Building mountain biodiversity: Geological and evolutionary processes

Abstract

Mountain regions are unusually biodiverse, with rich aggregations of small-ranged species that form centers of endemism. Mountains play an array of roles for Earth’s biodiversity and affect neighboring lowlands through biotic interchange, changes in regional climate, and nutrient runoff. The high biodiversity of certain mountains reflects the interplay of multiple evolutionary mechanisms: enhanced speciation rates with distinct opportunities for coexistence and persistence of lineages, shaped by long-term climatic changes interacting with topographically dynamic landscapes. High diversity in most tropical mountains is tightly linked to bedrock geology—notably, areas comprising mafic and ultramafic lithologies, rock types rich in magnesium and poor in phosphate that present special requirements for plant physiology. Mountain biodiversity bears the signature of deep-time evolutionary and ecological processes, a history well worth preserving.

Patterns of speciation are similar across mountainous and lowland regions for a Neotropical plant radiation (Costaceae:Costus)

“…5). Taken together, our results suggest that climatic divergence occurs in both mountain-influenced and Amazonian pairs, and that mountain-influenced taxa occupy the greater temperature variation the mountains offer (Rahbek et al 2019a). Despite hummingbird pollination being common in mountain-influenced species, it is not proportionally more common than in Amazonian species.…”

“…Tropical mountains exhibit extreme species richness and endemism, contribute substantially to latitudinal diversity gradients, and are thought to be cradles of recent speciation (Rahbek et al 2019a, Rahbek et al 2019b). The Neotropics, for example, contain three of the five most species-rich hotspots for plant diversity worldwide, including Costa Rica-Chocó, Atlantic Brazil, and Tropical Eastern Andes (Barthlott 2005), all of which are associated with mountain ranges.…”

Cradles and museums of generic plant diversity across tropical Africa

“…Indeed, East Africa has a greater elevation range than West or Central Africa (Guillocheau et al , ) and the tectonic activity that occurred in East Africa generated places that differ edaphically from surrounding areas. Edaphic complexity plays a great role in generating endemism (Bruchmann & Hobohm, ; Rahbek et al , ), and the habitat heterogeneity and fragmentation of montane regions are often associated with range‐restricted taxa (Moritz et al , ; Hughes & Eastwood, ; Kier et al , ; Fjeldså et al , ). Moreover, East Africa is acknowledged to be a ‘complex biogeographical mixture' containing distinct taxa adapted to various localized environmental gradients generated by the complex topography and climate (Linder et al , ; Droissart et al , ).…”

Why mountains matter for biodiversity

“…Kinabalu on Borneo (Merckx et al, 2015) and across the African continent (Gehrke & Linder, 2009). Mountains are therefore engines of diversity for entire biotic realms (Antonelli & Sanmartín, 2011;Antonelli, Zizka, et al, 2018;Gentry, 1982;Rahbek et al, 2019).…”

“…Without plate tectonics our planet would be a largely static, flat, dull surface. This mechanism is thus a cornerstone in promoting the diversification of life on Earth (Dietrich & Perron, 2006;Lammer et al, 2010;Rahbek et al, 2019;Spohn & Breuer, 2016;Stern, 2016).…”