bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial and temporal patterns of caterpillar performance and the suitability of two host plant species
Authors: Van Nouhuys Saskya , Singer Michael C. , Nieminen Marko
Published: December 2004

Abstract.1. The butterflyMelitaea cinxiauses two host plant species in the Åland Islands of south‐west Finland. Survey data show that host plant use is spatially variable and that the two species are not used (fed on byM.cinxialarvae) in proportion to their abundances. The pattern of host plant use byM.cinxiahas been attributed in part to plant distribution and spatial variation of butterfly oviposition preference.

2. The additional roles that may be played by spatial variation in host plant quality and larval physiology (performance ability) were investigated. Seven years of field survey data and a series of laboratory experiments were used to demonstrate that neither of these variables contributed measurably to the observed pattern of host plant use.

3. Specifically, while there was great variation among individuals in both the performance ability of caterpillars and host plant suitability, the two plant species appeared equally suitable, there was no within‐species geographic variation in plant suitability, and there was no evidence for adaptation of caterpillars to the locally used host plants.
Exocrine pancreatic dysfunction in sepsis
Authors: Tribl B. , Sibbald W. J. , Vogelsang H. , Spitzauer S. , Gangl A. , Madl C.
Published: December 2004

Background Sepsis in critical illness is associated with the progressive failure of multiple organs. This study aims to establish a correlation between the severity of sepsis and exocrine pancreatic dysfunction.

Materials and methods In a prospective cohort study pancreatic exocrine function was tested by means of a secretin‐cholecystokinin test in 21 critically ill, mechanically ventilated patients with sepsis according to criteria of the American College of Chest Physicians/Society of Critical Care Medicine Consensus Conference Committee (ACCP/SCCM): 11 patients with shock and 10 patients without shock. Data were compared with seven healthy controls.

Results The volume of duodenal fluid was not statistically different in the three groups. Sepsis patients without shock had significantly reduced content of amylase and chymotrypsin in duodenal juice compared with healthy controls (P < 0·01). Secretion of amylase, chymotrypsin, trypsin (P < 0·01 each) and bicarbonate in duodenal fluid (P < 0·05) was impaired in the septic shock patients when compared with the healthy controls. The content of trypsin was different between sepsis patients and septic shock patients (P < 0·05). Spearman correlation analysis was significant between the amylase secretion and the APACHE III and SOFA scores (P < 0·01). The SOFA score was also related to secretion of trypsin (P < 0·05). In patients on pressor therapy, use of norepinephrine was associated with a significant decrease in bicarbonate secretion (P < 0·05).

Conclusions Sepsis is associated with secretory pancreatic dysfunction that is worse in septic shock than in sepsis without shock. Impaired exocrine function was significantly correlated to the APACHE III and SOFA scores.
Effects of insulin lispro and chronic vitamin C therapy on postprandial lipaemia, oxidative stress and endothelial function in patients with type 2 diabetes mellitus
Authors: Evans M. , Anderson R. A. , Smith J. C. , Khan N. , Graham J. M. , Thomas A. W. , Morris K. , Deely D. , Frenneaux M. P. , Davies J. S. , Rees A.
Published: December 2004

Background Insulin therapy may influence cardiovascular disease (CVD) and lipid metabolism in type 2 diabetes (T2D). Exaggerated postprandial lipaemia (PPL) is a feature of diabetic dyslipidaemia affecting CVD via enhanced oxidative stress (OS) and endothelial dysfunction. We assessed endothelial function and OS during PPL following insulin and vitamin C. Twenty (17 M) T2D patients were studied (mean Hba1c 8·4%) at baseline, following 6 weeks of insulin lispro (0·2 Iu kg−1) and vitamin C 1‐g daily. Eight‐h lipid and glucose profiles were measured following a fatty meal. Endothelial function (flow‐mediated vasodilatation: FMD) and OS were measured at fasting, 4 h and 8 h.

Materials and methods Glucose, body mass index, and total and LDL cholesterol remained unchanged. FMD improved. Placebo group: fasting, 1·1 ± 1·2 to 4·2 ± 1·1% (P < 0·001); 4‐h, 0·3 ± 1·2 to 3·1 ± 0·9% (P < 0·01); 8‐h, 0·7 ± 1·1 to 3·76 ± 1·1% (P < 0·001). Vitamin C group: fasting, 0·9 ± 1·1 to 6·1 ± 1·3% (P < 0·001); 4‐h, 0·7 ± 1·5 to 4·9 ± 2·1% (P < 0·001); 8‐h, 0·8 ± 0·9 to 5·8 ± 0·6% (P < 0·01). Post‐prandial lipaemia was attenuated: TG area‐under‐curve (mmol L−1 8 h−1), 52·6 ± 11 to 39·1 ± 12·5 (placebo group), P < 0·02; and 56·9 ± 8 to 40·1 ± 10·3 (vitamin C group), P < 0·02. Oxidative stress was reduced, with greater changes in the vitamin C group.

