Scientists currently have contrasting views on the correlation between a biome’s diversity and its vulnerability to invasive species. Some believe that an environment with many species has higher competition for resources and will discourage invaders, while others believe that if many species can already share a niche in the environment an invasive one will logically be able to as well. Dzialowski (2010) tested these theories with the invasive plankton, Daphnia lumholtzi.
D. lumholtzi is invasive to North American lakes and rivers, so three native Daphnia species were raised both separately and in combination, then D. Lumholtzi was introduced to each test. While the number of species in the test did not directly correlate to the population of D. lumholtzi, one of the native species, D. magna, lowered the D. lumholtzi populations significantly in all tests where it was present. Dzialowski concludes that certain native species are more capable of outcompeting exotics, and that species-rich environments are more likely to contain such a species.
Dzialowski, A.R., 2010. Experimental effect of consumer identity on the invasion success of a non-native cladoceran. Hydrobiologia 652: 139-148.
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Elser from Arizona State University and his team conducted a study examining the distribution and competitive effects of the invasive zooplankton Daphnia lumholtzi in Arizona. First detected in Texas in 1990, this species indigenous to Africa, Australia, and India has spread throughout the midwestern and southern United States.
Elser conducted a field sampling of 12 reservoirs in central Arizona and a competition experiment involving water from Canyon Lake. The samplings demonstrated that D lumholtzi was dispersed across central Arizona in various watersheds, some with a greater percentage of the exotic zooplankton than others (ranging from none to more than the native species). This proves the persistence of this specie’s invasion in Arizona. The competition experiments found that the production of both species (D lumholtzi and native D pulex) decreased when both were present at the lake. Also, D lumholtzi reduced total zooplankton production. Therefore, communities dominated by D lumholtzi are expected to be less fertile and retain lower biomass.
Research on this detrimental species will continue because it impacts plankton communities and fish production since their spination renders them inedible.
Resource: Journal of the Arizona-Nevada Academy of Science Vol. 34(2): pp 89-94. (2002)
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