Abstract Detail



Macroevolution

Sapir, Yuval [1], Bar-Lev, Yamit [1], Osmolovsky, Inna [1], Wilson, Carol [2].

Eco-geographical patterns of speciation in Royal Irises, a species complex in the course of speciation.

Speciation, the process of divergence of populations into species and the maintenance of reproductive barriers among them, is often described as a continuous dynamic process, expressed by different magnitudes of reproductive isolation (RI) among groups in various levels of divergence. The continuous nature of speciation implies that species can be found at different stages of divergence, including those that can be best viewed as a complex of incipient species. The Middle East species of the Royal irises (Iris section Oncocyclus) are a young group of species in the course of speciation that are distributed across wide ecological niches, thus providing an ideal system for studying speciation. We quantified pre- and post-zygotic reproductive barriers between eight Israeli species of this complex and estimated total reproductive isolation (RI) among them. Pre-pollination barriers tested were eco-geographic divergence, calculated as divergence of species’ potential niches, and phenological differentiation, calculated as divergence of flowering times, both in wild populations and in a common garden experiment; these barriers were major contributors to RI among species. Post-pollination RI was tested for pollen-stigma interactions, fruit set, and seeds viability, all found to have a negligible contribution to total RI. The total extent of RI was not uniform across the species complex, suggesting that species may have diverged at different rates and indicating asymmetric gene flow. Phylogenetic analyses at the species level based on one low-copy nuclear and six plastid markers revealed weak relationships between geographical distribution and genetic relatedness. In addition, we used RAD sequencing of plants from 67 populations representing the eight species and clustered populations by nucleotide polymorphism across their genomes. We found only minor divergence among species and, except Iris bismarckiana that is hypothesized to be a cultivated form, there was little clustering by species. Overall, these results support the hypothesis that Royal Irises were spread across the Levant and diverged into separate species as a result of ecological adaptation more recently. Our study in a young, recently-diverged group of species provides insights into the first steps of speciation, suggesting a key role of ecology as a pre-zygotic barrier.


1 - Tel Aviv University Botanical Garden, Tel Aviv University, Ramat Aviv, Tel aviv, , 69978, Israel
2 - University of California, University and Jepson Herbaria, Berkeley, CA, USA

Keywords:
ecological speciation
ecological niche modelling
reproductive isolation
species divergence
species complex.

Presentation Type: Oral Paper
Number:
Abstract ID:248
Candidate for Awards:None


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