The genomes of two key bumblebee species with primitive eusocial organization
Authors: Sadd Ben M , Barribeau Seth M , Bloch Guy , de Graaf Dirk C , Dearden Peter , Elsik Christine G , Gadau Jürgen , Grimmelikhuijzen Cornelis JP , Hasselmann Martin , Lozier Jeffrey D , Robertson Hugh M , Smagghe Guy , Stolle Eckart , Van Vaerenbergh Matthias , Waterhouse Robert M , Bornberg-Bauer Erich , Klasberg Steffen , Bennett Anna K , Câmara Francisco , Guigó Roderic , Hoff Katharina , Mariotti Marco , Munoz-Torres Monica , Murphy Terence , Santesmasses Didac , Amdam Gro V , Beckers Matthew , Beye Martin , Biewer Matthias , Bitondi Márcia MG , Blaxter Mark L , Bourke Andrew FG , Brown Mark JF , Buechel Severine D , Cameron Rossanah , Cappelle Kaat , Carolan James C , Christiaens Olivier , Ciborowski Kate L , Clarke David F , Colgan Thomas J , Collins David H , Cridge Andrew G , Dalmay Tamas , Dreier Stephanie , du Plessis Louis , Duncan Elizabeth , Erler Silvio , Evans Jay , Falcon Tiago , Flores Kevin , Freitas Flávia CP , Fuchikawa Taro , Gempe Tanja , Hartfelder Klaus , Hauser Frank , Helbing Sophie , Humann Fernanda C , Irvine Frano , Jermiin Lars S , Johnson Claire E , Johnson Reed M , Jones Andrew K , Kadowaki Tatsuhiko , Kidner Jonathan H , Koch Vasco , Köhler Arian , Kraus F Bernhard , Lattorff H Michael G , Leask Megan , Lockett Gabrielle A , Mallon Eamonn B , Antonio David S Marco , Marxer Monika , Meeus Ivan , Moritz Robin FA , Nair Ajay , Näpflin Kathrin , Nissen Inga , Niu Jinzhi , Nunes Francis MF , Oakeshott John G , Osborne Amy , Otte Marianne , Pinheiro Daniel G , Rossié Nina , Rueppell Olav , Santos Carolina G , Schmid-Hempel Regula , Schmitt Björn D , Schulte Christina , Simões Zilá LP , Soares Michelle PM , Swevers Luc , Winnebeck Eva C , Wolschin Florian , Yu Na , Zdobnov Evgeny M , Aqrawi Peshtewani K , Blankenburg Kerstin P , Coyle Marcus , Francisco Liezl , Hernandez Alvaro G , Holder Michael , Hudson Matthew E , Jackson LaRonda , Jayaseelan Joy , Joshi Vandita , Kovar Christie , Lee Sandra L , Mata Robert , Mathew Tittu , Newsham Irene F , Ngo Robin , Okwuonu Geoffrey , Pham Christopher , Pu Ling-Ling , Saada Nehad , Santibanez Jireh , Simmons DeNard , Thornton Rebecca , Venkat Aarti , Walden Kimberly KO , Wu Yuan-Qing , Debyser Griet , Devreese Bart , Asher Claire , Blommaert Julie , Chipman Ariel D , Chittka Lars , Fouks Bertrand , Liu Jisheng , O’Neill Meaghan P , Sumner Seirian , Puiu Daniela , Qu Jiaxin , Salzberg Steven L , Scherer Steven E , Muzny Donna M , Richards Stephen , Robinson Gene E , Gibbs Richard A , Schmid-Hempel Paul , Worley Kim C 
Published: April 2015

Abstract
Background
The shift from solitary to social behavior is one of the major evolutionary transitions. Primitively eusocial bumblebees are uniquely placed to illuminate the evolution of highly eusocial insect societies. Bumblebees are also invaluable natural and agricultural pollinators, and there is widespread concern over recent population declines in some species. High-quality genomic data will inform key aspects of bumblebee biology, including susceptibility to implicated population viability threats.

Results
We report the high quality draft genome sequences of Bombus terrestris and Bombus impatiens, two ecologically dominant bumblebees and widely utilized study species. Comparing these new genomes to those of the highly eusocial honeybee Apis mellifera and other Hymenoptera, we identify deeply conserved similarities, as well as novelties key to the biology of these organisms. Some honeybee genome features thought to underpin advanced eusociality are also present in bumblebees, indicating an earlier evolution in the bee lineage. Xenobiotic detoxification and immune genes are similarly depauperate in bumblebees and honeybees, and multiple categories of genes linked to social organization, including development and behavior, show high conservation. Key differences identified include a bias in bumblebee chemoreception towards gustation from olfaction, and striking differences in microRNAs, potentially responsible for gene regulation underlying social and other traits.

Conclusions
These two bumblebee genomes provide a foundation for post-genomic research on these key pollinators and insect societies. Overall, gene repertoires suggest that the route to advanced eusociality in bees was mediated by many small changes in many genes and processes, and not by notable expansion or depauperation.