Date Published: January 26, 2017
Publisher: Public Library of Science
Author(s): Christopher M. Martinez, Daniel E. Duplisea, Robert M. Cerrato, Michael G. Frisk, Eric Gordon Lamb.
The interspecific abundance-occupancy relationship (AOR) is a widely used tool that describes patterns of habitat utilization and, when evaluated over time, may be used to identify large-scale changes in community structure. Our primary goal for this research was to validate the utility of AORs as temporal indicators of community state. We used long-term survey data in four regions of the northwest Atlantic coastal shelf (NWACS) to estimate the diversity of spatial behaviors in each community, which we modeled with negative binomial (NB) distributions. NB parameters were used to generate time series data for simulated communities, from which AORs were then estimated and evaluated for temporal trends. We found that AORs from simulated communities were similar in year-to-year variation to empirical relationships. In order to further understand the role of spatial diversity in the generation of AOR trends, we did additional simulations where NB parameters were manually manipulated. In one instance, we ran simulations while holding species’ parameters constant over time. This treatment effectively removed trends, suggesting that temporal change in community relationships was the result of genuine variation in intraspecific spatial use. In another set of simulations, we conducted a case study to evaluate the impact of a select group of schooling and spatially aggregating species on an especially rapid shift in AORs in the Gulf of Maine from 1973 to 1983. Removals of these species reduced the magnitudes of most trends, demonstrating their importance to observed community changes. This research directly links variation in AORs to distribution and density-related processes and provides a potentially powerful framework to identify community-level change and to test ecological and mechanistic hypotheses.
The relationship between organism and habitat is among the most basic concerns in ecology. A common tool to assess patterns of habitat utilization is the abundance-occupancy relationship (AOR). AORs have been applied to a variety of biological systems, from terrestrial [1, 2], to marine , freshwater , and experimentally controlled protist communities . In its interspecific form, the AOR is a collection of two measures for each species within a community; the proportion of all sampled locations where at least one individual was present (occupancy) and the number of individuals caught divided by either the total number of locations (global mean abundance, GMA) or by the number of occupied sites only (local mean abundance, LMA). The interspecific AOR has been used to investigate overriding patterns of spatial organization within communities, with its structure being attributed to factors such as species interactions , environmental/habitat change , niche breadth , and direct anthropogenic impacts . When compared in a temporal framework, these methods capture important macroecological information that reflects transitory properties of biological communities and their environment. Therefore, AORs provide a useful tool to assess large-scale patterns and drivers of community structure.
This research resulted in two key outcomes that further our understanding of AORs. First, simulated communities shared major patterns and features of variation with natural communities, validating empirical trends in the AOR by linking them to changes in species’ spatial distributions (NB parameters). Second, we showed that trends in AORs are sensitive to ecological processes. Here, a rapid shift in community structure in the GOM was a least partially attributed to a rise of schooling and aggregating species. Consequently, we suggest that the AOR is a suitable indicator of change at the community level, encompassing processes relating to assemblage structure, ecological interactions, and any other factor affecting habitat use.