Limited phylogeographic and genetic connectivity in Acacia species of low stature in an arid landscape

Widespread plant species are expected to maintain genetic diversity and gene flow via pollen and seed dispersal. Stature is a key life history trait that affects seed and potentially pollen dispersal, with limited stature associated with limited dispersal and greater genetic differentiation. We sampled Hill’s tabletop wattle (Acacia hilliana) and curry wattle (Acacia spondylophylla), two co‐distributed, widespread, Acacia shrubs of low stature, across the arid Pilbara region of north‐western Australia. Using chloroplast sequence and nuclear microsatellite data we evaluated patterns of population genetic and phylogeographic diversity and structure, demographic signals, ratios of pollen to seed dispersal, evidence for historical refugia, and association between elevation and diversity. Results showed strong phylogeographic (chloroplast, G_ST = 0.831 and 0.898 for A. hilliana and A. spondylophylla, respectively) and contemporary (nuclear, F_ST = 0.260 and 0.349 for A. hilliana and A. spondylophylla, respectively) genetic structure in both species. This indicates limited genetic connectivity via seed and pollen dispersal associated with Acacia species of small stature compared to taller tree and shrub acacias across the Pilbara bioregion. This effect of stature on genetic structure is superimposed on moderate levels of genetic diversity that were expected based on widespread ranges (haplotype diversity h = 25 and 12; nuclear diversity He = 0.60 and 0.47 for A. hilliana and A. spondylophylla, respectively). Contemporary genetic structure was congruent at the greater landscape scale, especially in terms of strong genetic differentiation among geographically disjunct populations in less elevated areas. Measures of diversity and connectivity were associated with traits of greater geographic population proximity, population density, population size, and greater individual longevity, and some evidence for range expansion in A. hilliana. Results illustrate that low stature is associated with limited dispersal and greater patterns of genetic differentiation for congenerics in a common landscape and highlight the complex influence of taxon‐specific life history and ecological traits to seed and pollen dispersal.

Pollen dispersal, pollen immigration, mating and genetic diversity in restoration of the southern plains Banksia

Evaluation of patterns of pollen dispersal, mating systems, population fitness, genetic diversity and differentiation in restoration and remnant plant populations can be useful in determining how well restoration activities have achieved their objectives. We used molecular tools to assess how well restoration objectives have been met for populations of Banksia media in the biodiversity hotspot of south-west Western Australia. We characterized patterns of pollen dispersal within, and pollen immigration into, two restoration populations. We compared mating system parameters, population fitness via seed weight, genetic diversity and genetic differentiation for restoration and associated reference remnant populations. Different patterns of pollen dispersal were revealed for two restoration sites that differed in floral display, spatial aggregation of founders and co-planted species. Proximity to remnant native vegetation was associated with enhanced immigration and more short-range pollen dispersal when other population variables were constant. Greater seed weights at remnant compared to restoration populations were not related to outcrossing rate. Equivalent mating system and genetic diversity parameters and low to moderate levels of genetic differentiation between restoration and remnant populations suggest pollinator services have been restored in genetically diverse restoration populations of local provenance B. media as early as four years from planting.

Persistence and stochasticity are key determinants of genetic diversity in plants associated with banded iron formation inselbergs

The high species endemism characteristic of many of the world's terrestrial island systems provides a model for studying evolutionary patterns and processes, yet there has been no synthesis of studies to provide a systematic evaluation of terrestrial island systems in this context. The banded iron formations (BIFs) of south-western Australia are ancient terrestrial island formations occurring within a mosaic of alluvial clay soils, sandplains and occasional granite outcropping, across an old, gently undulating, highly weathered, plateau. Notably, these BIFs display exceptionally high beta plant diversity. Here, we address the determinants and consequences of genetic diversity for BIF-associated plant species through a comprehensive review of all studies on species distribution modelling, phylogenetics, phylogeography, population genetics, life-history traits and ecology. The taxa studied are predominantly narrowly endemic to individual or a few BIF ranges, but some have more regional distributions occurring both on and off BIFs. We compared genetic data for these BIF-endemic species to other localised species globally to assess whether the unique history and ancestry of BIF landscapes has driven distinct genetic responses in plants restricted to this habitat. We also assessed the influence of life-history parameters on patterns of genetic diversity. We found that BIF-endemic species display similar patterns of genetic diversity and structure to other species with localised distributions. Despite often highly restricted distributions, large effective population size or clonal reproduction appears to provide these BIF-endemic species with ecological and evolutionary resilience to environmental stochasticity. We conclude that persistence and stochasticity are key determinants of genetic diversity and its spatial structure within BIF-associated plant species, and that these are key evolutionary processes that should be considered in understanding the biogeography of inselbergs worldwide.

