Declining coral calcification in massive Porites in two nearshore regions of the northern Great Barrier Reef

Temporal and spatial variation in the growth parameters skeletal density, linear extension and calcification rate in massive Porites from two nearshore regions of the northern Great Barrier Reef (GBR) were examined over a 16‐year study period. Calcification rates in massive Porites have declined by approximately 21% in two regions on the GBR ～450 km apart. This is a function primarily of a decrease in linear extension (～16%) with a smaller decline in skeletal density (～6%) and contrasts with previous studies on the environmental controls on growth of massive Porites on the GBR. Changes in the growth parameters were linear over time. Averaged across colonies, skeletal density declined over time from 1.32 g cm^?3 (SE = 0.017) in 1988 to 1.25 g cm^?3 (0.013) in 2003, equivalent to 0.36% yr^?1 (0.13). Annual extension declined from 1.52 cm yr^?1 (0.035) to 1.28 cm yr^?1 (0.026), equivalent to 1.02% yr^?1 (0.39). Calcification rates (the product of skeletal density and annual extension) declined from 1.96 g cm^?2 yr^?1 (0.049) to 1.59 g cm^?2 yr^?1 (0.041), equivalent to 1.29% yr^?1 (0.30). Mean annual seawater temperatures had no effect on skeletal density, but a modal effect on annual extension and calcification with maxima at ～26.7 °C. There were minor differences in the growth parameters between regions. A decline in coral calcification of this magnitude with increasing seawater temperatures is unprecedented in recent centuries based on analysis of growth records from long cores of massive Porites. We discuss the decline in calcification within the context of known environmental controls on coral growth. Although our findings are consistent with studies of the synergistic effect of elevated seawater temperatures and pCO₂ on coral calcification, we conclude that further data on seawater chemistry of the GBR are required to better understand the links between environmental change and effects on coral growth.     

The male postabdomen and reproductive system of Bibio marci Linnaeus, 1758 (Hexapoda: Diptera: Bibionidae)

The male postabdomen and the internal parts of the male genital system of Bibio marci (Bibionomorpha) were examined and reconstructed 3‐dimensionally. Several features differ from the presumptive dipteran groundplan. The bases of the gonopods are fused with each other and with tergite IX. The penis is not tube‐shaped and only sclerotized on the ventral side. The vasa deferentia are S‐shaped, and two pairs of accessory glands are present. In contrast to these characteristics, the arrangement of the internal parts is probably close to the ancestral condition. With its specific shape, the penis is well suited for the transfer of a spermatophore. The dorsal sclerite of the copulatory organ probably represents the medially fused parameres. A cladistic analysis of 27 characters of the postabdomen yielded two most parsimonious trees, with the strict consensus as follows: Nannochoristidae (outgroup) + (Culicidae [Culicomorpha] + ((Nymphomyiidae + (Tipulidae + Trichoceridae)) + (Tabanidae [Brachycera] + (Bibionidae, Anisopodidae, Axymyiidae [Bibionomorpha])))). Potential synapomorphies of Bibionomorpha (including Axymyiidae) and Brachycera are the fusion of sternum IX with the gonocoxites, the fusion of the parameres forming the dorsal sclerite and the presence of an entire series of postabdominal muscles (M4, M20, M23, M26, M27, M31, M35 and M37). The results of the analysis are preliminary as it is based on a single‐character system with a limited taxon sampling. However, the main result – a clade Bibionomorpha + Brachycera – is fully compatible with current hypotheses on dipteran phylogeny.     

Disentangling composite colour patterns in a poison frog species

A phylogenetic approach was performed to infer whether variation in conspicuous colour-patterns of a poison frog (Dendrobatidae: Dendrobates tinctorius ) has evolved neutrally or under selection. Colour and pattern were split into components that were separately analysed and subsequently re-grouped via principal component analysis. This revealed four different 'displayed' factors on the dorsal and lateral views versus one 'concealed' factor on the ventral view. Based on the assumption that current patterns of trait variation contain information about the evolutionary history of the phenotype, we correlated these trait components to a neutrally evolving gene fragment (cytochrome b ). The concealed factor was significantly correlated with the marker fragment, which identified it as having evolved under genetic drift. Noncorrelation of all displayed factors with the marker may indicate the evolution of colour patterns on dorsum and flanks under selection. In our example, colour pattern should therefore be regarded as a multicomponent signal system.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 433–444.     

