Praealbonemertes whangateaunienses n. gen. and n. sp., a new heteronemertean from New Zealand

Abstract

A new genus and species of heteronemertean, Praealbonemertes whangateaunienses n. gen. and n. sp., is described and illustrated. The species is characterised by inter alia a cephalic lacuna with strands of longitudinal muscle fibres, a proboscis with three muscle layers, and a well-developed muscle plate dorsal to the foregut and anterior intestine. The material was collected in New Zealand.     

Leaf and tepal anatomy, plastid ultrastructure and chlorophyll content in Galanthus nivalis L. and Leucojum aestivum L.

The leaf structure of Galanthus nivalis L. (snowdrop) and Leucojum aestivum L. (snowflake) is characterized by a homogeneous mesophyll tissue. The dominant characters of the leaves are cavities with mucose substance. There is a striking difference between these plants tepal anatomy. A central cavity occurs only in snowdrop tepals. Plastids from white parts of the tepals have a poorly developed membrane system. Leaves and green parts of tepals of both species possess amoeboid chloroplasts and contain chlorophyll a and b. The chlorophyll content in tepals is lower than in leaves, but the chlorophyll a:b ratio is always 2:1. Both, snowdrop and snowflake are from the family Amaryllidaceae, but their ecology is different. This paper presents common features related to systematic relatedness and differences induced by ecological factors.     

HGT is widespread in insects and contributes to male courtship in lepidopterans

1. Download : Download high-res image (178KB)
2. Download : Download full-size image

     

Comparison of methods for the demarcation between earlywood and latewood in tree rings of Norway spruce

The precise demarcation between earlywood and latewood is important for the detailed analysis of intra-annual tree ring features. Different techniques based on visual assessment, wood anatomy analysis and X-ray densitometry have been developed and are currently used for this purpose. Depending on the chosen method, tree species and environmental conditions, the results can significantly vary. Thus, it is important to determine the technique optimal for a particular research. Here, we investigated Norway spruce (Picea abies) tree rings to examine the agreement among the following demarcation methods: (1) direct visual assessment, (2) Mork’s index (anatomical definition of the transition from earlywood to latewood based on cell wall-lumen ratio) and (3) fixed and floating density thresholds applied to intra-ring density profiles. The aim was to modify both the Mork’s criterion and density thresholds on the basis of reference values given by visual identification of earlywood/latewood transition. A total of 231 tree rings were analysed by all methods. Our results showed that the usage of floating threshold (defined for each ring separately based on density profiles) is more reliable in comparison with fixed threshold (the same threshold value used for all tree rings and samples). Statistical analysis revealed the best correspondence between visual identification of earlywood/latewood transition and demarcation based on the standard Mork’s index and the floating density threshold derived as 80 % of maximum latewood density. In terms of Mork’s index calibration, the results showed that to determine latewood cells in Norway spruce trees growing in temperate conditions, it is sufficient to use an index value equal to 0.83. The results are applicable for the studied spruce population growing in a temperate climate. The methodology itself, however, is universal and can help to calibrate criteria for earlywood-latewood demarcation under specific conditions.     

Dendroclimatic potential of dendroanatomy in temperature-sensitive Pinus sylvestris

The most frequently and successfully used tree-ring parameters for the study of temperature variations are ring width and maximum latewood density (MXD). MXD is preferred over ring width due to a more prominent association with temperature. In this study we explore the dendroclimate potential of dendroanatomy based on the first truly well replicated dataset. Twenty-nine mature living Pinus sylvestris trees were sampled in North-eastern Finland at the cool and moist boreal forest zone, close to the latitudinal tree line, where ring width, X-ray MXD as well as the blue intensity counterpart MXBI were compared with dendroanatomical parameters. Maximum radial cell wall thickness as well as anatomical MXD and latewood density appeared to be the most promising parameters for temperature reconstruction. In fact, these parameters compare favorably to MXD derived from X-ray techniques as well as MXBI, in terms of shared variation and temperature correlations across frequencies and over time. The reasons for these results are thought to be the unprecedentedly high measurement resolution of the anatomical technique, which provide the optimal resolution – the cell – whereas X-ray techniques have a slightly lower resolution and BI techniques even lower. While the results of this study are encouraging, further tests on longer and multigenerational chronologies are required to more generally and fully assess the dendroclimate potential of anatomical parameters.     

A comparison of diversity estimators applied to a database of host–parasite associations

Understanding the drivers of biodiversity is important for forecasting changes in the distribution of life on earth. However, most studies of biodiversity are limited by uneven sampling effort, with some regions or taxa better sampled than others. Numerous methods have been developed to account for differences in sampling effort, but most methods were developed for systematic surveys in which all study units are sampled using the same design and assemblages are sampled randomly. Databases compiled from multiple sources, such as from the literature, often violate these assumptions because they are composed of studies that vary widely in their goals and methods. Here, we compared the performance of several popular methods for estimating parasite diversity based on a large and widely used parasite database, the Global Mammal Parasite Database (GMPD). We created artificial datasets of host–parasite interactions based on the structure of the GMPD, then used these datasets to evaluate which methods best control for differential sampling effort. We evaluated the precision and bias of seven methods, including species accumulation and nonparametric diversity estimators, compared to analyzing the raw data without controlling for sampling variation. We find that nonparametric estimators, and particularly the Chao2 and second-order jackknife estimators, perform better than other methods. However, these estimators still perform poorly relative to systematic sampling, and effect sizes should be interpreted with caution because they tend to be lower than actual effect sizes. Overall, these estimators are more effective in comparative studies than for producing true estimates of diversity. We make recommendations for future sampling strategies and statistical methods that would improve estimates of global parasite diversity.     

