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Reproductive isolation Reproductive isolation and the maintenance of species boundaries Reproductive isolation is the result of the action of reproductive barriers. Alex Widmer Plant Ecological Genetics Institute of Integrative Biology Reproductive barriers are “biological properties of individuals which prevent the interbreeding of populations that are actually or potentially sympatric” (Mayr 1970). Reproductive isolation Reproductive isolation 1 1 0 Reproductive isolation Reproductive isolation between most species pairs is due to multiple pre- and postzygotic reproductive barriers Reproductive isolation Reproductive isolation between most species pairs is due to multiple pre- and postzygotic reproductive barriers Alex Widmer Reproductive isolation Floral isolation Temporal isolation Habitat isolation 0 EPSO meeting Brussels, 7 April 2009 Alex Widmer EPSO meeting Brussels, 7 April 2009 Reproductive isolation 1 1 Reproductive isolation between most species pairs is due to multiple pre- and postzygotic reproductive barriers Reproductive isolation Hybrid sterility 0 Hybrid inviability Floral isolation Temporal isolation Reproductive isolation Reproductive isolation between most species pairs is due to multiple pre- and postzygotic reproductive barriers EPSO meeting Brussels, 7 April 2009 Alex Widmer EPSO meeting Brussels, 7 April 2009 EPSO meeting Brussels, 7 April 2009 Reproductive isolation is often incomplete Habitat isolation 0 Alex Widmer EPSO meeting Brussels, 7 April 2009 Hybrid sterility Hybrid inviability Floral isolation Temporal isolation Habitat isolation Alex Widmer Species Species and species boundaries The Biological Species Concept (BSC) states that “species are groups of organisms that are reproductively isolated from other such groups” (Mayr 1942). Depending on the stage of divergence, gene-flow between groups of organisms is more or less restricted. In contrast, the “genic view of the process of speciation” emphasizes that species possess “loci of differential adaptation” (Wu 2001). Wu & Ting (2004) Nature Reviews Genetics Alex Widmer EPSO meeting Brussels, 7 April 2009 Species and species boundaries Alex Widmer EPSO meeting Brussels, 7 April 2009 Our study species - Silene Depending on the stage of divergence, gene-flow between groups of organisms is more or less restricted. Silene latifolia (White Campion) Silene dioica (Red Campion) • Short-lived, perennial herbs • Overlapping distribution ranges across much of Europe • Dioecious & diploid Depending on the species concept, species boundaries are closed or open to gene flow in some parts of the genome. • Cross-compatible • Hybrids are viable and fertile • Hybrid zones occur in nature Wu & Ting (2004) Nature Reviews Genetics EPSO meeting Brussels, 7 April 2009 Alex Widmer Hybridization and introgression EPSO meeting Brussels, 7 April 2009 EPSO meeting Brussels, 7 April 2009 Alex Widmer Population genomics Alex Widmer EPSO meeting Brussels, 7 April 2009 Alex Widmer QTL analysis Genomic islands of divergence Genomic area of high interspecific divergence colocalizes with QTLs for species differences in a Silene species pair. Introgression can be substantial elsewhere in the genome and cause porous genomes. Alex Widmer EPSO meeting Brussels, 7 April 2009 Alex Widmer EPSO meeting Brussels, 7 April 2009 Genomic islands of divergence Genomic islands of divergence Genomic areas of high interspecific divergence have also been found e.g. in - oaks (Scotti-Saintagne et al. 2004) - palms (Savolainen et al. 2006) Genomic areas of high interspecific divergence have also been found e.g. in - oaks (Scotti-Saintagne et al. 2004) - palms (Savolainen et al. 2006) and may be a common phenomenon in species pairs with incomplete reproductive isolation. www.flickr.com EPSO meeting Brussels, 7 April 2009 Alex Widmer The fact that ‘good’ species often can exchange genes is of importance in the context of - plant ecology and evolution - agriculture: hybridization between crops and wild relatives www.flickr.com EPSO meeting Brussels, 7 April 2009 Alex Widmer Thank you for your attention Human activities can increase chances for secondary contact between plant species pairs and provide opportunities for hybridization as a consequence of - increased transfer of species among countries / continents - land-use changes - climate change EPSO meeting Brussels, 7 April 2009 Alex Widmer EPSO meeting Brussels, 7 April 2009 Alex Widmer
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