Climate niche shift in invasive species: the case of the brown anole

Anolis sagrei, a Cuba and Bahama native lizard, is a successful invader in Florida and adjacent areas. Herein, we focus on conservatism in its climate niche axes and possible congruencies with its natural history properties. The not mutually exclusive hypotheses of the present study explaining its northern range limit are: (1) climatic conditions within species' native and invasive ranges are identical; (2) the species is pre‐adapted to novel conditions as a result of historical climate variations; and (3) only some niche axes limit the species' invasive distribution and the observed pattern is explained by an interplay between the potential niche within its native range and life‐history. Species distribution models for native and invasive distributions were built on ten bioclimatic variables. Using Schoener's niche overlap index, the degree of niche conservatism among variables was identified. Significances of hypothesis (1) were tested using null‐model approaches. Possible climatic pre‐adaptations were evaluated by comparing its actual tolerance within its invasive range with that of the Last Glacial Maximum (LGM) within its native range (hypothesis 2). Results of (1) and (2) are discussed in relation to natural history, approaching hypothesis 3. We detect varying overlaps in niche axes, indicating that natural history properties are associated with conservative niche axes. Climatic comparisons with LGM of native and current conditions of invasive range suggest that pre‐adaptations are unlikely. Possible shifts in the fundamental niche of the species may have been facilitated by enhanced genetic diversity in northern invasive populations. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 943–954.     

Static and dynamic bending has minor effects on xylem hydraulics of conifer branches (Picea abies,Pinus sylvestris)

The xylem hydraulic efficiency and safety is usually measured on mechanically unstressed samples, although trees may be exposed to combined hydraulic and mechanical stress in the field. We analysed changes in hydraulic conductivity and vulnerability to drought‐induced embolism during static bending of Picea abies and Pinus sylvestris branches as well as the effect of dynamic bending on the vulnerability. We hypothesized this mechanical stress to substantially impair xylem hydraulics. Intense static bending caused an only small decrease in hydraulic conductance (?19.5 ± 2.4% in P. abies) but no shift in vulnerability thresholds. Dynamic bending caused a 0.4 and 0.8 MPa decrease of the water potential at 50 and 88% loss of conductivity in P. sylvestris, but did not affect vulnerability thresholds in P. abies. With respect to applied extreme bending radii, effects on plant hydraulics were surprisingly small and are thus probably of minor eco‐physiological importance. More importantly, results indicate that available xylem hydraulic analyses (of conifers) sufficiently reflect plant hydraulics under field conditions.     

Ascorbate promotes emission of mercury vapour from plants

Mercury vapour (Hg°) emission from plants contributes to the atmospheric mercury cycle. Although a part of this Hg° emission originates from Hg(II) uptake by the roots, the question how terrestrial plants reduce Hg(II) has not been addressed so far. Young barley plants grown on a hydroponic cultivation containing Hg(II) increased the Hg° emission significantly. Homogenates of barley leaves added to dissolved Hg(II) induced a powerful volatilization at alkaline but not at acidic pH. The same pH dependence and emission kinetic together with the highest reduction capacity was observed for ascorbic acid as compared to other phytoreductants. The electrochemical potentials of the reactions involved suggest an electron transfer from NADPH via GSH and ascorbate to Hg(II). The results support the assumption of a novel mechanism how plants transfer reduction equivalents from the antioxidative defense system via ascorbate to reduce Hg(II) ions, thus counteracting mercury toxicity by volatilizing the metal. This effect appears to be assisted by other light-dependent processes such as transpiration and ascorbate synthesis.     

Coupling microscale vegetation–soil water and macroscale vegetation–precipitation feedbacks in semiarid ecosystems

At macroscale, land–atmosphere exchange of energy and water in semiarid zones such as the Sahel constitutes a strong positive feedback between vegetation density and precipitation. At microscale, however, additional positive feedbacks between hydrology and vegetation such as increase of infiltration due to increase of vegetation, have been reported and have a large impact on vegetation distribution and spatial pattern formation. If both macroscale and microscale positive feedbacks are present in the same region, it is reasonable to assume that these feedback mechanisms are connected. In this study, we develop and analyse a soil‐vegetation‐atmosphere model coupling large‐scale evapotranspiration–precipitation feedback with a model of microscale vegetation–hydrology feedback to study the integration of these nonlinearities at disparate scales. From our results, two important conclusions can be drawn: (1) it is important to account for spatially explicit vegetation dynamics at the microscale in climate models (the strength of the precipitation feedback increased up to 35% by accounting for these microscale dynamics); (2) studies on resilience of ecosystems to climate change should always be cast within a framework of possible large‐scale atmospheric feedback mechanism (substantial changes in vegetation resilience resulted from incorporating macroscale precipitation feedback). Analysis of full‐coupled modelling shows that both type of feedbacks markedly influence each other and that they should both be accounted for in climate change models.     

