dna barcoding and evolutionary relationships in accipiter brisson,1760 (aves, falconiformes:...
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DNA barcoding and evolutionary relationships in Accipiter Brisson,1760 (Aves,
Falconiformes: Accipitridae) with a focus on African and Eurasian representatives
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Nomenclature
• A. gentilis: Nl; havik, Eng; gosshawk, Fr; Autour des palombes
• A. nisus: Nl; sperwer, Eng; sparrowhawk, Fr; epervier d’Europe
• Buteo buteo: Nl; buizerd, Eng; Common buzzard Fr; Buse variable
• Buteo albicaudatus; Nl; witstaart buizerd, Eng; white tailed hawk, Fr; Buse à queue blanche
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Content• DNA barcoding a short
introduction– General DNA barcoding– Mini barcodes– 10X threshold, best compromise
threshold– BCM and BM criteria– Character based identification
• Coverage– Sample origins– The dataset
• Methods– Character based method (CB)– The 10 X intraspecific distance
threshold (10 X)– The Best compromise threshold
(BCTh)– Best match and best close match
explained
• Results for DNA barcoding– Character based identification– Different thresholds
• Phylogeny reconstruction– 291 bp dataset– 647 bp dartaset
• Discussion• Conclusion
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DNA barcoding
• Identification of species with an agreed upon (part of a) gene (COI)
• 5’-3’ part of Cytochrome C Oxidase subunit I
• ~650bp in length
• Polymerase chain reactions and Sanger sequencing
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Mini barcodes
• Genetic material from museums is often degraded• Shorter fragments are needed• E.g. sequences of 250-300bp or, in some cases even
shorter, also work for identification purposes
Sonet et al. in press
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Sample coverage and origins
• African and European taxa are well represented
• The new world partially represented
• Australia and S-E Asia poorly represented
• Most samples from RMCA/RBINS (n=83/9)
• Supplemented with available genbank sequences (n=28)
sample distribution through time
0
10
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30
40
50
60
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<1900 >1900<1930
>1930<1960
>1960<1990
>1990
30-year periodsn
um
ber
of
sam
ple
s in
clu
ded
Series1
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The resulting dataset
• 25 European and African Accipiter species with a total of 140 specimens
• sequenced for a 291bp (mini) and 647bp (standard) BC fragment of the COI gene
• three datasets analysed:– dataset A: 25 species, 291bp
– dataset B: 19 species, 647bp
– dataset C: 19 species, 291bp
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Character based indentification
– Easy it is about detecting unique differences
– May be unreliable with insufficient sampling
– No threshold whatsoever is used
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10 X intraspecific distances and the barcoding gap
• Distances• Arbitrary• Does not always hold
(Tephritidae)• However, works well in
birds
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The Best compromise threshold (BCTh)
• Based on the intercept between cumulative intra and interspecific distances
• Based on the dataset under study rather than a predetermined threshold
• Results from one dataset not applicable to another
Lefébure et al. 2006
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BM and Best Close match
• Best Match (BM), assignes the species name of its best-matching sequence regardless of how similar the query and reference sequences were. Identification is considered correct when both sequences were from the same species, incorrect if the query species differed from the closest reference species or ambiguous if multiple species were the BM of the query species
• Best close match (BCM) also considers the threshold
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BM vs. BCM example• 4 taxa• 3 species: A. francesiae (n=2) A. badius (n=1) & A. toussenelii (n=1)• BM would assign A. badius and A. toussenelii to the “ambiguous” or
“incorrect” (dependent on the threshold) categories• BCM would classify them as impossible when the difference is larger than
the threshold
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Results character based identification
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Results BCTh vs. 10 X distance threshold
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• Different thresholds
• Partial overlap
• Caused by– A. nisus/rufiventris
– A. virgatus/gularis
– A. cooperii/gundlachi
• At or just below the BC treshold are– A. badius subsp
– A. gentilis subsp
Results BCTh vs. 10 X distance threshold
A. rufiventrisA. nisus
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Phylogeny reconstruction
• Hypothesis of evolution
• Clades are units of supported taxa (related by direct descent)
• This dataset is only suited for low taxonomic level inferences
• One genegene tree rather than species tree
• Comparison with the current taxonomy based on morphology and morphometrics
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Phylogeny based on 291bp
• 10 supported clades– [tachiro]
• A. tachiro subclades
– A. minullus– A. francesiae/ soloensis– [cooperii]– A. badius/ brevipes– A. nisus/ striatus/
erythronemius– A. ovampensis/
madagascariensis– [virgatus] including A.
fasciatus
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Phylogeny based on 291bp a closer look
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Phylogeny based on 647bp
• 19 supported clades– [tachiro]
• A. tachiro• A. toussenelii & subsp
– A. soloensis & A. francesiae subsp
– [gentilis]– [cooperii]– [nisus] (without A.
ovampensis/ madagascariensis
– [minullus] (without A. erythropus)
– [virgatus] including A. fasciatus
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Phylogeny based on 647bp a closer look
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Discussion
• Thresholds– The 10 X threshold would have considered A. brevipes and A. badius,
as well as A. gentilis and A. melanoleucus as belonging to the same species and
• Species concepts– Morphological– Distances based– Phylogenetic
• Support values– Models and interpretation remain issues of discussion
• Sampling– Incomplete or lacking in some cases
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Conclusions
• Molecular techniques provide a powerfull method for reviewing taxonomy
• Museum material works!
• The content of the dataset matters
• COI can identify 19 out of the 25 species included
• COI carries a phylogenetic signal suitable for molecular taxonomy on a low taxonomic level
• Parts of genus Accipiter may need revision
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Thank you for your attention