>Conclusion Insulin may thus exert vascular benefits in T2D, by modifying fasting and postprandial lipid metabolism resulting in reduced OS and improved EF. Vitamin C therapy may augment the vascular benefits of insulin in T2D through additional effects on OS and EF.
Elevated exhalation of hydrogen peroxide in patients with systemic sclerosis
Authors: Łuczyñska M. , Szkudlarek U. , Dziankowska‐Bartkowiak B. , Waszczykowska E. , Kasielski M. , Sysa‐Jȩdrzejowska A. , Nowak D.
Published: December 2004

Background Systemic sclerosis is accompanied by an influx of activated phagocytes into distal airways. These cells release H2O2, which may evaporate from the airways surface and be detected in expired breath condensate. We tested whether patients with systemic sclerosis exhale more H2O2 than healthy subjects and whether breath condensate H2O2 levels correlate with some clinical parameters.

Material and methods H2O2 was measured fluorimetrically in the expired breath condensate of 27 patients (22 women, five men, mean age 49 ± 13·1 years) with systemic sclerosis and 27 age‐ and sex‐ matched healthy controls.

Results Exhaled H2O2 levels were 3·5‐fold higher (0·88 ± 0·62 µM vs. 0·25 ± 0·17 µM, P < 0·001) in the patients with systemic sclerosis than in the controls. Treatment with cyclophosphamide and/or prednisone (29 ± 50 months, range 3–168 months) did not significantly decrease H2O2 exhalation (0·78 ± 0·50 µM, n= 10 vs. 0·94 ± 0·67 µM, n= 17, P > 0·05). No significant difference was found between patients with limited and diffuse scleroderma (1·03 ± 0·69 µM, n= 17 vs. 0·63 ± 0·41 µM, n= 10, P > 0·05). H2O2 levels correlated with disease duration (r = 0·38, P < 0·05) and time from the first Raynaud's episode (r = 0·44, P < 0·05).

Conclusions Patients with systemic sclerosis exhale more H2O2 than healthy controls, suggesting involvement of reactive oxygen species in disease processes. Lack of significant intergroups differences in H2O2 levels may have resulted from the small number of patients analyzed.
Discordance of endothelial nitric oxide synthase in the arterial wall and its circulating products in baboons: interactions with redox metabolism
Authors: Wang J. , Felux D. , VandeBerg J. , Wang X. L.
Published: December 2004

Background Although peripheral arteries and circulating factors have been frequently used to assess systemic or central arterial, such as coronary artery, endothelial nitric oxide synthase (eNOS) functions, there is no direct evidence to support that they are related.

Design We explored relationships in eNOS levels among coronary, aortic, carotid and brachial arteries, and interactions with redox metabolisms in 40 necropsied baboons (Papio hamadryas).

Results We found no correlations in eNOS or NOx levels among all four arteries (R: 0·02–0·19, P > 0·05). While eNOS levels were high in both coronary (133·78 ± 10·9 pg mg−1 protein) and aortic arteries (168·53 ± 16·32 pg mg−1 protein), they were low in brachial (82·88 ± 5·5 pg mg−1 protein) and carotid (89·83 ± 7·15 pg mg−1 protein) arteries. Arterial eNOS were not correlated with plasma NOx either. However, coronary and aortic eNOS were positively correlated with the corresponding arterial total antioxidant status (TAS) (r = 0·638, P= 0·001, and r = 0·615, P= 0·0001). Coronary eNOS was also negatively associated with coronary advanced glycation end products (AGE) (r = −0·454, P= 0·003). Furthermore, there were significant associations in TAS levels between plasma and arterial wall extracts (R: 0·344–0·369, P < 0·05) and among arteries of different anatomic sites (R: 0·637–0·877, P < 0·001). While arterial TAS was negatively correlated with corresponding arterial AGE, TAS in the arterial wall and plasma were positively associated with plasma AGE.

