Transition of Vegetation States Positively Affects Harvester Ants in the Great Basin, United States

Invasions by non-native plants can alter ecosystems such that new ecological states are reached, but less is known about how these transitions influence animal populations. Sagebrush (Artemisia tridentata) ecosystems are experiencing state changes because of fire and invasion by exotic annual grasses. Our goal was to study the effects of these state changes on the Owyhee and western harvester ants (Pogonomyrmex salinus Olsen and P. occidentalis Cresson, respectively). We sampled 358 1-ha plots across the northern Great Basin,which captured unburned and burned conditions across 1-31 years postfire. Our results indicated an immediate and consistent change in vegetation states fromshrubland to grassland between 1 and 31 years postfire. Harvester ant occupancy was unrelated to time since fire, whereas we observed a positive effect of fire on nest density. Similarly, we discovered that fire and invasion by exotic annuals were weak predictors of harvester ant occupancy but strong predictors of nest density. Occupancy of harvester ants wasmore likely in areas with finer-textured soils, low precipitation, abundant native forbs, and low shrub cover. Nest densitywas higher in arid locations that recently burned and exhibited abundant exotic annual and perennial (exotic and native) grasses. Finally,we discovered that burned areas that received postfire restoration had minimal influence on harvester ant occupancy or nest density compared with burned and untreated areas. These results suggest that fire-induced state changes from native shrublands to grasslands dominated by non-native grasses have a positive effect on density of harvester ants (but not occupancy), and that postfire restoration does not appear to positively or negatively affect harvester ants. Although wildfire and invasion by exotic annual grasses may negatively affect other species, harvester ants may indeed be one of the few winners among a myriad of losers linked to vegetation state changes within sagebrush ecosystems. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information

The Nuclear Cap-Binding Complex Mediates Meiotic Silencing by Unpaired DNA

In the filamentous fungus Neurospora crassa, cross walls between individual cells are normally incomplete, making the entire fungal network vulnerable to attack by viruses and selfish DNAs. Accordingly, several genome surveillance mechanisms are maintained to help the fungus combat these repetitive elements. One of these defense mechanisms is called meiotic silencing by unpaired DNA (MSUD), which identifies and silences unpaired genes during meiosis. Utilizing common RNA interference (RNAi) proteins, such as Dicer and Argonaute, MSUD targets mRNAs homologous to the unpaired sequence to achieve silencing. In this study, we have identified an additional silencing component, namely the cap-binding complex (CBC). Made up of cap-binding proteins CBP20 and CBP80, CBC associates with the 5′ cap of mRNA transcripts in eukaryotes. The loss of CBC leads to a deficiency in MSUD activity, suggesting its role in mediating silencing. As confirmed in this study, CBC is predominantly nuclear, although it is known to travel in and out of the nucleus to facilitate RNA transport. As seen in animals but not in plants, CBP20’s robust nuclear import depends on CBP80 in Neurospora. CBC interacts with a component (Argonaute) of the perinuclear meiotic silencing complex (MSC), directly linking the two cellular factors

Bird species distributions across woodland canopy structure gradients

The tree canopy characteristics of two broadleaved woods in southern England were quantified in terms of two independent measures of structure, canopy height (calculated using heights ≥ 1 m) and percentage canopy cover (derived using heights 0.90, p < 0.001), there was a positive correlation across bird species between the mean values of canopy height and canopy cover associated with the mapped locations of each species. We suggest that canopy height acts as an effective surrogate of woodland structure and can be applied as a predictor of bird community composition and distribution, at least in lowland British conditions. Species associated with young growth had narrower niche breadths, as measured by differences in canopy height and canopy cover between the two woods, than did species associated with taller canopies. Remote sensing of canopy height potentially offers a simple, effective way of assessing habitat availability for many species, at both woodland and landscape scales. This may be especially relevant for species dependent on highly transient vegetation structures associated with the early pre-canopy closure stages of forest growth