Species-time curves and population extremes: Ecological patterns in the fossil record

Accumulation of species in geological time follows species-time curves that are similar to species-area curves, as predicted by Preston. The z-values of these fossil species-time curves range from 0.30 to 0.36, similar to spe cies-area curves produced by sampling islands and other widely separated ha bitats. We suggest that such z-values in species-time curves occur because the episodic nature of fossil deposition essentially produces temporal 'isl ands' of widely spaced samples. We also find that marine fossil species ten d to exhibit increased variation of abundance with time (reddened spectra) in ways that are consistent with marine abundance patterns measured across much shorter ecological time-scales. This adds further support to the view that physical parameters in the ocean vary over larger temporal and spatial scales than on land, including geological scales.