Evol Ecol Res 12: 363-376 (2010)     Full PDF if your library subscribes.

The living and the fossilized: how well do unevenly distributed points capture the faunal information in a grid?

Juha Saarinen1, Emilia Oikarinen2, Mikael Fortelius1 and Heikki Mannila3

1Department of Geosciences and Geography, University of Helsinki, Helsinki, 2HIIT, Department of Computer Science, University of Helsinki, Helsinki and  3Department of Computer and Information Science and HIIT, Aalto University, Aalto, Finland

Correspondence: E. Oikarinen, Department of Geosciences and Geography, University of Helsinki, PO Box 64, FIN-00014 Helsinki, Finland.
e-mail: emilia.oikarinen@helsinki.fi


Background: Fossil data sets are typically point-like, i.e. they provide information about a fossil fauna only for scattered localities. Modern distribution data are typically based on grid cells, and provide a (nearly) full description of the fauna.

Question: How good are estimates of the characteristics of the whole fauna that one obtains by looking only at point-like data similar to fossil data sets?

Data: Locality-based occurrence data for Neogene terrestrial mammals taken from the NOW database, and grid-based modern mammal distribution data for extant terrestrial mammals of Europe taken from the EMMA database.

Analytical methods: We used the EMMA dataset to generate subsets of the data, which contain only information about those grid cells that correspond to the location of at least one fossil locality in the NOW data. For each such dataset, we compared the different characteristics of the fauna (such as diversity, trophic structure, hypsodonty, occupancy, and representation of spatial patterns) to the whole EMMA dataset.

Results: Grid cells corresponding to fossil localities detect about 60% of the known species. Community structure can be estimated very accurately from the data on these localities.

Conclusions: Grid cells containing fossil localities give good estimates about the total fauna known from all grid cells, especially for relative measures such as community structure. Limitation to grid cells has a stronger effect on spatial patterns, but the main trends are still observed. Adding noise to the data has a negligible effect in most cases. The terrestrial mammals present in the NOW database can thus be regarded as a reasonably good representation of the real fauna from which they are drawn.

Keywords: grid data, incompleteness of the fossil record, NOW database, point data.

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