Conclusions Our study shows that eNOS is differentially expressed in different anatomic sites and is not associated with plasma NOx, suggesting that brachial eNOS may not be used to assess coronary eNOS. The positive or negative associations between eNOS and TAS or AGE, especially in the coronary artery, indicate an important role of eNOS in arterial wall redox balance.
Disruption of nasopharyngeal epithelium by pneumococci is density‐linked
Authors: Lagrou K. , Peetermans W. E. , Verhaegen J. , Jorissen M. , Van Eldere J.
Published: December 2004

Background The aim of this project was to study the influence of pneumococci on nasopharyngeal epithelial integrity as a function of time and pneumococcal density.

Materials and methods Cell layers of an in vitro model of human nasopharyngeal epithelium were inoculated with different pneumococcal strains. The transepithelial electrical resistance (TEER), a measure of the integrity of the cell layers, and the pneumococcal concentration in the apical fluid on the epithelial cells were measured at different times after inoculation.

Results Pneumococci caused a decrease in the TEER when a density of 1 × 107 CFU mL−1 was reached. The growth rate of pneumococci in our in vitro model differed between the strains tested and, for the same strain, between in vitro culture on the epithelial cells and broth culture. Differences in timing of the onset of decrease in the TEER between strains were the result of differences in growth rate on the epithelial cells. Antibiotic‐induced lysis of pneumococci caused an immediate decrease in the TEER of the cell layers.

Conclusion Pneumococci cause a decrease in the TEER at a density of 1 × 107 CFU mL−1. Our hypothesis is that this decrease in the TEER is the result of quorum‐induced lysis of the pneumococci.
The economic value of recreational fisheries in Nordic countries
Authors: Toivonen A.‐L. , Roth E. , Navrud S. , Gudbergsson G. , Appelblad H. , Bengtsson B. , Tuunainen P.
Published: December 2004

Recreational fishing, whether free or at cost, has an economic value. This value was measured in five Nordic countries based on a contingent valuation mail survey. Regression models were used to identify demographic characteristics, types of fishing patterns and differences in the countries’ management regimes that can explain both actual fishing expenditure and willingness to pay for the non‐market benefits by persons participating in fishing or enjoying the benefits derived by it. Net benefit, i.e. willingness to pay over and above actual expenditure was highest amongst those fishing. In Denmark, the small number of generalist fishermen get the highest benefit. In Finland results are mixed but sports fishermen benefit on average even more than generalists. Urban sports fishing raises the highest benefit in Iceland while in Norway the benefit is more equally spread, with occasional anglers and women reaping the least. In Sweden the mean benefit is the lowest in the Nordic countries but evenly distributed among categories of fishermen. In the Nordic countries combined, nationality explains willingness to pay as being Norwegian or Finnish increases benefit and being Icelandic reduces it. The non‐use value of recreational fisheries was elicited through posing questions on willingness to pay for the preservation of the existence of current fish stocks and current quality of recreational fishing to persons participating in fishing or enjoying the benefits derived from it. For those not fishing or people in general, the power of the models to explain willingness to pay for the existence of recreational fisheries was very weak. The benefit, i.e. willingness to pay, is higher if somebody in the household fishes. Educated, young, urban, well‐off citizens also put value on the non‐use of the resource.
Fecundity, lifespan and egg mass in butterflies: effects of male‐derived nutrients and female size
Authors: OBERHAUSER K. S.
Published: December 2004

1. Effects of larval reserves and nutrients received as adults on fecundity and lifespan in female Danaus plexippus (the Monarch Butterfly) were measured to determine the relative importance of different sources of nutrients for reproduction and somatic maintenance.

2. Egg‐laying lifespan was correlated with female size but not with the amount of male‐derived nutrients or adult food concentration.

3. Lifetime fecundity was higher when females received a large first spermatophore, but was not affected by female size when lifespan was controlled or by adult food concentration.

4. At the end of their lives, females contained unlaid eggs and retained, on average, 88% of their initial mass. This proportion was unchanged in two years, although mean egg‐laying lifespan varied from 22·5 to 28·7 days.

5. Egg mass decreased over the female lifespan, and was correlated with female size.

6. These results suggest that larval reserves are more important for somatic maintenance than adult income, but that the protein‐rich nutrients received from males contribute to egg production. This supports theoretical predictions and empirical studies of other Lepidoptera showing that larval reserves are less likely to affect fecundity when the adult income can contribute substantially to egg production.
Clonal variation in life‐history traits and feeding rates in the gastropod, Potamopyrgus antipodarum: performance across a salinity gradient
Authors: JACOBSEN R. , FORBES V. E.
Published: December 2004

1. Parthenogenetic species are often geographically more widely distributed than their sexual relatives. This success in colonizing can be explained either by dispersal of one or a few clones of wide physiological tolerance or by the distribution of many locally adapted clones.

