Are the radiations of temperate lineages in tropical alpine ecosystems pre‐adapted?

Abstract

Aim Tropical mountains around the world harbour an extraordinarily rich pool of plant species and are hotspots of biodiversity. Climatically, they can be zoned into montane climates at mid‐altitudes and tropical alpine climates above the tree line. Around half of the tropical alpine species belong to plant lineages with a temperate ancestry, although these regions are often geographically distant. We test the hypothesis that these temperate lineages are pre‐adapted to the tropical alpine climate. Location New World, with a focus on tropical alpine Andes. Time period Miocene to present. Major taxa studied Flowering plants. Methods We build multidimensional environmental models representing the full space of New World climates. We quantify the environmental similarity between the tropical alpine ecosystem and those of potential source areas, while correcting for regional differences by kernel density smoothers. Based on spatial observations of the genus Hypericum (St John's Wort), we quantify niche overlap and test for niche conservatism following intercontinental dispersal using density‐weighted nonparametric tests. A dated species tree, biogeographical estimation, multi‐optima Ornstein–Uhlenbeck models and model selection approaches are used to test for niche shifts during establishment in the tropical alpine Andes. Results The tropical alpine ecosystem is isolated by its climate from adjacent regions and is climatically similar to temperate lowland biomes of both hemispheres. Niche conservatism is evident in the study group, except in the tropical alpine lineage that is characterized by niche expansion and shifts in temperature optima. Main conclusions Our results reject the pre‐adaptation hypothesis and instead suggest pronounced niche evolution during colonization of tropical alpine ecosystems. Establishment involved substantial niche shifts, mainly in temperature‐related variables, and resulted in a tremendous proliferation of species in the newly invaded tropical alpine ecosystem.

Island woodiness underpins accelerated disparification in plant radiations

“…). This is a result of reliance on mean heights as a proxy for growth form (Notes S1) and the similar disparity of growth forms in a woody North America clade (Nürk et al ., ). Second, as indicated earlier (see the Materials and Methods section), Lupinus species were coded as annual or perennial (rather than herbaceous or woody), because many North American species are herbaceous perennials.…”

“…(Asteraceae), which includes the Hawaiian silversword alliance and tarweeds from California and the California islands (Channel Islands, Guadalupe, and San Benito Islands), hereafter silverswords–tarweeds, plus two well‐studied Andean sky island radiations, Hypericum L. (Hypericaceae) and Lupinus L. (Fabaceae). For each group we used the best sampled time tree (C. S. Drummond et al ., ; Nürk et al ., ) or reconstructed a phylogeny using published sequence data and estimated divergence times under relevant age constraints using an uncorrelated lognormal relaxed‐clock model in Beast v.1.8 (A. J. Drummond et al . (); for details about sampled taxa, DNA sequence loci, and fossil constraints see Supporting Information Table S1; Methods S1).…”

Mapping mountain areas: learning from Global, European and Norwegian perspectives

“…The resulting map delineates 12 percent of global land area as mountainous; this includes the rugged parts of the Tibetan plateau and the Andean altiplano, both above 2500 masl, but not significant areas of low-elevation mountains with elevations from 300 to 1000 masl identified by Kapos et al (2000) -though it does include some areas below 300 masl. The underlying database forms the foundation for a global inventory of mountain areas and their biodiversity (http://www.mountainbiodiversity.org) which is being used as the basis for research (e.g., Nürk et al 2018).…”

Niches and radiations: a case study on the Andean sapphire‐vented puffleg Eriocnemis luciani and coppery‐naped puffleg E. sapphiropygia (Aves, Trochilidae)

“…Hence, forces in addition to variations in environmental parameters, such as natural selection or genetic drift, are prompting the radiation of these hummingbirds. Previous studies demonstrated the utility of niche modelling techniques to assess conservation, ecological, taxonomic biogeographic and evolutionary questions in the tropical Andes, including plants (Sanín et al 2016, Zutta and Rundel 2017, Nürk et al 2018, Oleas et al 2019, Testo et al 2019), insects (Moo-Llanes et al 2017, Scattolini et al 2018), amphibians (Ramos Pallares et al 2018, reptiles (Aguilar et al 2016), mammals (Ramoni-Perazzi et al 2012, Gutiérrez et al 2015, Gerstner et al 2018, Bennett et al 2019) and birds (Cadena and Cuervo 2010, Freile et al 2010, Jiguet et al 2010, Thomassen et al 2010, Velásquez-Tibatá et al 2013, Ramirez-Villegas et al 2014, Avendaño and Donegan 2015, Ramoni-Perazzi et al 2017. Thus, the results presented here are based on a solid background with regards to the applicability of niche modelling procedures in Neotropical environmental complex regions.…”