Search for: All records

Abstract The ant genus Tapinoma Foerster, 1850 is a moderately diverse group (81 valid species) that occurs worldwide. It includes the tramp species T. melanocephalum, whose evolutionary history, biogeographic origin, and population limits remain unclear. Here, we present a time-calibrated phylogeny and a biogeographic history inference of the genus based on thousands of Ultraconserved Element (UCE) loci. Focusing on T. melanocephalum, we used single nucleotide polymorphisms from UCE loci and COI sequences to analyze species boundaries based on nuclear and mitochondrial DNA. We recovered a monophyletic Tapinoma with an estimated crown age corresponding to middle Eocene (49.4 to 34.4 Ma). Phylogenomic data differentiated T. melanocephalum from T. jandai, a recently established species based on morphology, and revealed that the 2 species diverged ∼12 Ma. Population genetic analyses identified considerable molecular divergence among sampled T. melanocephalum populations, and a heterogeneous genetic structure, showing a weak relationship between genetic differentiation and geographic distance. A phylogeographic comparison of habitat preferences of T. melanocephalum revealed an ecological shift from undisturbed to urban environments, a phenomenon which may have facilitated its ubiquitous and global distribution. Our study presents the first phylogenomic framework for this globally distributed ant genus and molecularly delineates a worldwide pest ant species. 

Abstract Accurate species delimitation is critical to identifying the conservation status of species. Molecular species delimitation methods have revealed previously unrecognized cryptic species across the taxonomic spectrum. However, studies vary in the molecular markers selected, analytical approaches used, and taxon sampling, which sometimes results in conflicting conclusions. One example of such a conflict is seen in the species delimitation analyses of the western bumble bee,Bombus occidentalis. This species was once an abundant insect pollinator in western North America but has declined severely since the mid 1990s and is predicted to continue to diminish under even optimistic future climate scenarios. Complicating this conservation crisis, the species status ofB. occidentalishas varied over time, with most recent studies recognizing one or two species. Previous studies that used molecular methods to address this question focused on a Bayesian phylogeny of the mitochondrialcytochrome oxidase I(COI) gene. Phylogenetic studies that focus on a single gene are criticized for misrepresenting the evolutionary history of species because nuclear and mitochondrial genomes, and even some genes within them, may have different evolutionary patterns. We tested a two species hypothesis of theB. occidentaliscomplex using nuclear (ultraconserved elements) and mitochondrial (COI) markers to infer maximum likelihood and Bayesian phylogenies for the taxa. We present our results and conclusions from eight species delimitation methods. Based on the genomic, morphological and geographic differences between the taxa we find support for the two species hypothesis, withB. occidentalisandB. mckayias separate species. We discuss the strengths and limitations of each genetic dataset and delimitation method, make recommendations for best practices, and highlight opportunities for equitable knowledge and technology development for phylogenomics in conservation biology. 

Abstract The New World army ants (Hymenoptera: Formicidae) comprise the 5 genera of the Eciton species group, and together they are important keystone predators in tropical and subtropical environments. Generic boundaries in the group have been considered solid and stable for nearly 100 years. Workers of the widespread and diverse genus Neivamyrmex are readily separable from the other 4 genera by lacking a subapical tooth on the tarsal claw, while males can be separated with genitalic characters. The genus Labidus is also widespread and is often abundant, with several species that are conspicuous surface foragers. The least known species of Labidus is L. mars, the workers of which have the tarsal tooth but otherwise share many traits with some Neivamyrmex, being completely eyeless and subterranean. This led us to question its generic placement. Here, we used ultraconserved element (UCE) phylogenomics to show that Labidus mars belongs to the genus Neivamyrmex. All phylogenies, inferred using multiple partitioning schemes and a species tree analysis, recovered the same topology, placing Labidus mars workers within Neivamyrmex. Sequenced males of L. mars were found to be within Labidus and thus incorrectly associated with L. mars. Based on these results and review of key specimens, including types, the following taxonomic changes are made: Neivamyrmex mars (Forel 1912) is a new combination; Labidus nero (Santschi 1930) (rev. stat.) is a male-based taxon revived from synonymy under L. mars; and L. denticulatus (Borgmeier 1955) (new stat.), a male-based taxon and former subspecies of L. mars, is raised to species. 

