142.
Intense male–male competition for females may drive the evolution of male morphological dimorphism, which is frequently associated
with alternative mating tactics. Using modern techniques for the detection of discontinuous allometries, we describe male
dimorphism in the Neotropical harvestman
Longiperna concolor, the males of which use their elongated, sexually dimorphic legs IV in fights for the possession of territories where females
lay eggs. We also tested three predictions related to the existence of alternative mating tactics: (1) if individuals with
relatively longer legs IV (majors) are more likely to monopolize access to reproductive resources, they are expected to remain
close to stable groups of females more than individuals with relatively shorter legs IV (minors) do; (2) if minors achieve
fertilization by moving between territories, they are expected to be less faithful to specific sites; and (3) majors should
be observed in aggressive interactions more often. We individually marked all the individuals from a population of
Longiperna during the reproductive season and recorded the location of each sighting for males and females as well as the identity of
males involved in fights. Majors were more likely to have harems, and large majors were even more likely to do so. Majors
were more philopatric and all males involved in fights belonged to this morph. These results strongly suggest that the mating
tactic of the majors is based on resource defense whereas that of the minors probably relies on sneaking into the territories
of the majors and furtively copulating with females.
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