Scaling of metabolic rate in the lesser wax moth Achroia grisella does not fit the 3/4‐power law and shows significant sex differences

Allometric scaling of metabolic rates is commonly described as a power function and 0.75 is a widely accepted exponent. The universality of this exponent is in doubt and, particularly for insects, contradictory results have been obtained. Furthermore, sexual differences in scaling exponents are observed for several species that could lead to artefacts when they are not considered in intra‐ and interspecific scaling. Whether the metabolic scaling exponent in the lesser wax moth Achroia grisella differs significantly from 0.75 is tested, as well as whether it differs between the sexes. Adults of this moth neither feed nor drink, rendering them as suitable subjects for a study of metabolic rates. Neglecting sex differences, a metabolic scaling exponent of 0.8 is recorded. However, there are significant differences in metabolic scaling between the sexes. When considered separately, males scale with 0.96 and females with 0.67. Thus, in this species, a scaling exponent of 0.75 does not appear to exist either for males or females. The body size optimization model offers a potential explanation for the sex differences in metabolic scaling, although it remains to be tested in wax moths. With insects in particular, there is the need for more detailed studies on the scaling of metabolic rates that also take sexual differences into account.     

Comparative studies in phytochemistry and fruit anatomy of Thapsia garganica and T. transtagana,Apiaceae (Umbelliferae)

Thapsia garganica L. and T. transtagana Brot. are classified as synonymous in Flora Europaea. In the present investigation significant differences between the two taxa with regard to fruit anatomy and phytochemistry are demonstrated and they are considered as two separate species. Microscopic studies revealed a distinct difference in number and position of secretory spaces in the pericarp of fruits from the two species and in addition pronounced differences were found in the presence of thapsigargins, the bioactive constituents of the two species. Quantitative HPLC analyses of thapsigargins were carried out on different plant organs from T. garganica and T. transtagana collected from various locations. Thapsigargin, thapsigargicin, nortrilobolid and thapsivillosin I and J were dominant compounds in all organs of T. garganica whereas none of these compounds could be detected in any organ of T. transtagana. On the contrary, thapsitranstagin and trilobolid were main thapsigargins of T. transtagana. T. garganica may include two chemotypes, as trilobolid was detected in some specimens of T. garganica only. As this is the first time trilobolid has been detected in these two species, it was isolated from both and identified by ¹H NMR-spectroscopy.     

Multiple Pleistocene refugia and Holocene range expansion of an abundant southwestern American desert plant species (Melampodium leucanthum,Asteraceae)

Pleistocene climatic fluctuations had major impacts on desert biota in southwestern North America. During cooler and wetter periods, drought‐adapted species were isolated into refugia, in contrast to expansion of their ranges during the massive aridification in the Holocene. Here, we use Melampodium leucanthum (Asteraceae), a species of the North American desert and semi‐desert regions, to investigate the impact of major aridification in southwestern North America on phylogeography and evolution in a widespread and abundant drought‐adapted plant species. The evidence for three separate Pleistocene refugia at different time levels suggests that this species responded to the Quaternary climatic oscillations in a cyclic manner. In the Holocene, once differentiated lineages came into secondary contact and intermixed, but these range expansions did not follow the eastwardly progressing aridification, but instead occurred independently out of separate Pleistocene refugia. As found in other desert biota, the Continental Divide has acted as a major migration barrier for M. leucanthum since the Pleistocene. Despite being geographically restricted to the eastern part of the species’ distribution, autotetraploids in M. leucanthum originated multiple times and do not form a genetically cohesive group.     

Light,nutrients and grazing interact to determine stream diatom community composition and functional group structure

1. Benthic algal communities are shaped by the availability of nutrients and light and by herbivore consumption. Many studies have examined how one of these factors affects algal communities, but studies simultaneously addressing all three are rare. 2. We investigated the effects of nutrients, light and a herbivore (the snail Potamopyrgus antipodarum) on benthic stream algae in a fully factorial experiment in 128 circular streamside channels. Four nutrient levels (none added to highly enriched), four snail grazing pressures (no snails to 777 individuals m^?2) and two light levels (ambient and 65% reduced) were applied. Colonising algae were dominated by diatoms (Bacillariophyta), which were determined to species using acid‐cleaned samples and assigned to functional groups according to their physiognomic growth form. 3. Diatom community structure changed considerably in response to our manipulations. Light had the strongest influence (as indicated by manova effect size), whereas nutrients had an intermediate effect and grazing was fairly weak. Relative abundances of six common diatom taxa decreased under reduced light, whereas five others became more prevalent. Eight taxa benefitted from nutrient enrichment, while three became rarer. Grazing affected the relative density of only one common taxon, which increased at higher grazing pressure. 4. Diatom functional groups also responded strongly. ‘Low profile’ taxa dominated at low resource levels (nutrients and especially light), whereas ‘high profile’ and ‘motile’ taxa became markedly more prevalent at higher resource levels. 5. Two‐way interactions between experimental factors were quite common. For example, Planothidium lanceolatum and Rossithidium petersenii responded more strongly to nutrient enrichment at reduced than at ambient light, whereas Cocconeis placentula responded more strongly at ambient light. For diatom functional groups, the benefit of nutrient enrichment for ‘motile’ diatoms was greater at ambient than at reduced light. 6. Our results imply that multifactor experiments are required to determine the main forces driving the composition of benthic algal communities. Further, our findings highlight the considerable potential of using functional algal groups as indicators of changing environmental conditions to complement the traditional taxonomic approach.     

