Mountains, climate and niche heterogeneity explain global patterns of fern diversity

Abstract

Aim: It is well known that the distribution of species diversity is spatially heterogeneous, but understanding the factors contributing to this heterogeneity and to the formation of biodiversity hotspots remains a challenge. Here, we seek to improve our understanding of how historical, ecological and evolutionary processes contribute to current patterns of global fern diversity.Location: Worldwide. Taxon: Ferns.Methods: To evaluate the drivers of global fern diversity, we integrate over 800,000 georeferenced species occurrence records of nearly 8000 species, a time-calibrated phylogeny and seven climate and environmental layers. We use these data to summarize diversity and evolutionary patterns at a resolution of 100 × 100 km, and identify hotspots of fern species richness and endemism. We compare these hotspots to neighbouring non-hotspot regions to provide insight into the factors controlling global patterns of fern diversity.Results: Tropical and subtropical mountains harbour a disproportionate amount of species relative to the land area they occupy; 58% of global species richness occur in eight principally montane hotspots together comprising just 7% of Earth's land area.We identify hotspots of fern species richness and endemism that are universally characterized by disproportionately high ecological variation. We demonstrate that total fern species richness scales linearly with available climate space at regional and global scales.Main Conclusions: Areas of high environmental heterogeneity harbour a disproportionate amount of fern species, and global patterns of extant fern diversity reflect the distribution of these areas, especially in mountains at lower latitudes. Persistence of ancient lineages in areas with long-term climatic stability helps explain exceptional endemism in regions such as Malesia.

Global patterns of fern species diversity: An evaluation of fern data in GBIF

“…In an article by Suissa et al. (2021) , the authors analyzed species occurrence data downloaded from the Global Biodiversity Information Facility (GBIF) to address several questions.…”

“…(2018 , 2021b) , the completeness of the fern species lists for the 100 km × 100 km grid cells used in their study are likely very low, at least in some regions. Suissa et al. (2021) pointed out that “misidentified records or those with problematic localities can bias biodiversity analyses”, but they overlooked the problem of using substantially incomplete species lists in their study.…”

Spatial phylogenetics of Japanese ferns: Patterns, processes, and implications for conservation

“…Previous studies have identified temperature, water availability (Bickford and Laffan, 2006; Qian et al, 2012), or a combination of these (Nagalingum et al, 2015; Link-Pérez and Laffan, 2018; Qian et al, 2021) to be important drivers of spatial fern diversity. A hump-shaped pattern of richness along elevation (maximum richness at intermediate elevations) has been frequently observed in ferns on mountains in tropical or sub-tropical areas (Kessler et al, 2011; Suissa et al, 2021). Hypotheses to explain such a pattern include purely geometrical constraints as well as biological hypothesis positing maximally favorable environmental conditions at mid-elevations (Colwell et al, 2004).…”

“…We further cleaned the list prior to analysis by filtering out any occurrences not within the second-degree mesh and removing duplicate collections (300,685 specimens, 673 taxa after filtering). Given the high quality of our occurrence data and the fact that automated occurrence cleaning algorithms ( eg , CoordinateCleaner; Zizka et al, 2019) have the potential to erroneously exclude true occurrence points ( ie , false positives; Zizka et al, 2020), we chose not to apply additional automated cleaning steps to our data as is often done with occurrence records obtained from GBIF ( eg , Rice et al, 2019; Suissa et al, 2021).…”

Ferns and lycophytes from Ferradura Park, Canela (RS), Brazil

“…Overall, ferns and lycophytes are most diverse in mountains especially at lower latitudes, where the high environmental heterogeneity harbor a disproportionate number of species (Suissa, Sundue & Testo, 2021), reinforcing the importance of mountains in maintaining tropical fern diversity (Suissa & Sundue, 2020). Particularly, humid forests provide a suitable environment for high abundances and richness of fern and lycophyte species, where these organisms are able to develop in a wide range of biological forms (Senna & Waechter, 1997).…”