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Reviewof Palaeobotanyand Palynology91 (1996) 283-315

REVIEW OF PALAEOBOTANY AND PALYNOLOGY

Late-glacial palynology of the Myrtaceae of southern Chile
Mingming Zhou, C.J. Heusser
Department of Biology, New York University, New York, N Y IO003, USA Received 13 December 1994; revised and accepted 25 April 1995

Abstract

Systematic study of modem pollen of 24 speciesbelonging to nine genera of the Myrtaceae of Chile, using combined techniques of scanning electron microscopy, light microscopy, and computer imaging, indicates that genera and a number of species can be reliably distinguished by means of pollen type classification, differences in exine sculpture, and grain size. These criteria applied to the identification of fossil pollen in late-glacial deposits(14,000-10,000 radiocarbon yr BP), following the last glacial maximum (25,000-14,000 yr BP), provide grounds for the recognition of previously unidentifiable species of Myrtaceae and for the refinement of palaeoclimate interpretation. Fossil pollen of the Myrtaceae occurs in four late-glacial sequences from the southern Chilean Lake District and island of Chilo6 (41-43°S) with ages ranging between13,600 and 10,000 yr BP. The chronology is controlled by 21 conventional and AMS radiocarbon dates. Identifiable species indicate generally consistent temperature trends, which are compatible overall with trends inferred by pollen assemblages in the records. Major indicators are Amomyrtus, Ugni, Myrceugenia chrysocarpa, and Myrteola; Myrceugenia ovata and M. parvifolia are less important. Theimplication of the data is that temperatures moderated after 14,000 until about 13,000 yr BP and thereafter fluctuated until the end of the late-glacial.

I. Introduction

Among noteworthy taxonomic groups encountered in pollen records of Quaternary deposits in southern Chile (Figs. 1 and 2), the Myrtaceae have appeared to be intractable at the genus or species level of identification. The Myrtaceaeare both latitudinally and altitudinally wide-ranging and are found in a variety of plant formations. The identity of family members, as they occur in the Quaternary of southern Chile, is thus of palaeoecological importance. This is particularly relevant with regard to the late-glacial (14,000-10,000 radiocarbon yr BP), where the Myrtaceae first appear in abundance following the last glacialmaximum (25,000-14,000 yr BP), and for which 0034-6667/96/$15.00 © 1996ElsevierScienceB.V. All rights reserved SSDI 0034-6667 ( 95 ) 00076-3

time during deglaciation, diverse interpretations of the climatic sequence have been advanced from fossil pollen and beetle records. The Myrtaceae present in Chile (Fig. 3) are woody plants forming a major component of the vegetation. Landrum (1986, 1988)recognized nine genera and 29 naturally occurring species. Heusser (1971), using light microscopy, described pollen of 18 species of Chilean Myrtaceae and showed them to be variously colporate with sculpture ranging between scabrate and verrucate, but on the whole, species were not distinguishable. Identifications in most fossil studies are at the family level; however, in a study made on the island ofChilor, Villagr~n (1985) identified Myrceugenia and Amomyrtus types, as well as Tepualia.

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M. Zhou, CJ. Heusser/Review oj Palaeobotany and Palynology 91 (1996) 283-315

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