Ecological traps
Encyclopedia
Ecological traps are scenarios in which rapid environmental change
leads organisms to prefer to settle in poor-quality habitat
s.
The concept stems from the idea that organisms that are actively selecting habitat
must rely on environmental cues to help them identify high quality habitat. If either the habitat quality or the cue changes so that one does not reliably indicate the other, organisms may be lured into poor quality habitat. More specifically, traps are thought to occur when the attractiveness of a habitat increases disproportionately relative to its value for survival and reproduction. The result is preference of falsely attractive habitat and a general avoidance of high-quality but less-attractive habitats. While the demographic consequences of this type of maladaptive habitat selection behavior have been explored in the context of the sources and sinks, ecological traps are an inherently behavioral phenomena of individuals. The ecological trap concept was introduced in 1972 by Dwernychuk and Boag and the many studies that followed suggested that this trap phenomenon may be widespread due to anthropogenic habitat change.
As a corollary, novel environments may represent fitness opportunities that are unrecognized by native species if high-quality habitats lack the appropriate cues to encourage settlement; these are known as perceptual traps
. Theoretical and empirical studies have shown that errors made in judging habitat quality can lead to population declines or extinction. Such mismatches are not limited to habitat selection, but may occur in any behavioral context (e.g. predator avoidance, mate selection, navigation, foraging site selection, etc.). As such ecological traps are a subset of the broader phenomena of evolutionary traps.
As ecological trap theory developed, researchers have recognized that traps may operate on a variety of spatial and temporal scales which might also hinder their detection. For example, because a bird must select habitat on several scales (a habitat patch, an individual territory within that patch, as well as a nest site within the territory), traps may operate on any one of these scales. Similarly, traps may operate on a temporal scale so that an altered environment may appear to cause a trap in one stage of an organism’s life, yet have positive effects on later life stages. As a result, there has been a great deal of uncertainty as to how common traps may be, despite widespread acceptance as a theoretical possibility. However, given the accelerated rate of ecological change driven by human land-use change, global warming, exotic species invasions, and changes in ecological communities resulting from species loss ecological traps may be an increasing and highly underappreciated threat to biodiversity.
A recent addition to the literature on ecological traps provides guidelines for demonstrating the existence of an ecological trap. A study must show a preference for one habitat over another (or equal preference) and that individuals selecting the preferred habitat (or equally preferred habitat) have lower fitness (i.e., experience lower survival or reproductive success). To date, there appear to be few well-documented examples of ecological trap, but this paucity may, in part arise from the practical difficulty of demonstrating habitat preference in wild organisms. One study that was successful was able to show that Indigo Bunting
s preferred nesting in “winged” patches (with two narrow corridors projecting from opposite ends of the patch) over rectangular patches, despite a higher rate of nest predation. The authors found a higher percentage of older, presumably dominant male Indigo Buntings in the winged patches. The preference for the patches with more edge, combined with its much lower nest success rate, indicated that these patches were indeed ecological traps.
Because ecological and evolutionary traps are still very poorly understood phenomena, many questions about their proximate and ultimate causes as well as their ecological consequences remain unanswered. Are traps simply an inevitable consequence of the inability of evolution to anticipate novelty or react quickly to rapid environmental change? How common are traps? Do ecological traps necessarily lead to population declines or extinctions or is it possible that they may persist indefinitely? Under what ecological and evolutionary conditions should this occur? Are organisms with certain characteristics predisposed to being "trapped"? Is rapid environmental change necessary to trigger traps? Can global warming, pollution or exotic invasive species create traps? Embracing genetic and phylogenetic approaches may provide more robust answers to the above questions as well as providing deeper insight into the proximate and ultimate basis for maladaptation in general. Because ecological and evolutionary traps may lead to population declines, traps are an important research priority for conservation scientists. Given the rapid current rate of global environmental change, traps may be far more common that is realized and it will be important to examine the proximate and ultimate causes of traps if management is to prevent or eliminate traps in the future.
Environmental change
Environmental change is defined as a change or disturbance of the environment by natural ecological processes, and is described in the following articles:*Climate change*Environment...
leads organisms to prefer to settle in poor-quality habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s.
The concept stems from the idea that organisms that are actively selecting habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
must rely on environmental cues to help them identify high quality habitat. If either the habitat quality or the cue changes so that one does not reliably indicate the other, organisms may be lured into poor quality habitat. More specifically, traps are thought to occur when the attractiveness of a habitat increases disproportionately relative to its value for survival and reproduction. The result is preference of falsely attractive habitat and a general avoidance of high-quality but less-attractive habitats. While the demographic consequences of this type of maladaptive habitat selection behavior have been explored in the context of the sources and sinks, ecological traps are an inherently behavioral phenomena of individuals. The ecological trap concept was introduced in 1972 by Dwernychuk and Boag and the many studies that followed suggested that this trap phenomenon may be widespread due to anthropogenic habitat change.
