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Recreational fishing has the potential to cause evolutionary change in fish populations; a phenomenon referred to as fisheries-induced evolution. However, detecting and quantifying the magnitude of recreational fisheries selection in the wild is inherently difficult, largely owing to the challenges associated with variation in environmental factors and, in most cases, the absence of pre-selection or baseline data against which comparisons can be made. However, exploration of recreational fisheries selection in wild populations may be possible in systems where fisheries exclusion zones exist. Lakes that possess intra-lake freshwater protected areas (FPAs) can provide investigative opportunities to evaluate the evolutionary impact(s) of differing fisheries management strategies within the same waterbody. To address this possibility, we evaluated how two physiological characteristics (metabolic phenotype and stress responsiveness) as well as a proxy for angling vulnerability, catch-per-unit-effort (CPUE), differed between populations of largemouth bass (Micropterus salmoides) inhabiting long-standing (>70 years active) intra-lake FPAs and adjacent, open access, main-lake areas. Fish from FPA populations had significantly higher aerobic scope (AS) capacity (13%) and CPUE rates compared with fish inhabiting the adjacent main-lake areas. These findings are consistent with theory and empirical evidence linking exploitation with reduced metabolic performance, supporting the hypothesis that recreational fishing may be altering the metabolic phenotype of wild fish populations. Reductions in AS are concerning because they suggest a reduced scope for carrying out essential life-history activities, which may result in fitness level implications. Furthermore, these results highlight the potential for unexploited FPA populations to serve as benchmarks to further investigate the evolutionary consequences of recreational fishing on wild fish and to preserve high-performance phenotypes.

Using molecular simulation to aid in the analysis of neutron reflectometry measurements is commonplace. However, reflectometry is a tool to probe large-scale structures, and therefore the use of all-atom simulation may be irrelevant. This work presents the first direct comparison between the reflectometry profiles obtained from different all-atom and coarse-grained molecular dynamics simulations. These are compared with a traditional model layer structure analysis method to determine the minimum simulation resolution required to accurately reproduce experimental data. We find that systematic limits reduce the efficacy of the MARTINI potential model, while the Berger united-atom and Slipids all-atom potential models agree similarly well with the experimental data. The model layer structure gives the best agreement, however, the higher resolution simulation-dependent methods produce an agreement that is comparable. Finally, we use the atomistic simulation to advise on possible improvements that may be offered to the model layer structures, creating a more realistic monolayer model., Electronic Supplementary Information (ESI) available: All analysis/plotting scripts and figure files, allowing for a fully reproducible, and automated, analysis workflow for the work presented is available at \url{https://github.com/arm61/sim_vs_trad} (DOI: 10.5281/zenodo.2600729) under a CC BY-SA 4.0 license

A plastic-derived fuel production process was developed and has been shown to be effective for non-recyclable plastics that are widely used in agriculture and normally discarded. A machine was designed, constructed, and evaluated with regard to energy balance and fuel nugget production. The hydraulically driven machine processed dirty, non-recyclable plastics by first compacting and then extruding them through four internal channels of a heated die. The process produced plastic fuel nuggets with a thin, melted exterior which trapped unmelted plastic in the interior. The Plastofuel™ nuggets were 3.8 cm (1.5 in.) wide, 3.8 cm (1.5 in.) high, and were cut to a length of 5.1 cm (2 in.).

A machine capable of placing planting holes for a wide variety of spacings in plastic mulch beds with very little physical reconfiguration was designed and tested. The three-point hitch mounted machine was demonstrated with two horticultural crops which have widely varying within-row and between-row spacing requirements: onions and potatoes. The piercing mechanisms were powered by pneumatic cylinders, and the on-board controls allowed users to adjust the number and spacing of holes. Switches enabled between-row spacing to vary by placing from one to four planting holes across a standard 76-cm (30-in.) bed. For the algorithm used, a dial was set to create the within-row spacing between 15 and 61 cm (6 and 24 in.). These control settings and a fixed tractor speed acted as inputs to a microprocessor which calculated hole placement frequency and initiated cylinder activation.

