Stephanomeria exigua

Parent SpeciesStephanomeria malheurensis

Selfing Species

Asteraceae

Mimulus lewisii (low to mid-elevation)

Bee pollinated

Pink petals

Landing Platform

Small Amounts of nectar

Mimulus cardinalis (mid to high elevation)

(Bird Pollinated)

Reflexed petals, no landing platform

Large amounts of nectar

Red Petals

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

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.

YUP yup

yup YUPBradshaw and Schemske. 2003. Nature 426:176-178

YUP yup

yup YUP

The YUP gene controls carotenoid (yellow pigmentation).

When it is active/dominant it suppresses yellow pigment production.

When it is recessive it allows yellow pigment production.

A single allele change can cause a shift in pollinator types.

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Back up systems in angiosperms may predispose a species for further speciation

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Early

Mid

Late

Lonicera canadensis

L. dioica

Diervilla lonicera

Blooming Times

Caprifoliaceae

Saxifraga virginiensis - early Saxifraga tricuspidata - later

Saxifragaceae

Corallorhiza trifida C. striata C. maculata

Early Mid Late

Orchidaceae

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.