In the graph packing problem we are given several graphs and have to map them into a single host graph G such that each edge of G is used at most once. Much research has been devoted to the packing of trees, especially to the case where the host graph must be planar. More formally, the problem is: Given any two trees T1 and T2 on n vertices, we want a simple planar graph G on n vertices such th...

BACKGROUND The associations between pathogens and their hosts are complex and can result from any combination of evolutionary events such as codivergence, switching, and duplication of the pathogen. Mycoviruses are RNA viruses which infect fungi and for which natural vectors are so far unknown. Thus, lateral transfer might be improbable and codivergence their dominant mode of evolution. Accordi...

Bark beetles (Coleoptera: Curculionidae, Scolytinae) feed and breed in dead or severely weakened host trees. When their population densities are high, some species aggregate on healthy host trees so that their defences may be exhausted and the inner bark successfully colonized, killing the tree in the process. Here we investigate under what conditions participating with unrelated conspecifics i...

Ambrosia beetles tunnel into the heartwood of trees where they cultivate and feed upon a symbiotic fungus. We assessed the effectiveness of flood stress for making Cercis canadensis L. and Cornus florida L. trees attractive to attack as part of insecticide and fungicide efficacy trials conducted in Ohio and Virginia. Since female ambrosia beetles will not begin ovipositing until their symbiotic...

Few studies have investigated the roles that plant hybridization and individual plant genotype play in promoting population divergence within arthropod species. Using nrDNA sequence information and reciprocal transfer experiments, we examined how tree cross type (i.e., pure Populus angustifolia and P. angustifolia x P. fremontii F(1) type hybrids) and individual tree genotype influence host rac...

A literature survey revealed that the semi-parasitic evergreen shrub Viscum album subsp. album (Viscaceae) has been recorded on 53 taxa of deciduous trees and shrubs (including five hybrids) in the Czech Republic,. Of the host taxa, 26 are native and 27 alien to the Czech flora. The range of hosts covers 13 families. Salicaceae (11 taxa), Rosaceae (11) and Aceraceae (7) are most represented amo...

AIM: The present study aims to investigate for the first time antitumor and antibacterial activities of Viscum album L. grown on different host trees. METHODS: Two different bioassays (antitumor and antibacterial) were performed to evaluate the biological activities of European mistletoe (Viscum album L.) plants collected from 13 different host trees (Crataegus tanacetifolia, Crataegus monogyna...