Adding Biotic Interactions into Paleodistribution Models: A Host-Cleptoparasite Complex of Neotropical Orchid Bees

Orchid bees compose an exclusive Neotropical pollinators group, with bright body coloration. Several of those species build their own nests, while others are reported as nest cleptoparasites. Here, the objective was to evaluate whether the inclusion of a strong biotic interaction, such as the presence of a host species, improved the ability of species distribution models (SDMs) to predict the geographic range of the cleptoparasite species. The target species were Aglae caerulea and its host species Eulaema nigrita. Additionally, since A. caerulea is more frequently found in the Amazon rather than the Cerrado areas, a secondary objective was to evaluate whether this species is increasing or decreasing its distribution given South American past and current climatic conditions. SDMs methods (Maxent and Bioclim), in addition with current and past South American climatic conditions, as well as the occurrences for A. caerulea and E. nigrita were used to generate the distribution models. The distribution of A. caerulea was generated with and without the inclusion of the distribution of E. nigrita as a predictor variable. The results indicate A. caerulea was barely affected by past climatic conditions and the populations from the Cerrado savanna could be at least 21,000 years old (the last glacial maximum), as well as the Amazonian ones. On the other hand, in this study, the inclusion of the host-cleptoparasite interaction complex did not statistically improve the quality of the produced models, which means that the geographic range of this cleptoparasite species is mainly constrained by climate and not by the presence of the host species. Nonetheless, this could also be caused by unknown complexes of other Euglossini hosts with A. caerulea, which still are still needed to be described by science.     

Microbiota of the Orchid Rhizoplane

Six bacterial strains isolated from the underground roots of the terrestrial orchid Calanthe vestitavar. rubro-oculatawere found to belong to the genera Arthrobacter, Bacillus, Mycobacterium, and Pseudomonas.Strains isolated from the aerial roots of the epiphytic orchid Dendrobium moschatumwere classified into the genera Bacillus, Curtobacterium, Flavobacterium, Nocardia, Pseudomonas, Rhodococcus, and Xanthomonas.The rhizoplane of the terrestrial orchid was also populated by cyanobacteria of the genera Nostocand Oscillatoria, whereas that of the epiphytic orchid was populated by one genus, Nostoc.In orchids occupying different econiches, the spectra of the bacterial genera revealed differed. The microbial complex of the terrestrial orchid rhizoplane differed from that of the surrounding soil.     

Microbiota of the Orchid rhizoplane

Six bacterial strains isolated from the underground roots of the terrestrial orchid Calanthe vestita var. rubrooculata were found to belong to the genera Arthrobacter, Bacillus, Mycobacterium, and Pseudomonas. Strains isolated from the aerial roots of the epiphytic orchid Dendrobium moschatum were classified into the genera Bacillus, Curtobacterium, Flavobacterium, Nocardia, Pseudomonas, Rhodococcus, and Xanthomonas. The rhizoplane of the terrestrial orchid was also populated by cyanobacteria of the genera Nostoc and Oscillatoria, whereas that of the epiphytic orchid was populated by one genus, Nostoc. In orchids occupying different econiches the spectra of the bacterial genera revealed differed. The microbial complex of the terrestrial orchid rhizoplane differed from that of the surrounding soil.     

Pollen Tube Growth Inhibitors Involved in the Ovary of Self-Incompatible Japanese Pear

The growth inhibitors of pollen tubes in the pistils of Japanesepear ‘Chojuro’ were studied in vitro to elucidatethe physiological mechanism of self-incompatibility. Addition of water extracts from ovaries into a well dug in anagar medium containing sucrose and boric acid inhibited thegrowth of incompatible pollen tubes more strongly than thatof compatible ones. The substance, tentatively called Sinhibitor(self-inhibitor), was detectable in a relatively wide rangeof concentrations of the extract, from 10- to 60-fold dilution.However, it was absent in the stylar extract. S-inhibitor was stable, even though the extract was heated to100?C for 10 min. The chromatogram of the S-inhibitor followinga Sephadex G-10 gel filtration showed 2 peaks of inhibition:one peak corresponded to the peaks of protein and phenol (phenolsmay be conjugated with proteins), and the other to that of reducingsugar. The water extract from mature ovaries when diluted 10-fold wasa stronger growth inhibitor of incompatible pollen tubes comparedwith that from immature ones. This substance, tentatively calledA-inhibitor (adult-inhibitor), appeared to be different fromS-inhibitor. (Received May 20, 1986; Accepted December 22, 1986)     

