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Back to List of Background & Research Materials Assem, J. van den, H.A.J. in den Bosch & E. Prooy Melittobia COURTSHIP BEHAVIOUR:
A COMPARATIVE STUDY OF THE EVOLUTION OF A DISPLAY. Netherlands Journal of Zoology 32(4): 427 - 471. 1982. Abstract: Twenty-five batches of Melittobia (Hym., Chalcidoidea - Eulophidae) were available for a comparative study of courtship displays. Batches were crossbred to assemble them into "species"; batches were considered conspecific if interfertile. The species status of the majority was clear-cut. The outcome of some crosses led to ambiguities; the implications were discussed. Courtship displays were described and the nature of specific differences examined. Species were arranged in clusters and relative positions were discussed. We found a "relict" species (M. clavicornis) which we suppose to reflect a collection of ancestral conditions, both in its morphology and behaviour. We took its display behaviour as the starting point for further comparisons. Series of transformations were constructed. The extraordinary position of M. clavicornis made it possible to indicate the direction of transformations. The transition from a display with a continuous repetition of similar movements coupled with a periodic discharge of receptivity-inducing stimuli, to one with new elements being added underway and coupled with a single discharge at display's end is considered a major evolutionary change within the genus Melittobia. We presented a hypothesis for the origin of this development. Further important evolutionary changes refer to the timing of male willingness to copulate and to the duration of display sequences. We showed that sequence duration is largely determined by the male, which makes him independent of variable receptivity thresholds of females. In this way a male may space out successive copulations at a to-him most profitable rate. The sex ratio is extremely female-biased; one male could serve a large number of females. The spacing procedures may be necessary to avoid sperm depletion. Male pugnacity was discussed with respect to this point. We presented some speculation on the possible, ambivalent, origin of Melittobia displays. Melittobia Species Mentioned: Melittobia clavicornis, M. acasta, M. evansi (as species 3), M. digitata (as species 4), M. assemi (as species 5), M. sosui (as species 6), M. hawaiiensis (as species 7), M. nr. hawaiiensis (as species 7/8), and M. australica (as species 8). Comments: Various tables show results of confrontations of batches, quantitative data on courtship, and mating behavior of all studied species. A table shows subdivision of the genus based on behavioral criteria (represented also in figure 9). Another table compares courtship success between intact males and males with various injuries. There are three plates showing micro-scan photographs of male antennae, and photographs of males and of the male and female of different species during different phases of courtship. Figure 1 shows results of crossbreeding. Figures 2, 3 and 4 schematically represent the male and female during different courtship phases. Figure 5 schematically shows the duration characteristics of the succession of courtship cycles in Melittobia species. Figure 6 shows the behavioral characteristics used to subdivide the genus. Figure 7 shows chromosome patterns of some Melittobia species. Figure 8 shows sequential order of male leg movements while in courtship. Figure 10 diagrams the timing of key stimuli that induce female receptivity. Figures 11 to 14 are graphs of durations of courtship sequences of Nasonia vitripennis and Melittobia species. |