Parallel responses of bees to Pleistocene climate change in three isolated archipelagos of the southwestern Pacific

The impacts of glacial cycles on the geographical distribution and size of populations have been explored for numerous terrestrial and marine taxa. However, most studies have focused on high latitudes, with only a few focused on the response of biota to the last glacial maximum (LGM) in equatorial regions. Here, we examine how population sizes of key bee fauna in the southwest Pacific archipelagos of Fiji, Vanuatu and Samoa have fluctuated over the Quaternary. We show that all three island faunas suffered massive population declines, roughly corresponding in time to the LGM, followed by rapid expansion post-LGM. Our data therefore suggest that Pleistocene climate change has had major impacts across a very broad tropical region. While other studies indicate widespread Holarctic effects of the LGM, our data suggest a much wider range of latitudes, extending to the tropics, where these climate change repercussions were important. As key pollinators, the inferred changes in these bee faunas may have been critical in the development of the diverse Pacific island flora. The magnitude of these responses indicates future climate change scenarios may have alarming consequences for Pacific island systems involving pollinator-dependent plant communities and agricultural crops.     

Conserving large carnivores: dollars and fence

Conservationists often advocate for landscape approaches to wildlife management while others argue for physical separation between protected species and human communities, but direct empirical comparisons of these alternatives are scarce. We relate African lion population densities and population trends to contrasting management practices across 42 sites in 11 countries. Lion populations in fenced reserves are significantly closer to their estimated carrying capacities than unfenced populations. Whereas fenced reserves can maintain lions at 80% of their potential densities on annual management budgets of $500 km⁻², unfenced populations require budgets in excess of $2000 km⁻² to attain half their potential densities. Lions in fenced reserves are primarily limited by density dependence, but lions in unfenced reserves are highly sensitive to human population densities in surrounding communities, and unfenced populations are frequently subjected to density‐independent factors. Nearly half the unfenced lion populations may decline to near extinction over the next 20–40 years.     

The non-photochemical reduction of plastoquinone in leaves

Although it is generally assumed that the plastoquinone pool of thylakoid membranes in leaves of higher plants is rapidly oxidized upon darkening, this is often not the case. A multiflash kinetic fluorimeter was used to monitor the redox state of the plastoquinone pool in leaves. It was found that in many species of plants, particularly those using the NAD-malic enzyme C₄ system of photosynthesis, the pool actually became more reduced following a light to dark transition. In some Amaranthus species, plastoquinone remained reduced in the dark for several hours. Far red light, which preferentially drives Photosystem I turnover, could effectively oxidize the plastoquinone pool. Plastoquinone was re-reduced in the dark within a few seconds when far red illumination was removed. The underlying mechanism of the dark reduction of the plastoquinone pool is still uncertain but may involve chlororespiratory activity.Abbreviations apparent F_o observed fluorescence yield after dark adaptation - F_m maximum fluorescence when all Q_A is fully reduced - F_o minimum fluorescence yield when Q_A is fully oxidized and non-photochemical quenching is fully relaxed - F_s steady state fluorescence yield - PPFD photosynthetic photon flux density - PQ plastoquinone - Q_A primary quinone acceptor of the Photosystem II reaction center - Q_B secondary quinone acceptor to the Photosystem II reaction center - F F_m minus F_s     

Evidence for independent recruitment of zeta-crystallin/quinone reductase (CRYZ) as a crystallin in camelids and hystricomorph rodents

Zeta-crystallin/quinone reductase (CRYZ) is an NADPH oxidoreductase expressed at very high levels in the lenses of two groups of mammals: camelids and some hystricomorph rodents. It is also expressed at very low levels in all other species tested. Comparative analysis of the mechanisms mediating the high expression of this enzyme/crystallin in the lens of the Ilama (Lama guanacoe) and the guinea pig (Cavia porcellus) provided evidence for independent recruitment of this enzyme as a lens crystallin in both species and allowed us to elucidate for the first time the mechanism of lens recruitment of an enzyme- crystallin. The data presented here show that in both species such recruitment most likely occurred through the generation of new lens promoters from nonfunctional intron sequences by the accumulation of point mutations and/or small deletions and insertions. These results further support the idea that recruitment of CRYZ resulted from an adaptive process in which the high expression of CRYZ in the lens provides some selective advantage rather than from a purely neutral evolutionary process.      

