LASER MICROPROBE MASS SPECTROMETRY: PRINCIPLE AND APPLICATIONS IN BIOLOGY AND MEDICINE

Laser microprobe mass spectrometry (LMMS) is an interesting technique for micro- and surface analysis. It employs local ionization by a focused laser under high power density conditions and subsequent mass analysis of the generated ions. This paper surveys the main LMMS instruments and their operational principles. Sample preparation is discussed in the context of biological materials. The problem of quantification is addressed. Selected examples show the way that precise information on the molecular composition can be deduced from the detected signals. Both inorganic and organic substances can be identified, even without reference spectra, from in-situ analysis with a lateral resolution in the order of 1 to 5μm.     

Fire effects on insect herbivores in an oak savanna: the role of light and nutrients

Abstract.  1. Environmental heterogeneity created by prescribed burning provided the context for testing whether the distribution of an oak specialist (the lace bug, Corythuca arcuata ) could be explained by stoichiometric mismatches between herbivore and host plant composition.
2. Field observations showed that lace bug density was seven-fold higher in frequently burned than in unburned units.
3. Lace bug density did not increase with leaf nutrient concentrations, but was instead associated with higher light levels, higher concentrations of leaf carbon (C), lignin and total phenolics, and lower levels of cellulose. In addition, lace bugs reared on high-light leaves had higher levels of survivorship than those fed on low-light leaves.
4. Sampling restricted to full-sun leaves was used to test whether fire-related changes in leaf nitrogen (N) and phosphorus (P) concentrations have a secondary influence on lace bug success. This sampling provided only limited evidence for nutrient limitation, as decreases in leaf N and P were associated with an increase in lace bug mass but a decrease in density.
5. It is concluded that burning probably promotes lace bug population growth by increasing canopy openness, light penetration, and the availability of C-based metabolites, and thus simple stoichoimetric mismatches between herbivores and host plants are not of primary importance in this system.     

Isotopic composition of transpiration and rates of change in leaf water isotopologue storage in response to environmental variables

During daylight hours, the isotope composition of leaf water generally approximates steady‐state leaf water isotope enrichment model predictions. However, until very recently there was little direct confirmation that isotopic steady‐state (ISS) transpiration in fact exists. Using isotope ratio infrared spectroscopy (IRIS) and leaf gas exchange systems we evaluated the isotope composition of transpiration and the rate of change in leaf water isotopologue storage (isostorage) when leaves were exposed to variable environments. In doing so, we developed a method for controlling the absolute humidity entering the gas exchange cuvette for a wide range of concentrations without changing the isotope composition of water vapour. The measurement system allowed estimation of ¹⁸O enrichment both at the evaporation site and for bulk leaf water, in the steady state and the non‐steady state. We show that non–steady‐state effects dominate the transpiration isoflux even when leaves are at physiological steady state. Our results suggest that a variable environment likely prevents ISS transpiration from being achieved and that this effect may be exacerbated by lengthy leaf water turnover times due to high leaf water contents.     

The relative importance of birds and bees in the pollination of Metrosideros excelsa (Myrtaceae)

Exclusion experiments were used to assess the effect of different pollinator groups on outcrossing and seed production in Metrosideros excelsa. The main study site was Little Barrier Island, New Zealand where indigenous bird and native solitary bees are the main flower visitors. Our results showed that native birds were more important pollinators of M. excelsa than native bees. Seed production was much higher in open pollination than in two exclusion experiments where either birds were excluded and native bees only had access to flowers, or where all pollinators had been excluded. The number of fertile seeds per capsule was 45% higher after open pollination than in treatments with bee visitation only and 28% higher than in treatments where all flower visitors were excluded. Estimated outcrossing rates were significantly higher (t_m = 0.71) for open pollination in the upper canopy (>4 m above‐ground level) where bird visitation is presumed to be more frequent than for a treatment with native bee access only (t_m = 0.40). Our results also suggest that a large proportion of seeds (66%) arise from autonomous self‐pollination when all pollinators are excluded. In four trees of a modified mainland population with predominantly introduced birds and a mixture of introduced and native bees there was no decrease in seed production for the treatment allowing bee access only, indicating that – in contrast to native bees – honeybees may be more efficient pollinators of M. excelsa. Observation of the foraging behaviour of both groups of bees showed that native bees contact the stigma of flowers less frequently than honeybees. This is likely to be a consequence of their smaller body size relative to honeybees.     

