Metamorphosis & food resources

A very interesting article, "Study: Ecological effects of biodiversity loss underestimated" ^[1]that could change the way we consider the conservation of biodiversity. 

This study demonstrates that the "conventional wisdom" of saving 2 or 3 food resources of a species may not be satisfactory.  Those species that go through metamorphosis, a change of body form and physiology, exploit different food resources at each stage. Dr. Rudolf explains that as little as 10% overlap may exist between metamorphic forms.

Interestingly enough, metamorphosis is not a topic in IB Biology!

Metamorphosis has long been described in ecology as one mechanism by which a species partitions resources in the ecosystem  so as to reduce competition between adults and young forms.  Insects exhibit metamorphosis as either complete : egg, larva, pupa, adult or incomplete : egg, 1 or more larval stages, adult.  Crustaceans, amphibians, and many fish also go through metamorphic changes.

Frogs, for example seen in the image to the right, begin as eggs laid in watery environments.  The eggs hatch into tadpoles or larval frogs which are vegetarians.  This life form scrapes algae from under water surfaces.  As the tadpoles develop limbs and lungs, they move from purely aquatic to amphibian life styles.  Young and adult frogs are carnivorous, eating insects, worms and other animals on land and in the water.  Thus the various life forms do not compete for the same food resources, thus ensuring enough food for each stage. 

What the article focuses on is what might happen if the diversity of the insects that the adult frogs consume rapidly disappears.  Obviously, the species will not be able to reproduce.  Likewise, if the water ecosystem is changed such that the algae cannot grow, the larval forms will not develop to adults.

A corrollary issue would be the impact on biodiversity changes in the ranges of migrating species.  Consider the Northern Hemisphere bird species that winter in equatorial regions.  How would these birds gain enough reserves for them to return to breed the next summer?  This effect compounds as the birds are part of the food webs in the northern regions as predators and prey, thus impacting on many other species.