Dictionary:

paleoecology

  (pā'lē-ō-ĭ-kŏl'ə-jē)

The branch of ecology that deals with the interaction between ancient organisms and their environment.

Ecology of prehistoric times, extending from about 10,000 to about 3.5 × 10⁹ years ago. Although the principles of paleoecology are the same as those underlying modern ecology, the two fields differ greatly. Paleoecology is a historical science that must rely on empirical data from fossils and their enclosing sedimentary rocks to make inferences about past conditions. Experimental approaches and direct measurement of environmental parameters, which are critical components of modern ecology, are generally impossible in paleoecology. Furthermore, distortion and loss of information during fossilization means that fossil assemblages and distributions are rarely congruent with living communities. Hence, the resolution of ancient ecosystems must remain relatively imprecise. The lack of precision is compensated for by the fact that paleoecology deals with processes occurring over vast spans of time that are unavailable to modern ecology. Long-term changes in communities (replacement) may be discerned and related to patterns of environmental change. More significantly, overall patterns of ecological change in the global biosphere may be documented; evolutionary paleoecology focuses on recognition and interpretation of long-term ecological trends that have been critical in shaping evolution.

Among the goals of paleoecology are the reconstruction of ancient environments (primarily depositional environments), the inference of modes of life for ancient organisms from fossils, the recognition of recurring groupings of ancient organisms that define relicts of communities (paleocommunities), the reconstruction of the interactions of organisms with their environments and with each other, and the documention of large-scale and long-term patterns of stasis or change in ecosystems. See also Ecosystem.

To reconstruct ancient marine environments, many different parameters must be inferred, such as temperature, water salinity, oxygen levels, nutrient concentrations, and water movements and depth. In this regard, paleoecology interfaces directly with the fields of sedimentology and stratigraphy, including study of modern depositional environments. See also Depositional systems and environments; Stratigraphy.

Paleoautecology, the interpretation of modes of life (broadly, niches) of ancient organisms, involves a multidisciplinary approach. Although ancient modes of life cannot be determined completely, paleoecologists can often assign fossils to generalized guilds in terms of types of feeding, substrate preference, and degree of activity. A thorough understanding of the biology of closest modern analogs is particularly important in any attempt to reconstruct paleoautecology. See also Living fossils.

The fossil record contains highly biased remnants of past communities or paleocommunities. Paleocommunities are generally recognized as recurring associations of fossil species. Multivariate statistical techniques such as cluster analysis and ordination analysis are commonly employed to aid in discerning the recurrent groupings of fossil species.

Communities and paleocommunities are not static entities in time, but undergo important structural changes on at least three different time scales: succession, replacement, and evolution. Because it operates on a very short time scale, from decades to centuries, ecological succession can be resolved only in a few fossil samples. Longer-term changes in community composition, encompassing thousands of years, are not truly succession. These changes are properly termed community replacement, involving wholesale migration or restructuring of communities at particular locations due to changing environments. On a scale of millions of years, communities show evolutionary changes because their component species have evolved. See also Ecological communities; Ecological succession.

Organisms evolve within the context of other organisms, not in a vacuum. There is substantial fossil evidence to indicate increasing complexity of organism interactions through time. This escalation in the intensity of predatory interactions, for example, may have important implications for evolutionary change.

One of the most interesting aspects of paleoecology is the possibility of long-term shifts in organism habitats. Evolutionary innovations appear to arise preferentially in shallow-water areas, but through time these new faunas may migrate offshore. Evidence from the fossil record suggests that many paleocommunities were relatively resistant to major changes over long spans of time. These periods of relative stasis in community structure may be punctuated by minor or major crises, during which communities are restructured, with new species added while others become extinct. In many cases, shoreline biotas display very little change. Similarly, deep-oceanic benthic organisms may be little changed through time. In contrast, shallow-water, shelf-dwelling, and especially pelagic organisms may be strongly affected by environmental crises such as the lowering of average temperatures. See also Ecology; Paleoclimatology; Paleogeography; Paleontology.

The branch of ecology that deals with the interaction between ancient organisms and their environment.

The noun has one meaning:

Meaning #1: the branch of ecology that studies ancient ecology
  Synonym: palaeoecology

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