loxigilla noctis and l. barbadensis in the lesser...

Phylogeography and genetic differentiation between

Loxigilla noctis and L. barbadensis in the Lesser Antilles

Sophie Arnaud-Haond1, Carla Daniel2, Sébastien Motreuil3,

Julia Horrocks2 & Frank Cézilly3

1 IFREMER, Sète, France

2 Department of Biological and Chemical Sciences,

The University of the West Indies, Barbados 3 Université de Bourgogne, UMR CNRS 6282 Biogéosciences, Dijon, France

1st Caribaea Initiative Research and Conservation Workshop,22-24 March 2016, Martinique


The Caribbean region: a natural laboratory for the study of speciation

More than 100 species of anoles on the Greater

Antilles. (N) = number of species within each terminal clade.

Anolis roquet

Losos & Thorpe (2004)

Ecological speciation in Chondrilla nucula

reef mangrove

Duran &Rützler (2006)


Speciation in the Caribbean-endemic genus Loxigilla

(Raffaele et al. 1998)

Puerto Rican Bullfinch (L. portoricensis)

Greater Antillean Bullfinch (L. violacea),

Lesser Antillean Bullfinch (Loxigilla noctis)

Saint Kitts Bullfinch (L. portoricensis grandis) † end of the 19th century

(Raffaele 1977; Garrido & Wiley 2003).


Eurneornis campestris

L. portoricensis

L. violacea

Melanopyrrha nigra

Loxipasser anoxanthus

L. noctis

L. barbadensis

Tiaris canorus

Loxigilla spp.: a paraphyletic group !


Geographic variation within Lesser Antillean Bullfinches

Buckley & Buckley (2004)


Audet et al. 2014

Reduced sexual dimorphism in L. barbadensis


“we suggest that the form of ‘Lesser Antillean Bullfinch’ on Barbados is best

treated as a separate biological species, Barbados Bullfinch Loxigilla

barbadensis Cory 1886, which probably colonised Barbados from St Lucia

around 180,000–700,000 y BP, and which has achieved specific status since its

arrival. As such this represents one of the more rapid examples of avian

speciation”

Is Loxigilla barbadensis a true species?


Lovette et al. (1999) studied mtDNA from Lesser Antillean Bullfinches from Barbados (barbadensis), St Lucia (sclateri), and St Vincent (crissalis). Sequencing of the the entire 894–bp mtDNA genomes for ATPase 6 and ATPase 8 for five barbadensis and sclateri , + RFLP and sequencing for 21 barbadensis and 32 sclateri : 1. no evidence for founder-effect 2. One lineages on each islands (i.e., reciprocal monophyly) 3. Only 3 to 5 substitutions among the three islands: 0.60% nucleotide divergence between

barbadensis and crissalis and only 0.36% between barbadensis and sclateri, suggesting St Lucia to be Barbados’s source population;

4. Assuming a uniform molecular clock, a low level of mtDNA differentiation on Barbados indicates a relatively recent colonisation event.

Loxigilla sp.: a first biogeographical study


According to average observations and phylogeohgraphy,

one lineage per island, with L. barbadensis being easily

recognizable on the basis of its wholly black males, BUT

occasional occurrences of partially or wholly black male

bullfinches on Barbados (e.g. Hellmayr 1938, Bird 1983,

Cézilly et al. 2003):

• new St Lucia or St Vincent immigrants? • residual ancestral variation within barbadensis?

Loxigilla sp.: field observations


A population genetics analysis

One mitochondrial DNA (ab. 730 bp of the cytochrome b) and 14 microsatellite markers were used on samples from four Caribbean islands to provide

• A genetic test of taxonomic hypothesis

• A first step toward retracing the history of colonization of the islands: North South, South North, multiple colonizations?

Barbados

Sainte Lucie

Martinique

Guadeloupe

100 km

mtDNA: maternally inherited


Barbados

Sainte Lucie

Martinique

Guadeloupe

100 km

Mitochondrial DNA 234 sequences 727 base pair cytochrome b

H=13

When is a species a species?

• Biological species concept, according to Ernst Mayr (1940):

« groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups”

•Hardly amenable to experimental tests for most cases Looking for the best proxy:

Proxy for species delineation in biodiversity assessment?

• Morphology, Phenetic species concept: A species is a set of organisms that look similar to each other and distinct from other sets (Ridley, 1993).

But phenotypic plasticity, synonymous species, cryptic species…

• Genetic divergence, Evolutionary species concept: A species is a lineage (an ancestral-descendant sequence of populations) evolving separately from others and with its own unitary evolutionary roles and tendencies (Simpson, 1961).


Species or not species?

There seems to be

• Morphological differences

• Reciprocal monophyly with the Barbados, BUT 3 individuals with Ste Lucie or Martinique haplotypes caught in Barbados

• A large divergence of Guadeloupe compared to Ste Lucie and Martinique, despite some haplotypes of Guadeloupe are caught in Martinique

Yet all this based on one single loci (variance) only maternally inherited (what is migration is sex-specific?)

=> Real species on their way to accumulate more divergence, or diverge lineages on their way toward rehomogeneization?

With outgroups

L. violacea

L. portoricensis

L. noctis

L. barbadensis

?


Can nuclear DNA help? 14 microsatellites

DIVERSITY

• Similar level of allelic richness: between 7.6 and 8 once standardized for the lowest sample size (25)

• Similar levels of heterozygosity (0.67 to 0.72)

• Heterozygote deficiency from null in Barbados to 0.1 in Ste Lucy

DIFFERENTIATION

• Averaging methods:

Fst estimates show systematic differentiation, unclear: Martinique more different from Ste Lucie than from Barbados

Guadeloupe Martinique Sainte-Lucie Barbados

Guadeloupe 0.000 0.027 0.039 0.037

Martinique 0.000 0.033 0.030

Sainte-Lucie 0.000 0.030

Barbados 0.000


Nuclear DNA

Barbados

Sainte Lucie

Martinique

Guadeloupe

100 km

Clustering method: individual centered


Species or not species? 3 clusters

The second clusters seems to be a contact area with the other two genetic backgrounds, assignment tests confirm it may receives migrant from the Northern and Southern clusters

Barbados

Sainte Lucie

Martinique

Guadeloupe

100 km


Bottleneck tests

• Significant results to bottleneck tests on microsatellites data in the four islands (using an IAM or TPM model and Wilcoxon or standardized difference tests)

• Fu & Li test on mitochondrial sequences shows significant hints of a bottleneck in Barbados only


Summary

• Results show there are three genetic backgrounds from Guadeloupe to Sainte Lucie:

• L. noctis is differentiated with two distinct backgrounds both for mitochondrial and nuclear DNA in Guadeloupe versus Martinique & Ste-Lucie

• L. barbadensis is represented by the third genetic cluster/background, slightly more divergent on mtDNA

• L noctis from Martinique and Sainte-Lucie seem to receive influence from the other two genetic backgrounds

=>Are the observations of bottleneck and exchanges linked to recent anthropogenic influence or are they the remnant of the history of colonization?


Questions?

loxigilla noctis and l. barbadensis in the lesser...

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