Single beam acoustic ground discrimination systems (AGDS) based on standard echo sounders are routinely used for commercial and research applications. Analysis of the return echo signals using these systems produces indexes of seabed "roughness" and "hardness" which have been used to classify seabed type and are here used to map submerged archaeological materials.The aim of this paper is to assess the potential for this technology to characterize submerged archaeological sites. Benefits of characterizing sites in this way include the potential for assessing future impacts on the archaeological material based on the assessment of sediment type and stability from the acoustic data. The technology could offer a means by which sites can regularly be monitored for changes over time, allowing for mitigation strategies to be employed to prevent loss of cultural material.AGDS systems have already been shown to differentiate wide-ranging bottom types over large areas of seabed. Examples are given from two archaeological sites where trials of one particular AGDS indicate that it is possible for small areas of seabed containing exposed archaeological material to be readily distinguished from the surrounding seabed in terms of the character of the acoustic responses.Further research is necessary to determine if, on a site-to-site basis, relationships can be established between acoustic signature, generic archaeological material, sediment type and the degree of preservation of archaeological material.

This paper surveys the results obtained from the investigation of the homomorphic self-incompatibility polymorphisms in 19 species of flowering plants in terms of the number and frequency of alleles in their populations, the distribution of alleles between these populations and the total number of alleles in the species, and assesses the extent to which these results conform with theoretical expectations. The survey shows that, contrary to theory, the populations of most species do not contain a very large number of alleles and the same appears to be true for the total number of alleles in the species. Populations of Trifolium repens and T. pratense, however, appear to possess a large number of alleles for reasons which are unknown. Data on the distribution of alleles range from complete overlap to considerable differentiation between populations in respect of the complement of alleles they contain. The frequencies of alleles in populations of most species with gametophytic systems of self-incompatibility appear to be equal, as the theory suggests; frequencies in populations of Papaver rhoeas and Lolium perenne, however, appear to be significantly unequal. Allele frequencies in populations of sporophytic species are, as expected, unequal, those of dominant alleles being lower than those of recessive alleles. The implications of these results are discussed and the need for further, more comprehensive information on the attributes of these polymorphisms in natural populations is stressed.

A time series analysis of the population genetics of the self-incompatibility polymorphism. 1. Allele frequency distribution of a population with overlapping generations and variation in plant size

Atwood’s (1942, 1944) data on Trifolium repens, those of Williams & Williams (1947) on T. pratense and those of Williams (1951) on T. hybridum have been re-analysed to provide maximum likelihood estimates of the number of incompatibility alleles in the populations or breeders' stocks from which the samples investigated were obtained. These new estimates suggest that populations of T. repens contain about 100 alleles and those of T. pratense contain up to twice this number. The single estimate from T. hybridum, however, suggests that the species in North America possesses only 17 S-alleles. The estimates from clover populations are compared with those from the nine most thoroughly investigated species of other self-incompatible flowering plants and confirm the long-held belief that populations of T. repens and T. pratense contain more S-alleles than those of the latter. It is argued that the most likely explanation of the large number of S-alleles that natural populations of these species appear to contain is that they are substructured into a large number of semi-isolated neighbourhoods.

The population genetics of the self-incompatibility polymorphism in Papaver rhoeas . XI. The effects of limited pollen and seed dispersal, overlapping generations and variation in plant size on the variance of S-allele frequencies in populations at equilibrium

The population genetics of the self-incompatibility polymorphism in Papaver rhoeas . X. An association between incompatibility genotype and seed dormancy

Seed dormancy in a cross between wild Papaver rhoeas and its ‘Shirley’ cultivar appeared to be controlled by genes that displayed additive effects, dominance in the direction of low dormancy and non-allelic interaction of the duplicate type; in addition, there was a small maternal dominance effect in the direction of high dormancy. The genetics of seed dormancy in this cross is as predicted on Mather's theory of genetical architecture for a character that has been subject to strong directional selection. During the breeding of 'Shirley' poppies, at least six flower colour mutations were obtained in less than 20 years in a population whose effective size must have been very small. It is argued that, in view of the difficulty of detecting heritable variation for seed dormancy in wild poppies and the rarity of flower colour variants in wild P. rhoeas, it is possible that seed of the ‘Shirley’ cultivar lacks the dormancy of its wild ancestors because of mutation of one or two genes.

