Epiphytic lichen diversity along elevational gradients: biological traits reveal a complex response to water and energy

Abstract

Aim Patterns of epiphytic lichen diversity along elevational gradients covering the range of Norway spruce forests were analysed. The roles of water and energy variables in shaping the observed species-elevation relationship were tested, as well as how growth form and photobiont type distribution varied along the gradient.Location South Tyrol, northern Italy.Methods Eight sites were selected spanning the elevational range of spruce forests (900-1900 m a.s.l.) and the regional rainfall gradient. At each site, a pair of forest stands (one mature even-aged and one multilayered) was selected at three elevation steps. Epiphytic lichens were surveyed according to European guidelines for lichen diversity monitoring. Explanatory variables indicative of both forest structure and climate were included in the models.Results A positive relationship was found between number of species and elevation. This reflected the physiological response of epiphytic lichens to the main climatic factors, trait selection being the mechanism that determined the response at community level. Nonlinear species-temperature and trait-temperature relationships predicted that major changes may be expected in the intermediate part of the gradient. Lichens with a Trentepohlia algal partner were more frequent at lower elevations and proved to be sensitive to environmental factors indicative of forest structure. Lichen growth forms had contrasting patterns related to temperature, crustose species richness being enhanced by increasing values, and alectorioid and foliose lichens by decreasing values. Alectorioid lichens were also negatively influenced by rainfall.Main conclusions In a climate change scenario, lichen diversity in alpine regions will probably not benefit from an increase in air temperature in the same way as flowering plants. Monitoring variations in the proportions of growth form and photobiont type may represent a tool for detecting the effects of climate change on lichen species.

Contrasting patterns of lichen functional diversity and species richness across an elevation gradient

“…First, we found species having a crustose growth form at lower elevations while species having a foliose and fruticose growth form were more frequent at higher elevation sites. This is in line with elevational studies from the alpine region demonstrating similar patterns (Dietrich andScheidegger 1997, Nascimbene andMarini 2015). We argue that water availability at higher elevations is the main explanation for the prevalence of foliose and fruticose species.…”

“…air humidity) as a determinant of fruticose lichen distribution has been shown recently by Gauslaa (). Furthermore, Nascimbene and Marini () demonstrated an increase of fruticose species with elevation but with a negative response to a high level of precipitation. The importance of fog has a well understood influence on lichen growth forms in desert habitats (Rundel ) – and fruticose taxa occurred only in the fog‐influenced sites.…”

Bryophyte and macrolichen diversity show contrasting elevation relationships and are negatively affected by disturbances in laurel forests of Madeira island

“…Bryophyte and macrolichen richness per plot is quite high (as we only sampled 4 m 2 of forest floor and 0.64 m 2 of bark surface) compared with other regions (for lichens: Boch, Prati et al., ; Cleavitt, Clyne, & Fahey, ; Nascimbene & Marini, ; for bryophytes: Horvat, Heras, García‐Mijangos, & Biurrun, and Müller et al., ). We did not sample crustose lichen species, but as their richness is often much higher than that of macrolichens and both diversities are positively correlated (Bergamini, Stofer, Bolliger, & Scheidegger, ), we assume that the total lichen richness per plot also would exceed average values of most parts of other European countries.…”

“…() in a German low‐mountain range, Chongbang, Keller, Nobis, Scheidegger, and Baniya () in Eastern Nepal, Cleavitt et al. () in the northeastern United States, Cobanoglu and Sevgi () in Turkey, and Nascimbene and Marini () in northern Italy. This is probably a methodological issue as we, and the other studies reporting a linear increase in lichen species richness with elevation, sampled a local elevational gradient within forest ecosystems without exceeding the timberline.…”

Dispersal patterns of meiospores shape population spatial structure of saxicolous lichens

“…Dispersal limitations and establishment constraints are addressed to explain the dynamics of lichen populations (Scheidegger & Werth 2009;Ellis 2012;Schei et al 2012). Interactions between morphological and reproductive traits of different lichen species and micro-environmental conditions, including physical and chemical properties of substrates, microclimate and biotic features (Seaward 1977;Lawrey 1991;McIlroy de la Rosa et al 2013;Nascimbene & Marini 2015), are suggested to shape spatial distribution patterns (Ellis & Coppins 2007;Spitale & Nascimbene 2012;Giordani et al 2014). However, the dispersal and establishment patterns, and their significance for structuring species distribution, have only recently begun to be deeply explored, mainly focusing on epiphytic lichens (Scheidegger & Werth 2009;Ellis 2012;Leavitt & Lumbsch 2016).…”