As a corollary, novel environments may represent fitness opportunities that are unrecognized by native species if high-quality habitats lack the appropriate cues to encourage settlement; these are known as perceptual traps
Perceptual trap
A perceptual trap is an ecological scenario in which environmental change, typically anthropogenic, leads an organism to avoid an otherwise high-quality habitat...
. Theoretical and empirical studies have shown that errors made in judging habitat quality can lead to population declines or extinction. Such mismatches are not limited to habitat selection, but may occur in any behavioral context (e.g. predator avoidance, mate selection, navigation, foraging site selection, etc.). As such ecological traps are a subset of the broader phenomena of evolutionary traps.
As ecological trap theory developed, researchers have recognized that traps may operate on a variety of spatial and temporal scales which might also hinder their detection. For example, because a bird must select habitat on several scales (a habitat patch, an individual territory within that patch, as well as a nest site within the territory), traps may operate on any one of these scales. Similarly, traps may operate on a temporal scale so that an altered environment may appear to cause a trap in one stage of an organism’s life, yet have positive effects on later life stages. As a result, there has been a great deal of uncertainty as to how common traps may be, despite widespread acceptance as a theoretical possibility. However, given the accelerated rate of ecological change driven by human land-use change, global warming, exotic species invasions, and changes in ecological communities resulting from species loss ecological traps may be an increasing and highly underappreciated threat to biodiversity.
A recent addition to the literature on ecological traps provides guidelines for demonstrating the existence of an ecological trap. A study must show a preference for one habitat over another (or equal preference) and that individuals selecting the preferred habitat (or equally preferred habitat) have lower fitness (i.e., experience lower survival or reproductive success). To date, there appear to be few well-documented examples of ecological trap, but this paucity may, in part arise from the practical difficulty of demonstrating habitat preference in wild organisms. One study that was successful was able to show that Indigo Bunting
Indigo Bunting
The Indigo Bunting, Passerina cyanea, is a small seed-eating bird in the family Cardinalidae. It is migratory, ranging from southern Canada to northern Florida during the breeding season, and from southern Florida to northern South America during the winter. It often migrates by night, using the...
s preferred nesting in “winged” patches (with two narrow corridors projecting from opposite ends of the patch) over rectangular patches, despite a higher rate of nest predation. The authors found a higher percentage of older, presumably dominant male Indigo Buntings in the winged patches. The preference for the patches with more edge, combined with its much lower nest success rate, indicated that these patches were indeed ecological traps.
Because ecological and evolutionary traps are still very poorly understood phenomena, many questions about their proximate and ultimate causes as well as their ecological consequences remain unanswered. Are traps simply an inevitable consequence of the inability of evolution to anticipate novelty or react quickly to rapid environmental change? How common are traps? Do ecological traps necessarily lead to population declines or extinctions or is it possible that they may persist indefinitely? Under what ecological and evolutionary conditions should this occur? Are organisms with certain characteristics predisposed to being "trapped"? Is rapid environmental change necessary to trigger traps? Can global warming, pollution or exotic invasive species create traps? Embracing genetic and phylogenetic approaches may provide more robust answers to the above questions as well as providing deeper insight into the proximate and ultimate basis for maladaptation in general. Because ecological and evolutionary traps may lead to population declines, traps are an important research priority for conservation scientists. Given the rapid current rate of global environmental change, traps may be far more common that is realized and it will be important to examine the proximate and ultimate causes of traps if management is to prevent or eliminate traps in the future.
Polarized light pollution
Polarized light pollution is perhaps the most compelling and well-documented cue triggering ecological traps. Orientation to polarized sources of light is the most important mechanism that guides at least 300 species of dragonflies, mayflies, caddisflies, tabanid flies, diving beetles, water bugs and other aquatic insects in their search for the water bodies they require for suitable feeding/breeding habitat and oviposition sites. Because of their strong linear polarization signature, artificial polarizing surfaces (e.g., asphalt, gravestones, cars, plastic sheeting, oil pools, windows) are commonly mistaken for bodies of water. Light reflected by these surfaces is often more highly polarized than that of light reflected by water, artificial polarizers can be even more attractive to polarotactic aquatic insects than a water body and appear as exaggerated water surfaces acting as supernormal optical stimuli. Consequently, dragonflies, mayflies, caddisflies and other water-seeking specieis actually prefer to mate, settle, swarm and oviposit upon these surfaces than available water bodies.Further reading
- Caswell, H. 2001. Matrix population models: Construction, analysis, and interpretation. 2nd edition. Sinauer. Sunderland, Mass., USA.
- Williams, B. K., J. D. Nichols, and M. J. Conroy. 2001. Analysis and management of animal populations. Academic Press. San Diego, USA.