Phenotype–fitness relationships and pollen-transfer efficiency of five orchid species with different pollination strategies

Premise

Deceptive pollination, a fascinating mechanism that independently originated in several plant families for benefiting from pollinators without providing any reward, is particularly widespread among orchids. Pollination efficiency is crucial in orchids due to the aggregated pollen in a pollinarium, which facilitates pollen transfer and promotes cross-pollination as pollinators leave after being deceived.

Methods

In this study, we compiled data on reproductive ecology from five orchid species with different pollination strategies: three deceptive-strategy species (shelter imitation, food deception, sexual deception), one nectar-rewarding species, and one shelter-imitation but spontaneously selfing species. We aimed to compare the reproductive success (female fitness: fruit set; male fitness: pollinarium removal) and pollination efficiency of species representing these strategies. We also investigated pollen limitation and inbreeding depression among the pollination strategies.

Results

Male and female fitness were strongly correlated in all species but the spontaneously selfing species, which had high fruit set and low pollinarium removal. As expected, pollination efficiency was highest for the rewarding species and the sexually deceptive species. Rewarding species had no pollen limitation but did have high cumulative inbreeding depression; deceptive species had high pollen limitation and moderate inbreeding depression; and spontaneously selfing species did not have pollen limitation or inbreeding depression.

Conclusions

Pollinator response to deception is critical to maintain reproductive success and avoid inbreeding in orchid species with non-rewarding pollination strategies. Our findings contribute to a better understanding of the trade-offs associated with different pollination strategies in orchids and highlight the importance of pollination efficiency in orchids due to the pollinarium.

     

Thidiazuron enhances axillary and adventitious shoot proliferation in juvenile explants of Mediterranean provenances of maritime pine <Emphasis Type="Italic">Pinus pinaster</Emphasis>

The effectiveness of thidiazuron (TDZ) in promoting in vitro organogenesis in cultured embryo axes and cotyledons from two Spanish Mediterranean provenances of Pinus pinaster Aiton is reported. Application of 44.4 μM TDZ as a 6-d pulse on DCR medium and subsequent transference of maritime pine explants to the same medium without growth regulators, but supplemented with activated charcoal, produced between 17 and 19 axillary shoots per embryo axis with no differences between the two provenances. The same sequential treatment allowed adventitious shoot differentiation on 75% of the cotyledons, with a mean of 12.2 shoots regenerated per explant. Axillary and adventitious shoots were rooted ex vitro after an auxin pulse of indole-3-butyric acid and 1-naphthaleneacetic acid. The micropropagation protocols presented here should enable vegetative multiplication of selected families, and elite trees from these Spanish Mediterranean provenances of maritime pine.     

Characterization of phenology,physiology, morphology and biomass traits across a broad Euro‐Mediterranean ecotypic panel of the lignocellulosic feedstock Arundo donax

Giant reed (Arundo donax L.) is a perennial rhizomatous grass, which has attracted great attention as a potential lignocellulosic feedstock for bioethanol production due to high biomass yield in marginal land areas, high polysaccharide content and low inhibitor levels in microbial fermentations. However, little is known about the trait variation that is available across a broad ecotypic panel of A. donax nor the traits that contribute most significantly to yield and growth in drought prone environments. A collection of 82 ecotypes of A. donax sampled across the Mediterranean basin was planted in a common garden experimental field in Savigliano, Italy. We analysed the collection using 367 clumps representing replicate plantings of 82 ecotypes for variation in 21 traits important for biomass accumulation and to identify the particular set of ecotypes with the most promising potential for biomass production. We measured morpho‐physiological, phenological and biomass traits and analysed causal relationships between traits and productivity characteristics assessed at leaf and canopy levels. The results identified differences among the 82 ecotypes for all studied traits: those showing the highest level of variability included stomatal resistance, stem density (StN), stem dry mass (StDM) and total biomass production (TotDM). Multiple regression analysis revealed that leaf area index, StDM, StN, number of nodes per stem, stem height and diameter were the most significant predictors of TotDM and the most important early selection criteria for bioenergy production from A. donax. These traits were used in a hierarchical cluster analysis to identify groups of similar ecotypes, and a selection was made of promising ecotypes for multiyear and multisite testing for biomass production. Heritability estimates were significant for all traits. The potential of this ecotype collection as a resource for studies of germplasm diversity and for the analysis of traits underpinning high productivity of A. donax is highlighted.     

