INTRODUCTION

The controls of biodiversity today and throughout Earth history are an important theme to much of biology and geology. A recent study of the biodiversity of marine microorganisms spanning the past 50 m.y. (million years) has revisited an important topic concerning the influence of plate tectonics on biodiversity (Renema et al. 2008). By examining the genus-level alpha diversity component of benthic foraminifera throughout tropical to temperate portions of Europe, Asia, and Australia, Renema et al. (2008) measured the greatest alpha diversities during epochs of convergent tectonic activity. A related study of this topic that also covered the Indo-Australian Archipelago (IAA) was published more than two decades earlier by Whitmore (1982) who similarly showed that the essential component that determines the exceptional present day biodiversity there was convergent tectonics between Asia and Australia. Although the confluence of species gave the region an anomalously high biodiversity, earlier researchers were surprised to find that most species generally inhabited their original continent, with ranges that mirrored the plate boundary. Wallace (1860), too, was intrigued that species obeyed such a sharp zoogeographic boundary (Wallace's Line) and even alluded to a possible continental plate explanation for the phenomenon. 

In the rock record contribution from other factors such as species competition and moderate disturbance have no doubt been influential, but their observation has been difficult. Deterministic events such as bolide impacts (Schulte et al. 2010) or extensive volcanism (Renne et al. 1995; Self et al. 2006) are perennial favorites in geology that are invoked as explanations for biodiversity crashes and their subsequent biodiversification events. The strength of causality arguments for such coincidental events are limited because the Earth has many times been subjected to asteroid impacts (among other major calamities), and they are seldom associated with major extinctions. On the other hand, factors important to the study of present day biodiversity including coexistence, immigration, and resource gradients have received much less coverage by Earth scientists, in part because these factors are more difficult to quantify through fossil evidence. This situation is changing today, because fossil data sets now (e.g., Alroy et al. 2008) provide extensive information sufficient to test for other drivers of biodiversity and biogeography.

The focus of this paper is to simulate marine ecosystem habitat types in order to investigate patterns in biogeography in passive and convergent tectonic settings. To do so several diversity measures are compared at both the genus and species level (using complete and rarefied subsamples) between surface area standardized grid cell assemblages from eastern North America, Europe, and Japan. Our collection of assemblages spans the most recent 57 m.y., a period over which the continents have occupied roughly the same present day latitudes, and the fossil record is particularly well preserved. Ecosystem factors such as water depth were parameterized from the lithologic annotations of each fossil occurrence, and a k-means algorithm was used to designate habitat types and to compare patch structure between grid cells. We further discuss these relationships with regard to sampling bias, latitudinal gradients in species diversity, and sampling resolution, all of which set important bounds on the inferential scope of our results.