Provided that the seed collected from each plant in natural populations of a species is kept separate from that of every other, a rough estimate of the heritability of a quantitative character can be obtained from the natural progenies raised from this seed in a randomised evaluation trial; a knowledge of the reproductive biology of the species can help to make this estimate of the heritability of the character more precise.

A sample of about 172 plants, drawn at random from a population of a target species, is of sufficient size to conserve at a very high probability, all or very nearly all of the polymorphic genes that are segregating in the population, provided that their frequency is not less than 0.05, irrespective of whether the individuals of the species set all of their seed by self-or by cross-fertilisation or a mixture of both. When samples are taken from a number of populations, the size of the sample drawn from each need be no larger than 172 divided by the number of populations visited. It is pointed out that implementation of this conclusion could lead to very considerable saving of resources in both the collection and storage of material in gene banks.

A crossing procedure to extract one S- and one Z-allele, at random, from each of a number of plants of Lolium perenne, to examine the number and frequency of incompatibility alleles they contain is described. This procedure has been used on a random sample of plants from the long-established population of perennial ryegrass in North Meadow, Cricklade. In all, 17 different S-alleles and 17 different Z-alleles were found in a sample of 38 and 39 plants, respectively. The frequencies of these alleles were very unequal, one of the S-alleles occurring 12 times and two of the Z-alleles nine times each. The E2 estimator of O'Donnell & Lawrence (1984) gave estimates of 31 alleles at each locus, although these estimates are probably less than the actual number of S- and Z-alleles in this population. Analysis of the theoretical properties of the two-locus polymorphism, suggests that, with this number of alleles, the strength of the frequency-dependent selection that maintains the polymorphism must be weak, that a population will contain only a subset of the total number of genotypes and that the unequal allele frequencies might be caused by either or both of these effects.

This paper considers the hypothesis that the unequal S-allele frequencies in the British populations of Papaver rhoeas we have examined are caused by a sampling effect over and above that due to drift. The results obtained by simulating the polymorphism on the computer show that it takes between 70 and 80 non-overlapping generations before stochastic equilibrium is achieved with respect to allele frequency in a population of size 3720 containing 31 alleles, both when the frequencies of the alleles are initially as unequal as they were in the R106 sample (Campbell & Lawrence, 1981b) and when these frequencies are exactly equal. These results show that the strength of the frequency-dependent selection that maintains the polymorphism becomes very considerably attenuated as the number of alleles in the population increases. A review of the relevant genetical and ecological evidence suggests that the size of the British populations is considerably larger than the minimum required to maintain the number of alleles they are estimated to contain, so that opportunities for sampling effects to perturb the frequencies of these alleles appear to be limited. The results obtained from an investigation of the reproductive biology of the species, however, show that the distribution of progeny size is markedly non-random. It is possible that this may be the cause of the unequal allele frequencies observed in the the British populations.

