Phylogeography and genetic differentiation between Loxigilla noctis and L. barbadensis in the Lesser Antilles

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1 Phylogeography and genetic differentiation between Loxigilla noctis and L. barbadensis in the Lesser Antilles Sophie Arnaud-Haond 1, Carla Daniel 2, Sébastien Motreuil 3, Julia Horrocks 2 & Frank Cézilly 3 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

2 The Caribbean region: a natural laboratory for the study of speciation Losos & Thorpe (2004) Anolis roquet More than 100 species of anoles on the Greater Antilles. (N) = number of species within each terminal clade. Ecological speciation in Chondrilla nucula reef mangrove Duran &Rützler (2006)

3 Speciation in the Caribbean-endemic genus Loxigilla Saint Kitts Bullfinch (L. portoricensis grandis) end of the 19 th century (Raffaele 1977; Garrido & Wiley 2003). Puerto Rican Bullfinch (L. portoricensis) Greater Antillean Bullfinch (L. violacea), (Raffaele et al. 1998) Lesser Antillean Bullfinch (Loxigilla noctis)

4 Loxigilla spp.: a paraphyletic group! Eurneornis campestris L. portoricensis L. violacea Melanopyrrha nigra Loxipasser anoxanthus L. noctis L. barbadensis Tiaris canorus

5 Loxigilla spp.: a paraphyletic group! Eurneornis campestris L. portoricensis L. violacea Melanopyrrha nigra Loxipasser anoxanthus L. noctis L. barbadensis Tiaris canorus

6 Geographic variation within Lesser Antillean Bullfinches Buckley & Buckley (2004)

7 Reduced sexual dimorphism in L. barbadensis Audet et al. 2014

8 Is Loxigilla barbadensis a true species? 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 y BP, and which has achieved specific status since its arrival. As such this represents one of the more rapid examples of avian speciation

9 Loxigilla sp.: a first biogeographical study 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.

10 Loxigilla sp.: field observations 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?

11 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? mtdna: maternally inherited Guadeloupe Martinique Sainte Lucie Barbados 100 km

12 Mitochondrial DNA 234 sequences 727 base pair cytochrome b Guadeloupe Martinique Sainte Lucie Barbados 100 km H=13

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:

14 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).

15 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?

16 With outgroups L. noctis? L. violacea L. barbadensis L. portoricensis

17 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 Martinique Sainte-Lucie Barbados 0.000

18 Clustering method: individual centered Nuclear DNA Guadeloupe Martinique Sainte Lucie Barbados 100 km

19 Species or not species? 3 clusters Guadeloupe Martinique Sainte Lucie Barbados 100 km 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

20 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

21 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?

22 Questions?