Tree Species Composition Predicts Epiphytic Lichen Communities in an African Montane Rain Forest

Abstract

The ecology of many tropical rain forest organisms, not the least in Africa, remains poorly understood. Here, we present a detailed ecological study of epiphytic lichens in the equatorial montane rain forest of Bwindi National Park (331 km2), Uganda. We evaluated all major lichen growth forms, including selected groups of crustose lichens. In 14 transects at elevations of 1290 m to 2500 m, we sampled 276 trees belonging to 60 species. We recorded all lichen species on each tree trunk between ground level and 2 m above the ground, yielding 191 lichen species in 67 genera, with a mean of 4.7 species per tree. We used non‐metric multi‐dimensional scaling to separate epiphytic lichen assemblages according to tree species composition and elevation. Structural equation modeling indicated that elevation influenced tree species composition and that tree species composition largely determined lichen species composition. Thus, elevation acted indirectly on the lichen assemblages. Further studies examining factors such as bark properties and lichen colonization ecology may clarify what determines the association between tree species and lichen assemblages. The link between lichen assemblages and large‐scale elevation patterns, as well as disturbance and regrowth histories, warrants further study. An analysis of lichen species composition on individual tree species that occur over large elevation ranges would distinguish the effect of tree species on lichen assemblages from the effect of elevation and thus climate. Our study highlights the limited extent of our knowledge of tropical epiphytic lichens.

Corticolous lichen species as indicators of disturbed/undisturbed vegetation types in the central mountains of Sri Lanka

“…In this study correlations between all other within-plot habitat variables suggest that number of tree species represents the accumulated impact of all those factors on lichen species diversity. Undisturbed tropical forests support a high diversity of tree species that between them present diverse combinations of forest structure and tree microhabitats supporting high lichen richness and cover (Benítez et al 2012; Frisch et al 2015). Benítez et al .…”

“…Such causal relationships with lichens vary in different tropical forests with both high tree species diversity and high variation in composition (Wolseley 1997). Tree age and species composition have affected lichen community composition at smaller geographical scales, with narrower ranges of environmental variation observed for a tropical forest (Frisch et al 2015) or temperate forests (Will-Wolf et al 2006). Direct relationships between bark pH and lichen diversity are well documented in other studies (Kuusinen 1996; Herk 2001; Holz 2003; Cáceres et al .…”

“…Altitude, representing local gradients in temperature, rainfall and humidity, has in many studies worldwide been considered a reliable proxy for climate influencing lichen distribution (e.g. Frisch et al 2015; Nascimbene & Marini 2015). However, in tropical conditions in Sri Lanka there is considerable variation in temperature and rainfall with topography interacting with altitude (De Rosyro 1958; Balasubramamium 1991; Fernando 2010).…”

Experimental transplants reveal strong environmental effects on the growth of non‐vascular epiphytes in Afromontane forests

“…, Frisch et al . ). The abundance of epiphytic bryophytes and lichens in tropical upper montane forests is explained by the beneficial combination of ample moisture and light with relatively cool temperatures (Zotz , Zotz & Schleicher et al .…”

“…Upper montane forests tend to receive ample rain and often experience a high frequency of mist, and thus provide optimal conditions for epiphyte growth. Hence, abundant epiphyte cover is one physiognomic feature that helps to distinguish upper montane 'moss forests' from drier lower montane forests (Frahm & Gradstein 1991, Martin et al 2010, Frisch et al 2015. The abundance of epiphytic bryophytes and lichens in tropical upper montane forests is explained by the beneficial combination of ample moisture and light with relatively cool temperatures (Zotz 1999, Zotz & Schleicher et al 2003, Le on-Vargas et al 2006.…”