Spatial Variation in Abundance

Abstract

To quantify the magnitude and pattern of spatial variation in local population density within a single species, we analyzed large numbers of samples, representing a large geographic area or a wide range of ecological conditions. Our analyses focused on, but were not limited to, censuses of birds recorded in the North American Breeding Bird Survey. Birds and other organisms exhibited a common pattern: each species was represented by only a few individuals in most of the sample sites where it occurred, but was orders of magnitude more abundant in a few "hot spots." The highly clumped frequency distributions of intraspecific abundance among sample sites resemble distributions, such as the negative binomial, canonical lognormal, and broken stick, that have been used to characterize the distribution of abundances among species within local ecological communities. We hypothesize that the spatial variation in abundance largely reflects the extent to which local sites satisfy the niche requirements of a species. Several results are consistent with this hypothesis. First, a computer simulation model in which abundance is determined by the multiplicative combination of several independent environmental variables produces ranked distributions of abundances similar to those observed empirically. Second, geographic patterns of abundance of bird species have been relatively stable over several decades, indicating that different abundances are associated with particular places on the landscape. Third, the abundance of bird species varies in a systematic way over the geographic range, exhibiting positive spatial autocorrelation at small distances and a tendency to increase from the edges toward the center of the range. The magnitude and pattern of spatial variation in local population density has important implications for basic ecology and biogeography, especially for the dynamics and regulation of abundance on both space and time, the limits and internal structure of the geographic range, and the interspecific variation in abundance observed within local communities. Patterns of spatial and temporal variation in abundance should be considered in the design of nature reserves and the conservation of biological diversity.

Spatial synchrony of wader populations in inland lakes of the Iberian Peninsula

“…As many theoretical and empirical 416 studies have observed, identifying patterns and processes 417 of temporal population dynamics is not an easy task and 418 it is necessary to consider also the effect of random 419 events, like environmental and demographic stochastic-420 ity (Brown et al 1995;Ives and Klopfer 1997). Even the 421 lakes that received wastewater can dry in summer if the 422 water accumulated in winter was low.…”

Testing the independent species’ arrangement assertion made by theories of stochastic geometry of biodiversity

“…One of the principal goals of ecology is to understand the processes and mechanisms that control the distribution, abundance and coexistence of species [1,2]. Classical theoretical ecology predicts that two species competing for the same resources cannot stably coexist (the exclusion principle by Gause [3]).…”

Variación florística de especies arbóreas a escala local en un bosque de tierra firme en la Amazonia colombiana

“…El estudio de la distribución de especies de acuerdo con categorías de abundancia, además de indagar acerca de los efectos del tamaño de la muestra, busca explicar si la relación de éstas con su medioambiente, está reflejada en la distribución de las abundancias relativas (Brown et al 1995;Alonso et al 2008). En otras palabras, pretende indagar acerca de la diferencia adaptativa que supone ventajas competitivas de algunas especies respecto al uso de los recursos en un hábitat determinado (Preston 1962;Tilman y Pacala 1993;Brown et al 1995).…”

“…En otras palabras, pretende indagar acerca de la diferencia adaptativa que supone ventajas competitivas de algunas especies respecto al uso de los recursos en un hábitat determinado (Preston 1962;Tilman y Pacala 1993;Brown et al 1995). Según Preston (1962), las especies de abundancia intermedia pueden ser especialmente útiles como indicadores diferenciales de la adaptación al nicho.…”