Nancy A. Moran: Cycle

“Heteroecy appears to be a consequence of the seasonal polymorphism of aphids, which causes some morphs (the fundatrices) to be more evolutionarily constrained than others (the summer females) in their abilities to acquire hosts. Some aphid lineages have escaped this constraint by replacing the ancestral fundatrix morph and remaining all year on former secondary hosts, thus becoming secondarily autoecious. Most of the large and species-rich groups of Aphidinae on herbaceous angiosperms probably are derived from ancestors showing such life-cycle reduction.”

Nancy A. Moran

[The Evolution of Host-Plant Alternation in Aphids: Evidence for Specialization as a Dead End, The American Naturalist, 132, 5, November 1988, 681–706, 10.1086/284882]

Life , Appearance , Summer , Season

“Life cycles that incorporate discrete, morphologically distnct phases predominate among animals.”

Nancy A. Moran

[Annual Review of Ecology and Systematics, Adaptation and Constraint in the Complex Life Cycles of Animals, 25, 573–600, November 1994, 10.1146/annurev.es.25.110194.003041]

Life , Animals

“The aphid Pemphigus betae typically shows a complex life cycle, with annual alternation between cottonwood trees, where it forms leaf galls, and herbaceous plants, where it lives on roots. Distinct phenotypes are associated with each phase. In a population in Utah, aphid clones vary in their tendencies to undergo the cottonwood phase of the life cycle, with certain clones rarely producing the winged migrants that initiate the cottonwood phase.”

Nancy A. Moran

[Phenotype fixation and genotypic diversity in the complex life cycle of the aphid Pemphigus betae, June 1991, Evolution, 45, 4, 957–970, 10.1111/j.1558-5646.1991.tb04363.x]

Life , Tree

“Biogeographical and paleobotanical evidence suggests that the aphid subtribe Melaphidina has been associated with its sumac host plant since the early Eocene when these plants were continuously distributed across the Bering land bridge. Transfer experiments indicate that the American species, Melaphis rhois, shows an unusual complex life cycle, similar to that known in Chinese melaphidines, with some generations feeding on mosses as alternate host plants. As with the association with sumac, this complex life cycle may have been established in the melaphidine lineage before the southward retreat of sumac from Alaska 48 million years ago. This example suggests that the interactions and life histories shown by modern populations may be determined, in large part, by evolutionary commitments made in the distant past.”

Nancy A. Moran

[A 48-Million-Year-Old Aphid--Host Plant Association and Complex Life Cycle: Biogeographic Evidence, 10.1126/science.245.4914.173, Science, 245, 4914, 173–175, 14 July 1989, 17787877]

Life , History , Distant , Past