The Trans‐atlantic History of Diversity and Body Size in Ecological Guilds

Abstract

Abstract. Geographically separate biotas often show differences in species composition, diversity, and adaptations. Such differences, which often reflect historical differences in regimes of productivity and selection, have received little attention from ecologists. Here we concentrate on diversity and maximum body size in 18 guilds of shallow-water marine shellbearing mollusks and barnacles from the European and North American sides of the temperate North Atlantic. These guilds represent suspension-feeders (epifaunal, shallow infaunal, and deep infaunal), chemosymbiotic bivalves, predators, and grazers. Geographic patterns among Recent guilds were compared to those during Pliocene and early Miocene time in order to determine how diversity and maximum size changed over the last 17 million years in the face of high levels of extinction and species invasion.Recent European guilds are generally more diverse than their American counterparts, a finding consistent with previous biota-wide analyses. Diversity within Pliocene guilds was often higher on the American side, but this stems in part from the large subtropical component in preserved temperate Pliocene guilds in Virginia but not in Europe.The largest species in hard-bottom guilds in Europe reach greater sizes than those in comparable American guilds, but for sand-bottom guilds, American species almost always attain greater sizes than their European counterparts. These size differences have changed little since early Miocene time despite high levels of Pliocene and Pleistocene extinction in invasion, particularly on the American side. Large-bodied species are overrepresented among both extinct and invading lineages, meaning that lineage replacement has been the rule for the largest species in guilds on both sides of the Atlantic.Together with previous studies, these results may imply that sand-bottom environments in North America have been more productive and have experienced more far-reaching escalation between shell-bearing species and their predators than their European counterparts since early Miocene time. The Pliocene to Recent record of hard-bottom guilds implies that productivity and/or escalation in these systems may have been higher on the European side than in eastern North America. Shallow-water guilds on opposite sides of the Atlantic have retained differences despite great upheavals caused by extinctions and invasions during the last 3 million years.

Shifting sources of productivity in the coastal marine tropics during the Cenozoic era

“…From the perspective of sampling, large-bodied species are more easily collected and better known than their smaller counterparts. Moreover, previous work [4] indicates that maximum size is not correlated with overall diversity, a finding also supported in the present study.…”

“…Threats from competitors, predators and the weather limit access to resources, but these threats are reduced for competitively dominant species. Because large adult size typically confers competitive superiority and high demand for resources within a guild of species with similar habits and trophic roles, maximum body size of the largest species in a guild is a good indicator of resource supply as perceived by the organism itself given the individual's mobility, metabolic demand and feeding-related machinery [4]. Comparisons of maximum body sizes among co-occurring guilds can thus reveal the relative contributions of the various sources of production (such as phytoplankton and benthic plant-like organisms), whereas comparisons of maximum sizes within a guild over time track changes in the productivity of a given class of resources.…”

Comparative Ecology of North Atlantic Shores: Do Differences in Players Matter for Process?

“…A similar argument could be made for buccinid whelks in Europe, which are much smaller than their counterparts on western Atlantic shores where they are known to significantly impact infauna. As argued by Vermeij et al (2008), impact is clearly affected by both size and density of predators.…”

The Relation Between Productivity and Species Diversity in Temperate–arctic Marine Ecosystems

“…Indeed, historical processes may contribute to the gradient of decreasing epifaunal species richness observed in rock wall communities from east to west across the North Atlantic. Lower diversity of marine fauna on the North American vs. the European side of the Atlantic has been noted in several groups including molluscs, barnacles (Vermeij 1978, Ingolfsson 1992, Vermeij et al 2008, and algae (South 1987). Vermeij et al (2008) found that this trans-Atlantic diversity pattern belies a single explanation, such as a shorter time for colonization and diversity build up after the last glaciation on the North American side (Ingolfsson 1992), because the trans-Atlantic diversity differences pre-date Pleistocene glacial periods by millions of years.…”