsis spp., Rinodina spp., and Anaptychia spp.). Our observations preliminarily suggest that lichens play an important role for species of different trophic levels, ensuring adaptation and survival through camouflage. We call for more fieldbased empirical and experimental studies in various terrestrial ecosystems in other parts of the world to test the role of lichens in local adaption and evolutionary plasticity of regional species.

ISSN 0974-7907 (Online); ISSN 0974-7893 (Print) Wildlife populations of various taxa are experiencing an unprecedented loss worldwide. The 2020 Global Living Planet Index reported an average 68% decline in the populations of mammals, birds, amphibians, reptiles, and fishes within a period of 46 years . Many of the listed species are subjected to anthropogenic impacts and environmental alterations such as climate change, pollution, disease, invasive species, and land degradation (Kettlewell 1955;Gomulkiewicz & Holt 1995;Gonzalez et al. 2013;Maxwell et al. 2016). Species persistence may also depend on phenotypic plasticity or adaptive evolution (Carlson et al. 2014). The inherent J TT genetic variation in a species may help species to adapt towards stressors if these exert strong selection pressure (Gonzalez et al. 2013).
One of the fitness-relevant traits that support survival and foster evolutionary adaptation is camouflage ( Animals employ camouflage in multiple ways to facilitate various strategies including; background matching (i.e., animals resemble the shape of the habitat background) and disruptive coloration (i.e., developing high contrast patches to break up the body's edge). Cryptic coloration and display of specific behaviours may reduce visual detection or recognition by predators (Cuthill 2019). Cryptic coloration can occur seasonally (e.g., as in the form of change of coat colour from brown in summer to white in winter) and may change with patterns and color of habitat, affecting the selection of phenotypic traits for crypsis (Mills et al. 2013). A recent study identified polymorphic regions for some color molting mammal species (e.g., Snowshoe Hare Lepus americanus, Arctic Fox Vulpes lagopus), suggesting that these regions can function as evolutionary rescue sites in the rapidly changing world due to climate change (Mills et al. 2013).
The most quoted classic example of rapid plasticity in response to anthropogenic climate change affecting the effectiveness of camouflage is that of the Peppered Moth Biston betularia (Grant & Howlett 1988;Majerus et al. 2000;Cuthill 2019). During the industrial revolution (ca. 1760-1840), the Silver Birch Trees' Betula pendula bark became darker due to pollution (Grant & Howlett 1988). As a result, the melanic forms of the Peppered Moth (dark) in polluted regions had low predation pressure over lichen-like individuals (pale speckled), which were easily spotted by their avian predators due to contrasting dark background. When pollution levels in these regions declined, and the lichens grew back on the trees, the pale speckled morphs regained abundance (Kettlewell 1955;Grant & Howlett 1988). In an experimental study Walton & Stevens (2018) showed that the pale-speckled form of the Peppered Moth closely resembles the crustose lichen found on tree barks, making them less vulnerable to predation by birds, compared to melanic forms. This example provides striking evidence about the importance of the rapid evolutionary response of animals to environmental alterations under the influence of strong selection pressure. It also emphasizes the role of lichens in sustaining populations by providing important ecosystem services such as camouflage that helped reversing population decline (Walton & Stevens 2018).
There are several other examples reported from various parts of the world, where lichens were employed by various species not only as habitat and food source, but also for camouflage (Zedda & Rambold 2011). The larvae of insect species such as Lacewing (Neuroptera: Chrysopidae) and Bagworm (Lepidoptera: Psychidae) use lichens as food and camouflage to escape from predators (Skorepa & Sharp 1971;Cannon 2010

