Evolutionary diversification in the hyper-diverse montane forests of the tropical Andes: radiation ofMacrocarpaea(Gentianaceae) and the possible role of range expansion

Abstract

The humid mid-elevation montane forests (MMF) of the tropical Andes harbour high levels of plant species diversity, contributing to the exceptional overall diversity of the tropical Andean biodiversity hotspot. However, little is known about the diversification dynamics of MMF plant lineages compared to lineages in other Andean biomes. Here, we use Macrocarpaea (Gentianaceae) to investigate patterns of plant diversification in the MMF, using molecular dating with fossils and secondary calibration (from a family-wide phylogenetic analysis of Gentianaceae). We sequenced 76 of 118 recognized Macrocarpaea spp. for six markers to reconstruct a time-calibrated phylogenetic tree and infer the historical biogeography of Macrocarpaea using maximum-likelihood methods implemented in BioGeoBEARS, estimating diversification rates through time and among lineages with BAMM. We document a rapid radiation of Macrocarpaea in Andean MMF coinciding with rapid colonization and range expansion across the entire distribution of the genus in the Andes starting 7.2 Mya. Our results support allopatric founder-event speciation as the dominant process contributing to geographical phylogenetic structure across the genus. We propose that establishment of the MMF in the late Miocene, when the Andes attained critical elevation to modify regional climates, provided large new areas of suitable habitat for Macrocarpaea to quickly colonize and expand through repeated founder-events. We suggest that this wave of colonization and range expansion triggered rapid diversification, and, as the MMF became progressively occupied, the diversification rate slowed. Our study also supports the idea that MMF plant radiations are older and more slowly evolving than the quickly evolving lineages in the recent Andean high-elevation grasslands.

Contributions to Ecuadorian butterworts (Lentibulariaceae, Pinguicula): two new species and a re-evaluation of Pinguicula calyptrata

“…This has been demonstrated for many groups of organisms including numerous angiosperm taxa (e.g. Deanna et al 2018;Escobar et al 2018;Acuña-Castillo et al 2021;Landis et al 2021;Tejedor and Calatayud 2022;Vieu et al 2022) and only very recently also for the Lentibulariaceae. With the description of P. rosmarieae, the first narrowly endemic Pinguicula has been documented for the AHZ (Casper et al 2020).…”

Population Genetic Structure and Diversity of Cryptic Species of the Plant Genus Macrocarpaea (Gentianaceae) from the Tropical Andes

“…STRUCTURE was used with the default settings except for the application of the recessive allele option and the admixture model with correlated allele frequencies. The average membership coefficients for the three simulation runs of a given K value were generated with CLUMPAK v. 1.1 [68].…”