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N Knowlton

Publications and source records attributed to N Knowlton.

22 records · Page 2Linked to original sources
PubMed1982

Graft rejection in sponges. Genetic structure of accepting and rejecting populations.

Graft rejection frequencies in a population of the sponge Ectyoplasia ferox are reported in relation to the complexity of the histocompatibility system in this species. The frequency of graft acceptance is high but we show that, despite assumptions in the literature to the contrary, this does not imply that sponges accepting each other's grafts are genetically identical. This paper reports that graft-accepting pairs of sponges can have dissimilar plasmalemmal proteins. In addition, a theoretical analysis is presented of the types of histocompatibility systems that would account for the present results and those of others. We concluded that there is no evidence that sponges have highly polymorphic histocompatibility systems. The paper also reports on the histology of graft rejection and discusses some of the ecological relevance of the findings.

Alleles↗
PubMed1979

An evolutionarily stable strategy approach to indiscriminate spite.

AN individual behaves spitefully when it harms itself in order to harm another individual more(1). Hamilton(1,2) predicted that spite may evolve if it is expressed only in those encounters that occur between individuals of less than average relatedness. More recently Verner(3) suggested that territory size may become super-optimal because of a selective advantage arising from the spiteful exclusion of others from limited resources. His model is essentially different from Hamilton's in that spite is directed at individuals indiscriminately with respect to relatedness. Recently Rothstein(4) has shown analytically that the initial spread of spiteful traits will be very slow in all but the smallest populations. He also argued verbally that indiscriminate spite can never be evolutionarily stable even if it should spread (see also Davies(5)). The question of evolutionary stability is clearly important, but its resolution requires an analytical approach. We report here an approach based on Maynard Smith's(6) concept of the evolutionarily stable strategy (ESS), a strategy which, when common, does better than any alternative strategy played by a rare mutant. We show that spite can be an ESS, but that the magnitude of spite will be small in large populations.

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