Alex Collazo
March 31, 2011
Literature Summary #5
Takimoto, Gaku, David A. Spiller, and David M. Post. 2008. ECOSYSTEM SIZE, BUT NOT
DISTURBANCE, DETERMINES FOOD-CHAIN LENGTH ON ISLANDS OF THE BAHAMAS. Ecology
89:3001–3007. [doi:10.1890/07-1990.1]
Takimoto is with Department of Biology, Faculty of Science, Toho University, Funabashi, Chiba
274-8510 Japan and Department of Ecology and Evolutionary Biology, Yale University, New
Haven, Connecticut 06511 USA
Spiller is with Section of Evolution and Ecology, One Shields Avenue, University of California,
Davis, California 95616-8755 USA
Post is with Department of Ecology and Evolutionary Biology, Yale University, New Haven,
Connecticut 06511 USA
1) The research problem or question?
How does the size of a terrestrial ecosystem affect food chain length and does that have a
larger or smaller impact compared to disturbances?
2) The general background knowledge leading up to this study?
Strong disturbances put pressure upon food chain lengths and may be a reason as to why a
food chain is short; a food chain in an environment free of disturbances theoretically can
grow to be much larger. The larger the ecosystem, the greater the amount of species
present along with resources and aspects like predator/prey are more dynamic. The
amount to which each plays a role in food chain length is researched.
3) The methods used by the investigators?
A few islands in the Bahamas were used as the experimental grounds. In order to test for
disturbance, islands subjected to storm surges and islands protected from storm surges
were used as comparisons. To test for ecosystem size, islands of varying sizes (small,
medium and large) were compared. Two animals in particular top the food web in these
environments, the orb spiders and Anolis lizards. They are both omnivores and consume
arthropods. Isotope samples were taken from the collected specimens and used as a basis
for comparison in order to view the differences amongst the species in the different
islands.
4) The results of the study?
It was found that ecosystem size had a strong effect upon the size of the food chain, with
the food chain increasing one full trophic level from the smallest to largest island (Seen in
Figure 1). Disturbances had no effect on the food chain length. The two though did have an
effect upon the identity of the apical species in the food chains.
FIGURE 1
5) What are the weaknesses of the study?
The study seems to focus on disturbances to an ecosystem on a relatively minor level but
fails to test it on a larger scale, such as huge natural disasters or virulent epidemics
sweeping through the food chain. These could possibly affect food chain lengths but were
not tested- rather understandably since these conditions are difficult to reproduce.
6) What we learned new from the study?
It was discovered that food chain size was affected by the scope of the ecosystem and not
by disturbances to the ecosystem; although the two did effect the composition of the food
chain, mainly in the trophic level.
Article source: http://www.esajournals.org/doi/full/10.1890/07-1990.1