Investigation of the segregation ratios of the self-incompatibility (S-) alleles in three sets of full-sib families of Papaver rhoeas shows that these ratios depart significantly from Mendelian expectation. This indicates that the S-locus is subject to an extra effect of selection over and above that due to incompatibility in these families, and suggests that this is probably the chief cause of the unequal S-allele frequencies observed in the R102 and the other natural populations we have examined. Since, however, the selective advantage of an allele depends on the allele with which it is segregating in all of the families examined, the relationship between these results and the unequal 5-allele frequencies in populations appears to be complex. Furthermore, while in one family the extra effect of selection appears to be of the zygotic type, in the others it is of the gametic type - which, in most, involves the female gametophyte rather than the pollen. It is argued that the extra effect of selection is due to the linkage of the S-gene to one or more genes that are the chief target of this selection, rather than to pleiotropy. Though it is suggested that among candidates for linkage are genes controlling seed dormancy and albinism, the detection of an extra effect of selection acting on the female gametophyte and, in one case, on the pollen, implies that other genes of as yet unknown effect are more likely to be involved.

The population genetics of the self-incompatibility polymorphism in Papaver rhoeas . VII. The number of S-alleles in the species

The population genetics of the self-incompatibility polymorphism in Papaver rhoeas . V. Cross-classification of the S-alleles of samples from three natural populations

The population genetics of the self-incompatibility polymorphism in Papaver rhoeas . VI. Estimation of the overlap between the allelelic complements of a pair of populations

Summary A portion (1.5 kb) of the promoter region of an S63 S-locus related (SLR) glycoprotein gene from the sporophytically self-incompatible species Brassica oleracea was inserted upstream of the β-glucuronidase (GUS) gene in binary vector pBI101.1. The resulting construct was then introduced into Nicotiana tabacum through Agrobacterium-mediated transformation. The expression pattern of GUS under the control of the S63 SLR promoter fragment was found to be similar to that already reported for expression of the GUS gene directed by an S-locus specific gene promoter in transgenic N. tabacum. Furthermore, this pattern of expression resembled more closely that reported for S-genes of the self-incompatible species Nicotiana alata, which has a gametophytic self-incompatibility system, than the predicted pattern of expression of S-genes in B. oleracea.

In this study we have begun to dissect the molecular mechanism of the self-incompatibility reaction of Papaver rhoeas. In order to gain an insight into the cellular activities, which lead to the inhibition of pollen tube growth following a self-incompatible response, we have been studying the effects of various metabolic inhibitors on pollen-stigmatic extract interactions in vitro. The results indicate that both transcription and glycosylation are required for the full inhibition of pollen tube growth during an incompatible response in P. rhoeas. The ability of actinomycin D to alleviate an incompatible reaction suggests that during the response pollen gene expression is induced; we have evidence that this is indeed the case and have identified novel proteins produced in the pollen which are associated with the incompatibility response. These findings give a clear indication that de novo transcription of pollen genes which are specific to this response, play an important role in the inhibition of pollen tube growth in this species. This provides a significant step towards the elucidation of the mechanism whereby pollen tube growth is arrested following an incompatible reaction in this species. Ribonuclease assays have revealed that, in contrast to the S-linked glycoprotein of Nicotiana alata, there is no detectable ribonuclease activity that correlates with the presence of the functional stigmatic S-gene product in P. rhoeas.

The perennial salt marsh grass Spartina anglica is one of the classic examples of allopolyploid speciation. It originated on the south coast of England at the end of the nineteenth century following chromosome doubling in S. × townsmdii, a hybrid between the native British S. marilima and a species introduced from the United States, S. alterniflora. The nature of the origin of S. anglica is beyond doubt; however, it is not known whether it had a single or multiple origin. In order to address this problem we undertook a survey of the genetic variation in the parental species of S. anglica using isozyme electrophoresis. The results show that S. alterniflora has no detectable variation and that S. maritima has extremely low levels of variation. These results, unfortunately, prevent the question of a single or multiple origin from being answered. Possible reasons for the low levels of variation and its influence on the future of the species are discussed. Another problem concerning the parental species is the rapid decline of S. maritima in Britain. It is often assumed that the major factor in this regression is the invasion of its habitats by S. anglica. We have examined the status of S. marilima throughout its range in Britain and have found that S. anglica rarely co-occurs with S. maritima. We propose that the decline of S. maritima is largely due to the physical erosion of its habitats and that this erosion may produce suitable habitats for colonization by S. anglica.