2. Here we compare the influence of salinity on reproductive output, feeding rate, growth rate and size at birth between two genotypes of Potamopyrgus antipodarum to address the questions (i) Do these traits vary in response to changing salinity? (ii) Does the response to a salinity gradient differ between genotypes? (iii) Can the patterns of variation, in relation to salinity, contribute to explaining the geographical distribution of P. antipodarum in Europe?

3. Our results demonstrate that genetic variation among populations of P. antipodarum is reflected in differences in life‐history traits and feeding rates in response to a salinity gradient. The phenotypic differences between the genotypes are consistent with the geographical distribution of P. antipodarum clones in Europe.

4. The overall response to salinity of both genotypes of P. antipodarum suggests an optimum at ≈ 5‰ S; however, both genotypes showed a broad salinity tolerance and were able to feed, grow and reproduce over the entire salinity range tested (0–15‰ S). The broad environmental tolerance of both genotypes together with their widespread geographical distribution across Europe provide evidence consistent with the general‐purpose genotype hypothesis.
RHABDOID TUMOUR OF THE KIDNEY: a clinicopathological study of 22 patients from the International Society of Paediatric Oncology (SIOP) nephroblastoma file
Authors: Vujanić G.M. , Sandstedt B. , Harms D. , Boccon‐Gibod L. , Delemarre J.F.M.
Published: December 2004

We present 22 (0.9%) cases of rhabdoid tumour of the kidney diagnosed amongst 2392 renal tumours in children. The patients ages ranged from 3 weeks to 94 months (median 7 months) and the female:male ratio was 1.2 : 1. Clinically, they presented with an abdominal mass but four (18%) children also had hypercalcaemia and one (4.5%) developed a brain tumour (primitive neuroectodermal tumour). None of the children presented with stage I disease, five (23%) had stage II, ten (46%) stage III, and five (23%) stage IV disease. Two (9%) patients had bilateral tumours. Histologically, the vast majority (20/22) of the tumours exhibited a classical pattern but other histological patterns were also noted. Immunohistochemical studies performed in 12 cases showed vimentin positivity in all cases, CAM 5.2 in eight, epithelial membrane antigen in six, neuron specific enolase in four, S‐100 protein in eight, and desmin in one case. In only 12 of the 22 tumours was there agreement between the reporting pathologist and the panel on a diagnosis of rhabdoid tumour of the kidney. Eight tumours originally diagnosed as rhabdoid tumour of the kidney were found to be other renal tumours and in another ten cases the initial diagnosis was changed by the panel to rhabdoid tumour. Metastases developed in 18 (82%) of the children—in eight they were present at the time of diagnosis and in 10 they developed from 2 weeks to 9 months after initial diagnosis. Metastases were found in the lung, abdomen, lymph nodes, liver, bone and brain. Of the 19 children with adequate follow‐up, only two (10.5%) with stage II disease are alive, while 17 (89.5%) died 2 weeks to 20 months after the diagnosis.
Elderly patients' perceptions of their spiritual needs and care: a pilot study
Authors: Ross Linda A.
Published: December 2004

This paper describes a pilot study, in a small sample of elderly patients, designed to ascertain their perceptions of their spiritual needs and care. According to the nursing literature, spiritual care is part of the nurse's role. But it is not clear what spiritual needs are or how nurses are expected to give spiritual care. Ten patients from a care of the elderly assessment unit located in a hospital in Edinburgh, Scotland were interviewed about their spiritual needs in the summer of 1995. Eight patients admitted to having experienced spiritual needs at some time in their lives, six while in hospital. The types of needs experienced related to religion, meaning, love and belonging, morality, and death and dying. Their spiritual needs could have been better met if, for example, a quiet room for reflection/prayer had been available and if they had been told about hospital church services and provided with transport to attend. Although limited, the findings contribute to our understanding of spiritual need and spiritual care from the elderly in‐patients' view point. Further research, however, is needed to explore the type of spiritual help other elderly patients and other patient groups in different geographical locations feel they would like.
Malnutrition in geriatric patients: a neglected problem?
Authors: Elmståhl Sölve , Persson Mats , Andren Margareta , Blabolil Vlasta
Published: December 2004

