What does the male function hypothesis claim?

Paternal, rather than maternal, fitness consequences of reproductive traits are the lynchpin in many hypotheses about reproductive evolution in hermap hroditic angiosperms. These hypotheses often differ in their predictions, s o that supporting or contradictory evidence for one hypothesis may not refl ect similarly on another, even though both may be referred to as 'the male function hypothesis'. We provide graphical representations of four male fun ction hypotheses from the recent literature in order to highlight their dif ferences. We offer and explain two recommendations to reduce ambiguity in t erminology: (1) male function hypotheses should address the evolution of ex cess flowers per se, rather than total flower number, which is usually high ly plastic in modular organisms with open growth form; and (2) attention mu st be given to whole plant fitness, rather than fitness per flower or per i nflorescence. In empirical studies, we recommend the use of path analysis t o dissect the multiple pathways (through both male and female function) by which selection may act on excess flower number.