Lichens and animal camouflage in central Asian mountain ecoregion
Lichens are a symbiotic group of organisms that occur in terrestrial ecosystems. They cover approximately 8% of the global land surface (Nash 2008), and grow in wide arrays of colorations, compositions and patterns on substrates such as rocks, trees or shrubs' bark, and even anthropogenic material such as concrete (Nash 2008). They are specifically more diverse and abundant in dry high altitude grasslands and tundra ecosystems (Asplund & Wardle 2017). Lichens are sensitive to a wide range of pollutants and climatic alterations and thus serve as indicators of ecosystem health (Munzi et al. 2014;Root et al. 2015). For instance, the depletion of lichens also indicates population decline of Caribou in the arctic ecosystem (Joly et al. 2009).
Here, we describe the importance of lichens in providing camouflage to various animal species of central Asian mountain ecoregion. The Irano-Anatolian, Caucasus, and central Asian mountains ecoregions are mainly characterized by vast dry scrublands, grasslands and steppic mountainous landscapes and are categorized amongst the global biodiversity hotspots (Olson & Dinerstein 2008;Marchese 2015). These ecoregions are vulnerable to climate change as well as intense human

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use (Stone 2015). Despite several long-term ecological studies on many species from this region, no information is available on the role of regional lichen species in providing animal camouflage. We here present examples from four animal species (one mammal and three reptilian) that represent and occupy different trophic levels in the Irano-Anatolian, Caucasus, and central Asian mountains ecoregions. The Persian Leopard Panthera pardus saxicolor, synonym: P. p. tulliana was described by R.I. Pocock in 1927. The etymological meaning of 'saxicolor' in its scientific name is 'stone-grey' or 'stone-color' (Pocock 1927). Persian Leopard has a grey and yellowish-buff coat interspersed with black rosette patterns (Pocock 1927) that seem to closely match and merge with the colors and patterns of regional saxicolous lichen species such as Acarospora sp. (Ascosporaceae) and Circinaria sp. (Megasporaceae) (Image 1), and other families of lichens including Candelariaceae, Collemataceae, Lecanoraceae, Lecideaceae, Lichinaceae, Megasporaceae, Parmeliaceae, Physciaceae, Rhizocarpaceae, Teloschistaceae, Umbilicariaceae, and Verrucariaceae that are also found in their habitat in these ecoregions. The Persian Leopard is an apex predator of these ecoregions, that inhabits rocky mountainous habitats in western and central Asia (Jacobson et al. 2016). Their arid and rocky habitat is covered by saxicolous lichens that help them in camouflage, which is often useful in their ambush hunting technique. It reduces their chances of visual detection by their prey species and might improve their ambush predation success.
To further illustrate the importance of lichens in  We acknowledge that the camouflage of various animal species as described above due to the lichen species in their habitat might just be a perception due to limitations of human vision, which is different from what these animal species and their predators or prey perceive. An experimental study by Majerus et al. (2000) compared the ultra-violate characteristics of both forms of the Peppered Moths in the backdrop of foliose and crustose lichens. They report that the colour patterns of the pale-speckled moth is an effective cryptic match to the crustose lichen Lecanora conizaeoides, in both human-vision and ultra-violate visions to the crustose lichens. However, the camouflage behaviour in animals via matching habitat does not essentially depend on lichens (Walton & Stevens 2018), because habitat types and their background characteristics can largely vary across time and space and other factors like vegetation might play a role in camouflage as well (Baling et al. 2019). For example, the melanic form of the peppered moth is adapted closely to plain tree barks, whereas the speckled form adapted to the crustose lichens (Walton & Stevens 2018). In urban ecosystems, even the plain anthropogenic substrates such as roads and pavements are voluntarily selected by animal species that can play a crucial role in their adaptation and population persistence (Camacho et al. 2020).
We conclude that despite several examples of the role of lichens in animal camouflage for a handful of faunal species from a few selected ecosystems, there is insufficient knowledge about lichens and their role in animal camouflage in various terrestrial ecosystems of the world. Lichens are omnipresent and their species composition, richness, and phenotypic diversity might facilitate crypsis coloration and habitat matching by various animal species across different trophic levels. Under variable environments and changing climate www.threatenedtaxa.org The Journal of Threatened Taxa (JoTT) is dedicated to building evidence for conservation globally by publishing peer-reviewed articles online every month at a reasonably rapid rate at www.threatenedtaxa.org. All articles published in JoTT are registered under Creative Commons Attribution 4.0 International License unless otherwise mentioned. JoTT allows allows unrestricted use, reproduction, and distribution of articles in any medium by providing adequate credit to the author(s) and the source of publication.