Ribonuclease assays have revealed, in contrast to the self-incompatibility (SI) system of Nicotiana alata, there is no detectable ribonuclease activity that correlates with the presence of the functional stigmatic S-gene product in Papaver rhoeas. Thus, we have shown that the inhibition of incompatible pollen tube growth in P. rhoeas is not associated with ribonuclease activity. Furthermore, the finding that pollen from P. rhoeas, unlike that from N. alata, is insensitive to purified bovine pancreatic ribonuclease A at very high concentrations, suggests that the involvement of ribonucleases in the inhibition reaction of the SI response in P. rhoeas is unlikely. In addition, the level of ribonuclease activity in mature stigmas of P. rhoeas is very much lower than that in N. alata and significantly, the level of ribonuclease activity did not rise in conjunction with the developmental expression of SI. Therefore, as a result of these studies, we believe that SI in P. rhoeas does not involve ribonuclease activity.

summary In order to gain an insight into the cellular activities which lead to the inhibition of pollen tube growth following a self-incompatible response, we have been studying the effects of various metabolic inhibitors on pollen–stigmatic extract interactions in vitro. The results indicate that both transcription and glycosylation are required for the full inhibition of pollen tube growth during an incompatible response in Papaver rhoeas. The ability of actinomycin D to partially alleviate an incompatible reaction suggests that during the response, pollen gene expression is induced; we have found that this is indeed the case and have identified novel proteins produced in the pollen which are associated with the incompatibility response. These findings give a clear indication that de novo transcription of pollen genes which are specific to this response, play an important role in the inhibition of pollen tube growth in this species. This provides a significant step towards the elucidation of the mechanism whereby pollen tube growth is arrested following an incompatible reaction in this species.

Rapid accurate detection is a prerequisite for the successful control of meticillin-resistant Staphylococcus aureus (MRSA). The IDI-MRSA real-time polymerase chain reaction (PCR) assay was designed to provide rapid results from nasal specimens collected in Stuart's liquid transport medium. This study has evaluated the IDI-MRSA kit for use in a clinical laboratory by investigating the following parameters: (1) limits of detection (LoD), (2) performance with Amies' gel-based transport medium, (3) ability to detect strains of MRSA in a collection representative of MRSA in Ireland since 1974 (n=113) and (4) performance in a clinical trial with swabs from nose, throat and groin/perineum sites from 202 patients. LoDs (colony-forming units per ml) of the IDI-MRSA kit, direct culture on MRSA-Select chromogenic agar (CA) and salt-enrichment culture (with subculture onto CA) were 10(3), 10(3) and 10(2), respectively. LoDs with Stuart's and Amies' transport media were comparable. All except one of the 113 MRSA isolates were detected by the kit but, when six control strains carrying staphylococcal cassette chromosome mec (SCCmec) type IV element subtypes IVa-d and SCCmec types V and V(T) were tested, the kit failed to detect MRSA carrying SCCmec V. The sensitivity and specificity for detection of MRSA from nose, throat and groin/perineum specimens were comparable with slightly lower sensitivities from throat and groin/perineum specimens compared with nasal swabs (90%, 97%; 89%, 99%; 88%, 99%, respectively). Overall sensitivity, specificity and positive and negative predictive values for specimens from all sites were 88%, 99%, 94% and 97%, respectively. Further developments to improve the sensitivity of this highly worthwhile assay are required.

A 23-year-old man with similar pathology has presented in March 1998 for primary management of his diphallus and anorectal duplication.