Effects of small-scale turbulence on development time and growth of Acartia grani (Copepoda: Calanoida)

To test the effects of small-scale turbulence on developmentand growth of marine copepods, a series of 10 1 labortory microcosmswere used to follow the development, under turbulent and calmconditions, of a cohort of Acartia grani, a common coastal planktoniccopepod of temperate zones Aside from possible indirect effectsdue to differences in food availability, turbulence significantlyshortened development times and modified growth rates Theseinfluences seem to vary throughout its life history, late naupliiand early copepodites being more affected.     

The effect of various acrylonitriles and related compounds on prostaglandin biosynthesis

We have studied the effect of nearly 90 arylacrylonitrile derivatives, and several related compounds, on the biosynthesis of prostaglandins from bovine seminal vesicle microsomes. This effect was compared to that of triarylacrylonitrile derivatives known for their inhibiting properties. Several arylacrylonitrile derivatives have also proved good inhibitors, especially certain N-trisubstituted compounds: trans (dimethylamino-4 phenyl)-3 (methoxy-4' phenyl)-2 acrylonitrile was the best inhibitor of the group, with an IC50 of 0.07 microM. The absence of carboxy groups in these derivatives precludes the application of any of the site-models proposed to date. We suggest that the electronic charges carried especially by the three aromatic rings play an important role in the inhibiting mechanism.     

An electron microscopic investigation of age-dependent changes in the flight muscle of Musca domestica L.

The thoracic flight muscle from adult male NAIDM house flies was examined, from emergence to very old age. Thin sections stained with uranyl acetate and bismuth showed no myofibrillar or mitochondrial degeneration from 1 day to 19 days post-emergence, contrary to earlier reports. Some progressive loss in glycogen content and increase in mitochondrial size were observed for muscle from young to very old flies. However, there was no conclusive evidence of fusion of smaller mitochondria into larger ones with advancing age, despite exhaustive examination of representative sections of muscle samples of adult males of different ages.     

Relative species abundance estimation in artificial mixtures of insects using mito-metagenomics and a correction factor for the mitochondrial DNA copy number

Mito-metagenomics (MMG) is becoming an alternative to amplicon metabarcoding for the assessment of biodiversity in complex biological samples using high-throughput sequencing. Whereas MMG overcomes the biases introduced by the PCR step in the generation of amplicons, it is not yet a technique free of shortcomings. First, as the reads are obtained from shotgun sequencing, a very low proportion of reads map into the mitogenomes, so a high sequencing effort is needed. Second, as the number of mitogenomes per cell can vary among species, the relative species abundance (RSA) in a mixture could be wrongly estimated. Here, we challenge the MMG method to estimate the RSA using artificial libraries of 17 insect species whose complete genomes are available on public repositories. With fresh specimens of these species, we created single-species libraries to calibrate the bioinformatic pipeline and mixed-species libraries to estimate the RSA. Our results showed that the MMG approach confidently recovers the species list of the mixtures, even when they contain congeneric species. The method was also able to estimate the abundance of a species across different samples (within-species estimation) but failed to estimate the RSA within a single sample (across-species estimation) unless a correction factor accounting for the variable number of mitogenomes per cell was used. To estimate this correction factor, we used the proportion of reads mapping into mitogenomes in the single-species libraries and the lengths of the whole genomes and mitogenomes.     

Who wins in the weaning process? Juvenile feeding morphology of two freshwater mussel species

The global decline of freshwater mussels can be partially attributed to their complex life cycle. Their survival from glochidium to adulthood is like a long obstacle race, with juvenile mortality as a key critical point. Mass mortality shortly after entering into a juvenile state has been reported in both wild and captive populations, thus weakening the effective bivalve population. A similar phenomenon occurs during metamorphosis in natural and hatchery populations of juvenile marine bivalves. Based on a morphological analysis using scanning electron microscopy of newly formed juveniles of the freshwater species Margaritifera margaritifera (L.) (Margaritiferidae) and Unio mancus Lamarck (Unionidae), we show that a second metamorphosis, consisting of drastic morphological changes, occurs that leads to suspension feeding in place of deposit feeding by the ciliated foot. We hypothesize that suspension feeding in these two species improves due to a gradual development of several morphological features including the contact between cilia of the inner gill posterior filaments, the inner gill reflection, the appearance of the ctenidial ventral groove and the formation of the pedal palps. Regardless of the presence of available food, a suspension feeding mode replaces deposit feeding, and juveniles unable to successfully transition morphologically or adapt to the feeding changes likely perish.