Polyploidy: Tricky Taxonomic Delimitation

Ben Grady UW-Madison Botany Department 6 March 2007

Polyploidy and Taxonomy: an overview • • • “Defining” species • Polyploid complexes

Cardamine pratenesis Lepidium

What do we call a species?

• Biological Species Concept – Mayr 1942 • Evolutionary Species Concept – Wiley 1978 • Phylogenetic Species Concept – Cracraft 1989 • General consensus: diagnosable units with common evolutionary history From Futuyma 1998 and Judd et al. 2002

The Polyploid Complex

• Continued polyploidization in a group or lineage • Much overlap in morphological traits and ecological preferences • Difficult and time-consuming to fully understand relationships within a polyploid complex Grant 1981

The Polyploid Complex

• Wow, this

is

complex!

The Polyploid Complex

• Count some chromosomes

2n 2n 2n 2n 2n 4n 4n 2n 6n 4n 2n

The Polyploid Complex

• Determine source of genetic material

2n 2n 2n 2n 2n 4n 4n 2n 6n 4n 2n

The Polyploid Complex - Simplified

2n AA 4n AA AA 2n AA 4n AA AA 2n AA 6n AA AA AA

The prevalence of Polyploid Complexes • Polyploid complexes are common in certain families – Polypodiaceae – Trilliaceae – Onagraceae – Poaceae – Brassicaceae Grant 1981

Cardamine pratensis

complex

• Widespread distribution • Morphological variation not discrete • Post-glacial diversification • Hybridization and polyploidy rampant – 2n = 16, 24, 30, 32, 40, – 44, 46, 48, 56 • Iberian taxa:

C. pratensis

s.s.

– –

C. crassifolia C. castellana

Lihova et al. 2003 Photos © Carl Farmer

Lihova et al. 2003

C. pratensis C. pratensis C. castellana C. crassifolia

Lihova et al. 2003

C. pratensis

in the Iberian Peninsula Lihova et al. 2003 •

C. crassifolia

and

C. castellana

distinct (both taxa 2n=16) appear C. castellana C. crassifolia

AFLP analysis:

C. castellana

&

C. crassifolia

C. castellana 2n = 16 C. crassifolia 2n = 16

Lihova et al. 2003

Many intermediate characters

Lihova et al. 2003

Origins of

C. castellana

?

•

C. castellana

morphologically intermediate • Possible hybrid of

C. pratensis crassifolia

and

C.

• What then?

– Species? – Subspecies?

– No taxonomic recognition?

C. pratensis

in the Iberian Peninsula Lihova et al. 2003 •

C. pratensis

s.s. still poses a problem, or does it?

– Various polyploids still mostly interfertile (except diploids) – Morphological variation continuous – Multiple origins of polyploids?

AFLP analysis:

C. pratensis

s.s.

30 16 56 56 44

Lihova et al. 2003

Figure 5

Morphological Variation?

Lihova et al. 2003

Allopolyploidization – Lee et al. 2002

Lepidium

•

Lepidium

– 175 spp. worldwide – Crazy flowers, well for a mustard…

PI gene tree and evolution of stamen arrangement, green-Eurasia, orange Africa, blue-S.Amer., black-Austr., purple-N.Amer. lacking lateral stamens,

References

• • • • • • Futuyma, D.J. 1998. Evolutionary Biology. Sinauer Associates – Sunderland, Mass. U.S.

Grant, V. 1981. Plant Speciation. Columbia University Press, New York, pp. 324-346.

Judd W.S., C.S. Cambell, E.A. Kellogg, P.F. Stevens, & M.J. Donoghue. 2002. Plant Systematics: An Evolutionary Approach. Sinauer Associates – Sunderland, Mass. U.S.

Lee, J., K. Mummenhoff, & J. Brown. 2002. Allopolyploidization and evolution of species with reduced floral structures in

Lepidium

L. (Brassicaceae).

PNAS

99(26): 16835-16840.

Lihova, J., A. Tribsch, & K. Marhold. 2003. The polyploidy and distribution.

Taxon Cardamine pratensis

(Brassicaceae) group in the Iberian Peninsula: taxonomy, 52: 783-801.

Marhold, K., & J. Lihova. 2006. Polyploidy, hybridization and reticulate evolution: lessons from the Brassicaceae.

Pl. Syst. Evol.

259: 143-174.