The ortholog of the human proto‐oncogene ROS1 is required for epithelial development in C. elegans

The orphan receptor ROS1 is a human proto‐oncogene, mutations of which are found in an increasing number of cancers. Little is known about the role of ROS1, however in vertebrates it has been implicated in promoting differentiation programs in specialized epithelial tissues. In this study we show that the C. elegans ortholog of ROS1, the receptor tyrosine kinase ROL‐3, has an essential role in orchestrating the morphogenesis and development of specialized epidermal tissues, highlighting a potentially conserved function in coordinating crosstalk between developing epithelial cells. We also provide evidence of a direct relationship between ROL‐3, the mucin SRAP‐1, and BCC‐1, the homolog of mRNA regulating protein Bicaudal‐C. This study answers a longstanding question as to the developmental function of ROL‐3, identifies three new genes that are expressed and function in the developing epithelium of C. elegans, and introduces the nematode as a potentially powerful model system for investigating the increasingly important, yet poorly understood, human oncogene ROS1. genesis 51:545–561. © 2013 Wiley Periodicals, Inc.     

Non‐parallel recombination limits cre‐loxP‐based reporters as precise indicators of conditional genetic manipulation

Cre/LoxP‐mediated recombination allows for conditional gene activation or inactivation. When combined with an independent lineage‐tracing reporter allele, this technique traces the lineage of presumptive genetically modified Cre‐expressing cells. Several studies have suggested that floxed alleles have differential sensitivities to Cre‐mediated recombination, which raises concerns regarding utilization of Cre‐reporters to monitor recombination of other floxed loci of interest. Here, we directly investigate the recombination correlation, at cellular resolution, between several floxed alleles induced by Cre‐expressing mouse lines. The recombination correlation between different reporter alleles varied greatly in otherwise genetically identical cell types. The chromosomal location of floxed alleles, distance between LoxP sites, sequences flanking the LoxP sites, and the level of Cre activity per cell all likely contribute to observed variations in recombination correlation. These findings directly demonstrate that, due to non‐parallel recombination events, commonly available Cre reporter mice cannot be reliably utilized, in all cases, to trace cells that have DNA recombination in independent‐target floxed alleles, and that careful validation of recombination correlations are required for proper interpretation of studies designed to trace the lineage of genetically modified populations, especially in mosaic situations. genesis 51:436–442. © 2013 Wiley Periodicals, Inc.     

Recent multiple introductions of the gall‐forming aphid Pemphigus bursarius into Japanese islands

Recently, the number of collection records of Pemphigus galls from Populus nigra has been increasing in Japan. To identify the galls on P. nigra, mitochondrial COI sequences were analyzed from galling aphid samples collected on P. nigra in Tokyo and Hokkaido. From the BLAST search and neighbor‐joining (NJ) analysis, the aphid samples were identified as Pemphigus bursarius, which has not been recorded from Japan. Two samples from Tokyo and Hokkaido showed a genetic difference of 0.30%. This result suggests that different strains of P. bursarius might have been introduced into the Japanese islands at least twice.     

Projecting demographic responses to climate change: adult and juvenile survival respond differently to direct and indirect effects of weather in a passerine population

Few studies have quantitatively projected changes in demography in response to climate change, yet doing so can provide important insights into the processes that may lead to population declines and changes in species distributions. Using a long‐term mark‐recapture data set, we examined the influence of multiple direct and indirect effects of weather on adult and juvenile survival for a population of Song Sparrows (Melospiza melodia) in California. We found evidence for a positive, direct effect of winter temperature on adult survival, and a positive, indirect effect of prior rainy season precipitation on juvenile survival, which was consistent with an effect of precipitation on food availability during the breeding season. We used these relationships, and climate projections of significantly warmer and slightly drier winter weather by the year 2100, to project a significant increase in mean adult survival (12–17%) and a slight decrease in mean juvenile survival (4–6%) under the B1 and A2 climate change scenarios. Together with results from previous studies on seasonal fecundity and postfledging survival in this population, we integrated these results in a population model and projected increases in the population growth rate under both climate change scenarios. Our results underscore the importance of considering multiple, direct, and indirect effects of weather throughout the annual cycle, as well as differences in the responses of each life stage to climate change. Projecting demographic responses to climate change can identify not only how populations will be affected by climate change but also indicate the demographic process(es) and specific mechanisms that may be responsible. This information can, in turn, inform climate change adaptation plans, help prioritize future research, and identify where limited conservation resources will be most effectively and efficiently spent.     

