Re-creating ancient hybrid species' complex phenotypes from early-generation synthetic hybrids: three examples using wild sunflowers

Can the complex phenotypes that characterize naturally occurring hybrid species be re-created in early-generation artificial hybrids? We address this question with three homoploid hybrid species (Helianthus anomalus, Helianthus deserticola, Helianthus paradoxus) and their ancestral parents (Helianthus annuus, Helianthus petiolaris) that are phenotypically distinct and ecologically differentiated. These species, and two synthetic hybrid populations of the ancestral parents, were characterized for morphological, physiological, and life-history traits in greenhouse studies. Among the synthetic hybrids, discriminant analysis identified a few individuals with the multitrait phenotype of the natural hybrid species: 0.7%-1.1% were H. anomalus-like, 0.5%-13% were H. deserticola-like, and only 0.4% were H. paradoxus-like. These relative frequencies mirror previous findings that genetic correlations are favorable for generating the hybrid species' phenotypes, and they correspond well with phylogeographic evidence that demonstrates multiple natural origins of H. deserticola and H. anomalus but a single origin for H. paradoxus. Even though synthetic hybrids with hybrid species phenotypes are rare, their phenotypic correlation matrices share most of the same principal components (eigenvectors), setting the stage for predictable recovery of hybrid species' phenotypes from different hybrid populations. Our results demonstrate past hybridization could have generated hybrid species-like multitrait phenotypes suitable for persistence in their respective environments in just three generations after initial hybridization.

Vertical niche differentiation of ectomycorrhizal hyphae in soil as shown by T-RFLP analysis

•   Niche differentiation for different soil substrates has been proposed as a mechanism contributing to ectomycorrhizal fungal diversity. This hypothesis has been largely untestable because of a lack of techniques to study the in situ distribution of ectomycorrhizal hyphae. •   We developed a technique involving soil DNA extraction, PCR and terminal restriction fragment length polymorphism (T-RFLP) analysis for species identification to investigate the vertical distribution of fungal hyphae in four distinct layers of the forest floor (lower litter, F-layer, H-layer, and B-horizon) of a Pinus resinosa plantation. •   Fungal communities differed markedly among the four layers. Cluster analysis suggested six different patterns of resource utilization: litter-layer specialists, litter-layer generalists, F-layer, H-layer, and B-horizon species, and multilayer generalists. Known ectomycorrhizal species were found in all six clusters. •   This spatial partitioning observed among ectomycorrhizal fungi along a single, relatively simple substrate-resource gradient supports the niche differentiation hypothesis as an important mechanism contributing to ectomycorrhizal fungal diversity.