Potential Challenges of Climate Change to Orchid Conservation in a Wild Orchid Hotspot in Southwestern China

Southwestern China including Guangxi Province is one of nine world hotspots for orchid. Warming in the region in the past century was around 0.5°C, slightly lower than the global average of 0.7°C, while rainfall has remained the same. It is projected that the warming trend will continue for the next two centuries, while precipitation will increase slightly, and soil moisture level will decrease. We identify a number of threats due to climate changes to orchid community in the Yachang Orchid Nature Reserve in Guangxi (hereafter refer to as Yachang Reserve), a good representative of the region. Firstly, decreased soil moisture is likely to have a negative effect on growth and survival of orchids, especially terrestrial and saprophytic ones. Sixty eight (50%) orchid species in the Yachang Reserve are in this category. Secondly, the greater majority of the orchids in Yachang Reserve (72%) have populations on or close to the limestone mountain tops. These populations are likely to shrink or even become extinct as the warming continues because they have no higher places to which they are able to migrate. Natural poleward migration is unlikely for these populations because of the complex terrain, small size of the reserve and human-dominated surroundings. Species with narrow distributions (14%) and/or small population sizes (46%) will be the most vulnerable. In addition, populations represent the southern limit of the species (24%) are also prone to local extinction. Thirdly, extreme rainfall events are projected to occur more frequently, which can exacerbate erosion. This may impact orchid populations that grow on steep cliffs. Fifty seven species (42%) of the orchids in Yachang have cliff populations. Fourthly, the majority of orchid species have specialized insect pollination systems. It is unknown whether the change or lack of change in plant phenology will be in synchrony with the potential phenological shifts of their pollinators. Fifty four (40%) orchid species in Yachang Reserve flower in the spring and are potentially subject to this threat. Finally, mycorrhizal fungi are vital for seed germination for all orchids and important for post-seedling growth for some species. Yet there is a lack of knowledge of the nature of mycorrhiza on all orchids in the region, and little is known on the responses of these vital symbiotic relationships to temperature and soil moisture. Overall, 15% of the orchid species and a quarter of the genera bear high risk of population reduction or local extinction under the current projection of climate change. While studies on predicting and documenting the consequences of climate change on biodiversity are increasing, few identified the actual mechanisms through which climate change will affect individual species. Our study provides a unique perspective by identifying specific threats to a plant community.     

人工种植天麻的影响因子优化研究

天麻是一种名贵的中草药,可用于治疗多种疾病。自然条件下,天麻通过与真菌蜜环菌的共生从腐木获取营养进行生长。为了对人工大规模种植天麻的影响因子进行优化研究,利用正交设计方法,在昭通小草坝地区开展了一个样本量较大的种植实验。在测试的4种因子中,接种蜜环菌对种植天麻影响最大：其次,在露天灌木丛地种植的天麻产量明显高于在林地下的种植。此外,开展了12个树种对蜜环菌生长以及天麻种植的影响研究。结果发现十齿花（Dipentodonsinicus）对蜜环菌的生长最好,同时,也在天麻种植实验中有最高的产量;然而,添加磷、钾元素并不提高天麻的产量。     

