1. The genetics of adaptation in natural plant populations
Toby Bradshaw &
Doug Schemske

2. Natural variation = Adaptive variation
Bad things happen to good genes
Adaptation must be demonstrated, rather than assumed

3. Unanswered questions on adaptive evolution
What is the ‘genetic architecture’ of adaptive evolution in nature?
How many genes are involved?
What is the magnitude of effect of individual mutations?
Are these mutations dominant, recessive, additive?
What is the identity of genes mutated during adaptive evolution in nature?
Structural or regulatory?
Coding or noncoding?
Are adaptive evolutionary trajectories predictable and repeatable?
Does adaptation require specific mutations in a small subset of key genes?

4. Genetic architecture of adaptation in natural plant populations
Adaptation to bumblebee or hummingbird pollinators in Mimulus
Adaptation to elevation in Mimulus
Adaptation to serpentine soils in Linanthus

5. Bumblebee-pollinated
Hummingbird-pollinated
Pink
Red
Wide corolla opening
Narrow, tubular corolla
Inserted stigma/anther
Exserted stigma/anther
1-2ml nectar
40-100ml nectar
Mid-high elevation
Low-mid elevation

6. Components of reproductive isolation in M. lewisii and M. cardinalis
Pollinator
40.3%
Post-mating
0.9%
There is tremendous potential to increase the yield of biomass crops. Most of the sun’s radiant energy is not even captured by photosynthetic pigments (non-photosynthetically active radiation – PAR). Of the remainder, half is not intercepted by plants because of inadequate canopy cover (annuals) or seasonal leaf drop (perennials). Nearly all of what is left is lost to reflectance or cellular respiration to maintain plant function. Only about 1% of the sun’s energy is captured as fixed carbon, yet nearly all life depends on this small amount of net photosynthesis. Read the box!
Ecology
58.8%

8. Mimulus map Can a single QTL have a large effect on pollinator choice?
YUP
Mimulus map
Can a single QTL have a large effect on pollinator choice?

9. Near-isogenic lines (NILs)F2
NIL1
lewisii xL xL xL F1
cardinalis F2
NIL2 xC xC xC

10. N=1090
N=201
Bumblebees
Hummingbirds

11. N=180
N=3738
Bumblebees
Hummingbirds

12. Visitation rate ratio BEE:HUMMER 725 2 HUMMER:BEE 15 1284
A small shift in pollinator assemblage could give YUP mutants an advantage

13. Visitation rate ratio BEE YUP:yup 5.2 5.8 74.1 HUMMER yup:YUP 1.2 68.0
1.1
The F2 gave the right answer to the wrong question
A mutation at the YUP locus increases visitation by the new pollinator ~70-fold, and this response is symmetrical

14. Timberline 3050m Mather 1400m Stanford 30m
Collect M. lewisii and M. cardinalis from a zone of sympatry near Mather
Produce 500 F2 lines
Establish all lines in common gardens and allow natural selection to proceed
Estimate Dp at 200 AFLP loci across the genome
High abs(Dp) is the signature of selection; sign of Dp may change across elevation if QTL is involved in a tradeoff

15. Selection at White Wolf (2400m)
# planted
319
8146
1-yr survival
55%
27%
44%
1-yr flowering
25% 9%
20%
Dp in progress (Kristy Brady)

17. Conclusions
Complex phenotypes, such as reproductive isolation and fitness, can be measured in nature, and can be shown to be adaptive.
The number, chromosome position, magnitude of effect, and mode of action of QTLs responsible for adaptation to pollinators can be determined by genome mapping.
Substitution of one ‘mutant’ allele at a single locus controlling flower color can cause immediate divergence in pollinator preference of a magnitude much larger than predicted by an F2 population.
How will we identify the genes responsible for adaptive variation at QTLs?

18. FrankenMimulus

19. Funding University of Washington Royalty Research Fund
National Science Foundation
Schemske Fund
Bradshaw Trust