Green Fluorescent Protein (GFP) as a Reporter Gene for the Plant Pathogenic Oomycete Phytophthora ramorum

ABSTRACT. Transgenic Phytophthora ramorum strains that produce green fluorescent protein (GFP) constitutively were obtained after stable DNA integration using a polyethylene glycol and CaCl₂-based transformation protocol. Green fluorescent protein production was studied in developing colonies and in different propagules of the pathogen to evaluate its use in molecular and physiological studies. About 12% of the GFP transformants produced GFP to a level detectable by a confocal laser scanning microscope. Green fluorescent protein could be visualized in structures with vital protoplasm, such as hyphal tips and germinating cysts. In infection studies with Rhododendron , one of the GFP expressing strains showed aggressiveness equal to that of the corresponding non-labelled isolate. Thus, GFP could be used as a reporter gene in P. ramorum . Limitations of the technology are discussed.     

The circulatory system and its spatial relations to other major organ systems in Spelaeogriphacea and Mictacea (Malacostraca, Crustacea) – a three-dimensional analysis

Spelaeogriphacea and Mictacea are enigmatic taxa within malacostracan crustaceans that play a pivotal role in peracarid phylogeny. Anatomical data on both taxa that are suitable for use in cladistic analyses are still scarce. Here, we provide for the first time detailed three-dimensional information on the major organ systems of Spelaeogriphacea and Mictacea (the circulatory system, the digestive system, and the central nervous system) using semithin sections in combination with computer aided three-dimensional reconstruction techniques. The digestive system in both Spelaeogriphus lepidops and Mictocaris halope is made up of a short oesophagus leading to a voluminous stomach chamber. Posteriorly, a pylorus is attached to the stomach chamber. An antechamber of the midgut glands is situated at the transition into the midgut, from which up to four tubular midgut glands emanate. The midgut is a straight tube running through the body terminating in a short hindgut. The central nervous system in the cephalothorax is made up of a brain and a suboesophageal ganglion. Both species show some reduction of the protocerebrum caused by the lack of eyes. The circulatory system is made up of a tubular heart that is situated in the thorax. It is equipped with two pairs of incurrent ostia in S. lepidops and one pair in M. halope . The only artery leading off the heart is the anterior aorta, which runs into the cephalothorax. A dilation is formed between the brain and the anterior stomach wall, into which oesophageal dilator muscles are internalized. The function of this so-called 'myoarterial formation a' as an accessory pulsatile structure in the anterior cephalothorax of these animals is discussed.  © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society , 2007, 149 , 629–642.     

Biometrical evidence for adaptations of the salivary glands to pollen feeding in Heliconius butterflies (Lepidoptera: Nymphalidae)

The Neotropical genus Heliconius (Nymphalidae) is unique among butterflies for its pollen-feeding behaviour. With the application of saliva, they extract amino acids from pollen grains on the outside of the proboscis. We predicted that the salivary glands of pollen-feeding Heliconiinae would show adaptations to this derived feeding behaviour. A biometrical analysis of the salivary glands revealed that pollen-feeding butterflies of the genus Heliconius have disproportionately longer and more voluminous salivary glands than nonpollen-feeding Nymphalidae. The first two components in the principal component analysis explained approximately 95% of the total variance. The size-dependent factor score coefficients of body length and salivary gland parameters were predominately represented on axis 1. They significantly discriminated pollen-feeding from nonpollen-feeding heliconiines on that axis. Factor score coefficients for the volume of the secretory region of the salivary glands separated heliconiines from the outgroup species. The detailed biometrical analysis of salivary glands features thus provides strong evidence that the secretory regions of the salivary glands are larger in pollen-feeding butterflies. We concluded that pollen feeding is associated with a high production of salivary fluid.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 604–612.     

Palaeobiology of a Biradiolites mooretownensis rudist lithosome: seasonality,reproductive cyclicity and population dynamics

Hennhöfer, D., Götz, S. & Mitchell, S.F. 2012: Palaeobiology of a Biradiolites mooretownensis rudist lithosome: seasonality, reproductive cyclicity and population dynamics. Lethaia, Vol. 45, pp. 450–461. During the Cretaceous, rudist bivalves were among the most important benthic carbonate producers on tropical to sub‐tropical carbonate platforms. Yet questions concerning the biology of rudist bouquets remain unanswered to a great extent. In this study a monospecific bouquet of the small radiolitid rudist Biradiolites mooretownensis has been evaluated from a palaeobiological angle. Three‐dimensional, high‐resolution, quantitative analysis provides a detailed evaluation of growth and reproduction in an in situ rudist association. A total of 1237 consecutive tomograms with a vertical spacing of 0.1 mm were produced of which 1150 have been digitally measured for total area, number of specimens, packing density, spat density, recruitment, survival time, mortality and accommodation space. The results show constant coverage of about 60%, a stable packing density of 3.2 specimens per cm² and constant reproduction throughout the bouquet. Time series analysis (spectral analysis) using PAST statistical software shows cyclic spat density every 14.9 mm of vertical growth. Combined with the results of the δ¹⁸O isotope analysis (showing cyclicities of 14 mm) one reproduction cycle appears to be annual. 46.4% of all counted specimens died before 3 mm of vertical growth. More than 93% of the initial spat does not exceed 15 mm shell height or 1 year respectively. Two mortality peaks in the juvenile’s life at 4 and 10–15 mm shell height either represent important obstacles in the ontogenetic development of the species or reflect external influences. □ Biradiolites, grinding tomography, palaeobiology, population dynamics, reproduction, rudists, sclerochronology, seasonality.