Veget Hist Archaeobot DOI 10.1007/s00334-014-0432-8 1 SHORT COMMUNICATION 2 First records and potential palaeoecological significance 3 of Dianella (Xanthorrhoeaceae), an extinct representative 4 of the native flora of Rapa Nui (Easter Island) 5 Nu´ria Can˜ellas-Bolta` • Valentı´ Rull • 6 Alberto Sa´ez • Matthew Prebble • Olga Margalef 7 Received: 21 June 2013 / Accepted: 9 January 2014 8 Ó Springer-Verlag Berlin Heidelberg 2014 Author Proof 9 Abstract Easter Island, a remote island in the Pacific been linked to the existence of favorable paleoenviron- 22 10 Ocean, is currently primarily covered by grasslands, but mental conditions (peatland rather than the present-day 23 11 paleoecological studies have shown the former presence of lacustrine environment) during the early to mid Holocene. 24 12 different vegetation. Much of its original biota has been This finding contributesPROOF new knowledge about indigenous 25 13 removed during the last two millennia, most likely by plant diversity on Easter Island and reinforces the useful- 26 14 human activities, and little is known about the native flora. ness of further macrofossil and pollen analyses to identify 27 15 Macrofossil and pollen analyses of a sediment core from native species on Easter Island and elsewhere. 2829 16 the Raraku crater lake have revealed the occurrence of a 17 plant that is currently extinct from the island: Dianella cf. Keywords Dianella Á Easter Island Á Native plant Á 30 18 intermedia/adenanthera (Xanthorreaceae), which grew and Holocene Á Palaeoecology Á Local extinction 31 19 disappeared at the Raraku site long before human arrival. ED 20 The occurrence of Dianella within the Raraku sedimentary 21 sequence (between 9.4 and 5.4 cal. kyr B.P.) could have Introduction 32 Easter Island is a tiny isolated island in the South Pacific 33 A1 Communicated by A. E. Bjune. Ocean, famed as an example of environmental degradation 34 due to human overexploitation of natural resources (Flen- 35 A2 Electronic supplementary material The online version of this 36 A3 article (doi:10.1007/s00334-014-0432-8) contains supplementary ley and Bahn 2003; Diamond 2005; Rull et al. 2010a). A4 material, which is available to authorized users. Currently the island is covered nearly entirely by grass- 37 lands, but palaeoecological studies have suggested the 38 & Á A5 N. Can˜ellas-Bolta` ( ) A. Sa´ez occurrence of former forested vegetation dominated by 39 A6 Department of Stratigraphy, Paleontology & Marine 40 A7 Geosciences, Universitat de Barcelona, Martı´ Franque´ss/n, palms and the presence of several other tree and shrub A8 08028 Barcelona, Spain species (e.g. Flenley et al. 1991; Dumont et al. 1998; Azizi 41 A9 e-mail: [email protected] and Flenley 2008; Mann et al. 2008). Climatic changes and 42 human activities during the last two millennia have largely 43 ˜ ` Á A10 N. Canellas-Bolta V. Rull 44 A11 Palynology & Paleoecology Lab, Botanic Institute of Barcelona modified the island’s landscape and vegetation (Flenley A12 (IBB-CSIC-ICUB), Passeig del Migdia s/n, 08038 Barcelona, et al. 1991; Flenley 1993a; Azizi and Flenley 2008; Mann 45 A13 Spain et al. 2008; Butler and Flenley 2010;Can˜ellas-Bolta` et al. 46 2013). A consequence has been the local extinction of a 47 A14 M. Prebble 48 A15 Archaeology and Natural History, School of Culture History number of native species from the island. Among the most A16 and Languages, College of Asia and the Pacific, The Australian emblematic cases are the disappearance of the probably 49 A17 National University, Canberra, ACT 0200, Australia endemic palm Paschalococos disperta, a supposed close 50 relative of the extant Jubaea chilensis, distributed 51 A18 O. Margalef 52 A19 Institute of EarthUNCORRECT Sciences Jaume Almera (ICTJA-CSIC), throughout the coastland central areas of Chile, and the A20 Lluı´s Soler Sabarı´s s/n, 08028 Barcelona, Spain disappearance of Sophora toromiro, an endemic legume 53 123 Journal : Large 334 Dispatch : 19-1-2014 Pages : 8 Article No. : 432 h LE h TYPESET MS Code : VHAA-D-13-00041 h44CP h DISK Veget Hist Archaeobot 54 surviving only as a cultivated shrub on the island and in 55 some botanical gardens elsewhere (Flenley et al. 1991; 56 Zizka 1991; Maunder et al. 2000). 57 In addition to the disappearance of representatives of the 58 original flora, numerous exotic species, such as Eucalyptus 59 spp. and Melinis minutiflora, have been introduced in 60 recent times, and some of these, such as Psidium guajava 61 and Crotalaria grahamiana, have become invasive. Cur- 62 rently, the flora of Easter Island is composed of approxi- 63 mately 200 established vascular plant species (*180 64 flowering plants and *17 ferns), of which 30 flowering 65 species are considered native (Zizka 1991; Flenley 1993b). 66 In a recent revision, Dubois et al. (2013) only recognized 67 36 native and extant vascular plants (including ferns). 