Improved resolution of pollen taxonomy allows better biogeographical interpretation of post‐glacial forest development: analyses from the North American Pollen Database

Abstract

Summary1 Species-level pollen identifications within the genera Acer , Fraxinus and Juglans have the potential to increase the detail available from regional-and landscape-scale studies of palaeo-forest dynamics. 2 Data from the North American Pollen Database (NAPD) and the North American Modern Pollen Database (NAMPD) for sites in eastern North America for which species-level identifications have been recorded enabled us to consider pollen taxonomy at high resolution. 3 Species within each of Acer , Fraxinus and Juglans have important differences in habitat, functional type and responses to climatic change. Analysis of the modern distribution of these taxa and their pollen rains confirms that species-level pollen identifications provide detailed ecological information, but the lack of distinction to the species level in many fossil and modern pollen studies renders palaeoenvironmental reconstructions incomplete. 4 Within each of three selected high-resolution sites, ordinations indicate that individual species of Acer , Fraxinus and Juglans follow different trajectories through the Holocene, showing that analysing only generic categories results in the loss of ecologically valuable information. For example, pollen of Acer rubrum increased in abundance in response to canopy openings in a southern Ontario forest around 500 years ago, while that of A. saccharum declined. Similarly, Juglans nigra pollen percentages increased while J. cinerea decreased at this time. 5 Regional-scale comparisons of pollen percentage curves indicate that, despite the uncertainties associated with the low temporal resolution and the chronologies, it is reasonable to conclude that individual species of Acer , Fraxinus and Juglans responded synchronously to palaeoclimatic changes within each region. 6 Taking analyses to the specific level shows that different species followed different tracks in their post-glacial history, a fact previously blurred by less resolved taxonomy. This information is meaningful in biogeographical terms, providing much more specific evidence of how the selected trees behaved in the past.

How does taxonomic resolution affect chironomid-based temperature reconstruction?

“…Birks (1994) concluded that the transfer functions performed best if all taxa were included unless WA was calculated with tolerance down-weighting. In a second study, Finkelstein et al (2006) indicated that species-level identification of fossil pollen allowed more complete reconstruction of the vegetation history of eastern North America than records identified to genus-level.…”

Strengths and Weaknesses of Quantitative Climate Reconstructions Based on Late-Quaternary Biological Proxies

“…Within the vast literature about calibration data-sets, some papers critically identify and discuss in detail some of these potential errors (e.g. Birks et al 1990;Jones & Juggins 1995;Lotter et al 1997Lotter et al , 1998Engels et al 2001Engels et al , 2008Bigler et al 2002;Whitmore et al 2005;Finkelstein et al 2006;Heiri et al 2007;Gonzales et al 2009a;.…”

“…and associated climate data (X m ) is available. This data-set should be representative of the likely range of climate variables in the past (X f ), be of consistent and detailed taxonomy and nomenclature (Finkelstein et al 2006), be of comparable quality (data-extraction procedures, spatial scale, count size, sampling methodology, preparation procedures, counting techniques) and, in the case of surface samples, be from the same type of sedimentary environment as the fossil samples (e.g. lakes) (Bjune et al 2010) and hence have comparable taphonomies (cf.…”

Taxonomic resolution in parasite community studies: are things getting worse?

“…Taxonomic resolution is also important in biogeographical studies. For example, identification of pollen down to species level can reveal shifts in plant assemblages that are not apparent with lower resolution (Finkelstein et al 2006). In studies of environmental impact assessment, including many investigations of the impacts of pollution on aquatic habitats, low levels of taxonomic resolution can obscure important changes to the biota (Terlizzi et al 2003(Terlizzi et al , 2009Jones, 2008).…”