Department of Integrative Biology, University of California, Berkeley, California, United States of America.
Department of Biological Sciences, California State University, Los Angeles, California, United States of America.
PLoS One. 2020 Jul 22;15(7):e0235928. doi: 10.1371/journal.pone.0235928. eCollection 2020.
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.
已知几种旱地蓝藻存在于半透明岩石下的隐生体中。在莫哈韦沙漠，这些生物在乳白色石英下躲避强烈的太阳辐射，那里的湿度比相邻的土壤表面栖息地保持更长时间。沙漠苔藓，具有极强的耐旱性，也可以在这些隐生空间中出现，尽管对这种独特的苔藓微生境知之甚少，也不知道物种组成与相邻土壤表面群落的比较情况。为了解决这个问题，我们在莫哈韦沙漠西部高海拔地区的 18 块乳白色石英岩石下（石英平均中心厚度为 26±15 毫米）部署了微气候数据记录器并收集了苔藓样本。莫哈韦石英岩石的光透过率可能低至 1.2%，并且放置五个月的微气候数据记录器的数据支持了这样的假设，即石英提供了热缓冲作用和比土壤表面更高的相对湿度。在从隐生体和表面微生境收集的 53 个样本中，68%是莫哈韦沙漠生物土壤结皮的优势苔藓 Syntrichia caninervis。Tortula inermis 占样本的 28%，Bryum argenteum 占 4%。在苔藓群落组成的比较中，我们发现 S. caninervis 更有可能在土壤表面，但它在两个微生境中都很丰富，而 T. inermis 则更局限于隐生体，可能是因为它免受极端温度的影响。在我们的研究地点，隐生体和表面微生境之间的差异使得 T. inermis 和 S. caninervis 之间能够进行生态位分离，从而提高了 alpha 多样性。这项工作表明，在评估苔藓物种多样性和模拟物种分布时，需要彻底考虑微生境。这种关注在极端环境中尤为重要，在这些环境中，苔藓可能会在隐生体等微生境中躲避普遍的宏气候条件。
