Markwick 1995Abstr

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Markwick, P.J. (1995)
A new method for examining paleoclimatology and paleoecology using present day faunas assigned to climate stations

GSA Annual Meeting, New Orleans
(Please note: presentation of this abstract had to be cancelled due to unforeseen circumstances)

Abstract

Reconstructing the pattern of paleoclimate using fossil data relies heavily on analogy with Recent organisms. An understanding of the climate relationships of modern groups is therefore essential. In order to examine this I have compiled non-avian tetrapod faunal lists for North America, Europe, Australia, southern Africa, South America and Arabia together with global data for crocodilians, turtles and palms. Each of these lists is related to a climate station from Müller's 1982 compilation of climate data for vegetation studies. This information has been entered into a customized fully relational database that also includes data for 6000 fossil vertebrate localities. The direct assignment of the biota to climate provides the opportunity to address numerous issues, including the relation of diversity to climate and the position of each organic group in climate space. Derived conclusions can then be applied to the fossil record.

Here I present some results of this study pertaining to diversity gradients. Ectotherm diversity (species, genus and family level) is found to vary monotonically with absolute latitude and mean annual temperature (MAT), consistent with a primary dependence on external sources of energy. Alternatively, the behavior of endotherms (mammals) is more complex, with a peak in the lowest latitudes and a second in middle latitudes. This distribution is similar to that of precipitation and through this plant productivity, suggesting a potential link between mammal diversity and food resources. A more important relationship for paleoclimate is the strong linear relationship found between the proportion of each fauna represented by ectotherms and MAT. This linear relationship is used to retrodict the MAT for the middle Eocene lagerstätten fauna from Messel, Germany. A MAT of about 16.5±3.6°C is found using this method (based on the genus diversity regression). This is consistent with the presence of crocodilians and palms at this locality. However, this method is highly dependent on the degree of completeness of the fauna. It should be noted that in the published geological record the diversity of ectotherms is invariably underestimated. Such biases can be modeled using the modern dataset and this is in progress.

The relationship also implicitly predicts the potential response of terrestrial vertebrates to future climate change.