Title: Atlas of the tropical West African pollen flora

The accurate and consistent identification of fossil pollen is essential to allow robust inferences to be drawn with regard to past climate and vegetation change. Identifications are best achieved through the direct inspection of reference material. Most substantial reference collections are held at prestigious universities in Europe or the United States of America which can restrict access for researchers trying to advance palynology in less developed countries. Digital imaging and fast spreading access to the internet means that it is now possible to produce and disseminate high quality images from pollen reference collections. In this paper we contribute to this growing body of work by presenting images of 364 pollen taxa from West Tropical Africa both as printed plates with a key, and within an associated online searchable database.


Abstract
The accurate and consistent identification of fossil pollen is essential to allow robust inferences to be drawn with regard to past climate and vegetation change. Identifications are best achieved through the direct inspection of reference material. Most substantial reference collections are held at prestigious university's in Europe or the United States of America which can restrict access for researchers trying to advance palynology in less developed countries. Digital imaging and fast spreading access to the internet means that it is now possible to produce and disseminate high quality images from pollen reference collections. In this paper we contribute to this growing body of work by presenting images of 364 pollen/spore taxa from West Tropical Africa both as printed plates with a key, and within an associated online searchable database.

Introduction
The accurate identification of fossil pollen and spores underpins our ability to reconstruct past vegetation and subsequently infer variation in the Earth's system. Palaeo-palynology can provide, among other things, evidence for past changes in climate (e.g. Davis and Shaw, 2001;Overpeck et al., 1990), biome (e.g. Jolly et al., 1998;Tarasov et al., 1998;Williams et al., 2004) and biodiversity (e.g. Brown, 1999;Odgaard, 1999;Rull, 1987) across the geological record. At one extreme the incredible resilience of pollen/spore chemistry (sporopollenin) allows palynology to provide evidence for the evolution of plants on timescales of millions of years (e.g. Crane et al., 1995;Wikström et al., 2001). Whilst at the other, the influence of human activity upon plants allows the actions of people within the landscape to be traced in the recent past (10-100's years ago) (e.g. Brugam, 1978;Piperno and Flannery, 2001). The integrity of the information supplied by palynologists to all these areas is reliant on consistent typing or, where possible, identification of the specimens found in the fossil record.
Since its inception morphological identification of pollen grains has been standard practice through comparison with modern material (von Post, 1916(von Post, , reprinted 1967. Subsequently numerous atlases for pollen and spore identification have been produced from across the globe, including: Beug, 2004;Colinvaux et al., 1999;Faegri and Iversen, 1989;Moore et al., 1991;Reille, 1999;Roubik and Moreno, 1991. The proliferation of pollen/spore atlases has facilitated the expansion of the field of palynology and helped with international standardization of identifications. In addition, as computing power has developed, there has been an increase in the number, and sophistication, of online searchable pollen databases (e.g. Bush and Weng, 2007;Lezine, 2005;QPG, 2008). However, geographical coverage and access to images for pollen identification remains patchy.
The most substantial atlases for African pollen and spore identification are: (i) in print (Reille, 1998(Reille, , 1999, and (ii) online the African pollen database (Lezine, 2005). Both contain thousands of images of species within hundreds of families, and therefore provide good general coverage of taxa likely to be found in the fossil record. In addition, pollen/spore atlases for specific regions have also been produced, e.g. East Africa (Riollet and Bonnefille, 1976), as well as for individual countries: (i) Chad (Maley, 1970), (ii) Ethiopia (Bonnefille, 1971a, b), (iii) Ivory Coast (Ybert, 1979), (iv) Nigeria (Sowunmi, 1973), (v) South Africa (Scott, 1982;van Zinderen Bakker, 1953, 1956van Zinderen Bakker and Coetzee, 1959), and (vi) Sudan (El Ghazali, 1993). In this paper we contribute to this body of knowledge by presenting c. 3000 images and identification keys for >450 pollen and spore taxa commonly found in tropical West Africa.

Selection of pollen and spore taxa
Taxa were selected for inclusion within this tropical West African pollen atlas based upon two criteria: (i) they had been previously identified within fossil records obtained from terrestrial and marine settings within the region (Dupont et al., 2000;Elenga et al., 1994;Frédoux, 1994;Leroy and Dupont, 1994;Lezine and Vergnaud-Grazzini, 1993;Maley and Livingstone, 1983;Talbot et al., 1984), and/or (ii) they had been identified as significant in the regional flora (Hall and Swaine, 1981).

Organisation and presentation of images
Images are presented on 129 plates showing both polar and equatorial views of the grain where it was possible to obtain images. Plates are organised by pollen morphology to allow ease of reference when examining fossil pollen material; following (Beug, 2004). In addition, to facilitate interrogation of the images based on botanical classification the family, genera and species of the images are listed in Table 1 with reference to plate number. The paper is accompanied by a searchable online database which integrates the images presented here with the c. 6000 images of >1000 taxa from the Neotropical Pollen database (Bush and Weng, 2007). To access a Freeware version of the complete revised Tropical Pollen Database download and unpack the TopicalPollenDB2013.zip file from the supplementary online section of this paper. Please note due to the high number of pictures the file is large (2.77GB) and an Apple Macintosh computer running Mac OS X 10.6 or higher is required to run the software. We hope that the combination of our images with those of Bush and Weng (2007) within a freeware format online will promote further expansion by other research groups which will lead to the eventual development of a comprehensive pan-tropical searchable online pollen and spore identification tool.

Provenance of specimens and image capture
Images and descriptions of all pollen and spores were obtained from the reference collection of c. 30,000 specimens housed within the Department of Biology at Duke University which has been collected and curated by DAL. Reference material was sourced from herbaria and laboratories around the globe; full details for individual specimens can be found on the accompanying online database. Tetrorchidium didymostemon -Pore shape squared  Gaertnera paniculata -Pore shape rectangular (broad) (