Characterization of an alpine tree line using airborne LiDAR data and physiological modeling

Understanding what environmental drivers control the position of the alpine tree line is important for refining our understanding of plant stress and tree development, as well as for climate change studies. However, monitoring the location of the tree line position and potential movement is difficult due to cost and technical challenges, as well as a lack of a clear boundary. Advanced remote sensing technologies such as Light Detection and Ranging (LiDAR) offer significant potential to map short individual tree crowns within the transition zone despite the lack of predictive capacity. Process‐based forest growth models offer a complementary approach by quantifying the environmental stresses trees experience at the tree line, allowing transition zones to be defined and ultimately mapped. In this study, we investigate the role remote sensing and physiological, ecosystem‐based modeling can play in the delineation of the alpine tree line. To do so, we utilize airborne LiDAR data to map tree height and stand density across a series of altitudinal gradients from below to above the tree line within the Swiss National Park (SNP), Switzerland. We then utilize a simple process‐based model to assess the importance of seasonal variations on four climatically related variables that impose non‐linear constraints on photosynthesis. Our results indicate that all methods predict the tree line to within a 50 m altitudinal zone and indicate that aspect is not a driver of significant variations in tree line position in the region. Tree cover, rather than tree height is the main discriminator of the tree line at higher elevations. Temperatures in fall and spring are responsible for the major differences along altitudinal zones, however, changes in evaporative demand also control plant growth at lower altitudes. Our results indicate that the two methods provide complementary information on tree line location and, when combined, provide additional insights into potentially endangered forest/grassland transition zones.     

Driving factors of a vegetation shift from Scots pine to pubescent oak in dry Alpine forests

An increasing number of studies have reported on forest declines and vegetation shifts triggered by drought. In the Swiss Rhone valley (Valais), one of the driest inner‐Alpine regions, the species composition in low elevation forests is changing: The sub‐boreal Scots pine (Pinus sylvestris L.) dominating the dry forests is showing high mortality rates. Concurrently the sub‐Mediterranean pubescent oak (Quercus pubescens Willd.) has locally increased in abundance. However, it remains unclear whether this local change in species composition is part of a larger‐scale vegetation shift. To study variability in mortality and regeneration in these dry forests we analysed data from the Swiss national forest inventory (NFI) on a regular grid between 1983 and 2003, and combined it with annual mortality data from a monitoring site. Pine mortality was found to be highest at low elevation (below 1000 m a.s.l.). Annual variation in pine mortality was correlated with a drought index computed for the summer months prior to observed tree death. A generalized linear mixed‐effects model indicated for the NFI data increased pine mortality on dryer sites with high stand competition, particularly for small‐diameter trees. Pine regeneration was low in comparison to its occurrence in the overstorey, whereas oak regeneration was comparably abundant. Although both species regenerated well at dry sites, pine regeneration was favoured at cooler sites at higher altitude and oak regeneration was more frequent at warmer sites, indicating a higher adaptation potential of oaks under future warming. Our results thus suggest that an extended shift in species composition is actually occurring in the pine forests in the Valais. The main driving factors are found to be climatic variability, particularly drought, and variability in stand structure and topography. Thus, pine forests at low elevations are developing into oak forests with unknown consequences for these ecosystems and their goods and services.