The nutrient intake in geriatric long‐stay patients and the mortality risk associated with low energy intake were studied in 61 patients, 43 women and 18 men, with a mean age of 87 years, at a geriatric long‐stay care hospital during a 6‐month follow‐up. Dietary intake was assessed with a 9‐day dietary record. Energy expenditure was calculated assuming a physical activity level of 1.33 × basal metabolic rate (BMR), predicted from equations given by FAO/WHO. Mean energy intakes were 1557 kcal in men and 1280 kcal in women; 84% of the patients had an intake below estimated energy expenditure and 30% were below estimated BMR. Only 5% received dietary supplement. Eleven out of the 61 patients died during the follow‐up and the deceased had lower energy intake than the others (1185 kcal vs 1401 kcal, P<0.05). An energy intake below median (1378 kcal) was associated with an age adjusted increased 6‐month mortality risk, odds ratio 12.5. A high proportion of geriatric long‐stay patients report dietary intake far below present recommendations and are thereby at risk for having/developing malnutrition. Improved surveillance of geriatric long‐stay patients'dietary habits seems justified.
Perioperative treatment with octreotide minimizes technical complications after enteric conversion of bladder‐drained pancreas transplants
Authors: Bogetti Diego , Nazarewski Sławomir , Zieliński Adam , Sileri Pierpaolo , Testa Giuliano , Sankary Howard , Benedetti Enrico
Published: December 2004

Abstract:  We review our experience with enteric conversion of previously bladder‐drained pancreas transplants (PTx) using a short perioperative course of octreotide (OCT). Between July 1994 and December 2001, 45 consecutive primary bladder‐drained PTx were performed. Immunosuppression consisted of a combination of tacrolimus, mycophenolate mofetil and steroids after induction with monoclonal or polyclonal antibodies. A total of 16 patients underwent enteric conversion at an average of 3 months after the initial transplant. Each patient received OCT perioperatively. We report no technical complications with the exception of one superficial wound infection and good early and late PTx survival rates. Perioperative treatment with octreotide is well tolerated and may reduce technical complications while performing enteric conversion of previously bladder‐drained PTx.
The unrecognized posterior gastric artery: a potential cause of surgical complications in pancreas transplantation
Authors: Troppmann Christoph , Pirenne Jacques , Perez Richard V , Gruessner Rainer WG
Published: December 2004

Abstract: Background: Our report describes, for the first time, a pre‐transplant vascular complication in a pancreas graft related to the posterior gastric artery – a major, but relatively unknown side branch of the splenic artery. The posterior gastric artery that was overlooked by a surgical procurement team during donor pancreatectomy led to distortion of the peripancreatic vascular anatomy and set the stage for a splenic artery injury.

Methods: We identified the transected, partially resected graft splenic artery during backtable preparation of the pancreas, and repaired it using standard vascular surgical techniques.

Results: The recipient's post‐operative course was uncomplicated. At 9‐yr post‐transplant, the recipient is alive with good pancreas graft function.

Conclusions: The relevance of the posterior gastric artery with regard to general surgical procedures was only recently recognized. Our case demonstrates that the posterior gastric artery is also important in transplant surgery. Awareness of this anatomical structure during organ procurement would help minimize pre‐transplant vascular complications.
Immunization by blood‐type antigen in human immunoglobulin products before ABO‐incompatible kidney transplantation
Authors: Sawada Tokihiko , Ando Tetsuo , Sato Sumihiko , Kubota Keiichi , Fuchinoue Shohei , Teraoka Satoshi
Published: December 2004

Abstract:  A 29‐year‐old man wanted to receive an ABO‐incompatible kidney transplant. His blood type was O, and the donor, his father, was A1. After endoscopic splenectomy performed before kidney transplantation, the recipient developed a high fever and leukocytosis, and he was treated with antibiotics and 5 g of human immunoglobulin products by intravenous infusion for 3 d. Soon after the infusions, his anti‐blood type A antibody titer (anti‐A titer) rose, and several sessions of plasma‐exchange (PEX) and double‐filtration plasmapheresis (DFPP) failed to lower it. Three courses of anti‐CD20 monoclonal antibody were administered to suppress the antibody production more specifically, and the rituximab infusions and repeated PEX and DFPP session lowered the anti‐A titer and enabled kidney transplantation. Mild humoral rejection was observed 16 d after transplantation, but the recipient's serum creatinine was 1.5 mg/dL when discharged from the hospital. The increased anti‐A titer may have been due to immunization by blood‐type A antigen, with the human immunoglobulin products given to the patient being the source of the antigen. Administration of human immunoglobulin products to recipients of ABO‐incompatible kidney transplants should be avoided, because it may cause an unexpected increase in anti‐blood‐type antibody titer.
Pegylated interferon α‐2b plus ribavirin in the treatment of post‐liver transplant recurrent hepatitis C
Authors: Ross Andrew S , Bhan Atul K , Pascual Manuel , Thiim Michael , Benedict Cosimi A , Chung Raymond T
Published: December 2004

Abstract:  Background:  Histological recurrence of the hepatitis C virus (HCV) occurs in the majority of persons transplanted for cirrhosis as a result of HCV. Herein we analyze our experience with the use of both conventional and pegylated (PEG) interferon (IFN) in combination with ribavirin (RBV) in liver transplant recipients with recurrent HCV.

