BackgroundA fundamental and enduring problem in evolutionary biology is to understand how populations differentiate in the wild, yet little is known about what role organismal development plays in this process. Organismal development integrates environmental inputs with the action of gene regulatory networks to generate the phenotype. Core developmental gene networks have been highly conserved for millions of years across all animals, and therefore, organismal development may bias variation available for selection to work on. Biased variation may facilitate repeatable phenotypic responses when exposed to similar environmental inputs and ecological changes. To gain a more complete understanding of population differentiation in the wild, we integrated evolutionary developmental biology with population genetics, morphology, paleoecology and ecology. This integration was made possible by studying how populations of the ant species Monomorium emersoni respond to climatic and ecological changes across five ‘Sky Islands’ in Arizona, which are mountain ranges separated by vast ‘seas’ of desert. Sky Islands represent a replicated natural experiment allowing us to determine how repeatable is the response of M. emersoni populations to climate and ecological changes at the phenotypic, developmental, and gene network levels.ResultsWe show that a core developmental gene network and its phenotype has kept pace with ecological and climate change on each Sky Island over the last ∼90,000 years before present (BP). This response has produced two types of evolutionary change within an ant species: one type is unpredictable and contingent on the pattern of isolation of Sky lsland populations by climate warming, resulting in slight changes in gene expression, organ growth, and morphology. The other type is predictable and deterministic, resulting in the repeated evolution of a novel wingless queen phenotype and its underlying gene network in response to habitat changes induced by climate warming.ConclusionOur findings reveal dynamics of developmental gene network evolution in wild populations. This holds important implications: (1) for understanding how phenotypic novelty is generated in the wild; (2) for providing a possible bridge between micro- and macroevolution; and (3) for understanding how development mediates the response of organisms to past, and potentially, future climate change.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0448-4) contains supplementary material, which is available to authorized users.

Raids by the army ant Neivamyrmex rugulosus (tribe Ecitonini) on a nest aggregation of the fungus-growing ant Trachymyrmex arizonensis (tribe Attini) resulted in major brood loss and partial destruction of the fungus-gardens in the attacked nests. T. arizonensis workers attempted to rescue their brood by carrying them to ad-hoc shelters under rocks above ground, but the army ants pursued the workers to retrieve much of the brood. Raids on single colonies lasted about half an hour, after which the escaped T. arizonensis workers returned to their nest with any rescued brood. Raids on single nests occurred repeatedly during the 24-hour period the army ants swept through the T. arizonensis nest aggregation. Compared to unraided colonies, raided colonies were left with only about 25 % of their brood. Army ant predation thus is an important source of brood loss to T. arizonensis and probably also to all attine ant species. The behavioral, morphological, and nest-architectural defenses of fungus-growing ants against army ant predation are discussed.

Studying the behavioral and life history transitions from a cooperative, eusocial life history to exploitative social parasitism allows for deciphering the conditions under which changes in behavior and social organization lead to diversification. The Holarctic ant genus Formica is ideally suited for studying the evolution of social parasitism because half of its 172 species are confirmed or suspected social parasites, which includes all three major classes of social parasitism known in ants. However, the life history transitions associated with the evolution of social parasitism in this genus are largely unexplored. To test competing hypotheses regarding the origins and evolution of social parasitism, we reconstructed a global phylogeny of Formica ants. The genus originated in the Old World ∼30 Ma ago and dispersed multiple times to the New World and back. Within Formica, obligate dependent colony-founding behavior arose once from a facultatively polygynous common ancestor practicing independent and facultative dependent colony foundation. Temporary social parasitism likely preceded or arose concurrently with obligate dependent colony founding, and dulotic social parasitism evolved once within the obligate dependent colony-founding clade. Permanent social parasitism evolved twice from temporary social parasitic ancestors that rarely practiced colony budding, demonstrating that obligate social parasitism can originate from a facultative parasitic background in socially polymorphic organisms. In contrast to permanently socially parasitic ants in other genera, the high parasite diversity in Formica likely originated via allopatric speciation, highlighting the diversity of convergent evolutionary trajectories resulting in nearly identical parasitic life history syndromes.

The presence of the ant subfamily Myrmeciinae is established in the Early Eocene (Ypresian) Okanagan Highlands localities of Horseßy River, Falkland, McAbee (British Columbia, Canada) and Republic (Washington state, United States) and in the Mo-clay Ølst and Fur Formations (Denmark). Nine new species in four new genera (three orthotaxa: Ypresiomyrma n. gen., Avitomyrmex n. gen., and Macabeemyrma n. gen.; one parataxon: Myrmeciites n. gen.) are described. Seven are placed in the Myrmeciinae: Ypresiomyrma orbiculata n. sp., Ypresiomyrma bartletti n. sp., Avitomyrmex elongatus n. sp., Avitomyrmex mastax n. sp., Avitomyrmex systenus n. sp., Macabeemyrma ovata n. sp., and Myrmeciites herculeanus n. sp.; two further species are tentatively placed in the subfamily, Myrmeciites (?) tabanifluviensis n. sp. from Horseßy River, and Myrmeciites (?) goliath n. sp. from McAbee. Two further myrmeciine ants are treated as Myrmeciites incertae sedis, a male from Falkland and a female (worker or queen) from Republic. Pachycondyla rebekkae Rust and Andersen, from the earliest Ypresian of Denmark, is reassigned to the genus Ypresiomyrma, within the Myrmeciinae. The fossil record indicates a northern hemisphere origin of the subfamily. The presence of Ypresiomyrma in Denmark and British Columbia further reßects the well-documented Paleogene cross-North Atlantic distributions of biota. The known fossil record of the Myrmeciinae is restricted to the Eocene.

Aim Continents harbour unique faunas, and only a small percentage of species naturally inhabit more than a single continent. This pattern is most evident in the insects, a morphologically small and extremely diverse group. Nevertheless, 12 species of ants have traditionally been recognized as native to both North America and Eurasia, the Holarctic region. Since intercontinental dispersal is presumably rare in ants, allopatric speciation in the absence of gene flow can be expected over evolutionary time. Here, we reassess the existence of Holarctic ant species and reconstruct their biogeographical history. Location The Holarctic. Taxon All known ant species with purportedly Holarctic distributions. Methods We reconstructed the phylogenetic relationships, biogeographical history and reassessed the taxonomic status of all known ants with Holarctic distributions using genetic data based on one mitochondrial and three nuclear genes and an ancestral area reconstruction of 310 specimens and 73 species (the 12 Holarctic species plus outgroup taxa). Results Contrary to the currently accepted hypothesis, only three ant species have Holarctic native ranges, while six taxa separate into distinct Palearctic and Nearctic species. Four species are shown to be recent introductions from Europe to North America by human activity, one of which was thought to be native. Genetic diversity is considerably higher within the North American than within European species as currently defined. Main conclusions The Formicidae have repeatedly dispersed through Beringia, during and after land bridge formation, and in both directions between the Palearctic and Nearctic regions. However, only three cold‐tolerant species crossed the Bering Strait in relatively recent time. Our results highlight the potential existence of many unknown Nearctic ant taxa. Reliance on an evolutionarily labile morphological character, erect hairs, seems to have obscured species delimitation in these ant taxa. Based on our investigation, the typical time for speciation in allopatry for ants is 2–5 Ma.