Speciation l The actual origin of species l

Speciation l The actual “origin of species” l Reduction in gene flow, genetic and phenotypic change in populations l The study of speciation requires that species be real

Speciation l Speciation is the antidote to sex l Keeps together adaptive groups of traits l New species most often uniparental l Phylogeny is genealogy of species l Branching tree

Hybridization l Mules l Fertile interspecific hybrids are common in perennial plants

Hybrid speciation l New species form from interspecific hybrids l Two parents l Phylogenetic pattern is reticulate l Enough examples to make it interesting l Not enough to disrupt the generally divergent pattern of phylogeny

Alloploidy l Chromosome doubling (unreduced gametes or somatic doubling) l Alloploid effectively has one diploid set from each parent species l Instant Speciation™

Homoploid hybrid speciation l No chromosome doubling l Two theoretical modes, both documented § Recombinational speciation § Speciation with external barriers

Recombinational speciation l F 1 s of reduced fertility, chromosome differences l F 2 s more fertile than backcrosses l Fertility restored in new species by recombination of chromosome segments

Speciation with external barriers l F 1 s not of reduced fertility l Few or no chromosomal differences between parents l Formation of backcrosses reduced by external barriers

A long time ago, in a desert close at hand…

So what’s an Encelia? l Asteraceae (sunflower family) l Mostly shrubs l Dry habitats, mostly deserts l Brittlebush (E. farinosa)

A hybrid under every bush l “The bushes are hybrids” l All species are interfertile l No apparent reduction of fertility in F 1, F 2, backcross l Is it a syngameon?

Spontaneous natural hybrids 1. 2. 3. 4. 5. 6. 7. 8. 9. E. farinosa × E. frutescens E. farinosa × E. californica E. farinosa × E. palmeri E. farinosa × E. halimifolia E. californica × E. asperifolia E. ventorum × E. palmeri E. ventorum × E. asperifolia E. virginensis × E. frutescens E. actoni × E. frutescens

Encelia ×laciniata Named as a species l Hybrids between E. ventorum and E. palmeri l Selection against recombinants l

Phylogeny: always a good place to start l The days of cladistics before DNA l Two well-defined clades (californica clade and frutescens clade) l Relationships within clades less clear

Not just morphology—phenotype Standard morphology of heads, capitulescences, leaves l Micromorphology, especially trichomes l Secondary chemistry l Ultraviolet floral patterns l Anatomy of stems and leaves (petioles turned out to be useful) l More that I’ve probably forgotten l

Cladograms based on phenotype

DNA sequence analysis l ITS (internal transcribed spacer of ribosomal DNA) l DNA doesn’t work so well for closely related species l Hybridization is more likely to be confusing in DNA sequence analysis than in morphological analysis

Identifying species of hybrid origin l Species of hybrid origin not always intermediate between parents l Species of intermediate morphology not always of hybrid origin

Preponderance of evidence l Intermediate morphology l Agreement with F 1 s l Apomorphies shared with parents

Species of hybrid origin E. virginensis (parents: E. actoni and E. frutescens subsp. frutescens) E. asperifolia (parents: E. californica and E. frutescens subsp. glandulosa)

Encelia virginensis

E. actoni E. virginensis E. frutescens

Shared phenotypic apomorphies – E. virginensis l With E. frutescens § broad multicellular-based hairs l With E. actoni § none (E. actoni has no clear autapomorphies, but E. virginensis resembles it morphologically)

Agreement with F 1

1. 2. 3. 4. 5. 6. 7. 8. length of petiole width of leaf height of head width of head pedicel width number of rays length of ray length of leaf

Research by Gery Allan

Chimeric ITS: E. virginensis (13 base difference)

Encelia asperifolia

E. californica E. frutescens subsp. glandulosa E. asperifolia

Shared phenotypic apomorphies – E. asperifolia With E. frutescens § broad multicellular-based hairs § no benzopyrans or benzofurans § yellow stigmas l With E. californica § UV-reflective ray corollas § brown disk corollas § moniliform hairs l

RAPD data: E. asperifolia l Shared § § § with E. californica UBC 218 (0. 8 kbase, 1. 6 kbase) UBC 382 (1. 4 kbase) UBC 409 (0. 5 kbase) UBC 478 (1. 4 kbase) Operon B 8 (0. 75 kbase) l Shared with E. frutescens § UBC 149 (0. 7 kbase) § UBC 375 (1. 0 kbase)

Chimeric ITS: E. asperifolia (21 base difference)

Hybrid speciation by external barriers l E. ×laciniata provides a model

Conclusion I’m done l What are the traits that adapt the new species to their new habitats? l Are there transgressive traits? l Plenty of other plant genera l

Acknowledgments Allan, Gery J. Axelrod, Daniel Braden, Gerald Bryant, Stephen Budzikiewicz, Herbert Carpenter, Kevin J. Charest, Nancy A. Clark, Emily Ehleringer, James R. Harrington, Daniel F. Isman, Murray B. Kinney, Michael Koukol, Scott R. Kyhos, Donald W. Lahmeyer, Sean C. Laufenberg, Gabriela Lee, Gregory J. Maepo, Linda Miller, David Nishida, Joy H. Panero, José Parra, Mima Patterson, Mark Politt, Ursula Proksch, Peter Rieseberg, Loren Rodriguez, Eloy Saccoman, Stephanie Sanders, Donald L. Schilling, Edward Thompson, William C. Weiler, Jeff Weisman, Kathy Wisdom, Charles Wollenweber, Eckhard Wray, Victor