Genus humidophila from caves in Serbia with an improved detailed description of rare H. brekkaensoides

Phototrophic microorganisms can be found in biofilms at entrances to caves where they have access to sufficient sunlight, water and nutrients; however, they can also be found inside caves, where they are carried by animals and people, and can proliferate in the presence of artificial light. Although the genus Humidophila includes some well-known cosmopolitan species, further exploration of its rare, insufficiently investigated representatives in different geographical areas and unusual habitats is necessary. Caves remain unknown, little-explored habitats, and many species currently known to science were recorded for the first time. This study aimed to report species belonging to the genus Humidophila that were identified in 19 caves in Serbia. A total of ten species of this genus were recorded and some of them are documented for the first time in Serbia. The most abundant species were H. contenta (found in 16 caves), H. paracontenta, and H. aerophila (found in 13 caves), whereas H. pyrenaica was identified in only one cave. The rare species, H. brekkaensoides and H. vidalii, were also documented and described, but with different dimensions from those provided in current identification keys. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 176018, Grant no. 176020, Grant no. 37009, and Project FP7 “Capacities” Program]