68 Among the many species that have been introduced, only 69 *15 are considered to have been brought by the original 70 Polynesian settlers in the last millennia, while the rest are 71 modern introductions occurring after European contact in Author Proof 72 the 18th century (Flenley et al. 1991; Flenley 1993b; 73 Dubois et al. 2013). Moreover, most of the native plants are 74 currently considered to be endangered due to human 75 activities and are very scarce and restricted to particular PROOF 76 habitats (Zizka 1991; Dubois et al. 2013). 77 Because of these striking vegetation changes, including 78 local extinctions and introductions, occurring after human Fig. 1 Above map of current distribution of Dianella intermedia/ 79 occupation, the native flora of the island remains poorly adenanthera in the Pacific Islands (shaded) (see ‘‘Discussion’’ section 80 characterized. It has been speculated that the native flora for further information). Note that with the presence on Easter Island, 81 could have been poor due to the small size and the extreme the occupation area of the plant extended over practically all the 82 tropicalED and subtropical fringe of the South Pacific Ocean. Map isolation of the island (Skottsberg 1956; Zizka 1991). modified from Elix and McCarthy (2008). Below a map of the island 83 Descriptions provided by some of the early European vis- showing the location of Lake Raraku (Rano Raraku). In the box, 84 itors to the island supply some information on the flora, but position of the coring point in the lake is shown 85 few collections were made and many of the descriptions 86 were imprecise (Zizka 1991; Hunt 2007). This information 87 has been complemented with archaeological studies of Study site 107 88 microfossils—pollen, phytoliths, and starch grains (e.g., 89 Cummings 1998; Horrocks and Wozniak 2008)—as well as Easter Island is a subtropical volcanic island located in the 108 90 studies of macrofossils and wood charcoal (Orliac and South Pacific Ocean (27°70S, 109°220W; Fig. 1) approxi- 109 91 Orliac 1998; Orliac 2000), which have provided more mately 3,700 km west of the Chilean coast and 2,030 km 110 92 details on the flora following human settlement. However, east of the nearest inhabited island (Pitcairn). The island 111 93 direct evidence of the flora and its changes before human has a roughly triangular shape, with three main volcanic 112 94 arrival is only provided by palaeoecological records, lar- cones, situated one in each corner, and an area of only 113 95 gely based on palynological surveys of lake sediment cores *164 km2. The topography is characterized by the exis- 114 96 (e.g., Flenley et al. 1991; Azizi and Flenley 2008; Mann tence of these three main volcanoes, nearly 70 vents and 115 97 et al. 2008; Butler and Flenley 2010) and a few macrofossil the rolling surfaces of the lava flows between them. The 116 98 records (Mann et al. 2008; Can˜ellas-Bolta` et al. 2012). highest point is the summit of the Terevaka volcano 117 99 Here, we report the existence of a previously unobserved (511 m). No permanent surface streams are present 118 100 plant (Dianella sp.) that was part of the native Easter Island because of the high permeability of volcanic rocks (Herrera 119 101 flora during the early to middle Holocene, long before and Custodio 2008). At present, only the bottoms of the 120 102 human arrival, and which is now extinct. This species has craters of Rano Raraku and Rano Kau (now occupied by 121 103 been identified on the basis of its characteristic pollen and lakes), and Rano Aroi (now filled by a fen) permanently 122 104 seeds, found in a sediment core from Lake Raraku. The contain closed freshwater bodies. Currently, the island is 123 105 ecological preferencesUNCORRECT and the potential palaeoecological mostly (90 %) covered by grasslands, with a few tree 124 106 usefulness of Dianella are discussed. plantations, shrub areas and pioneer vegetation (Etienne 125 123 Journal : Large 334 Dispatch : 19-1-2014 Pages : 8 Article No. : 432 h LE h TYPESET MS Code : VHAA-D-13-00041 h44CP h DISK Veget Hist Archaeobot 126 et al. 1982). The climate is subtropical, with an average protocols for pollen analysis, slightly modified (Rull et al. 157 127 annual temperature of 21 °C and a range of average 2010b), including KOH, HCl and HF digestions and ace- 158 128 monthly temperatures between 16 and 18 °C (July–Sep- tolysis. Lycopodium tablets (batch 177745, Lund Univer- 159 129 tember) and 24–26 °C (January–March) (Mann et al. 2008; sity, Sweden) were added to each sample before chemical 160 130 Sa´ez et al. 2009). The total annual precipitation is highly processing as an exotic marker and used to calculate the 161 131 variable, ranging between 500 and 2,000 mm, with long pollen concentration.