Between 1999 and 2003, meticillin-resistant Staphylococcus aureus (MRSA) isolates recovered from blood cultures in Irish hospitals that participate in the European Antimicrobial Resistance Surveillance System were investigated by epidemiological typing using antibiogram–resistogram (AR) typing, biotyping, and DNA macrorestriction digestion using SmaI followed by pulsed-field gel electrophoresis (PFGE). PFGE patterns were assigned five-digit pulsed-field type (PFT) numbers, and PFTs of apparently related patterns were abbreviated to two-digit PFT groups (PFGs). AR and PFGE typing results were combined to produce AR-PFG types. Representative isolates of each AR-PFG type recovered in 2002 were typed by multilocus sequence typing and staphylococcal cassette chromosome (SCC) mec analysis. Isolates from 1999 and 2000 were also typed by phage typing. The extent to which epidemiological types of MRSA from blood cultures could be extrapolated to the total MRSA population was investigated by comparing results obtained with isolates from the total MRSA population versus those obtained with blood cultures during three study periods. Over the 5 years from 1999 to 2003, 1,580 blood culture isolates from 1,495 patients were analysed. Typeability and discriminatory indices were as follows: AR typing, 1 and 0.97; phage typing, 0.29 and 0.89; PFGE, 0.99 and 0.95; AR-PFG typing, 1 and 0.95. The most frequently occurring AR-PFG types were 06-01, 07-02, 13-00, and 14-00 and were exhibited by 57, 7, 14, and 12% of isolates, respectively. During the study period, the distribution of AR-PFG type changed markedly, with the prevalence of one type (AR-PFG 06-01) increasing by 880%, from 22% (39/181) in 1999 to 80% (343/430) in 2003. Investigation of whether epidemiological types among blood culture isolates of MRSA were representative of the total MRSA population showed that there was no significant difference in most instances. MLST and SCCmec typing showed that AR-PFG types 06-01, 07-02, 13-00, and 14-00 were ST22–MRSA-IV, ST36–MRSA-II, ST8–MRSA-IID, and ST8–MRSA-IIE, respectively.

An assay of the number of incompatibility alleles in an experimental cultivar of Lolium perenne found 17 S- and 13 Z- alleles in samples of 40 and 43 plants examined, respectively, which yielded estimates of 26 S- and 18 Z-alleles in the population. This cultivar was founded, however, on only five plants that between them could have contained no more than 10 alleles at each locus. It is suggested that the additional alleles originated by migration of pollen from neighbouring populations of ryegrass during seed-multiplication rather than from mutation.

The physicochemical characteristics of N,N-dimethyl-N-(3-dodecylcar- bonyloxypropyl)amineoxide (DDCPNO), a biodegradable analogue of a N, N-dimethylalkylamine-N-oxide, are compared with those of N, N-dimethyldodecylamine-N-oxide (DDNO) to establish the effect on the properties of DDNO of inserting a propoxy linker between the hydrophobic tail and hydrophilic head region. Surface tension measurements gave a critical micelle concentration of 0.33 mM for DDCPNO compared with a value of 1.57 mM for DDNO, suggesting that the former was the more hydrophobic surfactant. This result was confirmed by laser light scattering studies in which total intensity light scattering indicated the presence of DDCPNO micelles of aggregation number 85.0. Photon correlation spectroscopy studies yielded a limiting hydrodynamic diameter of 4.0 nm in comparison with values of 57.5 and 3.3 nm obtained for the aggregation number and the limiting hydrodynamic size, respectively, of DDNO micelles. Studies demonstrated that neither a dilute aqueous solution of DDCPNO or DDNO exhibited a cloud point within the temperature range 293-373 K. Solubilization studies showed that the capacity of DDCPNO micelles for a range of drugs of varying size and polarity was less than that observed with DDNO micelles at an equivalent surfactant concentration. As a further measure of solubilization, the ability of DDCPNO to form oil-in-water microemulsions with a range of ethyl ester oils was investigated and found to be slightly higher than that achieved with DDNO. Together these studies suggest that the presence of the semipolar linker significantly alters the properties of this low molecular weight surfactant.

