Elevational shifts in phylogenetic diversity of angiosperm trees across the subtropical Brazilian Atlantic Forest

Abstract

Elevation gradients are drivers of species diversity, and, recently, studies have considered the evolutionary process in shaping community assembly patterns. Patterns of plant species richness across elevational gradients have been studied in different parts of the Atlantic Forest; however, little is known about plant phylogenetic diversity patterns. Thus, we aimed to analyse the phylogenetic diversity of angiosperm trees along an elevation gradient in southern Brazilian Plateau, in the subtropical portion of the Atlantic Forest. We expected a decrease in phylogenetic diversity along the elevation gradient, from lowlands towards to highlands, where species may be evolutionary closely related as many tropical lineages are not capable to inhabit colder conditions. We also investigated the distribution of phylogenetic clades along the elevation gradient through principal coordinates of phylogenetic structure. Data were obtained from 28 phytosociological surveys distributed across different elevation levels, ranging from 40 to 975 m. We found a negative association between phylogenetic diversity and the elevation gradient. The representativeness of families Myrtaceae and Lauraceae increased with elevation, while most of the families decreased in species richness and are replaced by temperate families such as Winteraceae (Drimys) in higher elevations. The decrease in phylogenetic diversity with increasing elevation may be linked to niche conservatism of tropical lineages that retain their historical climatic niches and thus many species are not capable to inhabit colder environments. Most tropical clades are restricted to lower elevations; however, Myrtaceae and Lauraceae probably evolved tolerance to colder temperatures during glacial cycles. Furthermore, the probably long-term climate stability in lowlands than highland areas may have promoted the co-occurrence of distantly related species, resulting in higher phylogenetic diversity. Finally, we observed how historical imprints and current environmental conditions shape the phylogenetic diversity of angiosperm tree species in subtropical Atlantic Forest.

Dissecting the difference in tree species richness between Africa and South America

“…Meanwhile, most Rubiaceae clades have a complex biogeographic history, and their high diversity in South America seems to be linked to the rise of the Andes ( 74 ). Families like Myrtaceae and Lauraceae are more commonly found in moist environments and, in South America, have acquired adaptations to colder temperatures, enabling them to diversify in higher elevations ( 75 ), which could explain their high diversity in South America and low diversity in Africa. In contrast, Ebenaceae, particularly the genus Diospyros, is known for its morphological and species diversity in Africa, coupled with a geographically wide distribution ( 76 , 77 ).…”

Evolutionary Diversity Peaks at Mid-Elevations Along an Amazon-to-Andes Elevation Gradient

“…Observations to date provide mixed support for the TNC, OTT, and OTL hypotheses: latitudinal decreases in evolutionary diversity (Kerkhoff et al, 2014) and angiosperm family ages (Hawkins et al, 2011;Romdal et al, 2013) have been reported, but also an increase in basal−weighted phylogenetic beta diversity to high latitudes (McFadden et al, 2019). Evolutionary diversity has been found to decrease with elevation in tropical montane forest (Bergamin et al, 2020), but also to increase along with increasing family age (Qian et al, 2014;Tiede et al, 2015).…”

Both Constitutive and Infection-Responsive Secondary Metabolites Linked to Resistance against Austropuccinia psidii (Myrtle Rust) in Melaleuca quinquenervia

“…In Australasia, Myrtaceae predominate in most ecosystems, with more than 2250 species recorded [1]. They are also found in biological hotspots around the globe [2,3]. As such, A. psidii infection is a threat to many fragile ecosystems characterised by a high rate of endemism [4][5][6].…”