Full-glacial-late-glacial palaeoclimate of the southern Andes: Evidence from pollen, beetle and glacial records

Palaeoecological studies carried out in the Chilean Lake District and Chilotan Archipelago (41 degrees-43 degrees S) record full-glacial and late-glacial pollen assemblages beginning just after 21000 and beetle assemblages after 18000, both sets extending until 10000 C-14 yr BP. Pollen records indicate that Subantarctic Parkland, the vegetation of the early millennia of record, changed after about 14000 yr BP to become open woodland and later North Patagonian Evergreen Forest. Assemblages of plants and beetles, responding more or less in unison to a strong rise in temperature (greater than or equal to 6 degrees C), behaved in accord at around 14000 until 13000-12500 yr BP, the beetle fauna displaying a marked increase in obligate forest types. During full-glacial conditions (17400-16100 and 15300 and 14400 yr BP) and in the late-glacial interval (after about 13000 yr BP), however, climate evidently coerced populations dissimilarly, the pollen sequence showing an increase in plant taxa indicative of colder climate, whereas the beetle fauna underwent little or no variation. Contrasting climate modes implied by plants and beetles may be attributed to differential responses to apparent low-order temperature changes (less than or equal to 2-3 degrees C).