We report the complete sequence of a paralogous copy of elongation factor-1 alpha (EF-1 alpha) in the honeybee, Apis mellifera (Hymenoptera: Apidae). This copy differs from a previously described copy in the positions of five introns and in 25% of the nucleotide sites in the coding regions. The existence of two paralogous copies of EF-1 alpha in Drosophila and Apis suggests that two copies of EF-1 alpha may be widespread in the holometabolous insect orders. To distinguish between a single, ancient gene duplication and parallel, independent fly and bee gene duplications, we performed a phylogenetic analysis of hexapod EF-1 alpha sequences. Unweighted parsimony analysis of nucleotide sequences suggests an ancient gene duplication event, whereas weighted parsimony analysis of nucleotides and unweighted parsimony analysis of amino acids suggests the contrary: that EF-1 alpha underwent parallel gene duplications in the Diptera and the Hymenoptera. The hypothesis of parallel gene duplication is supported both by congruence among nucleotide and amino acid data sets and by topology-dependent permutation tail probability (T-PTP) tests. The resulting tree topologies are also congruent with current views on the relationships among the holometabolous orders included in this study (Diptera, Hymenoptera, and Lepidoptera). More sequences, from diverse orders of holometabolous insects, will be needed to more accurately assess the historical patterns of gene duplication in EF-1 alpha.

Hybrid incompatibilities (HIs) cause reproductive isolation between species and thus contribute to speciation. Several HI genes encode adaptively evolving proteins that localize to or interact with heterochromatin, suggesting that HIs may result from co-evolution with rapidly evolving heterochromatic DNA. Little is known, however, about the intraspecific function of these HI genes, the specific sequences they interact with, or the evolutionary forces that drive their divergence. The genes Hmr and Lhr genetically interact to cause hybrid lethality between Drosophila melanogaster and D. simulans, yet mutations in both genes are viable. Here, we report that Hmr and Lhr encode proteins that form a heterochromatic complex with Heterochromatin Protein 1 (HP1a). Using RNA-Seq analyses we discovered that Hmr and Lhr are required to repress transcripts from satellite DNAs and many families of transposable elements (TEs). By comparing Hmr and Lhr function between D. melanogaster and D. simulans we identify several satellite DNAs and TEs that are differentially regulated between the species. Hmr and Lhr mutations also cause massive overexpression of telomeric TEs and significant telomere lengthening. Hmr and Lhr therefore regulate three types of heterochromatic sequences that are responsible for the significant differences in genome size and structure between D. melanogaster and D. simulans and have high potential to cause genetic conflicts with host fitness. We further find that many TEs are overexpressed in hybrids but that those specifically mis-expressed in lethal hybrids do not closely correlate with Hmr function. Our results therefore argue that adaptive divergence of heterochromatin proteins in response to repetitive DNAs is an important underlying force driving the evolution of hybrid incompatibility genes, but that hybrid lethality likely results from novel epistatic genetic interactions that are distinct to the hybrid background.

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We performed a phylogenetic analysis of the species, species groups, and subgenera within the predominantly eusocial lineage of Lasioglossum (the Hemihalictus series) based on three protein coding genes: mitochondrial cytochrome oxidase I, nuclear elongation factor 1alpha and long-wavelength rhodopsin. The entire data set consisted of 3421 aligned nucleotide sites, 854 of which were parsimony informative. Analyses by equal weights parsimony, maximum likelihood, and Bayesian methods yielded good resolution among the 53 taxa/populations, with strong bootstrap support and high posterior probabilities for most nodes. There was no significant incongruence among genes, and parsimony, maximum likelihood, and Bayesian methods yielded congruent results. We mapped social behavior onto the resulting tree for 42 of the taxa/populations to infer the likely history of social evolution within Lasioglossum. Our results indicate that eusociality had a single origin within Lasioglossum. Within the predominantly eusocial clade, however, there have been multiple (six) reversals from eusociality to solitary nesting, social polymorphism, or social parasitism, suggesting that these reversals may be more common in primitively eusocial Hymenoptera than previously anticipated. Our results support the view that eusociality is hard to evolve but easily lost. This conclusion is potentially important for understanding the early evolution of the advanced eusocial insects, such as ants, termites, and corbiculate bees.

Females of many animal species store sperm for taxon-specific periods of time, ranging from a few hours to years. Female sperm storage has important reproductive and evolutionary consequences, yet relatively little is known of its molecular basis. Here, we report the isolation of a loss-of-function mutation of the Drosophila melanogaster Acp29AB gene, which encodes a seminal fluid protein that is transferred from males to females during mating. Using this mutant, we show that Acp29AB is required for the normal maintenance of sperm in storage. Consistent with this role, Acp29AB localizes to female sperm storage organs following mating, although it does not appear to associate tightly with sperm. Acp29AB is a predicted lectin, suggesting that sugar-protein interactions may be important for D. melanogaster sperm storage, much as they are in many mammals. Previous association studies have found an effect of Acp29AB genotype on a male's sperm competitive ability; our findings suggest that effects on sperm storage may underlie these differences in sperm competition. Moreover, Acp29AB's effects on sperm storage and sperm competition may explain previously documented evidence for positive selection on the Acp29AB locus.