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Ecological success?

Studies on fish reproduction, ants, invasive plants, and light pollution

Ecological Society of America


Maturity Matters

In "Maternal Age is a determinant of larval growth and survival in a marine fish, Sebastes melanops," scientists Steven Berkeley,* Colin Chapman* (Oregon State University) and Susan Sogard (National Marine Fisheries Service) studied larvae from 20 female black rockfish (Sebastes melanops). Their experiment showed that larvae from the oldest female rockfish not only grew up to three times faster than offspring from younger mothers, but also survived starvation for a longer time period. The authors suggest that changes in age-structure due to heavy fishing may "have severe consequences for long-term sustainability of fish populations."

*Berkeley currently at University of California, Santa Cruz; Chapman at S. P. Cramer and Associates, Oregon.

Size Matters

In "Ant body size predicts the dispersal distance of ant-adapted seeds: implications of small-ant invasions" J. H. Ness and J. L. Bronstein (University of Arizona, Tucson), A. N. Anderson (CSIRO Tropical Ecosystems Research Centre, Northern Territory, Australia) and J. N. Holland (Rice University) describe the negative effects invasive smaller ants have on plant reproduction. According to the authors, exotic ants disrupt native ant-seed dispersal patterns, disturbing mutualistic patterns, communities, and ecosystems.

Ecological Monographs

Successful Invasions

Native to Europe, Asia, and North Africa, St. John's wort was first introduced to the United States in 1793 in Lancaster, Pennsylvania, spreading to the West Coast by the early 1900's. By 1945, St. John's Wort became so abundant in the western US it became the first plant in which biocontrol was attempted, through the introduction of a beetle. Yet, not all exotic species introduced become invasive. What makes some exotic species one successful and others fail has never been fully understood.

In an attempt to understand the role of evolution in exotic plant invasions, John Maron (University of Montana, Missoula), Montserrat Vila (University of Barcelona, Spain), Riccardo Bommarco (Swedish University of Agricultural Sciences, Uppsala) Sarah Elmendorf (University of California, Davis) and Paul Beardsley (University of Washington, Seattle) examined whether St. John's wort evolved adaptations in its new introduced range in "Rapid evolution of an invasive plant."

The team of researchers established common gardens in California and Washington in the United States, and in Spain and Sweden. Each of the gardens contained plants collected from both native European and non-native western and central North American locations. The gardens were located in areas where St. John's wort currently occurs.

One trend observed in the study involved clinal, or physical differences due to latitude and climate, changes. The native European plant subjects showed genetic clinal variation in size, seed production, and leaf area, based on the latitude where the population originated. Similarly, plants from southern clines grew larger and reproduced more in southern gardens, and northern plants survived better than southern plants in northern gardens.

In the introduced populations, these same trends were also observed, but not necessarily in coordination with their genetic European site of origin. Based on genetic testing, populations in California living around latitude 39 N are most closely related to plants from Germany, which reside at latitude 50.73 N. Other groups contained genes from western and central North American populations, suggesting one group founded the other, or both came from similar European genetic stocks. This evidence suggests the plants are responding to conditions they encounter in their new environments.

According to the report, the researchers "found substantial molecular genetic variation among introduced St. John's wort." The introduced populations also expressed as much, and sometimes more, variability in phenotypes as well, than plants from native populations.

"Exotic plants appear to have rapidly evolved adaptations to novel conditions in their introduced range," said John Maron, lead author of the study.


Turn out those lights!

Travis Longcore and Catherine Rich (Urban Wildlands Group in California) explain the potential dangers of artificial night lighting in "Ecological light pollution." Possible pitfalls include altering natural patterns of night and day, new advantages for predators, and death of some migrating birds. The sources of ecological light pollution range from street lights to buildings "to flares on offshore oil platforms and even lights on undersea research vessels." They suggest more research on the effects of artificial night lighting on organisms and ecosystems.


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