Résumé
The Heliconius butterflies are a widely studied adaptive radiation of 46
species spread across Central and South America, several of which are
known to hybridize in the wild. Here, we present a substantially improved
assembly of the Heliconius melpomene genome, developed using novel methods
that should be applicable to improving other genome assemblies produced
using short read sequencing. First, we whole-genome-sequenced a pedigree
to produce a linkage map incorporating 99% of the genome. Second, we
incorporated haplotype scaffolds extensively to produce a more complete
haploid version of the draft genome. Third, we incorporated ∼20x coverage
of Pacific Biosciences sequencing, and scaffolded the haploid genome using
an assembly of this long-read sequence. These improvements result in a
genome of 795 scaffolds, 275 Mb in length, with an N50 length of 2.1 Mb,
an N50 number of 34, and with 99% of the genome placed, and 84% anchored
on chromosomes. We use the new genome assembly to confirm that the
Heliconius genome underwent 10 chromosome fusions since the split with its
sister genus Eueides, over a period of about 6 million yr.