Document: RAL-3-56-11

Morphological defenses against fish predation - A key factor for the success of an invading species?

TOLLRIAN, R.*

Ludwig-Maximilians-Universität, München, Germany ¹

Abstract:
A remarkable feature of cladocerans is their morphological plasticity. Daphnia lumholtzi is the cladoceran species which forms the most pronounced helmets and tail spines. Its native range are tropical and subtropical lakes in East Africa, Australia, and the Indian subcontinent. However it appeared in Texas in 1990 and has since spread to many North American lakes and stream systems. Biological invasions focus the attention of scientists both on the conservation issues and the chance to study non-equilibrium competitive interactions and the factors which allow for successful invasions of non-native species. Helmets and tail spines in D. lumholtzi are inducible by chemicals associated with the presence of fish. Different clones isolated from North America exhibit a surprisingly large clonal diversity in their ability to form helmets, ranging from non-helmeted, non-inducible clones through inducible clones to clones with permanent, large helmets. Predation experiments with both morphs of D. lumholtzi showed that the helmets act as defense against both small and larger fish. Additionally the helmets offer protection against invertebrate predation. D. lumholtzi is the only cladoceran species so far which forms distinct inducible morphological defenses against fish predators. This defense is an advantage compared to native cladoceran species and is possibly an important factor behind its successful invasion into North America.

Keywords: phenotypic plasticity, inducible defenses, biological invasions, fish predation, predator - prey interactions, daphnia lumholtzi

This abstract is being presented at: 1:30 PM in session:
Oral Session #48: Anti-Predator Responses: Fish to Sagebrush.