Wednesday, May 06, 2009

Eco reads

A first rate essay on reproductive timing and interdependencies among species in nature.

The winter moth caterpillar is partial to the leaves of apple and cherry trees, but any deciduous tree will do. Around Arnhem, in the Netherlands, it feeds on oak leaves. But the caterpillar has a delicate timing problem: it must hatch just when the new leaf buds burst open, revealing the young leaves. If it hatches too early, or too late, it may starve. Too early, and there are no leaves to eat; too late, and increased tannin concentrations make the leaves less digestible. Either circumstance leads to a lower weight at pupation or to a longer larval period, resulting in a higher probability of the caterpillar’s being eaten. The date of the oak bud burst is cued largely by spring temperatures and can vary considerably from year to year. There is strong selection pressure on the winter moth to synchronize its egg hatching to the oak bud burst. But the moth’s timing mechanism is determined by the relationship between frost-days (below 0°C, or 32° F) and those days with a temperature above 3.9°C (39° F), rather than mean temperature alone.
... Those organisms that succeed will be the ones with the flexibility to change and adapt to the new temporal regime faster than the speed of the changes in seasonal timing. Some species may migrate poleward. Others may move to higher altitudes. But complete communities will not simply move north or south in synchrony with changing temperatures. Instead, the blend of plants and animals will change. Climate change could create ecosystems that are unknown today. We do not know what plants and animals they will contain. We do not know what will result when the temporal webs that connect plants and animals are broken. It may be that generations to come will see nature’s wonders. But it is more likely that much of the awe and wonder that obtain from the diversity of life on earth that we know at present will be lost.

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