SREL Reprint #0817
Disruptive Selection:
A Tall Color Polymorphism in Acris Tadpoles in Response to Differential
Predations
Janalee
P. Caldwell
Abstract
Previous workers have noted that cricket frog
tadpoles of the genus Acris have black tail tips.
My initial collections of Acris crepitans tadpoles from
various localities in Kansas revealed a polymorphism in tail color associated
with habitat type: ponds primarily
have black-tailed tadpoles, whereas lakes and creeks have mostly plain-tailed
forms. Collections of potential
predators from these localities showed that the black-tailed pond populations
co-occur with a high density of the aeshnid dragonfly larva, Anax junius,
and led to the hypothesis that the black tail functions as a deflection
mechanism to divert he attach of the Anax larva to the tail of the
tadpole and away from the more vulnerable head and body.
Plain-tailed tadpoles are found primarily in lakes and creeks where fish
are the major predators. Tail
damage data from natural populations and data from predator – prey experiments
support the hypothesis. Disruptive selection is cost likely the mechanism
responsible for maintenance of this polumorphism.
Gene exchange occurs as adult frogs migrate from one habitat type to
another, but selection on tadpoles by different predator regimes is habitat
specific.
SREL Reprint #0817
Caldwell, J.P. 1982. Disruptive selection: a tail color
polymorphism in Acris tadpoles in response to differential
predation. Canadian Journal of Zoology 60:2818-2827.
