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Geology topics

John M. Emlen

Publications and source records attributed to John M. Emlen.

20 records · Page 2Linked to original sources

Interaction assessment II: A tool for population and community management

To successfully preserve or manage a species, we must understand how the community of which it is a part functions. We must know how environmental alterations affect the fitness not only of the species of interest, but also that of its competitors, predators, and prey; and we must know the form and intensity of the pertinent inter-species interactions. Interaction Assessment (INTASS) is a non-manipulative approach to constructing quantitative expressions for fitness, written as functions of measured environmental variables including local population densities of conspecifics and other interacting species. We applied this approach to, and evaluated its consistency from, data on the European land snail (Cepaea nemoralis), American eel (Anguilla rostrata), longnosed and blacknosed dace (Rhinichthys cataractae and R. atratulus), and small-mouth bass (Micropterus dolomieu) until data sets can be compiled on more typically studied vertebrates. INTASS analyses on key species of a community can provide the tools for predicting community-wide ramifications of environmental disturbances. They also can permit the planned manipulation of relative species abundances through habitat alteration.

Journal of Wildlife Management↗

Heterosis and outbreeding depression: A multi-locus model and an application to salmon production

Both artificial propagation and efforts to preserve or augment natural populations sometimes involve, wittingly or unwittingly, the mixing of different gene pools. The advantages of such mixing vis-à-vis the alleviation of inbreeding depression are well known. Acknowledged, but less well understood, are the complications posed by outbreeding depression. This paper derives a simple model of outbreeding depression and demonstrates that it is reasonably possible to predict the generation-to-generation fitness course of hybrids derived from parents from different origins. Genetic difference, or distance between parental types, is defined by the drop in fitness experienced by one type reared at the site to which the other is locally adapted. For situations where decisions involving stock mixing must be made in the absence of complete information, a sensitivity analysis-based conflict resolution method (the Good-Bad-Ugly model) is described.

Fisheries Research↗