a b s t r a c tDrill cores obtained from Lake Peté n Itzá , Peté n, Guatemala, contain a $85-kyr record of terrestrial climate from lowland Central America that was used to reconstruct hydrologic changes in the northern Neotropics during the last glaciation. Sediments are composed of alternating clay and gypsum reflecting relatively wet and dry climate conditions, respectively. From $85 to 48 ka, sediments were dominated by carbonate clay indicating moist conditions during Marine Isotope Stages (MIS) 5a, 4, and early 3. The first gypsum layer was deposited at $48 ka, signifying a shift toward drier hydrologic conditions and the onset of wet-dry oscillations. During the latter part of MIS 3, Peté n climate varied between wetter conditions during interstadials and drier states during stadials. The pattern of clay-gypsum (wet-dry) oscillations during the latter part of MIS 3 ($48-23 ka) closely resembles the temperature records from Greenland ice cores and North Atlantic marine sediment cores and precipitation proxies from the Cariaco Basin. The most arid periods coincided with Heinrich Events when cold sea surface temperatures prevailed in the North Atlantic, meridional overturning circulation was reduced, and the Intertropical Convergence Zone (ITCZ) was displaced southward. A thick clay unit was deposited from 23 to 18 ka suggesting deposition in a deep lake, and pollen accumulated during the same period indicates vegetation consisted of a temperate pine-oak forest. This finding contradicts previous inferences that climate was arid during the Last Glacial Maximum (LGM) chronozone (2172 ka). At $18 ka, Peté n climate switched from moist to arid conditions and remained dry from 18 to 14.7 ka during the early deglaciation. Moister conditions prevailed during the warmer Bolling-Allerod (14.7-12.8 ka) with the exception of a brief return to dry conditions at $13.8 ka that coincides with the Older Dryas and meltwater pulse 1A. The onset of the Younger Dryas at 12.8 ka marked the return of gypsum and hence dry conditions. The lake continued to precipitate gypsum until $10.3 ka when rainfall increased markedly in the early Holocene.

The use of lake sedimentary DNA to track the long-term changes in both terrestrial and aquatic biota is a rapidly advancing field in paleoecological research. Although largely applied nowadays, knowledge gaps remain in this field and there is therefore still research to be conducted to ensure the reliability of the sedimentary DNA signal. Building on the most recent literature and seven original case studies, we synthesize the state-of-the-art analytical procedures for effective sampling, extraction, amplification, quantification and/or generation of DNA inventories from sedimentary ancient DNA (sedaDNA) via high-throughput sequencing technologies. We provide recommendations based on current knowledge and best practises.

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Multiproxy palaeoenvironmental and palaeolimnological analyses of two Holocene-age sediment cores from the margin of Lago Cardiel, a 76 m deep, closed-basin lake in southern Patagonia (latitude 49°S), provide information on lake-level changes that can be related to regional palaeoclimate scenarios. Sedimentol ogic (magnetic susceptibility, organic and inorganic carbon content) and environmental indicators (pollen, dia toms, ostracodes and stable isotopes on ostracodes) show lake levels markedly higher than today during the early Holocene, following a rapid lake-level rise after a desiccation phase prior to 11000 BP. After about 6000 BP, lake levels were generally lower, but underwent repeated fluctuations. These inferred changes support the previously proposed view that the southern westerly stormtracks were focused (zonal) north of latitude 50°S during the early Holocene, allowing for Antarctic cold fronts to bring easterly moisture to southern Patagonia, whereas during the late Holocene the stormtracks shifted seasonally, with an overall more meridional behaviour, resulting in less and more variable moisture at these latitudes.

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