Orchid mycorrhiza: implications of a mycophagous life style

Orchid mycorrhiza probably affects about 25 000 plant species and thus roughly one tenth of all higher plants. Histologically, this symbiosis resembles other kinds of endomycorrhiza, the fungal hyphae growing within living plant cells. Considerable evidence, however, suggests that it is not a two‐way exchange relationship and thus not potentially mutualistic, such as the wide‐spread endomycorrhiza between plants and Glomalean fungi, known as arbuscular mycorrhiza. During the achlorophyllous seedling stage orchids are obligately dependent on the fungi; some species remain so through life, while others establish photosynthesis but to varying degrees remain facultatively dependent of /responsive to fungal infection as adults. None of the fungi involved are so far known to depend on the symbiosis with orchids. Transfer of organic carbon compounds from hyphae to the orchid has been demonstrated repeatedly, but it is not clear to what extent this takes place during a biotrophic phase while the intracellular hyphae remain intact, or during the subsequent extensive degradation of the hyphal coils. The advantage of viewing orchid mycorrhiza basically as a unilateral mycophagous relationship, in spite of hypothetical beneficial spin‐offs to the mycobiont, is that it provides a conceptual framework similar to that of other parasitic or fungivore relationships; mechanisms known in such relationships could be searched for in future studies of the orchid–fungus symbiosis. These could include mechanisms for recognition, attraction and selection of fungi, physiological regulation of internal hyphal growth, breakdown, and material transfer, nutritional consequences of the plant's preference(s) and trophic changes, fungal avoidance mechanisms, and consequences at population and ecosystem levels. A whole range of possible life strategies becomes apparent that could support divergent evolution and lead to the proliferation of species that has indeed occurred in the orchid family. We outline some of the possible physiological mechanisms and ecological implications of this approach.     

Promotion of the Growth of Self-Incompatible Pollen Tubes in Lily by cAMP

Cyclic AMP, forskolin and 3-isobutyl-1-methylxanthine promotedthe elongation of self-incompatible pollen tubes in Lilium longiflorum.It appears that a functional cAMP-regulated system that involvesadenylate cyclase and phosphodiesterase is present in the lilystyle and is involved in the regulation of elongation of self-incompatiblepollen tubes. (Received January 21, 1993; Accepted June 19, 1993)     

Thrips Cross-Pollination of Popowia pisocarpa (Annonaceae) in a Lowland Dipterocarp Forest in Sarawak1

This paper reports thrips (Thysanoptera) cross-pollination in the primitive angiosperm, Popowia pisocarpa (Annonaceae), in lowland rain forest of Sarawak, Malaysia. Flowers of P. pisocarpa have a tiny pollination chamber (3–4 mm in depth) with the entrance almost closed by the disk-shaped stigmatic heads, allowing only small insects to enter. Experiments showed that thrips were effective pollinators and flowers ofP. pisocarpa were self-incompatible. Seed set was limited by pollen. Clumped adult trees had higher seed-set than more distant individuals (>5 m from nearest flowering neighbor), indicating limited inter-tree movement by thrips.     

Leaves of the Orchid Twayblade (Listera ovata) Contain a Mannose-Specific Lectin

A new lectin was isolated from leaves of the twayblade (Listera ovata). It is a dimeric protein built up of two subunits of M_r 12,500. This lectin, which is the first to be isolated from a species of the family Orchidaceae, exhibits exclusive specificity towards mannose.     

Adding Adhesion to a Chemical Signaling Model for Somite Formation

Somites are condensations of mesodermal cells that form along the two sides of the neural tube during early vertebrate development. They are one of the first instances of a periodic pattern, and give rise to repeated structures such as the vertebrae. A number of theories for the mechanisms underpinning somite formation have been proposed. For example, in the “clock and wavefront” model (Cooke and Zeeman in J. Theor. Biol. 58:455–476, 1976), a cellular oscillator coupled to a determination wave progressing along the anterior-posterior axis serves to group cells into a presumptive somite. More recently, a chemical signaling model has been developed and analyzed by Maini and coworkers (Collier et al. in J. Theor. Biol. 207:305–316, 2000; Schnell et al. in C. R. Biol. 325:179–189, 2002; McInerney et al. in Math. Med. Biol. 21:85–113, 2004), with equations for two chemical regulators with entrained dynamics. One of the chemicals is identified as a somitic factor, which is assumed to translate into a pattern of cellular aggregations via its effect on cell–cell adhesion. Here, the authors propose an extension to this model that includes an explicit equation for an adhesive cell population. They represent cell adhesion via an integral over the sensing region of the cell, based on a model developed previously for adhesion driven cell sorting (Armstrong et al. in J. Theor. Biol. 243:98–113, 2006). The expanded model is able to reproduce the observed pattern of cellular aggregates, but only under certain parameter restrictions. This provides a fuller understanding of the conditions required for the chemical model to be applicable. Moreover, a further extension of the model to include separate subpopulations of cells is able to reproduce the observed differentiation of the somite into separate anterior and posterior halves. N.J. Armstrong was supported by a Doctoral Training Account Studentship from EPSRC. K.J. Painter and J.A. Sherratt were supported in part by Integrative Cancer Biology Program Grant CA113004 from the US National Institute of Health and in part by BBSRC grant BB/D019621/1 for the Centre for Systems Biology at Edinburgh.     

