This is the final version of the article. Available from the publisher via the DOI in this record.BACKGROUND: With over 20 parapatric races differing in their warningly colored wing patterns, the butterfly Heliconius erato provides a fascinating example of an adaptive radiation. Together with matching races of its co-mimic Heliconius melpomene, H. erato also represents a textbook case of Müllerian mimicry, a phenomenon where common warning signals are shared amongst noxious organisms. It is of great interest to identify the specific genes that control the mimetic wing patterns of H. erato and H. melpomene. To this end we have undertaken comparative mapping and targeted genomic sequencing in both species. This paper reports on a comparative analysis of genomic sequences linked to color pattern mimicry genes in Heliconius. RESULTS: Scoring AFLP polymorphisms in H. erato broods allowed us to survey loci at approximately 362 kb intervals across the genome. With this strategy we were able to identify markers tightly linked to two color pattern genes: D and Cr, which were then used to screen H. erato BAC libraries in order to identify clones for sequencing. Gene density across 600 kb of BAC sequences appeared relatively low, although the number of predicted open reading frames was typical for an insect. We focused analyses on the D- and Cr-linked H. erato BAC sequences and on the Yb-linked H. melpomene BAC sequence. A comparative analysis between homologous regions of H. erato (Cr-linked BAC) and H. melpomene (Yb-linked BAC) revealed high levels of sequence conservation and microsynteny between the two species. We found that repeated elements constitute 26% and 20% of BAC sequences from H. erato and H. melpomene respectively. The majority of these repetitive sequences appear to be novel, as they showed no significant similarity to any other available insect sequences. We also observed signs of fine scale conservation of gene order between Heliconius and the moth Bombyx mori, suggesting that lepidopteran genome architecture may be conserved over very long evolutionary time scales. CONCLUSION: Here we have demonstrated the tractability of progressing from a genetic linkage map to genomic sequence data in Heliconius butterflies. We have also shown that fine-scale gene order is highly conserved between distantly related Heliconius species, and also between Heliconius and B. mori. Together, these findings suggest that genome structure in macrolepidoptera might be very conserved, and show that mapping and positional cloning efforts in different lepidopteran species can be reciprocally informative.The work was funded by U.S. National Science Foundation grants IOB
0344705 and DEB 0715096 to WOM. The H. erato BAC library was constructed
by C. Wu, H. Zhang (TAMU), and M. R. Goldsmith (URI) under
NSF Grant IBN-0208388. In addition, the Computational Biology Service
Unit at Cornell University, which is partially funded by Microsoft Corporation,
provided bioinformatics support for our analysis of genomic repeat
structure. AFLP analysis and sequencing of PCR products was carried out
at the Sequencing and Genotyping Center at the University of Puerto RicoRio
Piedras. We thank Nicola Flanagan, Alexandra Tobler, Karla Maldonado,
Jenny Acevedo Gonzales, Hector Alejandro Merchan, Yhadi Cotto,
Kelitt Santiago and Felix Araujo Perez for help in rearing and maintaining
butterfly stocks. Finally, a special thanks to Daniel P. Lindstrom for his support
and helpful suggestions during manuscript preparation