Methods:  Patients transplanted between 1992 and 2001 with post‐orthotopic liver transplantation (OLT) histological recurrence of HCV, and who were treated with at least 6 months of IFN or PEG‐IFN in combination with RBV were included in this analysis. A retrospective chart review was performed.

Results:  A total of 31 patients were included. Fifteen were treated with IFN/RBV and 16 with PEG‐IFN/RBV. Of these 16, 11 had been begun on IFN/RBV and were changed to PEG‐IFN/RBV because of persistent viremia. Three patients (20%) in the IFN/RBV group and six patients (37.5%) in the PEG‐IFN/RBV group experienced a virologic response (VR) on therapy. Of the six patients experiencing VR in the PEG‐IFN/RBV group, three (50%) were IFN/RBV non‐responders. There were two sustained VRs (SVR). The 65.6% of all patients experienced a biochemical response (BR) on therapy. Seven deaths were observed. Dose modifications of IFN or PEG‐IFN (87.1%) and RBV (80.6%) and the requirement for hematopoietic growth factors were frequent.

Conclusions:  Treatment of recurrent HCV infection with combination of IFN or PEG‐IFN and RBV produced an on‐therapy VR in 29% and BR in 65% of patients. Hematologic toxicity and dose modifications were frequent. Our experience with antiviral therapy for HCV post‐OLT remains disappointing but PEG‐IFN + RBV appears to produce VR in a sizable portion of IFN + RBV non‐responders.
The Tangled Bank: The maintenance of sexual reproduction through competitive interactions
Authors: Koella Jacob C.
Published: December 2004

The maintenance of sexual reproduction is discussed using a model based on the familiar Lotka‐Volterra competition equations. Both the equilibrium and the stability conditions that allow a sexual population to resist invasion by a single asexual clone are considered. The equilibrium conditions give results similar to previous models: When the cost of sex, within phenotype niche width, and environmental variance are low, the sexual population coexists with the asexual clone and remains at a high density. However, the asexual clone is never completely excluded. Analysis of the stability conditions shows a different picture: The introduction of an asexual clone considerably reduces the stability of the community. However, owing to its larger total niche width, the sexual population exists partly in a “competitor‐free space” where the asexual clone has almost no influence on the outcome of the interactions. Therefore the asexual clone is less stable than the sexual population and has a higher probability of extinction. In contrast, the sexual population does not become extinct, since the extreme phenotypes remain at a stable, though low, density, and the central phenotypes, where stability is low, are recreated every generation through recombination. I therefore conclude that the ecological conditions under which sexual reproduction is favored over asexual reproduction are fairly easily attained and are more general than previous analyses had suggested.
Variation in sex determination in natural populations of a shrimp
Authors: Naylor Caroline , Adams Jonathan , Greenwood Paul J.
Published: December 2004

Strategies of sex determination were studied in Gammarus duebeni, a brackish water shrimp (Crustacea, Amphipoda). Animals from Budle Bay, northern England, have environmental sex determination (e. s. d.), in accord with a population studied in Germany. Males are produced in long day photoperiods and females in short days. By contrast, animals from southern England show no significant sex ratio variation with daylength. This is the first report of such variation in sex determination for an invertebrate. Detailed studies of Budle Bay animals show that sex is determined several weeks after young are released by the mother; that the critical daylength is longer at Budle Bay than in Germany; and that the critical response is cued at the onset of a photophase. The nature of sex determination in G. duebeni may be associated with population dynamics. Males gain greater relative fitness by large size than females. E. s. d. is then adaptive where the breeding season produces significant growth differences between early and late animals, but where generations do not overlap. Comparisons are drawn with the flexible sex determining system in Menidia menidia (Pisces).
Plasticity in age and size at maturity in male guppies (Poecilia reticulata): An experimental evaluation of alternative models of development
Authors: Reznick David N.
Published: December 2004

