Macroevolutionary patterns of male reproductive investment in a clade of parasitic hermaphrodites

The Eucestoda is particularly relevant for questions concerning reproductiv e investment in male gametes because no other parasitic group displays such diversity in testis size and number within and among species. This diversi ty has long been used as a valuable taxonomic character. but few researcher s have ever investigated its evolutionary significance. In this paper we in vestigate the evolution of testis number and size within Rhinebothroides (P latyhelminthes: Eucestoda). Our comparative, phylogenetic analysis revealed that overall allocation to male functions, as measured by relative testicu lar area,does not change within the clade, even though the packaging of tha t investment in numerous testes is highly variable within, and diverse amon g, members of the group.