Dew moisture regime of endolithic and epilithic lichens inhabiting limestone cobbles and rock outcrops, Negev Highlands, Israel

Endolithic and epilithic lichens proliferate on calcareous cobbles and rock outcrops in the Negev Highlands, Israel. Whereas epilithic lichens predomi nate in shaded mesohabitats, extensively covering rock outcrops, endolithic lichens proliferate on loose cobbles. Endolithic lichens were thought to p redominate in habitats having a poor dew regime. Dew measurements were carried out at habitats of endolithic and epilithic l ichens. The measurements took place on loose and partially embedded cobbles with 90-100% of endolithic lichen cover, and on rock outcrops inhabited by epilithic lichens (75-90% cover). In addition, independent dew measurement s were carried out with the Flare Cloth Method (CPM). A rotal of 60 days of measurements was performed. Average daily dew amount as obtained by the CPM was 0.20 nun, as compared t o 0.18 mm obtained on the loose cobbles, 0.09 mm obtained by the partially embedded cobbles and 0.04-0.08 mm obtained on the bedrock surfaces. The dew amounts obtained on the cobbles were significantly higher than those obtai ned on the bedrock surfaces (paired t-test, p < 0.001). Thus, although expo sed to the first sun beams during the early morning hours, cobbles, due to their excessive heat loss and subsequent higher cooling rates, form a mesic microhabitat las far as dew amount is concerned) within an unshaded and he nce xeric las far as dew duration is concerned) mesohabitat. The results po int out that endolithic lichens are not necessarily adapted to a poor dew r egime. The advantage of the endolithic habitat in light of the present find ings is discussed.