I present two models for the genesis of phenotypic variation in age and size at maturity in male guppies. Both are qualitatively consistent with the observation that age at maturity increases and size at maturity decreases as food availability (and growth rate) decline. The first model (“fixed development”) has a constant size which signals the initiation of the process of maturation and a constant time interval between the initiation and completion of maturation. There is thus no response in the pattern of development to differences in growth rate. Variation in age at maturity results from the different amounts of time required to reach the size at initiation. Variation in size results from different amounts of growth between the initiation and completion of maturation. Phenotypic variation is therefore an epiphenomenon of expressing a fixed pattern of development in different environments. In the second model (“flexible development”), fast growers initiate maturation at a larger size than slow growers; this results in a later age and larger size at maturation than their fast growing counterparts in the fixed development model. Slow growers mature at an earlier age and smaller size than their counterparts in the fixed development model. In the second model, the pattern of development changes with the environment. Two experiments with guppies demonstrate that the second model accurately describes their pattern of development. I conclude that phenotypic plasticity is in part the product of plastic development and may represent an adaptation. Testing whether or not the response is adaptive will require further investigations. A general message of this investigation is that characterizing the reaction norm alone is not sufficient to evaluate the adaptive significance of plasticity; one must also consider the processes that generate this plasticity.
Rapid evolution of life history traits in populations of Poa annua L.
Authors: Till‐Bottraud Irène , Wu Lin , Harding James
Published: December 2004

Two populations of Poa annua L., one from an irrigated area and one from a dry area, were studied to test the following hypothesis: different life cycles should be selected in habitats of contrasting mortality regime. Plants from the irrigated area exhibited a typical perennial habit (indeterminate growth and low reproductive effort) while those from the dry area showed traits characteristic of annuals (determinate growth, high reproductive effort and flowering synchrony) although total annuality was not achieved. The antagonism between growth and reproduction was expressed at the individual tiller level and was reflected in the life history traits of the populations. The characters studied exhibited a high broad sense heritability which is required for a rapid evolution of life cycles when selection pressures are strong. Different levels of constraints (ecological, evolutionary, physiological and developmental) have to be taken into account in order to understand this evolution.
Temperature‐related divergence in experimental populations of Drosophila melanogaster. III. Fourier and centroid analysis of wing shape and relationship between shape variation and fitness.
Authors: Cavicchi Sandro , Giorgi Gianfranco , Natali Vanna , Guerra Daniela
Published: December 2004

From a laboratory stock of Drosophila melanogaster (Oregon), reared for more than 20 years at 18°C, two new populations were derived and maintained at 25° and 28°C for 8 years. The chromosomal and cytoplasmic contribution to genetic divergence between the two more extreme populations was estimated at 18°C and 28°C. Wing shape and two fitness components (fecundity and fertility) were taken into account. Fourier descriptors and the position of the centroid were taken as indicators either of wing shape variation, determined by a different response of the two wing compartments to temperature selection, or of wing shape variation determined by both compartments. The descriptors appear to be good characters: they show a variability which is genetically controlled and ascribable to genes located on specific chromosomes. The third chromosome is responsible for the adaptive difference to temperature. The genes which control wing shape are located on the second and third chromosome, although the contribution of each chromosome depends on the environment in which the flies develop. Cytoplasmic genes display an effect as large as that of chromosomes, and nucleus × cytoplasm interaction is present. The correlation between the genetic contributions to compartment‐dependent wing shape variation and the contributions to fitness is highly significant, especially at 28°C. Wing shape has, therefore, an adaptive significance in relation to temperature, which is particularly expressed in the environment where selection occurred.
Non‐equilibrium gene frequency divergence: persistent founder effects in natural populations
Authors: Boileau Marc G. , Hebert Paul D. N. , Schwartz Steven S.
Published: December 2004

The estimation of gene flow using gene frequency divergence information has become increasingly popular because of the difficulty involved in the direct determination of gene flow among populations. The present study examined allozyme gene frequencies in populations of eighteen aquatic invertebrate taxa at two sites in northern Canada. Gene frequencies at polymorpic loci were significantly different among 8–31 localized populations of all species at Igloolik and among 10–36 populations at Churchill confirming the generality of gene pool fragmentation in pond‐dwelling organisms. Measures of gene flow estimated from gene frequency divergence, which assume that gene frequency distributions are at equilibrium, were inconsistent with the probable dispersal capacities of taxa. This provoked an examination of historical events as alternative explanations. Both theory and computer simulations demonstrated that when populations grow rapidly in size after founding from few individuals, the gene frequency divergence established during colonization is resistant to decay by gene exchange. Our work suggests that gene frequency distributions are often not in equilibrium and that caution should be employed in attempts to infer gene flow from them in natural populations.
Parasitism as a constraint on the rate of life‐history evolution
Authors: Hochberg M. E. , Michalakis Y. , De Meeus T.
Published: December 2004

