title: A "crown of thorns" is an inducible defense that protects Daphnia against an ancient predator.
abstract: Genetic data has become an essential part of ecological studies, because the analyses of diversity within and among natural populations may grant access to previously overlooked ecological and evolutionary causalities, especially among cryptic species. Here, we present an example of how phylogenetic analysis of molecular data obtained within a DNA barcoding study, in combination with morphological and ecological data from the field and laboratory experiments, unraveled a striking predator-prey interaction between aquatic organisms. The "crown of thorns," a conspicuous morphological feature among water fleas of the Daphnia atkinsoni species complex (Crustacea: Cladocera), is considered to represent a species-specific trait. However, our study, initiated by the analysis of sequence variation in 2 mitochondrial genes, shows that this feature is phenotypically plastic and is induced by chemical cues released by Triops cancriformis, the tadpole shrimp (Notostraca). The trait acts as an effective antipredator defense, and is found in several Daphnia lineages coexisting with notostracans. These facts suggest that the "crown of thorns" evolved in coexistence with this ancient predator group.
authors.affiliation: Department of Ecology, Faculty of Science, Charles University, Vinicná 7, CZ-12844 Prague, Czech Republic.
authors.forename: Adam
authors.initials: A
authors.lastname: Petrusek
authors.forename: Ralph
authors.initials: R
authors.lastname: Tollrian
authors.forename: Klaus
authors.initials: K
authors.lastname: Schwenk
authors.forename: Andreas
authors.initials: A
authors.lastname: Haas
authors.forename: Christian
authors.initials: C
authors.lastname: Laforsch
mesh_terms: D000818:Animals; D005075:Biological Evolution; D019070:Cell Lineage; D033361:Cladocera; D004272:DNA, Mitochondrial / Q000378:metabolism; D003621:Daphnia / Q000033:anatomy & histology / Q000378:metabolism* / Q000502:physiology*; D004463:Ecology; D003576:Electron Transport Complex IV / Q000378:metabolism; D020387:Food Chain; D006801:Humans; D008953:Models, Anatomic; D008954:Models, Biological; D010641:Phenotype; D010802:Phylogeny; D011235:Predatory Behavior
chemical_list: D004272:DNA, Mitochondrial; D003576:Electron Transport Complex IV