Clocks and Alternative Lifestyles

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Science  01 Sep 2000:
Vol. 289, Issue 5484, pp. 1435
DOI: 10.1126/science.289.5484.1435b

North American cicada nymphs (Magicicada spp) spend 13 or 17 years underground, depending on species, before emerging synchronously to spend their final few weeks as reproducing adults. This extraordinary lifestyle has been a subject of research for over a century.

Karban et al. have found that cicadas track time by counting the seasonal cycles of vegetation, rather than years. Cicada nymphs feed on root xylem sap, and the amount of nutrient obtained varies according to season. Manipulating the seasonal cycle of host peach trees (double cropping) induced early metamorphosis of nymphs into adults.

Two studies examine speciation. Simon et al. report evidence for an “instantaneous” speciation event by a shift in reproductive timing (life cycle) of 17-year cicadas; a 13-year lineage, recently derived from a 17-year lineage, now overlaps geographically with a genetically distinct, pre-existing 13-year lineage. Marshall and Cooley find that male mating calls and female preferences differ between two 13-year species where they overlap, reinforcing reproductive isolation, yet the calls of 13-year and 17-year species are indistinguishable. — AMS

Ecol. Lett.3, 253 (2000); Evolution54, 1326 (2000); Evolution54, 1313 (2000).

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