Paleoecologic Record

William Miller III

imagine a community ecologist venturing into the literature of marine paleoecology for the first time. Let us say that her first exposure will be in the reading of a volume of contributed chapters, such as this one. If our colleague scratches her head each time she is confused over inconsistent and illogical usage of unit definitions, by the end of the book she might be bald. This would be no reflection on the quality of data or analytical rigor in such volumes, but rather a consequence of a prevailing indifference to fundamental properties of the ecologic entities recorded in fossil deposits. Should paleoecologists do something about the situation or continue to promote depilation in this way?

Paleoecology is usually considered to be the study of ecologic properties of fossil organisms or assemblages of organisms. A better definition would state that paleoecology is more concerned with organisms and assemblages viewed at larger or more inclusive spatial and temporal scales than those typically considered in neoecology. What paleoecologists do is fairly clear, but why they do it, the purpose of paleoecology, is far from clear. Although this chapter will seem at first to be a rehashing of terminology, it is really about the issue of purpose, the approach here being an assessment of the entities, or things, paleoecologists study. Specifically, the approach will consist of a review of recent systems of paleoecologic unit classification and a proposal of a way to evaluate entities detected in the fossil record that could stabilize terminology and help to settle the ontologic aspect of purpose. I also illustrate some of the consequences of ignoring these issues.

The relationships of paleoecology to evolutionary biology in general and ecology in particular have always been uncertain, and occasionally someone says so unambiguously (Hoffman 1979,1983; Gould 1980; Kitchell 1985; All-mon 1992; A. I. Miller 1993). One way to see this uncertainty is to notice how liberally paleoecologists have borrowed concepts and techniques from ecology, but how oblivious most ecologists seem to be about what goes on in paleo-ecology. As ecologists have begun to scale up their observations to encompass large units of biotic organization, large-scale environmental contexts, and climate history, they have started to work at levels familiar to paleoecologists. The ecologists, however, are developing their own brand of macroecology (e.g., Turner 1989; Delcourt and Delcourt 1991; Gilpin and Hanski 1991; Brown 1995; Hansson, Fahrig, and Merriam 1995; Wu and Loucks 1995). Perhaps the reason for the continuing separation of disciplines has to do with our attending separate conferences, publishing in different journals, or using different methods, but it might also relate to the fact that paleoecology somehow skipped a crucial stage in its conceptual development that Eldredge (1985:163) has described as "... frankly groping for an ontology of ecological entities " Terms such as community, paleocommunity, assemblage, and biofacies are used to mean almost any kind of multispecies aggregate. Ecologists are not entirely free from this confusion over terms (Mcintosh 1985,1995; Fauth et al. 1996), but paleoecologists, in terms of words available for use and spatiotemporal scaling dimensions, have more to be confused about.

If we take deme and species-lineage to be potentially real things whose meaning and significance need to be understood before evolutionary patterns and processes are interpreted satisfactorily (Mayr 1970, 1988; Stanley 1979; Eldredge 1989; Ereshefsky 1992; Gould 1995), why should we be unconcerned about the validity of the terms community and ecosystem? This is not the same as the debate over whether multispecies assemblies are strongly interacting, stable entities (the Clementsian-Eltonian view) or happenstance aggregations of populations merely tolerating local environmental factors (the Gleasonian view) (DeMichele et al., chapter 11, this volume). Instead, what I attempt to address is the problem, for instance, of letting a community be any of the following: fossils loaded into a sample bag at a particular locality; samples having generally similar fossil content collected at several different localities or strati-graphic levels; or statistically defined clusters of taxa or samples at many scales of resolution.

TABLE 3.1. Kauffman-Scott System of Units"

Global biota

Contemporaneous global biota Realm Region Province

Subprovince

Endemic center Ecosystem Sere

Assemblage

Community (paleocommunity) Association (many kinds) Population

Individual organism

" Kauffman 1974; Kauffman and Scott, 1976.

TABLE 3.2. Boucot-Brett System"

Ecological-Evolutionary Units

Ecological-Evolutionary Subunits Assemblage

Biofacies / community group / community type Community a Boucot 1975,1983, 1990a,b,c; Brett, Miller, and Baird 1990; Brett and Baird 1995

TABLE 3.3. Bambach-Bennington System (1996)

Community type (paleocommunity type) Community (paleocommunity)

Local community (local paleocommunity) Avatar (no fossil equivalent)

Classifications of Paleoecologic Units

Here I review five essentially hierarchical classification systems for fossil deposits that have a more or less explicit ecologic character (whether or not real ecologic entities or systems are in fact represented) and have been fairly well publicized (tables 3.1-3.4). There are other, mostly older, systems, but these are the ones paleoecologists are likely to think about when they consider units. To build a consensus regarding terminology, the practice of redefining units in every new publication should be discouraged. Parts of the classifications are compared in table 3.5.

TABLE 3.4. Valentine System"

Biosphere system

Historical biotic system Province system

Regional ecosystem Biotope system Local ecosystem

Ecologic association / interaction cell Local population system / avatar Individual organism a Based on Valentine 1968, 1973; Eldredge and Salthe 1984; Eldredge 1985; W. Miller 1990,1991, 1996

TABLE 3.5. Possible Correlation of Units Employed in Recent Paleoecologic Literature

Kauffman-Scott

Boucot-Brett

Bambach-Bennington

Valentine

Global biota

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