Different Predictors Shape the Diversity Patterns of Epiphytic and Non-epiphytic Liverworts in Montane Forests of Uganda

Abstract

We studied the influence of regional and local variables on the liverwort diversity within natural forest vegetation of Uganda to contribute to our understanding of the mechanisms and processes determining species richness. To this end, we compared the species richness distribution patterns of epiphytic and non-epiphytic liverworts (Marchantiophytina) in 24 plots in the forests of four Ugandan national parks. We recorded a total of 119 species and subspecies from 18 families, including 16 new species records for the country. We used generalized linear models (GLMs) and the relative variable importance of regional and local climatic and environmental variables to assess their respective impact on the species diversity. We found that the richness patterns of total and epiphytic richness were largely driven by regional climatic factors related to temperature and water-availability. In contrast, species diversity of non-epiphytic and rare species was additionally strongly determined by local-scale microhabitat factors such as height of forest canopy and slope inclination, reflecting the availability of suitable microhabitats. We conclude that macroclimatic variables perform well in predicting epiphytic liverwort richness, whereas the adequate prediction of nonepiphytic richness requires site-specific variables. Also, we propose that richness of epiphytic liverworts will be impacted more directly by climate change than richness of non-epiphytic and rare species.

The global pattern of epiphytic liverwort disparity: insights from Frullania

“…In this case, the evolution of selected traits is expected to be influenced by some climatic factors that are related to water-availability [53,54], concerning their ecological functions, e.g., uptake of water and mineral nutrition from the surrounding air [48,55]. Therefore, the higher disparity of epiphytic liverworts at low latitudes may be related with an increase of ecological opportunities provided by tropic and subtropic forests, e.g., rich diversity of vascular plants as epiphytic substrates and extensive resources [41,56], and / or the relaxed ecological constraints, e.g., high humidity [34,53], and / or phenotypic innovation that facilitate ecospace expansion [13,57,58]. This assumption can also be used to explain the observations in some temperate regions, e.g., East Asia, which also exhibit high diversity and disparity (Fig.…”

Liverworts show a globally consistent mid‐elevation richness peak

“…Finally, the models separating epiphytic and non‐epiphytic liverwort species richness contained much less data (163 records from 16 and 90 records from nine locations, respectively) than the data set for the overall species richness (where published data often did allow the separation of epiphytic and non‐epiphytic records), which probably hampered the detection of a clear global trend. Furthermore, particularly non‐epiphytic species richness of liverworts has been shown to be strongly associated with local‐scale variables such as relative humidity, vegetation structure, and exposure (Mandl et al, 2009 ; Maul et al, 2020 ), which may obscure global trends especially with limited data. We thus do not further explore the results of these analyses.…”

“…Furthermore, particularly non-epiphytic species richness of liverworts has been shown to be strongly associated with local-scale variables such as relative humidity, vegetation structure, and exposure (Mandl et al, 2009;Maul et al, 2020), which may obscure global trends especially with limited data. We thus do not further explore the results of these analyses.…”

Host Tree and Geography Induce Metabolic Shifts in the Epiphytic Liverwort Radula complanata

“…It is well documented that the phorophyte itself plays a role in shaping the epiphytic community that exists upon it, in addition to the microclimate surrounding it [ 16 ]. In general, the largest factor influencing the composition of epiphytic communities appears to be water availability, which can be impacted by both bark characteristics and microclimate [ 17 ]. In Western Scotland, the epiphytic communities of Quercus and Fraxinus were largely shaped by the height, angle, and texture of the tree bark [ 18 ].…”