Life under quartz: Hypolithic mosses in the Mojave Desert

Abstract

Several species of dryland cyanobacteria are known to occur as hypoliths under semi-translucent rocks. In the Mojave Desert, these organisms find refuge from intense solar radiation under milky quartz where moisture persists for a longer period of time than in adjacent soil surface habitat. Desert mosses, which are extremely desiccation-tolerant, can also occur in these hypolithic spaces, though little is known about this unique moss microhabitat and how species composition compares to that of adjacent soil surface communities. To address this question, we deployed microclimate dataloggers and collected moss samples from under and adjacent to 18 milky quartz rocks (quartz mean center thickness 26 ± 15 mm) in a western high elevation Mojave Desert site. Light transmission through Mojave quartz rocks may be as low as 1.2%, and data from microclimate loggers deployed for five months support the hypothesis that quartz provides thermal buffering and higher relative humidity compared to the soil surface. Of the 53 samples collected from hypolith and surface microhabitats, 68% were Syntrichia caninervis, the dominant bryophyte of the Mojave Desert biological soil crust. Tortula inermis accounted for 28% of the samples and 4% were Bryum argenteum. In a comparison of moss community composition, we found that S. caninervis was more likely to be on the soil surface, though it was abundant in both microhabitats, while T. inermis was more restricted to hypoliths, perhaps due to protection from temperature extremes. In our study site, the differences between hypolithic and surface microhabitats enable niche partitioning between T. inermis and S. caninervis, enhancing alpha diversity. This work points to the need to thoroughly consider microhabitats when assessing bryophyte species diversity and modelling species distributions. This focus is particularly important in extreme environments, where mosses may find refuge from the prevailing macroclimatic conditions in microhabitats such as hypoliths.

Holistic Approach to the Restoration of a Vandalized Monument: The Cross of the Inquisition, Seville City Hall, Spain

“…Isermann [25] found Tortula truncata, Tortula muralis, Syntrichia ruralis and many other species of bryophytes in the campus of Bremen University. Ekwealor and Fisher [26] found Syntrichia caninervis and Tortula inermis, with a high tolerance to desiccation, under the rocks of the Mojave Desert, demonstrating their resistance in hypolithic habitats.…”

Ecology and responses to climate change of biocrust-forming mosses in drylands

“…Also, the acclimation capacity of desert mosses to different degrees of UV radiation is remarkable. A major mechanism is the ability to adjust photoprotective compounds according to the risks of suffering light damage by using pigmentation plasticity ( Ekwealor and Fisher, 2020 ). As UV stress increases, mosses can reduce the chlorophyll to total pigment content ratio and increase the levels of zeaxanthin (a potential antioxidant) and chlorophyll a : b and carotenoid:chlorophyll ratios ( Hamerlynck et al , 2002 ; Ekwealor et al , 2021 ).…”

Mosses: Accessible Systems for Plant Development Studies

“…As a mostly avascular lineage, Bryophytes, that include mosses, liverworts and hornworts, thrive in mostly moist niches near the surface and stay compact (<10 cm), with some neovascularised exceptions that grow up to 65 cm [3][4][5]. Their cosmopolitan distribution in a variety of biotopes including moist and arid environments, can be explained by unique adaptations like drought, freezing and salinity tolerance [4,6,7]. Mosses' life cycle is dominantly gametophytic (the photosynthetic and growing phase is haploid), and the size and architecture of their organs is smaller and simpler than that of vascular plants, with leaf-like structures (phyllids) and sexual organs (antheridia and archegonia) of often only one cell of thickness, stem-like structures of circa ten cells and spore-bearing containers (sporangia) of single-cell spores [4,[8][9][10].…”