Light induces jasmonate‐isoleucine conjugation via OsJAR1‐dependent and ‐independent pathways in rice

The bioactive form of jasmonate is the conjugate of the amino acid isoleucine (Ile) with jasmonic acid (JA), which is biosynthesized in a reaction catalysed by the GH3 enzyme JASMONATE RESISTANT 1 (JAR1). We examined the biochemical properties of OsJAR1 and its involvement in photomorphogenesis of rice (Oryza sativa). OsJAR1 has a similar substrate specificities as its orthologue in Arabidopsis. However, osjar1 loss‐of‐function mutants did not show as severe coleoptile phenotypes as the JA‐deficient mutants coleoptile photomorphogenesis 2 (cpm2) and hebiba, which develop long coleoptiles in all light qualities we examined. Analysis of hormonal contents in the young seedling stage revealed that osjar1 mutants are still able to synthesize JA‐Ile conjugate in response to blue light, suggesting that a redundantly active enzyme can conjugate JA and Ile in rice seedlings. A good candidate for this enzyme is OsJAR2, which was found to be able to catalyse the conjugation of JA with Ile as well as with some additional amino acids. In contrast, if plants in the vegetative stage were mechanically wounded, the content of JA‐Ile was severely reduced in osjar1, demonstrating that OsJAR1 is the most important JA‐Ile conjugating enzyme in the wounding response during the vegetative stage.     

Photosynthetic performance,DNA damage and repair in gametes of the endemic Antarctic brown alga Ascoseira mirabilis exposed to ultraviolet radiation

Abstract Stress physiology on the reproductive cells of Antarctic macroalgae remained unstudied. Ascoseira mirabilis is endemic to the Antarctic region, an isolated ecosystem exposed to extreme environmental conditions. Moreover, stratospheric ozone depletion leads to increasing ultraviolet radiation (280–400 nm) at the earth's surface, thus it is necessary to investigate the capacity of reproductive cells to cope with different UV irradiances. This study is aimed to investigate the impact of exposure to different spectral irradiance on the photosynthetic performance, DNA damage and gamete morphology of the A. mirabilis. Gametangia, gametes and zygotes of the upper sublittoral brown alga A. mirabilis were exposed to photosynthetically active radiation (PAR = P; 400–700 nm), P + UV‐A radiation (UV‐A, 320–400 nm) and P + UV‐A + UV‐B radiation (UV‐B, 280–320 nm). Rapid photosynthesis versus irradiance curves of freshly released propagules were measured. Photosynthetic efficiencies and DNA damage (in terms of cyclobutane pyrimidine dimers) were determined after 1, 2, 4 and 8 h exposure as well as after 2 days of recovery in dim white light. Saturation irradiance (I_k) in freshly released propagules was 52 μmol photons m⁻² s⁻¹. Exposure for 1 h under 22 μmol photons m⁻² s⁻¹ of PAR significantly reduced the optimum quantum yield (F_v/F_m), suggesting that propagules are low light adapted. Furthermore, UVR significantly contributed to the photoinhibition of photosynthesis. Increasing dose as a function of exposure time additionally exacerbated the effects of different light treatments. The amount of DNA damage increased with the UV‐B dose but an efficient repair mechanism was observed in gametes pre‐exposed to a dose lower than 5.8 × 10³ J m⁻² of UV‐B. The results of this study demonstrate the negative impact of UV‐B radiation. However, gametes of A. mirabilis are capable of photosynthetic recovery and DNA repair when the stress factor is removed. This capacity was observed to be dependent on the fitness of the parental sporophyte.