Global domination by crazy ants: phylogenomics reveals biogeographical history and invasive species relationships in the genus Nylanderia (Hymenoptera: Formicidae)

Nylanderia (Emery) is one of the world's most diverse ant genera, with 123 described species worldwide and hundreds more undescribed. Fifteen globetrotting or invasive species have widespread distributions and are often encountered outside their native ranges. A molecular approach to understanding the evolutionary history and to revision of Nylanderia taxonomy is needed because historical efforts based on morphology have proven insufficient to define major lineages and delimit species boundaries, especially where adventive species are concerned. To address these problems, we generated the first genus-wide genomic dataset of Nylanderia using ultraconserved elements (UCEs) to resolve the phylogeny of major lineages, determine the age and origin of the genus, and describe global biogeographical patterns. Sampling from seven biogeographical regions revealed a Southeast Asian origin of Nylanderia in the mid-Eocene and four distinct biogeographical clades in the Nearctic, the Neotropics, the Afrotropics/Malagasy region, and Australasia. The Nearctic and Neotropical clades are distantly related, indicating two separate dispersal events to the Americas between the late Oligocene and early Miocene. We also addressed the problem of misidentification that has characterized species-level taxonomy in Nylanderia as a result of limited morphological variation in the worker caste by evaluating the integrity of species boundaries in six of the most widespread Nylanderia species. We sampled across ranges of species in the N. bourbonica complex (N. bourbonica (Forel) + N. vaga (Forel)), the N. fulva complex (N. fulva (Mayr) + N. pubens (Forel)), and the N. guatemalensis complex (N. guatemalensis (Forel) + N. steinheili (Forel)) to clarify their phylogenetic placement. Deep splits within these complexes suggest that some species names – specifically N. bourbonica and N. guatemalensis – each are applied to multiple cryptic species. In exhaustively sampling Nylanderia diversity in the West Indies, a ‘hot spot’ for invasive taxa, we found five adventive species among 22 in the region; many remain morphologically indistinguishable from one another, despite being distantly related. We stress that overcoming the taxonomic impediment through the use of molecular phylogeny and revisionary study is essential for conservation and invasive species management.     

Genic homozygosity in an ancient reptile (Alligator mississippiensis)

Proteins assayed electrophoretically showed variation at only three of 49 presumed genetic loci in alligators from southwestern Louisiana. Average heterozygosity per individual was 0.021±0.012; proportion of polymorphic loci was 0.06. Data on the history, structure, and ecology of this alligator population are consistent with natural selection as the primary factor accounting for this low genetic variability. However, neither a historic population bottleneck nor some genetic mechanism limiting variability can be dismissed as a possible factor.The study was supported by NSF Grant BMS 73-0125 to H.C.D.     

Long-term effect of retrobulbar hematomas on the vision of cynomolgus monkeys.

Using the monkey model previously developed, we investigated the long-term effects of retrobulbar hematoma-induced retinal ischemia on functional vision and retinal histology. In this experimental model, ischemic periods of up to 120 minutes did not cause permanent visual deficits, as measured by flashed evoked visual potentials. Similarly, retinal histology showed no evidence of ischemic injury. From this we conclude that blindness after blepharoplasty is not due to retrobulbar hematomas alone and that additional predisposing factors are involved. The most likely additional factor is preexisting occult vascular ocular pathology.     

A histocytochemical study of the macrophages present in tissue responses to adult Onchocerca volvulus

Summary Immunocytochemical and histochemical properties of macrophages present in the subcutaneous chronic inflammatory responses surrounding adultOnchocerca volvulus (nodules) in human tissues were examined. Macrophages with strong non-specific esterase (NSE) and acid phosphatase (AcPase) activities but weak adenosine triphosphatase (ATPase) activity and HLA-DR expression (NSE⁺⁺⁺, AcPase⁺⁺⁺, ATPase^–/+, HLA-DR^–/+) were present in the centre of nodules. Many of the cells adhering to the surface of worms were NSE⁺⁺⁺, AcPase⁺⁺⁺, ATPase^–, HLA-DR⁺⁺⁺. The inner zone of the fibrous capsule of nodules contained macrophages with the profile NSE⁺⁺⁺, AcPase^–, ATPase^–/+, HLA-DR^–/+. A fourth type, NSE⁺⁺⁺, AcPase^–/+, ATPase^–/+, HLA-DR⁺⁺⁺, was located in the outer zone of the capsule, frequently within perivascular accumulations of macrophages, lymphocytes and plasma cells. Active fibroblasts were identified at the inner edge of the fibrous capsule by alkaline phosphatase staining. A feature of all nodules examined was the presence of lipid-filled macrophages, demonstrated by Oil Red O stain; these cells were usually situated in zones adjacent to the centre of nodules, and were of the NSE⁺⁺, AcPase⁺⁺, ATPase^–/+, HLA-DR^–/+ type. Lipid accumulation was not found to be related to the clinical status of the patients studied. The origin and functional significance of this lipid is unknown.     

The mechanism of low-frequency sound production in muscle.

Frog gastrocnemius muscles stimulated isometrically in a saline bath at 20 degrees C were found to produce a single ringing sound event beginning just before the tension record began to rise. The sound event was substantially over by the time the isometric tension began to fall. Results from studies correlating the spatial pattern of the sound, the amplitude and frequency of the sound as a function of the muscle length, and the response of both the passive and active muscle to a transverse pluck were found to be consistent with the conclusion that the sounds in these muscles are caused primarily by transverse resonant vibrations. As the muscle develops force, its lack of cylindrical symmetry gives rise to lateral motions, which are most likely the initiators of the bending vibrations detected as sound.