The evolution of myrmicine ants: phylogeny and biogeography of a hyperdiverse ant clade (Hymenoptera: Formicidae)

This study investigates the evolutionary history of a hyperdiverse clade, the ant subfamily Myrmicinae (Hymenoptera: Formicidae), based on analyses of a data matrix comprising 251 species and 11 nuclear gene fragments. Under both maximum likelihood and Bayesian methods of inference, we recover a robust phylogeny that reveals six major clades of Myrmicinae, here treated as newly defined tribes and occurring as a pectinate series: Myrmicini, Pogonomyrmecini trib.n. , Stenammini, Solenopsidini, Attini and Crematogastrini. Because we condense the former 25 myrmicine tribes into a new six‐tribe scheme, membership in some tribes is now notably different, especially regarding Attini. We demonstrate that the monotypic genus Ankylomyrma is neither in the Myrmicinae nor even a member of the more inclusive formicoid clade—rather it is a poneroid ant, sister to the genus Tatuidris (Agroecomyrmecinae). Several species‐rich myrmicine genera are shown to be nonmonophyletic, including Pogonomyrmex, Aphaenogaster, Messor, Monomorium, Pheidole, Temnothorax and Tetramorium. We propose a number of generic synonymies to partially alleviate these problems (senior synonym listed first): Pheidole = Anisopheidole syn.n. = Machomyrma syn.n. ; Temnothorax = Chalepoxenus syn.n. = Myrmoxenus syn.n. = Protomognathus syn.n. ; Tetramorium = Rhoptromyrmex syn.n. = Anergates syn.n. = Teleutomyrmex syn.n. The genus Veromessor stat.r. is resurrected for the New World species previously placed in Messor; Syllophopsis stat.r. is resurrected from synonymy under Monomorium to contain the species in the hildebrandti group; Trichomyrmex stat.r. is resurrected from synonymy under Monomorium to contain the species in the scabriceps‐ and destructor‐groups; and the monotypic genus Epelysidris stat.r. is reinstated for Monomorium brocha. Bayesian divergence dating indicates that the crown group Myrmicinae originated about 98.6 Ma (95% highest probability density 87.9–109.6 Ma) but the six major clades are considerably younger, with age estimates ranging from 52.3 to 71.1 Ma. Although these and other suprageneric taxa arose mostly in the middle Eocene or earlier, a number of prominent, species‐rich genera, such as Pheidole, Cephalotes, Strumigenys, Crematogaster and Tetramorium, have estimated crown group origins in the late Eocene or Oligocene. Most myrmicine species diversity resides in the two sister clades, Attini and Crematogastrini, which are estimated to have originated and diversified extensively in the Neotropics and Paleotropics, respectively. The newly circumscribed Myrmicini is Holarctic in distribution, and ancestral range estimation suggests a Nearctic origin. The Pogonomyrmecini and Solenopsidini are reconstructed as being Neotropical in origin, but they have subsequently colonized the Nearctic region (Pogonomyrmecini) and many parts of the Old World as well as the Nearctic region (Solenopsidini), respectively. The Stenammini have flourished primarily in the northern hemisphere, and are most likely of Nearctic origin, but selected lineages have dispersed to the northern Neotropics and the Paleotropics. Thus the evolutionary history of the Myrmicinae has played out on a global stage over the last 100 Ma, with no single region being the principal generator of species diversity. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub: BB6829C4‐DA79‐45FE‐979E‐9749E237590E .     

c-AMP and Morphogenesis of Acetabularia

The c-AMP content has been found to double when Acetabularia develop from 5–10 mm long to grown or almost full-grown algae.
The biological significance of this fact has been approached by studying the effects of drugs known to influence the intracellular c-AMP content on the development of Acetabularia. When grown in the presence of theophyllin or papaverin, inhibitors of phosphodiesterase, the Acetabularia display a striking response during the exponential growth period; the final length, however, is not affected. Both substances increase the c-AMP content of the algea. Isoproterenol, which activates adenylate cyclase in many systems, also influences Acetabularia during the exponential growth period and, in addition, slightly affects cap formation.
The change in c-AMP content in the course of development and the effects of drugs influencing (theophyllin and papaverin) or likely to influence (isoproterenol) the c-AMP content of the algae suggest that this nucleotide plays a role at the time of intense growth.
The same phosphodiesterase activity has been found in the 5–10 mm and the 19–25 mm long algae, whereas two enzymes were found in cap-bearing Acetabularia.
The results are discussed as well as the involvement of c-AMP in the development of this alga.     

Dynamics of microplankton communities at the ice-edge zone of the Lazarev Sea during a summer drogue study

Microzooplankton grazing and community structure were investigatedin the austral summer of 1995 during a Southern Ocean Drogueand Ocean Flux Study (SODOFS) at the ice-edge zone of the LazarevSea. Grazing was estimated at the surface chlorophyll maximum(5–10 m) by employing the sequential dilution technique.Chlorophyll a concentrations were dominated by chainformingmicrophytoplankton (>20 µm) of the genera Chaetocerosand Nitzschia. Microzooplankton were numerically dominated byaloricate ciliates and dinoflagellates (Protoperidinium sp.,Amphisoleta sp. and Gymnodinium sp.). Instantaneous growth ratesof nanophytoplankton (<20 µm) varied between 0.019and 0.080 day^–1, equivalent to between 0.03 and 0.12 chlorophylldoublings day^–1. Instantaneous grazing rates of microzooplanktonon nanophytoplankton varied from 0.012 to 0.052 day^–1.This corresponds to a nanophytoplankton daily loss of between1.3 and 7.0% (mean = 3.76%) of the initial standing stock, andbetween 45 and 97% (mean = 70.37%) of the daily potential production.Growth rates of microphytoplankton (>20 µm) were lower,varying between 0.011 and 0.070 day^–1, equivalent to 0.015–0.097chlorophyll doublings day^–1. At only three of the 10 stationsdid grazing by microzooplankton result in a decrease in microphytoplanktonconcentration. At these stations instantaneous grazing ratesof microzooplankton on microphytoplankton ranged between 0.009and 0.015 day^–1, equivalent to a daily loss of <1.56%(mean = 1.11%) of initial standing stock and <40% (mean =28.55%) of the potential production. Time series grazing experimentsconducted at 6 h intervals did not show any diel patterns ofgrazing by microzooplankton. Our data show that microzooplanktongrazing at the ice edge were not sufficient to prevent chlorophylla accumulation in regions dominated by rnicrophytoplankton.Here, the major biological routes for the uptake of carbon thereforeappear to be grazing by metazoans or the sedimentation of phytoplanktoncells. Under these conditions, the biological pump will be relativelyefficient in the drawdown of atmospheric CO₂.