Contrasting patterns of clonality and fine-scale genetic structure in two rare sedges with differing geographic distributions

For plants with mixed reproductive capabilities, asexual reproduction is more frequent in rare species and is considered a strategy for persistence when sexual recruitment is limited. We investigate whether asexual reproduction contributes to the persistence of two co-occurring, rare sedges that both experience irregular seed set and if their differing geographic distributions have a role in the relative contribution of clonality. Genotypic richness was high (R=0.889±0.02) across the clustered populations of Lepidosperma sp. Mt Caudan and, where detected, clonal patches were small, both in ramet numbers (⩽3 ramets/genet) and physical size (1.3±0.1 m). In contrast, genotypic richness was lower in the isolated L. sp. Parker Range populations, albeit more variable (R=0.437±0.13), with genets as large as 17 ramets and up to 5.8 m in size. Aggregated clonal growth generated significant fine-scale genetic structure in both species but to a greater spatial extent and with additional genet-level structure in L. sp. Parker Range that is likely due to restricted seed dispersal. Despite both species being rare, asexual reproduction clearly has a more important role in the persistence of L. sp. Parker Range than L. sp. Mt Caudan. This is consistent with our prediction that limitations to sexual reproduction, via geographic isolation to effective gene exchange, can lead to greater contributions of asexual reproduction. These results demonstrate the role of population isolation in affecting the balance of alternate reproductive modes and the contextual nature of asexual reproduction in rare species.

Extensive long-distance pollen dispersal and highly outcrossed mating in historically small and disjunct populations of Acacia woodmaniorum (Fabaceae), a rare banded iron formation endemic

BACKGROUND AND AIMS

Understanding patterns of pollen dispersal and variation in mating systems provides insights into the evolutionary potential of plant species and how historically rare species with small disjunct populations persist over long time frames. This study aims to quantify the role of pollen dispersal and the mating system in maintaining contemporary levels of connectivity and facilitating persistence of small populations of the historically rare Acacia woodmaniorum.

METHODS

Progeny arrays of A. woodmaniorum were genotyped with nine polymorphic microsatellite markers. A low number of fathers contributed to seed within single pods; therefore, sampling to remove bias of correlated paternity was implemented for further analysis. Pollen immigration and mating system parameters were then assessed in eight populations of varying size and degree of isolation.

KEY RESULTS

Pollen immigration into small disjunct populations was extensive (mean minimum estimate 40 % and mean maximum estimate 57 % of progeny) and dispersal occurred over large distances (≤1870m). Pollen immigration resulted in large effective population sizes and was sufficient to ensure adaptive and inbreeding connectivity in small disjunct populations. High outcrossing (mean tm = 0·975) and a lack of apparent inbreeding suggested that a self-incompatibility mechanism is operating. Population parameters, including size and degree of geographic disjunction, were not useful predictors of pollen dispersal or components of the mating system.

CONCLUSIONS

Extensive long-distance pollen dispersal and a highly outcrossed mating system are likely to play a key role in maintaining genetic diversity and limiting negative genetic effects of inbreeding and drift in small disjunct populations of A. woodmaniorum. It is proposed that maintenance of genetic connectivity through habitat and pollinator conservation will be a key factor in the persistence of this and other historically rare species with similar extensive long-distance pollen dispersal and highly outcrossed mating systems.

The maintenance of disparate levels of clonality, genetic diversity and genetic differentiation in disjunct subspecies of the rare Banksia ionthocarpa

The evolutionary potential of plant species that reproduce via predominantly clonal means and the conditions under which clonality is favoured are not well known. Long-term clonal reproduction is expected to result in a number of readily detectable genetic signals not present in populations that reproduce by sexual means. We use a hierarchical sampling strategy to assess genotype probabilities and confirm that two rare sister taxa of Banksia ionthocarpa have contrasting modes of reproduction. Banksia ionthocarpa subsp. chrysophoenix reproduces clonally. Populations had low levels of genotypic diversity and were comprised of large clonal patches consisting of many ramets that covered hundreds of square metres and showed little intermixing. The taxon was genetically depauperate (mean Na = 1.97, mean P = 0.66, mean He = 0.282), had high levels of genetic differentiation between populations (θ = 0.481), and populations exhibited excess heterozygosity and linkage disequilibrium (LD) among loci, suggesting historically high levels of clonality. In contrast, the sister taxon B. ionthocarpa subsp. ionthocarpa, which occurs in an area with more than twice the annual rainfall and less extreme minimum and maximum temperatures, showed no evidence of clonality, high levels of genotypic diversity, greater genetic diversity (mean Na = 3.31, mean P = 0.81, mean He = 0.405), lower levels of genetic differentiation between populations (θ = 0.253) and no evidence of excess heterozygosity or LD among loci. We suggest that the development of clonality in subsp. chrysophoenix is associated with its more marginal environment and enhanced by response to recurrent fires.

Characterization of polymorphic microsatellite DNA markers in Banksia nivea, formerly Dryandra nivea

A genomic library was constructed and 10 novel polymorphic microsatellite markers were developed for Banksia nivea subsp. uliginosa, a woody shrub endemic to the southwest of Western Australia. Polymorphism was investigated for these markers in 30 individuals from one population located in restricted habitat at the base of the Whicher Range east of Busselton. Expected heterozygosity ranged from 0.124 to 0.898 and averaged 0.570. Observed heterozygosity ranged from 0.133 to 0.933 and averaged 0.544. The number of alleles per locus ranged from 2.0 to 16.0 and averaged 7.3. These markers also produced amplification products in three other Banksia species and will be used to assay genetic diversity in these species.

