Bryophyte Diversity in the Khaybar White Volcano Geopark (Saudi Arabia)—Floristic Patterns and Conservation Perspectives

Recent bryological surveys conducted at the Khaybar White Volcano site (northwest Saudi Arabia) led to the documentation of 51 bryophyte species, including five liverworts and 46 mosses. Representing approximately 30% of the national bryophyte flora within less than 0.3% of the country's surface, this site emerged as a regional hotspot of bryological diversity. A systematic catalog was compiled, presenting the biogeography, local distribution, demography, fertility, taxonomy and ecology of all recorded taxa. Notably, two Arabian endemics-<i>Crossidium deserti</i> and <i>Tortula mucronifera</i>-were identified in Khaybar, alongside six previously unknown on the Arabian Peninsula (<i>Anoectangium euchloron</i>, <i>Geheebia erosa</i>, <i>Grimmia capillata</i>, <i>Molendoa sendteriana</i>, <i>Pterygoneurum subsessile</i>, and <i>Ptychostomum torquescens</i>) and six species newly recorded for Saudi Arabia (<i>Anoectangium aestivum</i>, <i>Husnotiella revoluta</i>, <i>Syntrichia pagorum</i>, <i>Tortella nitida</i>, <i>Tortula lindbergii</i>, and <i>Tuerckheimia svihlae</i>). These findings highlighted the conservation value of Khaybar, whose unique geothermal microhabitats (active fumaroles) supported a suite of tropical and thermophilous species otherwise absent in northern Arabia, such as <i>Fissidens sciophyllus</i>, and <i>Plagiochasma eximium</i>. Comparative analysis with the AlUla region revealed a comparable species richness despite Khaybar's smaller area and indicated substantial ecological divergence. While AlUla's bryoflora was primarily associated with lithological heterogeneity, Khaybar's was shaped by geothermal activity. Conservation recommendations emphasize the vulnerability of these specialized bryophyte communities to grazing, trampling, and climate change, and call for long-term monitoring, regulated access, and integration into national biodiversity management strategies.