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Stephanomeria exigua Parent Species Stephanomeria malheurensis Selfing Species Asteraceae Pink petals Small Amounts of nectar Landing Platform Mimulus lewisii (low to mid-elevation) Bee pollinated Red Petals Large amounts of nectar Reflexed petals, no landing platform Mimulus cardinalis (mid to high elevation) (Bird Pollinated) F1 Hybrid Cross between Mimulus lewisii and M. cardinalis F2 generation plants were placed in a grid in the field and scored for pollinators. •Yellow pigment reduces visits by bees. •High nectar volume increases visits by birds. How might shifts in pollinators affect speciation rates? Two different pollinators acting on one species could result in reproductive isolation and speciation YUP yup yup YUP Figure 1 Near-isogenic lines of M. lewisii and M. cardinalis with alternate alleles at the YUP locus. a, b, M. lewisii; c, d, M. cardinalis.The wild-type allele at the YUP locus (a, c) has been substituted by introgression with the allele from the other species (b, d). Flowers in each NIL pair (a and b, c and d) are full siblings. Bradshaw and Schemske. 2003. Nature 426:176-178 The YUP gene controls carotenoid (yellow pigmentation). YUP yup When it is active/dominant it suppresses yellow pigment production. When it is recessive it allows yellow pigment production. yup YUP A single allele change can cause a shift in pollinator types. ? ? ? ? ? Back up systems in angiosperms may predispose a species for further speciation ? Lonicera canadensis Caprifoliaceae L. dioica Early Diervilla lonicera Mid Blooming Times Late Saxifraga virginiensis - early Saxifraga tricuspidata - later Saxifragaceae Orchidaceae Corallorhiza trifida C. striata C. maculata Early Mid Late Raphanobrassica, an allotetraploid, was first created by the Russian, G. Karpenchenko in 1928. He crossed two species in the Brassicaceae, Radish, Raphanus sativus (2N = 18) X Cabbage, Brassica oleracea (2N = 18) Raphanobrassica has 2N = 36-- so it has a complete diploid set of chromosomes from each parent. Karpenchenko had hoped to get the tops of the cabbage and the bottoms of a radish. Unfortunately the result was the tops of the radish (shown above) and the bottoms of the cabbage. It is cultivated in Scotland for fodder for sheep and cattle.