The Hemipepsis wasp‐pollination system in South Africa: a comparative analysis of trait convergence in a highly specialized plant guild

Pollinator‐mediated convergence in floral traits is the fundamental basis for pollination syndromes, but it has seldom been rigorously analysed. Here we synthesize information on a guild of South African plants that are pollinated by functionally similar pompilid wasps in the genus Hemipepsis and investigate the extent of trait convergence in guild members. The guild includes members from three plant families (Apocynaceae, Orchidaceae and Asparagaceae subfamily Scilloideae) and contains remarkably high levels of functional specialization with 18 of the 23 known guild members being pollinated exclusively by Hemipepsis wasps. The distribution of the guild is centred in the moist upland grasslands of eastern South Africa. Qualitative similarities among guild members include dull greenish‐ or brownish‐white flowers, often with purple blotches, mid‐summer flowering, sweet spicy scent and exposed nectar. To assess the extent of convergent evolution within the guild, we compared floral traits of guild members with those of congeneric non‐wasp‐pollinated species. Guild members typically produce moderate volumes (> 4 µL per flower per day) of concentrated (> 50% sugar by weight) sucrose‐dominant nectar. The nectar properties of guild members did not, however, differ significantly from those of congeneric species pollinated by other vectors. Non‐metric multidimensional scaling of scent data for 15 guild members and 17 congeners (obtained through gas chromatography–mass spectrometry of headspace samples and supplemented with published data) yielded little evidence for convergent evolution in the overall scent composition of guild members. However, convergence in floral spectral reflectance was evident in the guild members; in particular, loci for colours of guild members were significantly closer to the guild centroid than loci for colours of congeners, and they formed a distinct cluster in the blue to blue–green region of the hymenopteran colour hexagon. The colours of guild members were also significantly closer to the colour of background vegetation than those of congeneric species, suggesting a role for cryptic colouring in this system. These results confirm convergence in the floral colours of plants that are pollinated by Hemipepsis spider‐hunting wasps, but also suggest that other traits, such as nectar properties, do not necessarily evolve during shifts between pollination systems. Identification of particular scent compounds and non‐sugar nectar constituents that influence wasp behaviour will be essential for illuminating the extent of biochemical convergence in the guild members. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 168 , 278–299.     

Microsatellite evidence for monogamy and sex-biased recombination in the Western Australian seahorse Hippocampus angustus

Four polymorphic microsatellite loci were used to assess biological parentage of 453 offspring from 15 pregnant males from a natural population of the Western Australian seahorse Hippocampus angustus . Microsatellite genotypes in the progeny arrays were consistent with a monogamous mating system in which both females and males had a single mate during a male brooding period. Multilocus genotypes implicated four females in the adult population sample as contributors of eggs to the broods of collected males, but there was no evidence for multiple mating by females. Based on genotypic data from the progeny arrays, two loci were linked tightly and the recombination rate appeared to be ≈ 10-fold higher in females than in males. The utility of linked loci for parentage analyses is discussed.     

The postcranial anatomy of Coloradisaurus brevis (Dinosauria: Sauropodomorpha) from the Late Triassic of Argentina and its phylogenetic implications

Abstract: Basal sauropodomorphs from the Upper Triassic Los Colorados Formation of north‐western Argentina have been known for several decades but most of them are only briefly described. New postrcanial remains of Coloradisaurus brevis, the most gracile sauropodomorph from this unit, are described here and evaluated within a phylogenetic context. These materials belong to a single individual and include elements of the vertebral column, pectoral girdle, incomplete forelimb, pelvis and hindlimb. These elements share an autapomorphic feature with the type specimen of Coloradisaurus brevis and provide novel and unique features that diagnose this taxon, such as pubic apron with semicircular cross‐section and with a depression on its anterior surface, distal surface of the tibia deflected and facing posterodistally and well‐developed pyramidal dorsal process of the posteromedial corner of the astragalus. Several postcranial characters of Coloradisaurus are exclusively shared with Lufengosaurus, from the Lower Jurassic of China. The inclusion of this information in two recent phylogenetic data sets depicts Coloradisaurus as closely related to Lufengosaurus and well nested within Plateosauria. Both data sets used indicate strong character support for the inclusion of Coloradisaurus and Lufengosaurus within Massospondylidae.     