Patient-controlled epidural fentanyl following spinal fentanyl at Caesarean section

Spinal fentanyl can improve analgesia during Caesarean section. However, there is evidence that, following its relatively short-lived analgesic effect, there is a more prolonged spinal opioid tolerance effect. The effectiveness of postoperative epidural fentanyl analgesia may therefore be reduced following the use of spinal fentanyl at operation. This randomised, double-blind study was designed to assess whether patient-controlled epidural fentanyl could produce effective analgesia following 25 microg of spinal fentanyl at operation. Patients undergoing elective Caesarean section received spinal bupivacaine combined with either fentanyl 25 microg (fentanyl group; n = 18) or normal saline (saline group; n = 18). Patient-controlled epidural fentanyl was used for postoperative analgesia. The fentanyl group used a mean of 23.4 (SD 14.5) microg x h(-1) of fentanyl, compared with 27.0 (10.8) microg x h(-1) for the saline group (p =0.41). Using a 0-100 mm visual analogue score for pain, the maximum pain score recorded at rest for the fentanyl group was median 24 [IQR 15-35] mm, compared with 15 [13-45] mm for the saline group (p = 0.41). The maximum pain score recorded on coughing for the fentanyl group was 29 [24-46] mm, compared with 27 [19-47] mm for the saline group (p = 0.44). Nine of the fentanyl group rated postoperative analgesia as excellent and nine as good, compared with 10 of the saline group who rated it as excellent and eight as good (p = 0.74). Epidural fentanyl can produce effective analgesia following the use of 25 microg spinal fentanyl at Caesarean section.

The place of research and development in nurse education

The National Health Service (NHS) document Research for Health, a research and development strategy for the NHS, provides a starting point to explore the place of research and development in nurse education. The thesis focuses on whether research and development in nurse education is the concern of education or nursing. Some parallels are drawn between nursing and teaching. A way forward for the realization of a place for research and development in nurse education is suggested.

Early endoscopic sphincterotomy for retained bile duct stones after gallbladder surgery

Endoscopic sphincterotomy (ES) was performed in 36 patients (age range 33-88 years; median 63 years) with retained bile duct stones after cholecystectomy (32 patients) or cholecystostomy (4 patients). The median time interval between surgery and ES was 28 days (range 10-216 days). At the time of ES, 23 patients had a T-tube in situ. Clearance of the bile duct was achieved by T-tube irrigation in 15 patients, and by basket or balloon extraction in seven patients. Spontaneous clearance of the duct after ES occurred in 12 patients, while two patients required widening of the sphincterotomy to allow successful basket extraction. Complications occurred in four patients (11%). Two patients sustained significant haemorrhage from the ES site and subsequently died. One patient developed mild acute pancreatitis while another had persisting cholangitis before and after ES. Both of these patients recovered with conservative management. While ES performed soon after gallbladder surgery allows for early bile duct clearance, the small but significant risk of potentially lethal haemorrhage suggests that its use should be reserved for patients in whom other non-operative methods have failed or are inappropriate.

Endoscopic sphincterotomy for bile duct stones in patients with intact gallbladders

Endoscopic sphincterotomy was performed in 121 patients (age ranged 34-92 years; median 80 years) with intact gallbladders and bile duct stones. Clearance of the duct by basket or balloon extraction was attempted in 97 patients (80 per cent) and achieved in 93 of these patients (96 per cent). In 24 patients the duct was left to empty spontaneously and this occurred in 22 patients. Immediate complications due to endoscopic sphincterotomy occurred in five patients (two haemorrhage, two perforation, one haemorrhage and perforation). Of the 101 patients reviewed 12-72 months (median 24 months) after endoscopic sphincterotomy, 76 (75 per cent) have remained asymptomatic throughout the follow-up period. Eighteen patients (18 per cent) required cholecystectomy for recurrent gallbladder symptoms 1-24 months after endoscopic sphincterotomy. One of the asymptomatic patients underwent cholecystectomy on the advice of his consultant. A further seven had recurrent biliary colic or cholangitis necessitating enlargement of the sphincterotomy and further stone retrieval in three of these patients. Endoscopic sphincterotomy is an effective treatment for bile duct stones in high risk patients, but subsequent cholecystectomy is required in a significant number of patients owing to continuing gallbladder symptoms.

The early diagnosis of acute gall-bladder disease: the accuracy of overnight eight-hour infusion cholangiography

The reliability of overnight 8-hour infusion cholangiography in confirming the diagnosis of acute cholecystitis or biliary colic was assessed by a prospective study in 100 patients. 55 positive infusion cholangiograms were subsequently confirmed at operation in 45 patients and by cholecystogram in 10 patients who did not have surgical treatment. The absence of false positive examinations is of fundamental importance if early cholecystectomy is to be performed without the risk of an unnecessary laparotomy. Infusion cholangiography proved to be a safe, simple and reliable investigation in the confirmation of acute gall-bladder disease.