Palynological differentiation between genera of the Moraceae family and implications for Amazonian palaeoecology Michael J. Burn ⁎ , Francis E. Mayle School of Geosciences, University of Edinburgh, Drummond Street, Edinburgh EH8 9XP, UK Received 19 June 2007; received in revised form 3 December 2007; accepted 5 December 2007 Available online 4 March 2008 Abstract The Moraceae family is one of the most abundant and ecologically important families in Neotropical rainforests and is very well-represented in Amazonian fossil pollen records. However, difficulty in differentiating palynologically between the genera within this family, or between the Moraceae and Urticaceae families, has limited the amount of palaeoecological information that can be extracted from these records. The aim of this paper is to analyse the morphological properties of pollen from Amazonian species of Moraceae in order to determine whether the pollen taxonomy of this family can be improved. Descriptive and morphometric methods are used to identify and differentiate key pollen types of the Moraceae (mulberry) and Urticaceae (nettle) families which are represented in Amazonian rainforest communities of Noel Kempff Mercado National Park (NKMNP), Northeast Bolivia. We demonstrate that Helicostylis, Brosimum, Pseudolmedia, Sorocea and Pourouma pollen can be identified in tropical pollen assemblages and present digital images of, and a taxonomic key to, the Moraceae pollen types of NKMNP. Indicator species, Maquira coriacea (riparian evergreen forest) and Brosimum gaudichaudii (open woodland and upland savanna communities), also exhibit unique pollen morphologies. The ability to recognise these ecologically important taxa in pollen records provides the potential for much more detailed and reliable Neotropical palaeovegetation reconstructions than have hitherto been possible. In particular, this improved taxonomic resolution holds promise for resolving long-standing controversies over the interpretation of key Amazonian Quaternary pollen records. © 2007 Elsevier B.V. All rights reserved. Keywords: Moraceae; pollen; morphology; Quaternary; Bolivia; Amazon Basin; rainforest; riparian forest 1. Introduction There is considerable controversy regarding the interpreta- tion of Amazonian fossil pollen records (Colinvaux and de Oliveira, 2000; Pennington et al., 2000; Bush, 2002; Bush et al., 2004; Mayle et al., 2004; Anhuf et al., 2006), which hampers progress in our understanding of Late Quaternary vegetation dynamics, the testing of climate and ‘earth-system’ models (Valdes, 2000; Cowling et al., 2005) and in obtaining improved estimates of past carbon storage (Behling, 2002; Mayle and Beerling, 2004; Beerling and Mayle, 2006). Much of this controversy arises from the sparse distribution of fossil pollen sites within the Amazon Basin and the extent to which they are representative of Amazonia as a whole. More problematic, however, is our inability to identify many Amazonian pollen types to species, or even genus level, resulting in poor taxonomic resolution in many fossil pollen records. Pennington et al. (2000) point out that, when operating at such a low taxonomic resolution, up to 80% of fossil pollen types attributed to ‘tropical rain forest’ taxa, equally characterise ‘seasonally dry-forest’ taxa (e.g. Pleistocene pollen assemblages of Lake Pata in central Amazonia, Colinvaux et al., 1996). This sizeable overlap may be overcome with the increasing availability of pollen rain data that establish pollen signatures for tropical forest communities based upon differences in the abundance of their constituent taxa (e.g. Bush et al., 2004; Weng et al., 2004; Gosling et al., 2005). Similarly, improving the taxonomic resolution at which Amazonian pollen can be identified, should allow these communities to be much more readily differentiated by the presence or absence of ecosystem-specific indicator taxa. The mulberry family (Moraceae) comprises ca. 37 genera and over 1100 species worldwide and is one of the most abundant and ecologically important families growing in tropical rainforests of Available online at www.sciencedirect.com Review of Palaeobotany and Palynology 149 (2008) 187 – 201 www.elsevier.com/locate/revpalbo ⁎ Corresponding author. Tel.: +44 0131 6502533; fax: +44 0131 6502524. E-mail address: Michael.J.Burn@ed.ac.uk (M.J. Burn). 0034-6667/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.revpalbo.2007.12.003