A SMALL-SCALE STUDY OF SAMPLING BIAS - THE CHALK OF HAMPSHIRE, UK

The fossil record captures past biodiversity imperfectly. Does sampling bias obscure biological diversity signals in palaeontological richness data? Global studies find a correlation between sampling proxies and sampled fossil diversity. However, regional studies find that this relationship breaks down on small scales, or that the strength of this relationship depends on the taxon, tectonic and depositional setting and rock exposure. The relationship between global (gamma) and local (alpha) diversity measures is of course modified by inter-regional differentiation (beta diversity), but comparisons across scales are intriguing. A newly-compiled dataset of fossil occurrences from the Chalk of Hampshire, UK, is presented. Analysis of diversity in this succession per formation and per map square reveals a correlation between diversity and sampling effort measured at this scale. Genus richness counts are driven by sampling bias in this dataset, but this masks real local faunal turnover as demonstrated by the episodic nature of species distributions in the Chalk and similarity indices for each formation.