Reduced fecundity in large populations of a Mediterranean orchid – Evidence for pollinator limitation

Increased anthropogenic influence is expected to reduce the size of natural populations, which may decrease individual fecundity and long-term survival. However, it is unclear whether populations of a species that occur in a variety of habitats will suffer decreased fecundity similarly. Certain habitats, such as those in agricultural landscapes that used to undergo traditional management, may be altered more than others and therefore individuals within such populations may be more prone to decreased fecundity. This is particularly important to quantify in Mediterranean landscapes, where habitat change is a major threat to biodiversity. We examined the fecundity of 88 populations of the orchid Spiranthes spiralis, across multiple habitats on the Greek island of Lesvos. In each population we recorded both the habitat and geological substrate. At the end of the flowering season, population size was quantified in each population by counting the number of fruiting plants and the percentage fruit set was determined. To test whether seed set was reduced due to pollination limitation we performed a pollen supplementation experiment. Large populations had significantly lower fruit set than small populations, and this effect was most pronounced in olive groves. Pollen supplementation showed that S. spiralis may suffer reduced seed set due to pollen limitation. The results of this study show that larger olive grove populations may be pollinator-limited and there may be two reasons for this: first, olive groves are less favourable sites for honeybees – the major and more efficient pollinators of S. spiralis on Lesvos; second, such populations have been suffering severe management changes in recent years (e.g. chemical treatments, chopping) and are most vulnerable to reductions in reproductive output.     

Sweet Cherry Cultivar Identification by High-Resolution-Melting (HRM) Analysis Using Gene-Based SNP Markers

Single nucleotide polymorphisms (SNPs) provide an important tool for cultivar identification in studies of genetic diversity, but until now, the time-consuming and costly nature of DNA sequencing has limited the identification of new markers. Herein, we describe the application of high-resolution melting (HRM), a recent enhancement to traditional DNA melting analysis, for the characterization of polymerase chain reaction products and the identification of nine gene-based SNPs for distinguishing the main Greek sweet cherry cultivars. The expected heterozygosity value of nine SNPs averaged at 0.518. The combined power of discrimination for the SNP markers was 0.999969. The ability of HRM to accurately discern nucleotide changes in a DNA sequence makes it a cost- and time-effective alternative to traditional sequencing for the detection of gene-based SNPs.     

The Cretan type of non-deletional hereditary persistence of fetal hemoglobin [Aγ–158C→T] results from two independent gene conversion events

We report a new type of non-deletional hereditary persistence of fetal hemoglobin that is due to a C→T transition at position –158, relative to the Cap site of the human Aγ-globin gene. This mutation was identified in three unrelated adult cases presenting slightly elevated levels of fetal hemoglobin (Hb F), i.e. 2.9–5.1%, and normal hematological indices. Our sequencing results, from both polymerase chain reaction-amplified and subcloned DNA fragments, indicate that the Aγ–158C→T mutation occurred by two independent gene conversion events in the three cases studied. In addition, hematological and molecular data, including restriction fragment length polymorphism haplotyping in the β-globin gene cluster, extended haplotype analysis inside the γ-globin gene region and routine analysis of three tandem repeat loci (D1S80, 3′-HVR/apoB and F8vWf), led us to conclude that the Aγ–158C→T mutation in one of the three cases occurred recently in the parental germ line (P=99.47%), representing the first example of a de novo gene conversion event identified in humans. Received: 10 November 1997 / Accepted: 10 February 1998     

Global change and plant–pollinator communities in Mediterranean biomes

Aim

Occurring in five distinct global regions, Mediterranean-type ecosystems (MTEs) include both centres of agricultural production and hotspots of extratropical biodiversity – particularly for plants and bees. Considerable research has addressed the persistence of highly diverse biological communities within MTEs, despite their typically long histories of anthropogenic and natural disturbance. However, important questions remain, especially regarding the limits of ecological resilience in the face of accelerating environmental change. Here, we explore current knowledge regarding the effects of disturbance on MTE plant–pollinator communities.

Location

Mediterranean Basin, California, Cape Province in South Africa, Central Chile and Southern South-Western Australia.

Taxa Studied

Flowering plants and pollinators (insects, birds and mammals).

Methods

We reviewed the available literature about MTE plant–pollinator communities via a systematic search that yielded 234 case studies. We analysed this dataset to quantify research efforts across regions and taxonomic groups, the proportion of surveys addressing ecological interactions (i.e. rather than only taxonomic diversity) and the availability of work addressing community responses to specific stressors (viz. climate change, landscape alteration, fire, farming, grazing, urbanization and species introductions).

