Flora 213 (2015) 77–84 Contents lists available at ScienceDirect Flora journal homepage: www.elsevier.com/locate/flora The effect of dew on flint and limestone lichen communities in the Negev Desert Marina Temina a,∗ , Giora J. Kidron b a Institute of Evolution, University of Haifa, 199 Aba-Hushi Avenue, Mount Carmel, Haifa 3498838, Israel b Institute of Earth Sciences, The Hebrew University, Jerusalem 91904, Israel a r t i c l e i n f o Article history: Received 9 September 2014 Received in revised form 2 April 2015 Accepted 21 April 2015 Edited by Brigitta Erschbamer. Available online 22 April 2015 Keywords: Chert Endolithic lichens Epilithic lichens Dew a b s t r a c t Although lichens are important components of arid ecosystems, the influence of microclimatic factors (particularly dew) conducive to their distribution on rock habitats in the Negev Desert are still not suffi- ciently investigated. Here, we present a study on adjacent lichen communities inhabiting slightly acidic flint (chert) and slightly alkaline limestone cobbles in the north-facing slopes of two sites in the Negev Desert, Nizzana, NIZ (with long-term mean precipitation of 95 mm and average daily dew amount of 0.1 mm) and Sede Boqer, SB (with long-term mean precipitation of 95 mm and average daily dew amount of 0.2 mm). The communities on flint consisted of either scarce or lush cover of exclusively epilithic species, while endolithic lichens predominated on limestone. Following previous measurements that indicated that similar dew amounts characterize limestone and flint cobbles, we hypothesized that dif- ferences in the flint- and limestone-lichen communities may stem from differences in dew duration. Our results pointed indeed to the fact that while non-significant differences characterized the amounts of dew condensed on both substrates, dew duration on some of the flint cobbles (such as flat cobbles that readily permits long-lasting condensation) was by ∼1.2 longer. With longer dew duration, the cover of the epilithic lichens Aspicilia contorta subsp. hoffmanniana and Buellia sorediosa on flint increased along with the cover of the fruticose lichen Ramalina maciformis. Some of the species (Caloplaca circumalbata var. circumalbata, Caloplaca flavocitrina, Caloplaca oasis, Candelariella minuta, Diplotomma epipolium) inhab- ited both substrates pointing to the possibility that dew duration rather than alkalinity determines their distribution. While not explaining the higher lichen cover on limestone, dew duration explains the sig- nificantly higher cover of epilithic lichens and chlorophyll content (per inhabited surface) on flint in comparison to limestone. © 2015 Elsevier GmbH. All rights reserved. 1. Introduction Functioning of arid and semiarid ecosystems is largely influ- enced by lichens (Whitford, 2002; Wirth, 2010; Lüttge, 2013; Concostrina-Zubiri et al., 2014). Lichens play a pivotal role in the terrestrial food chain of arid and semiarid regions (Shachak et al., 1987), and as providers of nutrients and organic matter to these ecosystems (Evans and Lange, 2001; Elbert et al., 2012). By exten- sively covering rock outcrops and cobbles, lichens also play an important role in rock weathering (Fry, 1927; Danin and Garty, 1983; Schwartzman and Volk, 1989; Wessels and Büdel, 1989; Chen et al., 2000; Stretch and Viles, 2002; Favero-Longo et al., 2011) and ∗ Corresponding author. Tel.: +972 4 8249697. E-mail addresses: temina@research.haifa.ac.il (M. Temina), kidron@mail.huji.ac.il (G.J. Kidron). soil formation (Syers and Iskandar, 1973; Schwartzman and Volk, 1989). Due to the scarcity of plants in arid environments, the weath- ering role played by lichens and their role as a provider of organic matter are of high importance. These processes are however not only climate-dependent but also substrate-dependent, with rock properties affecting lichen activity (Brodo, 1973; Concostrina- Zubiri et al., 2014; Giordani et al., 2014). Rock properties may also affect lichen communities (Spitale and Nascimbene, 2012). Generally, two main substrate-specific groups can be distinguished: alkaline and acidic (Brodo, 1973). While cal- cicolous lichens characterize rocks with high Ca content such as limestone, silicicolous lichens characterize rocks with high Si con- tent, such as flint (chert). Both rock types can be found in the Negev Desert. However, while lichen diversity on limestone was exten- sively studied in the Negev (Galun and Reichert, 1960; Galun, 1963, 1970; Friedmann and Galun, 1974; Insarov and Insarova, 1995; Galun and Mukhtar, 1996; Temina et al., 2005; Temina and Nevo, http://dx.doi.org/10.1016/j.flora.2015.04.005 0367-2530/© 2015 Elsevier GmbH. All rights reserved.