Radiation, biological diversity and host-parasite interactions in wild roses, rust fungi and insects

Abstract

One of the major tasks in evolutionary ecology is to explain how interspecific interactions influence the dynamics of evolutionary processes and enable radiation and genesis of biological diversity. The bewildering diversity of dog roses is generated by a heterogamous reproductive system. Genetic distance between rose taxa was analysed as base line for the explanation of subsequent radiation of the two host-dependent parasite groups, rust fungi and insects. We investigated the interaction between each host-parasite system and between the parasite groups. We learned that the functional diploidy at the meiotic level is not reflected at the phenotypic level in dog roses. The phytophagous insect community shows only minor differences in composition on different rose species. These invertebrates seem not to be negatively affected by glandular trichomes, but for the rust fungi, Phragmidium glandular trichomes matter, because they are negatively correlated with the infection. The abundance of two rose specialists, the rose hip fly Rhagoletis alternata Fall. and the rose gall wasp Diplolepis rosae L., differed on rose species, but Rh. alternata showed neither any genetic differentiation on host species nor geographical differentiation. As a basic result, we detected that genetic diversity of dog roses is not translated into a host-specific radiation of the parasites. We assume that intensive reticulate evolution of dog roses prevents co-speciation.