Dating on earth asianmediawiki
First, we sequenced whole chloroplast genomes from 12 cacti and relatives (Table S1) and combined these data with a larger whole-chloroplast data matrix of 90 seed plants (8) to build a broadly sampled phylogeny of angiosperms. We then identified the timing of major radiations in cacti and their relatives by implementing a likelihood approach that optimizes the number and placement of shifts in diversification rate across a phylogeny (9).We then used multiple fossil calibration points within a Bayesian framework to estimate divergence times and confidence intervals for several key nodes in cacti and relatives (Fig. To look more specifically at patterns and timing of diversification within the major cactus lineages, we performed a series of additional dating analyses on a second phylogeny generated from fewer loci but that included a greatly expanded taxon sampling within the cacti (Fig. Time-calibrated phylogeny of the cacti and their relatives.However, major diversification events in cacti were more recent, with most species-rich clades originating in the late Miocene, ≈10–5 Ma.
Previous work has emphasized the fact that the cacti are extremely diverse yet almost exclusively New World in distribution, suggesting a possible origin between 90 and 65 Ma, which would allow maximal time for diversification and a spatial separation of Africa and South America (3, 4).There has been much speculation about their age, but progress in dating cactus origins has been hindered by the lack of fossil data for cacti or their close relatives.Using a hybrid phylogenomic approach, we estimated that the cactus lineage diverged from its closest relatives ≈35 million years ago (Ma).We identified five additional shifts in diversification rate in the cacti, the majority occurring within the last 8 Ma (Table 1).With the exception of the genus (the prickly pears), these shifts occurred at nodes nested within or just outside named taxonomic groups (2).While not being especially species rich (≈12 spp), their diversification began ≈17 Ma; crown , the largest and arguably most succulent lineage, is ≈11 Ma. This node age is substantially older than a previous report that suggested a rapid radiation in this group 8.7–3.8 Ma (14); however, our taxon sampling of core Ruschioideae was too sparse to allow for investigation of diversification shifts within this group that, of course, may have occurred more recently.Our crown age estimate of core Ruschioideae (the ice plants, Aizoaceae), an extremely species-rich and fundamental component of the Succulent Karoo flora of South Africa, is ≈17 Ma (Figs. CO2, global temperature, C4 origins, C4 grasslands, and the diversification of succulent plants during the late Miocene/Pliocene.Major cactus radiations were contemporaneous with those of South African ice plants and North American agaves, revealing a simultaneous diversification of several of the world's major succulent plant lineages across multiple continents.This short geological time period also harbored the majority of origins of C would also substantially exacerbate plant water stress in marginally arid environments, providing preadapted succulent plants with a sharp advantage in a broader set of ecological conditions and promoting their rapid diversification across the landscape. 9pm (all ages)w/ the talented GABE BONDOC :) records on ITUNES! The cacti are one of the most celebrated radiations of succulent plants.