BIOTIC INVASIONS, SPATIAL SCALE, AND TEMPORAL RESOLUTION IN THE FOSSIL RECORD

Species invasions, which may range from local ephemeral events to globally ubiquitous phenomena, have a deep geological history. As defined here, these events occur when species move into new habitats or geographic regions, and as such they can result in significant ecological and evolutionary impacts. Modern ecologists are well aware of the short-term (annual to decadal) impacts of species invasions, although longer-term impacts are difficult to establish in the absence of historical or subfossil archives. Analyses of species invasions over long periods of time and in the face of changing environments are therefore best derived from the fossil record.

Such studies are not without difficulty. The temporal resolution of the fossil record is typically coarser than ecological timescales, meaning that the short-lived transport and establishment stages of species invasions are unlikely to be preserved. More often documented are the sudden appearance in the fossil record of fully established populations. Additionally, taphonomic processes, whether they be postmortem or diagenetic, and larger-scale destructive geological phenomena result in a patchy record. This has implications for understanding vectors of transport, region of origin, and the environmental factors that supported the invasion. However, the deep time archive does provide numerous opportunities for investigating the nature of invasions, such as long-term records of paleoclimate and paleoceanographic proxies, sea level fluctuations, and natural experiments of tectonically-mediated seaway and land corridors openings.

A review of published literature on species invasions is provided here, with particular emphasis on aspects of temporal resolution and spatial scales. The goal is to provide a framework within which to assess the potential of paleontological case studies to identify invasions, vectors of transport, source populations, and the environmental factors facilitating such exchange. These differences in spatial scale and temporal resolution introduce challenges for direct application of lessons from the paleontological record for modern invasive species management and science.