Generic revision and phylogeny of Microweiseinae (Coleoptera: Coccinellidae)

The monophyly and phylogenetic relationships of the subfamily Microweiseinae were investigated. Twenty‐three in‐group taxa, representing all known genera of Microweiseinae (except for Microcapillata Gordon) were included in a cladistic analysis, based on 45 adult morphological characters. The parsimony analysis of the resulting data matrix supported the monophyly of Microweiseinae, Carinodulini, Serangiini and Microweiseini (inclusive of Sukunahikonini). The recognition of Sukunahikonini renders Microweiseini paraphyletic, and consequently both tribes were synonymized, retaining Microweiseini as a senior family‐group name ( syn.n. ). Genera and tribes of Microweiseinae are diagnosed thoroughly, illustrated and keys to their identification are provided. The following nomenclatural changes were made: Hikonasukuna Sasaji and Orculus Sicard are synonymized with Scymnomorphus Weise ( syn.n. ); Gnathoweisea Gordon is synonymized with Microweisea Cockerell ( syn.n. ); Hikonasukuna monticola Sasaji and Orculus castaneus Sicard are transferred to Scymnomorphus ( comb.n. ); Smilia planiceps Casey, Gnathoweisea hageni Gordon, Gnathoweisea ferox Gordon, Gnathoweisea micula Gordon and Gnathoweisea texana Gordon are transferred to Microweisea ( comb.n ). Three new genera are described: Allenius gen.n. for Allenius californianus sp.n. (type species) from Mexico and Allenius iviei sp.n. from U.S.A.; Gordoneus gen.n. (type species Gnathoweisea schwarzi Gordon from U.S.A.); and Cathedrana gen.n. (type species Cathedrana natalensis sp.n. from South Africa). The first African member of Carinodulini, Carinodulina ruwenzorii sp.n. is described. The genera Microweisea, Coccidophilus, Serangium and Delphastus are well‐known predators of sternorrynchous Hemiptera, such as scale insects (Diaspididae) and whiteflies (Aleyrodidae), and play a significant role in agricultural ecosystems as biocontrol agents. Host data and biological records are summarized for each genus.     

Post‐tectonic limitations on Early Devonian (Emsian) reef development in the Gobi‐Altai region,Mongolia

Pellegrini, A.F.A., Soja, C.M. & Minjin, C. 2011: Post‐tectonic limitations on Early Devonian (Emsian) reef development in the Gobi‐Altai region, Mongolia. Lethaia, Vol. 45, pp. 46–61. This study investigates a Lower Devonian (Emsian) carbonate sequence from the Chuluun Formation where it is exposed in the Gobi‐Altai region of southern Mongolia. Quantification of abundance patterns across guild, morphotype and general taxonomic levels was based on stratigraphical and thin‐section analyses. Comparison with other Emsian carbonate platforms allowed the factors that influenced community development in the wake of a tectonic perturbation to be determined. Our evidence reveals that potential reef‐building biotas preserved in the Chuluun Formation experienced rapid colonization of a newly submerged carbonate platform following an episode of tectonic uplift and the development of a coastal alluvial fan. Although critical reef‐building organisms were present, colonial corals and stromatoporoids exhibited limited vertical growth and showed no significant lateral expansion of individuals or biotic assemblages. Nor did those taxa experience significant increases in abundance, density, or size. We conclude that incomplete succession and the lack of reef development occurred most likely because of an unsuitable substrate, limited accommodation space and isolation that reduced colonization potential. □Community succession, Emsian, palaeoecology, reef suppression.     

The relationship between rainfall,water source and growth for an endangered tree

Abstract It is now reasonably well understood that the human impact on the environment since industrialization has led to significant changes in climate. Here we attempt to develop a predictive understanding of the effects that future changes in climate may have on vegetation structure and species diversity. We do this through a determination of the relationship between radial growth and water source for Widdringtonia cedarbergensis Marsh. Our results show that there was no significant relationship between monthly radial growth, as determined using dendrometer bands, and rainfall. There is, however, a significant relationship between the δ¹⁸O composition of the water extracted from the trees and the rain δ¹⁸O values. We speculate that W. cedarbergensis exploits water derived from rain that flows off the rocky substrate of the study area into sumps between the bedding planes of the rocks on which they grow. This runoff occurs rapidly during rain events resulting in δ¹⁸O values for the trees sourcing this water not to be significantly different from that of the rain. Rainfall therefore has to be sufficient to refill these sumps on which the trees are dependent. The dendrometer bands reflect a slow but steady growth of the trees at the study site. While this growth is not dependent on rainfall, it is dependent on reliable access to available water. If climate change predictions for the region are realized and rainfall is reduced then this species will be affected. W. cedarbergensis is endemic to only a very small area within the Cedarberg Mountains in South Africa and is also one of the few trees growing in the fynbos. The extinction of this species in the wild will fundamentally affect both the vegetation structure and species composition of the region.