The biogeography of the megadiverse genusAnthurium(Araceae)

Abstract

The tropics of the New World are a biodiversity hotspot, the genus Anthurium being an example of a megadiverse taxon with currently > 1000 described species. In this study, we provide detailed information on species distributions and analyse patterns of diversity and endemism, with a particular focus on the comparison of epiphytic and terrestrial congenerics. Using a dataset of occurrence records for 1041 Anthurium spp. (c. 98% of the genus), we modelled geographical species distributions using climate-based species distribution models or buffered convex hulls depending on the number of occurrences available. We identified nine bioregions using cluster analysis. The Andean slopes, Central America, the Chocó and the Atlantic Forest in eastern Brazil are the most important centres of diversity for Anthurium, whereas endemism is highest in the central Andes. These macroecological patterns agree largely with diversity centres for other Neotropical plant groups. Epiphytes, accounting for about two-thirds of all species, have much larger range sizes than terrestrials, but do not differ in elevational ranges. Almost 40% of all Anthurium spp. are restricted to the lowlands, but a few species grow at elevations of almost 4000 m. Although individual species have an average elevation range of just c. 1000 m, there are taxa that cover > 3500 m of elevation.

The geographic range size and vulnerability to extinction of angiosperm epiphytes in the Atlantic Forest of Brazil

“…However, epiphytes have long been reported to have larger geographic ranges than terrestrial species (Schimper, 1888) based largely on studies conducted before the availability of modern large‐scale databases of plant occurrence records (e.g. Ibisch et al, 1996; Kessler, 2002; Schimper, 1888), although a recent study focused on the Araceae genus Anthurium also supports the claim (Reimuth & Zotz, 2020). This apparent contradiction is intriguing, although rarely highlighted in the literature (but see Kreft et al, 2004), and merits further investigation based on updated sources of evidence.…”

“…orchids, Tillandsioideae bromeliads) and fleshy fruits dispersed by birds and bats (e.g. aroids, Bromelioideae bromeliads, Peperomia ) to greater distances compared to ground level (Einzmann & Zotz, 2017; Fischer & Araujo, 1995; Kessous et al, 2022; Reimuth & Zotz, 2020; Thomson et al, 2011). Second, the stressful and extreme environmental conditions of the epiphytic habitat would require greater eco‐physiological plasticity (Ibisch et al, 1996).…”

A global study of the geographic range size of epiphytes

“…In the orchid genus Galeandra, epiphytic species tended towards smaller range size than terrestrial counterparts 16 . In contrast, epiphytic Anthurium species had mean range size eight times larger than terrestrial species in the genus 17 . Analyses of angiosperms in Brazil’s Atlantic Forest showed epiphytes having among the highest percentages of small-ranged species among lifeforms 1,18 .…”

“…Although seed weight in epiphytes follows a bimodal distribution (consistent with the hypothesis that light wind-dispersed and heavier, fleshy bird-dispersed seeds are both effective for tree-to-tree dispersal), epiphytes do not generally have smaller seeds than confamilial terrestrial plants, evidence that closely related epiphytic and terrestrial taxa exhibit similar traits 47 . However, dispersal of anemochorous seeds is likely more successful from greater heights in the canopy than from the ground, thereby predisposing epiphytic taxa to larger ranges than morphologically-similar, closely related terrestrial taxa 17 . Bird-dispersed epiphyte seeds may also reach greater distances if canopy-inhabiting birds and bats forage over greater distances than forest-floor birds 14,44 .…”

“…Adaptations for tree-to-tree dispersal predispose epiphytes to high dispersal capabilities 15 , contributing to large range sizes 19 . Tree height favours dispersal of wind-, bird- or bat-dispersed seeds of canopy-dwelling epiphytes 17,20 . Conversely, plant clades which have undergone rapid diversification tend to have small-ranged species, especially when speciation mechanisms isolate small populations 21,22 .…”