Recent developments in mesophyll conductance in C3, C4, and crassulacean acid metabolism plants

The conductance of carbon dioxide (CO₂) from the substomatal cavities to the initial sites of CO₂ fixation (g_m) can significantly reduce the availability of CO₂ for photosynthesis. There have been many recent reviews on: (i) the importance of g_m for accurately modelling net rates of CO₂ assimilation, (ii) on how leaf biochemical and anatomical factors influence g_m, (iii) the technical limitation of estimating g_m, which cannot be directly measured, and (iv) how g_m responds to long‐ and short‐term changes in growth and measurement environmental conditions. Therefore, this review will highlight these previous publications but will attempt not to repeat what has already been published. We will instead initially focus on the recent developments on the two‐resistance model of g_m that describe the potential of photorespiratory and respiratory CO₂ released within the mitochondria to diffuse directly into both the chloroplast and the cytosol. Subsequently, we summarize recent developments in the three‐dimensional (3‐D) reaction‐diffusion models and 3‐D image analysis that are providing new insights into how the complex structure and organization of the leaf influences g_m. Finally, because most of the reviews and literature on g_m have traditionally focused on C₃ plants we review in the final sections some of the recent developments, current understanding and measurement techniques of g_m in C₄ and crassulacean acid metabolism (CAM) plants. These plants have both specialized leaf anatomy and either a spatially or temporally separated CO₂ concentrating mechanisms (C₄ and CAM, respectively) that influence how we interpret and estimate g_m compared with a C₃ plants.     

New Caledonian crows plan for specific future tool use

The ability to plan for future events is one of the defining features of human intelligence. Whether non-human animals can plan for specific future situations remains contentious: despite a sustained research effort over the last two decades, there is still no consensus on this question. Here, we show that New Caledonian crows can use tools to plan for specific future events. Crows learned a temporal sequence where they were (a) shown a baited apparatus, (b) 5 min later given a choice of five objects and (c) 10 min later given access to the apparatus. At test, these crows were presented with one of two tool–apparatus combinations. For each combination, the crows chose the right tool for the right future task, while ignoring previously useful tools and a low-value food item. This study establishes that planning for specific future tool use can evolve via convergent evolution, given that corvids and humans shared a common ancestor over 300 million years ago, and offers a route to mapping the planning capacities of animals.     

Acknowledging uncertainty in evolutionary reconstructions of ecological niches

Reconstructing ecological niche evolution can provide insight into the biogeography and diversification of evolving lineages. However, comparative phylogenetic methods may infer the history of ecological niche evolution inaccurately because (a) species' niches are often poorly characterized; and (b) phylogenetic comparative methods rely on niche summary statistics rather than full estimates of species' environmental tolerances. Here, we propose a new framework for coding ecological niches and reconstructing their evolution that explicitly acknowledges and incorporates the uncertainty introduced by incomplete niche characterization. Then, we modify existing ancestral state inference methods to leverage full estimates of environmental tolerances. We provide a worked empirical example of our method, investigating ecological niche evolution in the New World orioles (Aves: Passeriformes: Icterus spp.). Temperature and precipitation tolerances were generally broad and conserved among orioles, with niche reduction and specialization limited to a few terminal branches. Tools for performing these reconstructions are available in a new R package called nichevol.     

Comparison of Morphological and Anatomical Characteristics of <i>Taxus chinensis</i> var. <i>mairei </i>Seedlings Root under Waterlogging Stress in Different Substrates

Four different ratios of river sand, ceramic pellets, vermiculite and perlite (1:1), and field soil were selected as the substrates in this experiment, and four gradient levels of root waterlogging, half waterlogging, full waterlogging and normal were set to investigate the effects of different gradients of waterlogging stress on the root morphology of Taxus chinensis var. mairei seedlings under different substrates. In this study, the root anatomical structure of Taxus chinensis var. mairei under different waterlogging stress was observed by the paraffin section method. The roots of T. chinensis var. mairei were diarch, with no pith and resin canals. There was a large number of tannins in the pericycle of the aerial adventitious roots of seedlings adapted to waterlogging. Also, the endodermis has obvious casparian strip thickening, and there were 4-5 layers of large parenchymatous cells in the close to the inner side of the pericycle in the vascular cylinder, which could increase the storage capacity, and transport capacity of the root. Under the treatment of root waterlogging stress, the development of plant roots in the mixed substrate of vermiculite and, perlite was the earliest. Under half waterlogging stress, T. chinensis var. mairei seedlings treated with various substrates all could better adapt to the environment of waterlogging stress. Under the stress of fully waterlogging, the roots of seedlings planted in river sand substrate developed secondary growth.