A 1.8 million year history of Amazon vegetation

Whole genomes show contrasting trends of population size changes and genomic diversity for an Amazonian endemic passerine over the late quaternary

“…This time frame includes the transition from LIG to LGM and, therefore, is representative of the past full glacial cycle in the Amazon. As mentioned previously, paleoclimatic and paleoecological evidence support major shifts in vegetation types across the Amazon during this time frame, mediated primarily by changes in fire frequency, CO 2 levels, rainfall, and temperature (Kern et al, 2023;Sato et al, 2021;Wang et al, 2017).…”

“…their N e dynamics between LIG and LGM -suggesting the existence of bottlenecks and drift effects prior to LIG in this sector of the Amazon, as supported by (Kern et al, 2023) and our MSMC2 estimates (Figure A5). Finally, the wide range of demographic patterns recovered by PSMC and MSMC2 for Willisornis lineages toward the LGM throughout the Amazon (which includes declines, continuous expansion, and overall stability) are consistent with highly variable and complex local savanna/dry forest/rainforest replacements documented for the Late Quaternary across the biome (Häggi et al, 2017;Hermanowski et al, 2012;Kern et al, 2023;Martins et al, 2022). (Gomes et al, 2020;Kern et al, 2023;Nobre et al, 2016;Sato et al, 2021).…”

“…or dry forest types during the LGM (Kern et al, 2023;Rossetti et al, 2017), which may have led to the formation of two major humid forest blocks separated for the most part by an open vegetation corridor running across Central Amazon (Sato et al, 2021;van der Hammen & Absy, 1994). According to the model presented by Sato et al (2021), the area to the south and east of the Amazon and Tapajos rivers, respectively, where all ecotonal Willisornis individuals were sampled (Figure 1e,g,i), was the one with the most reduction in humid forest cover during the LGM.…”

Quantitative species delimitation, tests for gene flow, and migration models uncover complex, recent speciation in tree squirrels

“…Reconstructions of the Amazonian vegetation dynamics over the past 1.8 Mya largely agree with the Neotropical tree squirrel diversification history. Between 1.8-1.0 Mya, rainforest vegetation, along with extensive riparian wetland vegetation, dominated the Amazonian landscape, especially in western Amazonia where there was a larger concentration of wetland ecosystems (Hoorn et al, 2010); after 1.0 Mya, contractions of both forests and wetlands started taking place; and from around 400 Kya, about the timing of most speciation events within Guerlinguetus , stronger synchrony between changes in vegetation and glacial-interglacial climate cycles is reported (Kern et al, 2023). During this last period, in warmer interglacial times the vegetation was dominated by lowland tropical rainforests, and in cooler glacial periods tropical seasonal forests expanded towards the eastern Amazonia (Kern et al, 2023), coinciding with the Guerlinguetus colonization of eastern South America (Figure 6).…”

The southern Brazilian tropical forest during the penultimate Pleistocene glaciation and its termination

“…The American continent is continuous nearly from pole to pole and thus provides an excellent laboratory for examination of the connections between high and low latitudes in both hemispheres, more specifically the climatic teleconnections in the Southern Hemisphere (Markgraf, 2001; Shulmeister et al, 2006). Since the mid‐Pleistocene, the expansion and regression phases of ice volume have been orbitally paced by a 100 000‐year cycle that, in turn, has affected the tropical hydrological cycle in the high Andes (Hanselman et al, 2011; Torres et al, 2013; Rodbell et al, 2022) as well as in the lowlands (Kern et al, 2023). However, differences in the expression of the glacial epochs and more particularly between the last glacial, Marine Isotopic Stage (MIS) 2–4, and the penultimate glacial, MIS 6, suggest the influence of other forcings on climate and vegetation at millennial scale (Zheng et al, 2013).…”