Application of diallel analysis to experiments in plant competition

Abstract

Graphical and statistical analyses based on the methods of DURRANT (1965) are applied to data on plant competition experiments previously presented by WILLIAMS (1962) and MCGILCHRIST (1965) and to new data from a comparable experiment in barley.The primary objectives of the analysis are to determine: 1. whether the differences between species grown together are a function of the differences between them when grown separately (beta competition), (2) whether the individual species are uniformly increased or decreased when grown with the other species (alpha competition), (3) which species influence the other species most and which species are influenced most by other species, (4) to what extent the change of one species results in a compensating change in the species grown with it, (5) whether the mixtures give more or less yield than the unmixed species.Data from both experiments are similar in showing large competitive effects in their reciprocal differences which are compensating, the larger species increasing and the smaller decreasing, but whereas the one could be interpreted in terms of beta competition and the mixture means tended to the smaller species, the other could only be interpreted in terms of alpha competition, and the mixture means tended towards the larger species. It is possible that the differences may be a reflection of the environmental differences imposed by the pot culture of the first, and the field plot conditions of the second. INTRODUCTIONThe plant breeder is required to evaluate the performance of species and species combinations on the field scale, his ultimate aim being the successful exploitation of environmental resources for crop and stock production. He is particularly concerned with the manipulation of density in order to obtain optimum yields in pure stands and also in the performance of mixtures of different varieties from the same, or from different species, in studying the interactions of mixed populations it has been customary to grow the species or varieties together in pairs or higher groupings and to compare their performance in mixtures with that of the components grown alone. A most useful layout from an experimental standpoint is to grow the varieties or strains in all possible pair combinations. Such a competition "diallel" may be likened to a genetic diallel table where the species grown alone e.g. A and B correspond to the parental genotypes, and the species grown in mixtures, e.g. AB, correspond to the F 1 crosses. In each mixture both the difference between A and B (the reciprocal

Seedling competition between native cottonwood and exotic saltcedar: implications for restoration

“…As potential competitors, cottonwood and saltcedar have similar requirements for germination (Horton et al 1960), however, following recruitment, the two species have different growth dynamics with cottonwoods often growing more rapidly following germination (Merkel and Hopkins 1957;Horton et al 1960;Fenner et al 1984). Based on theories of plant competition, plants with higher growth rates should be competitively superior to plants with slower growth rates, because of greater resource access and utilization (Grime 1977;Goldberg and Landa 1991).…”

Interspecific Competitive Interactions and the Maintenance of Genotypic Variation within Two Perennial Grasses

“…Previous studies of genotypic competition have focused on con specific competitive interactions between different lines of crop plants. The evidence suggests that: 1) different lines do differ in competitive performance, 2) the performance of different lines is a function ofa particular association of neighboring genotypes, and 3) overcompensation, although uncommon, does occur (Sakai, 1955(Sakai, , 1961(Sakai, , 1965Norrington-Davies, 1967;Allard and Adams, 1969;Trenbath, 1974 and references therein;Trenbath, 1975). Overcompensation has been reported for mixtures of grasses (de Wit, 1961;de Wit and van den Bergh, 1965), grasses and legumes (Berendse, 1983), and for two annual herbs (Martin and Harding, 1981).…”

A Statistical Study of Mate Choice: Sexual Selection in a Plethodontid Salamander (Desmognathus ochrophaeus)

“…Using this approach to analyze male-female courtship encounters, we can evaluate the importance of separate terms for male effects, females effects, and male-female interactions while controlling for variation associated with other factors such as sequence of mates or season. Similar symmetrical designs are used by quantitative geneticists to analyze pairwise crosses between a series of inbred strains (diallel crosses) and by ecologists and behavioralists to analyze competition or behavioral interactions between strains or species (competitional diallels) (Jinks, 1954;Hayman, 1954;Griffing, 1956;McGilchrist, 1965;Breese and Hill, 1973;Hay, 1974;Norrington-Davies, 1967;Durrant, 1965;McClintock and Adler, 1978). Crossley and McDonald (1979) used individuals from a single strain of Drosophila in a diallel design to study courtship behavior.…”