Evidence of independent gene duplications during the evolution of archaeal and eukaryotic family B DNA polymerases

Eukaryotes and archaea both possess multiple genes coding for family B DNA polymerases. In animals and fungi, three family B DNA polymerases, alpha, delta, and epsilon, are responsible for replication of nuclear DNA. We used a PCR-based approach to amplify and sequence phylogenetically conserved regions of these three DNA polymerases from Giardia intestinalis and Trichomonas vaginalis, representatives of early-diverging eukaryotic lineages. Phylogenetic analysis of eukaryotic and archaeal paralogs suggests that the gene duplications that gave rise to the three replicative paralogs occurred before the divergence of the earliest eukaryotic lineages, and that all eukaryotes are likely to possess these paralogs. One eukaryotic paralog, epsilon, consistently branches within archaeal sequences to the exclusion of other eukaryotic paralogs, suggesting that an epsilon-like family B DNA polymerase was ancestral to both archaea and eukaryotes. Because crenarchaeote and euryarchaeote paralogs do not form monophyletic groups in phylogenetic analysis, it is possible that archaeal family B paralogs themselves evolved by a series of gene duplications independent of the gene duplications that gave rise to eukaryotic paralogs.      

Effects of fungicides and bactericides on orchid seed germination and shoot tip cultures in vitro

Amphotericin B, benomyl, gentamycin, nystatin, quintozene penicillin G, sodium omadine, and vancomycin singly and in several combinations have no deleterious effects on the germination of orchid seeds, but inhibit the growth in vitro of shoot tip explants.     

Analysis of Light-Induced Depressions of Photosynthesis in Leaves of a Wheat Crop during the Winter

The photosynthetic performances of individual leaves of a wheat (Triticum aestivum cv Bezostaya) crop were assessed daily and throughout individual days during the winter when temperature and light levels were fluctuating. Measurements of chlorophyll fluorescence induction and the maximum quantum yield of O₂ evolution were made on individual leaves. Depressions in the ratio of variable to maximal fluorescence (F_v/F_m) were correlated with low temperatures and high light levels throughout the winter and during the course of individual days. Depressions in F_v/F_m observed in the field during the day were not accompanied by any significant change in the ability of photosystem II complexes to bind 3-(3,4-dichlorophenyl)-1-dimethyl urea, indicating that the depressions in F_v/F_m were not attributable to photodamage to the D1 protein of the photosystem II reaction center. Decreases in F_v/F_m were associated with increases in the rate of dissipation of excitation energy by radiationless decay processes and decreases in the quantum efficiency of CO₂ assimilation, indicative of a rapidly reversible light-induced “downregulation” of photosynthesis. No major changes were observed in the maximum quantum efficiency of O₂ evolution of leaves throughout periods of fluctuating temperature and light, because light-induced depressions in photosynthetic efficiency recovered within the time required to make these measurements.     

Detection and verification of quantitative trait loci for resistance to Dothistroma needle blight in<Emphasis Type="Italic"> Pinus radiata</Emphasis>

Six related radiata pine (Pinus radiata) full-sib families were used to detect and independently verify quantitative trait loci (QTLs) for resistance to Dothistroma needle blight, caused by Dothistroma septospora. The detection families had from 26 to 30 individuals each, and had either a common maternal (31053) or paternal (31032) parent; one family (cross 4) consisted of progeny from both parents, 31053×31032. Approximately 200 additional progeny from cross 4 were clonally replicated and planted at two sites, with at least five to seven ramets of each individual per site. Marker segregation data were collected from a total of 250 RFLP and microsatellite markers, and single factor ANOVAs were conducted separately for each family and marker. A number of putative associations were observed, some across more than one family. Permutation tests were used to confirm expected probabilities of multiple associations based on chance alone. Seven markers representing at least four QTLs for resistance to Dothistroma were identified as being significant in more than one family; one of these was significant at P<0.05 in three families and highly significant at P<0.01 in a fourth. Further confirmation was obtained by testing those markers that were significant in more than one of the detection families (or highly significant in cross 4) in the clonally replicated progeny from cross 4. Four QTL positions were verified in the clonal populations, with a total percent variation accounted for of 12.5.Communicated by D.B. Neale     

Mice and Monkeys as Assay Animals for Clostridium perfringens Food Poisoning

Spores and vegetative cells of Clostridium perfringens, in combination with meat or starch paste, sterile culture filtrates, lecithinase, and phosphorylcholine, were administered to mice and rhesus monkeys in an attempt both to evaluate the animals as test agents and, if possible, to elucidate the active factors producing food-poisoning symptoms caused by this organsim. Some of the preparations were administered to the monkeys by stomach tube; others, in gelatin capsules which were treated with formaldehyde so that the release of their contents was delayed and presumably reached the intestines of the animals. Any changes in intestinal passage times and in consistency of stools of the animals were observed, and the counts of C. perfringens in the feces of the monkeys previous and subsequent to treatment were recorded. The results obtained were inconclusive. Diarrhea occurred only relatively infrequently in both species, regardless of the substance fed or the mode of administration. The changes in intestinal passage times were not great, although in the monkeys there appeared to be a slight trend toward reduction as the magnitude of the bacterial load increased. Phosphorylcholine appeared to have little, if any, effect in reducing intestinal passage time of mice or monkeys. No procedures explored in these experiments could be said to be satisfactory as a means of animal assay for food poisoning strains of C. perfringens since typical symptoms did not appear with regularity.