Myrmecophily in beetles (Coleoptera): evolutionary patterns and biological mechanisms
Socially parasitic myrmecophily has evolved numerous times in arthropods, but myrmecophilous lineages are non-randomly distributed across phylogeny. Evolution of this way of life is heavily biased towards the Coleoptera, within this order towards rove beetles (Staphylinidae), and within rove beetles to two subfamilies. Here, I provide an overview of the diversity of myrmecophilous beetles and discuss advances in comprehending their biology, systematics, and evolution. I address possible factors underlying the skewed phylogenetic distribution of myrmecophily across the Coleoptera. Accounting for this trend requires knowledge of ancestral ecologies and phenotypic attributes in clades where taxa are predisposed to undergo the evolutionary transition from free-living to myrmecophilous. Clades that are primitively predatory, small in body size, and possess defensive strategies, either physical or chemical, that permit some degree of protection from policing worker ants, appear to be preadapted to evolve myrmecophily repeatedly. I propose that the mode of colony exploitation employed during the initial phase of evolution, combined with the potential evolvability of the body plan, has important consequences for subsequent evolutionary steps: These parameters influence if and how different taxa undergo specialisation to colony life and the mechanisms the most advanced myrmecophiles employ to achieve social integration. Myrmecophily is a paradigm of intricate symbiosis, which in certain clades of beetles evolves recurrently from an ancestral preadaptive ground state and follows a relatively predictable phenotypic trajectory. These clades are potentially powerful systems to explore the evolution and mechanistic bases of symbiotic relationships in animals.
FREE licensed under CC BY 3.0. Received 24 August 2015; revision received 22 October 2015; accepted 30 October 2015. Subject Editor: Daniel J.C. Kronauer I'm grateful to several colleagues who provided feedback or new information for the sections on myrmecophily in different beetle taxa: Mike Caterino and Alexey Tishechkin (histerids), James Hogan (carabids), P.J. Johnson (elaterids), Darren Mann (scarabaeids), Paweł Jałoszyński (scydmaenines) and Alfred Newton (whose database provided exact numbers of species and genera in Staphyliniformia, and whose literature catalogue yielded several references on myrmecophily in Staphylinidae previously unknown to me). I thank Larry Gilbert for providing the observation on Glenus myrmecophagy, as well as Stelios Chatzimanolis for identifying the specimen. Christoph von Beeren, Taro Eldredge, Margaret Thayer, Alfred Newton and two reviewers provided invaluable critiques of the entire manuscript that improved it greatly, and for which I am truly appreciative. I acknowledge the kindness of many colleagues who provided specimen images: Karolyn Darrow, Roman Dudko, Taro Eldredge, Martin Fikáček, Paweł Jałoszyński, Takashi Komatsu, Pavel Krásenský, Munetoshi Maruyama, Harald Schillhammer, Taku Shimada, Maxim Smirnov, Alexey Tishechkin, and Zi-Wei Yin. Finally, I thank the editors of Myrmecological News for the opportunity to contribute this article.
Published - mn22_65-108_printable.pdf