ABSTRACT AimInsect brood parasites (i.e., cleptoparasites), like cuckoo bees, typically attack hosts within specific lineages, but seem to be less constrained by the biogeographical movements of their hosts compared to obligate parasites. Cuckoo bees depend on stable host populations, being particularly sensitive to environmental changes and thus valuable bioindicators of the bee community health. We here test the congruence between the biogeographical history of cuckoo oil bees and their oil bee hosts. LocationThe Americas. TaxonBees (Hymenoptera, Apidae). MethodsUsing phylogenomic and Sanger sequence data, we present new time‐calibrated phylogenies for cuckoo oil bees in the ericrocidine line and their oil bee hosts,CentrisandEpicharis.We estimate their ancestral ranges using six historical biogeographical models on a set of 100 trees, randomly sampled from the posterior distribution of phylogenies in each group, thus accounting for uncertainties in divergence time estimates and model selection. ResultsThe origin of the hosts stem in the Cretaceous precedes the origin of their cleptoparasite's stem in the Palaeocene. Cleptoparasite and host crown origins were synchronous in the Eocene, and both took place in tropical South America. While the pair Rhathymini‐Epicharisremained mostly associated within this region,Centrisand their cleptoparasites expanded their distribution to other parts of Neotropical and Nearctic regions in independent range expansions events. In all cases, host range shifts preceded the cleptoparasite shifts. Main ConclusionThe biogeographical history of cleptoparasitic oil bees and oil‐collecting hosts is generally congruent in time and space. Events of range expansion mainly occurred in the more species‐rich lineages of cleptoparasites. Range shifts in cleptoparasites followed the distribution of their hosts and coincided with the distribution of oil‐producing plants visited by the host bees. Our results broaden our understanding of the complex biogeography of interacting partners and on how changes in host distributions may impact cleptoparasitic bees. 

Abstract We present the first chromosome-level genome assembly for Bombus pensylvanicus, a historically widespread native pollinator species that was distributed across eastern North America but has subsequently undergone declines in range area and local relative abundance. This species has been of significant interest as a model for understanding both patterns and possible causes of bumble bee decline in the region, including the role of genetic variation. Here we present a chromosome-level reference genome assembled using Pacific Biosciences singe-molecule HiFi sequences and Hi-C data and annotated using evidence derived from RNA sequencing of multiple tissue types. The B. pensylvanicus genome has a total length of ∼352.6 Mb and was assembled into a total of 224 scaffolds, with 19 primary pseudomolecules representing putative chromosomes and an N50 = 14.872 Mb. Annotation with the Eukaryotic Genome Annotation Pipeline—External (EGAPx) identified 11,411 genes (10,263 protein coding), and BUSCO analysis of 5,991 Hymenoptera-specific BUSCO groups indicated a completeness for the proteins of 99.0% (98.6% single-copy, 0.5% duplicated) and for the genome of 98.5% (98.2% single-copy, 0.3% duplicated). We present synteny analyses with other recently assembled Bombus genomes representing different subgenera and examine the distribution of repetitive regions of the genome relative to the distribution of genes and noncoding RNAs. 

Obligatory ant–plant symbioses often appear to be single evolutionary shifts within particular ant lineages; however, convergence can be revealed once natural history observations are complemented with molecular phylogenetics. Here, we describe a remarkable example of convergent evolution in an ant–plant symbiotic system. Exclusively arboreal,Myrmelachistaspecies can be generalized opportunists nesting in several plant species or obligately symbiotic, live-stem nesters of a narrow set of plant species. Instances of specialization withinMyrmelachistaare known from northern South America and throughout Middle America. In Middle America, a diverse radiation of specialists occupies understory treelets of lowland rainforests. The morphological and behavioural uniformity of specialists suggests that they form a monophyletic assemblage, diversifying after a single origin of specialization. Using ultraconserved element phylogenomics and ancestral state reconstructions, we show that shifts from opportunistic to obligately symbiotic evolved independently in South and Middle America. Furthermore, our analyses support a remarkable case of convergence within the Middle American radiation, with two independently evolved specialist clades, arising nearly simultaneously from putative opportunistic ancestors during the late Pliocene. This repeated evolution of a complex phenotype suggests similar mechanisms behind trait shifts from opportunists to specialists, generating further questions about the selective forces driving specialization.