To determine how the structures of peptides influence their alveolar permeability.The studies were performed using 14 synthetic 'model' peptides, labelled with a novel, non-intrusive amino acid fluorophore, and their transport studied using rat alveolar cell monolayers cultured on permeable supports.The passage of the peptides across the epithelial cell monolayers is shown to be primarily paracellular, with an inverse dependence on molecular size, and an enhanced flux observed for cationic peptides. The apparent permeability coefficients (Papp) for the peptides (together with those for other organic solutes, taken from the literature) are shown to be well-modelled assuming two populations of 'pores' in the monolayers, modelled as cylindrical channels of radii 15 A and 22 nm. The former pores are shown to be numerically equitable with the monolayer tri-junctional complexes, and the latter are taken as monolayer defects.The various monolayer Papp values correlate well with the results from in vivo transport experiments, and the conclusion is drawn that the pulmonary delivery of peptide drugs is perfectly exploitable.

The apparent permeability coefficient (P(app)) of two fluorescently tagged model hydrophilic peptides, acXASNH(2) and acXAS(GAS)(7)NH(2), and (14)C-mannitol across monolayers of cultured rat alveolar epithelial cells of varying transepithelial electrical resistance (TER) has been examined. In line with their design features, the peptides were not degraded under the conditions of the test. Furthermore, no concentration dependence of transport of the tripeptide acXASNH(2) was observed over the concentration range studied, nor was any directional transport seen for either of the model peptides, indicating that under the conditions of the test they were not substrates for any transporters or efflux pumps. From the hydrophilic nature of the peptides (as assessed by their log P), and their inverse dependence of transport with molecular weight and TER, it was assumed that the peptides were transported across the cell monolayer passively via the paracellular route. The observed P(app) for the transport of (14)C-mannitol and the peptides across rat alveolar epithelial cell monolayers were found to be inversely (though not linearly) related to the measured TER and could be well-modeled assuming the presence of two populations of "pores" in the cell monolayer, namely, cylindrical pores of diameter 1.5 nm and large pores of diameter 20 nm. The relative populations of the two types of pores varied with the TER of the monolayer, with the number of large pores decreasing with an increase in TER (and the number of small pores taken as fixed). These results suggest that if the cell monolayer is well characterized with respect to the passage of a range of probe molecules across monolayers of varying electrical resistance, it should be possible to predict the P(app) of any hydrophilic peptide or drug crossing the membrane by the paracellular route at any desired TER using a monolayer of any electrical resistance, above a minimum value.

Over the last decade, there has been an exponential growth in interest and investigation of the problem of how best to conserve populations of endangered species. As a result, there is now a very extensive and widely scattered literature on this subject. Among recent papers which cite a large number of references are those of Boyce (1992), Ellstrand and Elam (1993) and Nunney and Campbell (1993). Soule’s (1987) book gives a valuable survey of the subject, in which the chapter by Lande and Barrowclough (1987) deals with the population genetics of the problem. Much of this literature is concerned with the conservation of species where ex situ conservation is not a realistic alternative. The demographic and population genetics theory on which discussion of this broader issue is based, however, is also relevant to the special case of those species where the conservation of material in gene banks is possible. The purpose of this chapter is to give a brief outline of the population genetics theory on which discussion of in situ conservation is based and to introduce some of the terms and concepts used in the literature. We also indicate the kinds of experimental investigation of populations which are necessary to produce better recommendations about minimum viable population size than are possible at present.

