Table 5.

Putative plesiomorphic and apomorphic traits considered liable for adaptive radiation of the viviparous gyrodactylids.

Character change (See Fig. 1)	Character	Evolutionary status (viviparous clade)	Relative adaptive advantage
A	Ectoparasitism	Symplesiomorphic	Direct access to new hosts
A	Monoxenic life cycle	Symplesiomorphic	Less constraint on host switching
B	Loss of oncomiracidium	Symplesiomorphic	Increased survival of offspring; quick maturation
C	Preadult/adult transmission	Symplesiomorphic	Reduced mortality during transmission
D	Progenetic development	Apomorphic	Accelerated reproductive activity
D	Loss of sticky egg*	Apomorphic	Release of constraints associated with host groups
D	Hyperviviparity	Apomorphic	Accelerated establishment of reproductively active infrapopulation
D	Protogyny	Apomorphic	Accelerated maturation and reproductive activity
D	Parthenogenesis	Apomorphic	Release of required exchange of gametes when population levels are small; colonization of new host accomplished by single worm

^* A consequence of development of hyperviviparity.