24 Oral - Evolution I
Thursday April 07, 4:30 PM - 4:45 PM

Authors:
Erina A. Ferreira ^1,2; Cathy C. Moore ³; David Ogereau ¹; Arnaud Suwalski ²; Héloïse Bastide ¹; Jean R. David ¹; Rebekah L. Rogers ³; Amir Yassin ^1,2

Affiliations:
1) Laboratoire Évolution, Génomes, Comportement et Écologie, CNRS, IRD, Université Paris-Saclay, Gif-sur-Yvette, France; 2) Institut Systématique Evolution Biodiversité (ISYEB) CNRS, MNHN, Sorbonne Université, EPHE, Paris, France; 3) Department of Bioinformatics and Genomics, University of North Carolina, Charlotte, NC

Keywords:
f. speciation; a. genome evolution

During the early stages of speciation, genetic differences tend to accumulate more rapidly at certain regions of the genome leading to the formation of genomic islands of divergence (GIDs). However, this pattern that has been observed in a wide range of organisms may either be due to selection on beneficial alleles contained within the GIDs and/or difference in the rate of recombination due to structural variation (e.g., inversions, heterochromatic content, etc.). Here, we investigate the possible causes of GIDs in Drosophila yakuba mayottensis, a subspecies of D. yakuba specializing on toxic noni (Morinda citrifolia) fruits on the island of Mayotte. We have previously described this specialization based on a population from a single locality collected in 2013, and identified multiple GIDs through genome comparison with mainland generalist D. y. yakuba populations. In 2017, we recollected flies from Mayotte and found D. y. mayottensis to be present in three localities, always on noni fruits, reconfirming its strong association with the toxic plant. We sequenced the genomes of the three populations in pools as well as from individual isofemale lines. Comparing these sequences to mainland genomes, we identified 7 GIDs. We assembled a new genome for D. y. mayottensis using a combination of Illumina short-read and Oxford Nanopore long-read sequencing methods. We identified 10 genomic regions with major chromosomal rearrangements. Three of those inversions (on the X, 2L and 2R chromosomal arms) overlapped with the GIDs. Experimental evolution using four replicate populations issued from crosses between D. y. mayottensis and D. y. yakuba showed that the three inversions were likely involved in adaptation on noni, suggesting a partial role of the genomic architecture in host shift. Interestingly, no chromosomal inversions have been detected in Drosophila sechellia, the only other Drosophila species known to be specialist on noni in the Seychelles archipelago. Despite some similarities at the genic level that we have previously described between the two noni-specialist species, our results indicate that distinct genomic architectures underlie convergent response to common selective pressures in independent lineages.