The S3 allele of the S gene has been cloned from Papaver rhoeas cv. Shirley. The sequence predicts a hydrophilic protein of 14.0 kDa, showing 55.8% identity with the previously cloned S1 allele, preceded by an 18 amino acid signal sequence. Expression of the S3 coding region in Escherichia coli produced a form of the protein, denoted S3e, which specifically inhibited S3 pollen in an in vitro bioassay. The recombinant protein was ca. 0.8 kDa larger than the native stigmatic form, indicating post-translational modifications in planta, as was previously suggested for the S1 protein. In contrast to other S proteins identified to date, S3 protein does not appear to be glycosylated. Of particular significance is the finding that despite exhibiting a high degree of sequence polymorphism, secondary structure predictions indicate that the S1 and S3 proteins may adopt a virtually identical conformation. Sequence analysis also indicates that the S1 and S3 proteins may adopt a virtually identical conformation. Sequence analysis also indicates that the P. rhoeas S alleles share some limited homology with the SLG and SRK genes from Brassica oleracea. Previously, cross-classification of different populations of P. rhoeas had revealed a number of functionally identical alleles. Probing of Western blots of stigma proteins from plants derived from a wild Spanish population which contained an allele functionally identical to the Shirley S3 allele with antiserum raised to S3e, revealed a protein (S3s) which was indistinguishable in pI and Mr from that in the Shirley population. A cDNA encoding S3s was isolated, nucleotide sequencing revealing a coding region with 99.4% homology with the Shirley-derived clone at the DNA level, and 100% homology at the amino acid level.

The potential to exploit self-incompatibility (SI) in plant breeding and its attraction as a system in which to investigate the molecular basis of cell-cell recognition and signaling has resulted in it becoming one of the most intensively studied and exciting topics in plant biology. Much research has encompassed the molecular cloning of genes involved in SI; consequently many reviews of this subject have focused on this area. In this article we have attempted to strike a somewhat different balance, with the objective of giving as broad a picture of the topic of SI as is possible within the confines of a single article. We provide a comprehensive summary of the genetics and population genetics of SI and, in describing progress toward the elucidation of the molecular basis of SI, have surveyed a much wider range of species than has previously been reviewed.

We present the identification, cloning, and characterization of a self-incompatibility (S) gene from Papaver rhoeas that has no significant homology to any previously reported gene sequences, including S genes from other species. This result suggests that a different self-incompatibility mechanism may be operating in this species and has important implications for the evolutionary relationships between the S genes. The S1 cDNA was cloned by using an oligonucleotide based upon N-terminal amino acid sequence data from stigmatic proteins that show complete linkage with the S1 gene. The single-copy gene has been expressed in Escherichia coli to test biological activity. Although the recombinant S1 protein (S1e) is not processed in the same way as the protein produced in the plant, it exhibits, in vitro, the specific pollen inhibitory activity expected of an S gene product; pollen carrying the S1 allele is inhibited, whereas pollen not carrying S1 is not inhibited. These results provide definitive demonstration that the product of a cloned S gene has S-specific pollen inhibitory activity.

One of the earliest stages in the process of pollination and fertilization in flowering plants is the recognition and acceptance or rejection of pollen grains alighting on the stigma of the recipient plant. Thus, these events involve some sort of interaction between male and female cells. Self-incompatibility (SI) is a mechanism employed by many plants whereby self-fertilization is prevented. This is under tight genetic control, usually a single gene, which is denoted the S-gene. These highly specific recognition/rejection events are both developmentally expressed and tissue specific. Studies aimed at the characterization of the S-gene, its product(s) and elucidation of the mechanism of how this system functions has therefore attracted some attention, especially since the advent of molecular biology. Much work has been carried out in an attempt to identify the molecules involved in SI, especially those on the female side. S-linked glycoproteins from styles and stigmas, and the genes that encode them, have been identified and cloned (Nasrallah et al. 1985; Anderson et al. 1986; McClure et al. 1989; berger et al. 1991). Less progress has been made with the pollen component. We initiated our study of the molecular and cellular basis of SI in Popover rhoeas L. (the Field Poppy) in 1985, with the aim of elucidating the mechanism of the SI response. Progress towards an understanding of the molecular basis of SI in this species has recently been made in several directions, and will be reviewed in this article.

The process of pollination and fertilization in flowering plants involves a series of interactive events between male and female cells. One of the earliest stages in the process of fertilization is the recognition, and acceptance or rejection, of pollen grains alighting on the stigma of the recipient plant. Self- incompatibility (SI) involves these processes. We are particularly interested in the mechanism whereby incompatible pollen is inhibited, and the events that occur during a SI reaction.