Ten species in one: DNA barcoding reveals cryptic species in the

neotropical skipper butterfly Astraptes Fulgerator

Paul Hebert, Erin Penton, John Burns, Daniel Janzen & Winnie Hallwachs

Proceedings of the National Academy of Sciences2004

Content: JanCritique: Emily

In

DNA Barcoding

What is it?● Large scale screening of just a few reference genes for species ‘barcodes’.

e.g. COI (Cytochrome C Oxidase 1) mtDNA

Two purposes:

1) Molecular classification of unknown individuals to identified taxa.

(e.g. the field barcoder)

2) Discovery of previously unknown species.

(e.g. cryptic species)

DNA Barcoding

Is it anything really new? ………NO ………. BUT!

Scale & Standardization

‘One gene fits all’

DNA BarcodingHowever, ‘Barcoding’ is a bit of a misnomer…

… not all individuals have the same ‘barcode’!

Thus required that:

Intraspecific variation << Interspecific variation

DNA Barcoding

For example in moths and birds it has been shown that:

- Intraspecific sequence variation < 0.5% .

- Interspecific sequence variation > 5%.

Thus the general rule that > 3% sequence divergence is indicative of separate species.

Recognised sister taxa generally show > 3% sequence divergence.

Study Species

• Described in 1775

• Single Species

• Common

• USA to Argentina

• Near desert to rainforest

Neotropical Skipper Butterfly

Astraptes fulgerator

Study SpeciesHowever…

• Diversity of Food Plants

• Caterpillar Color Pattern

• V. subtle differences in adult morphology.

6 – 7 Species???

Years more work…

But wait……

‘DNA barcoding’ is here!

Methods

• 484 museum specimens.• Data on food plant, caterpillar color pattern

& adult morphology.• ‘legs away for DNA’• Barcoding at Guelph:

– Extraction– Amplification of 648bp COI region– Sequencing

Methods

• Sequences aligned.

• Divergence measured with K-2-P distance model.

• Displayed in neighbour joining tree.

Results

10 Distinct Sequence Groups

Close correspondence with other

characteristics

Key Points

Branch lengths

Other characters

Intraspecific v Interspecific

TRIGO & CELT

> 3% Sequence Divergence

Diverged ~ 2 & 4 mya

Unique food plants

Distinct Spp?

FABOV, HIHAMP & INGCUP

< 0.5% Sequence Divergence

Diverged < 0.5 mya

Host plants not exclusive

???Distinct Spp???

Conclusion

Not one species

BUT…..

A complex of 10 cryptic species!

Conclusion

• How many more such complexes are out there?

• Crucial to our estimates of global biodiversity and extinction rates.

• DNA barcoding could provide the answers.

Conclusion

Isn’t DNA Barcoding great?

Recorded debate on DNA Barcoding at:

www.conferences.uiuc.edu/peet/video.html