title: Reproductive isolation between populations of Iris atropurpurea is associated with ecological differentiation.
abstract: Background and Aims Speciation is often described as a continuous dynamic process, expressed by different magnitudes of reproductive isolation (RI) among groups in different levels of divergence. Studying intraspecific partial RI can shed light on mechanisms underlying processes of population divergence. Intraspecific divergence can be driven by spatially stochastic accumulation of genetic differences following reduced gene flow, resulting in increased RI with increased geographical distance, or by local adaptation, resulting in increased RI with environmental difference. Methods We tested for RI as a function of both geographical distance and ecological differentiation in Iris atropurpurea, an endemic Israeli coastal plant. We crossed plants in the Netanya Iris Reserve population with plants from 14 populations across the species' full distribution, and calculated RI and reproductive success based on fruit set, seed set and fraction of seed viability. Key Results We found that total RI was not significantly associated with geographical distance, but significantly increased with ecological distance. Similarly, reproductive success of the crosses, estimated while controlling for the dependency of each component on the previous stage, significantly reduced with increased ecological distance. Conclusions Our results indicate that the rise of post-pollination reproductive barriers in I. atropurpurea is more affected by ecological differentiation between populations than by geographical distance, supporting the hypothesis that ecological differentiation is predominant over isolation by distance and by reduced gene flow in this species. These findings also affect conservation management, such as genetic rescue, in the highly fragmented and endangered I. atropurpurea.
authors.affiliation: The Botanical Garden, Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel.
authors.forename: Gil
authors.initials: G
authors.lastname: Yardeni
authors.affiliation: Department of Biology, University of Haifa, Oranim, Tivon, Israel.
authors.forename: Naama
authors.initials: N
authors.lastname: Tessler
authors.affiliation: Institut des Sciences de l'Evolution CNRS, IRD, University Montpellier 2, Montpellier, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Imbert
authors.forename: Yuval
authors.initials: Y
authors.lastname: Sapir
keywords: 
            Iris atropurpurea Baker; 
            Iris section Oncocyclus; Adaptive divergence; aster modelling; isolation by distance; isolation by ecology; local adaptation; post-zygotic reproductive barriers