Results

Current knowledge on MTE plant–pollinator communities is dominated by work from the northern Mediterranean Basin, while the Southern Hemisphere and California are markedly understudied by comparison. Taxonomic coverage is similarly uneven, with 58% of studies focusing only on a single pollinator group. Furthermore, less than half of the surveys address ecological networks. Finally, despite some pioneering work addressing fire, climate and species introductions, only 13% focus on the impact of stressors on interaction networks.

Outlook

Based on our findings, we identify a need for coordinated international research efforts focusing on (i) community-level studies, observational and experimental, (ii) ecological networks, (iii) functional traits mediating post-disturbance recovery and (iv) impacts of combined/synergistic stressors. Progress in these areas will facilitate predictions about the long-term impacts of global change on MTE plant–pollinator communities.     

Intrafloral patterns of color and scent in Capparis spinosa L. and the ghosts of its selection past

Premise

Capparis spinosa is a widespread charismatic plant, in which the nocturnal floral habit contrasts with the high visitation by diurnal bees and the pronounced scarcity of hawkmoths. To resolve this discrepancy and elucidate floral evolution of C. spinosa, we analyzed the intrafloral patterns of visual and olfactory cues in relation to the known sensory biases of the different visitor guilds (bees, butterflies, and hawkmoths).

Methods

We measured the intrafloral variation of scent, reflectance spectra, and colorimetric properties according to three guilds of known visitors of C. spinosa. Additionally, we sampled visitation rates using a motion-activated camera.

Results

Carpenter bees visited the flowers eight times more frequently than nocturnal hawkmoths, at dusk and in the following morning. Yet, the floral headspace of C. spinosa contained a typical sphingophilous scent with high emission rates of certain monoterpenes and amino-acid derived compounds. Visual cues included a special case of multisensory nectar guide and color patterns conspicuous to the visual systems of both hawkmoths and bees.

Conclusions

The intrafloral patterns of sensory stimuli suggest that hawkmoths have exerted strong historical selection on C. spinosa. Our study revealed two interesting paradoxes: (a) the flowers phenotypically biased towards the more inconsistent pollinator; and (b) floral display demands an abundance of resources that seems maladaptive in the habitats of C. spinosa. The transition to a binary pollination system accommodating large bees has not required phenotypic changes, owing to specific eco-physiological adaptations, unrelated to pollination, which make this plant an unusual case in pollination ecology.     

Conformationally constrained human calcitonin (hCt) analogues reveal a critical role of sequence 17-21 for the oligomerization state and bioactivity of hCt.

Calcitonin (Ct) is a 32-residue peptide hormone that is mainly known for its hypocalcemic effect and the inhibition of bone resorption. Our previous studies have led to potent, side-chain lactam-bridged human Ct (hCt) analogues [Kapurniotu, A. Kayed, R., Taylor, J.W. & Voelter W. (1999) Eur. J. Biochem. 265, 606-618; Kapurniotu, A. & Taylor, J.W. (1995) J. Med. Chem. 38, 836-847]. We have hypothesized that a possibly type I beta turn/beta sheet conformation in the region 17-21 may play an important role in hCt bioactivity. To investigate this hypothesis, analogues of the potent hCt agonist cyclo17,21-[Asp17,Lys21]hCt (1) bearing type I (and II') or II beta turn-promoting substituents at positions 18 and 19 were designed, synthesized and their solution conformations, human Ct receptor binding affinities and in vivo hypocalcemic potencies were assessed. The novel analogues include cyclo17,21-[Asp17,D-Phe19, Lys21]hCt (2), cyclo17,21-[Asp17,Aib18,Lys21]hCt (3), cyclo17,21-[Asp17,D-Lys18,Lys21]hCt (4), corresponding partial sequence peptides containing the lactam-bridged region 16-22, and nonbridged control peptides. Only 1 showed a higher Ct receptor binding affinity than hCt, whereas analogues 2-4 had similar receptor affinities to hCt. In the in vivo hypocalcemic assay, 3 and 4 were as potent as 1, whereas 2 completely lost the high potency of 1, suggesting that type I (and II') beta turn-promoting substituents are fully compatible with in vivo bioactivity. CD spectroscopy showed that analogues 1-4 were markedly beta sheet-stabilized compared to hCt and indicated the presence of distinct beta turn conformeric populations in each of the analogues. Unexpectedly, the D-amino acid- or Aib-containing cyclic analogues 2-4 but not 1 or hCt self-associated into SDS denaturation-stable dimers. Our results demonstrate a crucial role of the conformational and topological features of the residues in sequence 17-21 and in particular of residues 18 and 19 for human Ct receptor binding and in vivo bioactivity and also for the self association state of hCt. These results may assist to delineate the structure-function relationships of hCt and to design novel hCt agonists for the treatment of osteoporosis and other bone-disorder-related diseases.