A Challenge for the Seed Mixture Refuge Strategy in Bt Maize: Impact of Cross-Pollination on an Ear-Feeding Pest,Corn Earworm

To counter the threat of insect resistance, Bacillus thuringiensis (Bt) maize growers in the U.S. are required to plant structured non-Bt maize refuges. Concerns with refuge compliance led to the introduction of seed mixtures, also called RIB (refuge-in-the-bag), as an alternative approach for implementing refuge for Bt maize products in the U.S. Maize Belt. A major concern in RIB is cross-pollination of maize hybrids that can cause Bt proteins to be present in refuge maize kernels and negatively affect refuge insects. Here we show that a mixed planting of 5% nonBt and 95% Bt maize containing the SmartStax traits expressing Cry1A.105, Cry2Ab2 and Cry1F did not provide an effective refuge for an important above-ground ear-feeding pest, the corn earworm, Helicoverpa zea (Boddie). Cross-pollination in RIB caused a majority (>90%) of refuge kernels to express ≥ one Bt protein. The contamination of Bt proteins in the refuge ears reduced neonate-to-adult survivorship of H. zea to only 4.6%, a reduction of 88.1% relative to larvae feeding on ears of pure non-Bt maize plantings. In addition, the limited survivors on refuge ears had lower pupal mass and took longer to develop to adults.     

On the Reproduction Number of a Gut Microbiota Model

A spatially structured linear model of the growth of intestinal bacteria is analysed from two generational viewpoints. Firstly, the basic reproduction number associated with the bacterial population, i.e. the expected number of daughter cells per bacterium, is given explicitly in terms of biological parameters. Secondly, an alternative quantity is introduced based on the number of bacteria produced within the intestine by one bacterium originally in the external media. The latter depends on the parameters in a simpler way and provides more biological insight than the standard reproduction number, allowing the design of experimental procedures. Both quantities coincide and are equal to one at the extinction threshold, below which the bacterial population becomes extinct. Optimal values of both reproduction numbers are derived assuming parameter trade-offs.     

Use of a Commercial Bleaching Agent to Improve Separation of Orchid Chromosomes

The tendency of orchid chromosomes to stick together and thus impair squash preparations can be overcome by a chlorine-containing macerating fluid. After living root tips are soaked 1 hr in distilled, water, they are placed in the following mixture: conc. HCI, 10; 50% ethanol, 10; and a commercial bleach (Clorox, Purex or Hy-Pro), 5; v/v. Heat the mixture gently, allow it to cool, add the root tips and heat gently again. Allow action until the specimens are soft enough to squash (about 10 min).     

TRF1 Ensures the Centromeric Function of Aurora-B and Proper Chromosome Segregation

A cancer is a robustly evolving cell population originating from a normal diploid cell. Improper chromosome segregation causes aneuploidy, a driving force of cancer development and malignant progression. Telomeric repeat binding factor 1 (TRF1) has been established as a telomeric protein that negatively regulates telomere elongation by telomerase and promotes efficient DNA replication at telomeres. Intriguingly, overexpression of a mitotic kinase, Aurora-A, compromises efficient microtubule-kinetochore attachment in a TRF1-dependent manner. However, the precise role of TRF1 in mitosis remains elusive. Here we demonstrate that TRF1 is required for the centromeric function of Aurora-B, which ensures proper chromosome segregation. TRF1 depletion abolishes centromeric recruitment of Aurora-B and loosens sister centromere cohesion, resulting in the induction of merotelic kinetochore attachments, lagging chromosomes, and micronuclei. Accordingly, an absence of TRF1 in human and mouse diploid cells induces aneuploidy. These phenomena seem to be telomere independent, because a telomere-unbound TRF1 mutant can suppress the TRF1 knockdown phenotype. These observations indicate that TRF1 regulates the rigidity of the microtubule-kinetochore attachment, contributing to proper chromosome segregation and the maintenance of genomic integrity.