There are a number of ways in which a host can respond in evolutionary time to reductions in survival and reproduction due to a virulent parasite. These include evolving physiological morphological, or behavioural mechanisms of resistance to infection (or to proliferation, once infection has occurred). But a more unexpected tactic is also possible. This is for hosts to reproduce (slightly) sooner when in the presence of a virulent parasite as compared to when the parasite is less virulent or absent. As such, hosts which reproduce younger may be at a selective advantage, since they can both evade parasitism in time and, even when parasitised, can reduce the likely impact of the parasite on survival and reproductive success. We employ a simple mathematical model to propose that parasites and pathogens can act as important agents in the evolution of the timing of reproduction and associated life‐history characters (e.g. body size). Once established in a semelparous host population, evolutionary increases in parasite virulence should result in the evolution of shorter lived hosts; whereas the evolution of less virulent forms of the parasite should be accompanied by the evolution of longer lived hosts. We argue that in the presence of a sufficiently virulent parasite the evolution of longer pre‐reproductive life‐spans should require the previous or concomitant evolution of morphological, behavioural or physiological resistance to parasitic infection and proliferation.
The inversion polymorphism of D. subobscura revisited: Synthetic maps of gene arrangement frequencies and their interpretation*
Authors: Menozzi P. , Krimbas C. B.
Published: December 2004

Principal component maps of the gene arrangement frequencies of 108 natural populations in Europe, North Africa and the Middle East were prepared to investigate the evolutionary forces shaping the geographic variation of inversion frequencies. Principal component maps were also prepared from ten climate variables at 347 localities of the same region. The first inversion principal component (18% of total variation) showed a N‐S cline strikingly similar to the pattern exhibited by the first principal component of climatic variables. This resemblance is interpreted as showing the outcome of a selective process, which favors the increase in frequency of the Standard gene arrangements when moving to the north. This interpretation is corroborated by the fact that such clines were formed in South and North America, following recent colonization by this species. Patterns shown by the second (12% of total variance) and third (8% of total variance) principal components are interpreted as related to historical events, the migrational advance to the north after the end of the last glaciation and the locations of the species refugia at that time.
Allelic ratios and sterility in the agamic complex of the Maximae (Panicoideae): evolutionary role of the residual sexuality
Authors: Noirot M.
Published: December 2004

The agamic complex of the tribe Maximae is constituted by two pools characterized by their own breeding system (sexuality on the one hand, facultative apomixis on the other hand). Facultative apomicts shows two types of embryo‐sacs (aposporic or meiotic). Presence of aposporic embryo‐sacs is genetically controlled by the dominant allele A (all apomictic plants are Aaaa). Meiotic embryo‐sacs, constituting residual sexuality, can allow crosses between apomicts and theoretically the generation of other genotypes than Aaaa. Additionally, some cases of sterile apomicts appears in a breeding system known to bypass it.

This led us to study these two paradoxes. In fact, the sterility would exist when the ratio A/a is greater than 0.25. This would prevent the total overrunning of an apomictic population by AAAA genotypes. The role of residual sexuality is then to allow generation of true sexuals (aaaa) from apomicts (Aaaa).
The evolution of unusual chromosomal systems in sciarid flies: intragenomic conflict and the sex ratio
Authors: Haig David
Published: December 2004

A model is presented for the evolution of the sciarid chromosomal system. In this model, a driving X chromosome caused female‐biased sex ratios. The drive was exploited by maternal autosomes that segregated with the X at spermatogenesis. Genes in mothers converted some of their XX daughters into sons by eliminating a paternal X from the embryonic soma. L chromosomes were derived from X chromosomes and favored male‐biased sex ratios. An X' chromosome arose that suppressed the effects of L chromosomes. The 1:1 sex ratio is a stalemate between the X' and X'X mothers causing all‐female broods and the L chromosomes in XX mothers causing all‐male broods. Any element (such as an L chromosome) that is preferentially transmitted through one sex will be selected to bias the sex ratio towards this sex.
On the origin of the cyanogenic polymorphism in Trifolium repens L.
Authors: Kakes P. , Hakvoort H. W. J.
Published: December 2004

Trifolium repens
L. and
Trifolium nigrescens
Viv. are two of the approximately six cyanogenic species known in the genus Trifolium. The two species are closely related:
T. nigrescens
is considered to be one of the diploid ancestors of the amphidiploid
T. repens
. We studied morphology, meiosis and the cyanogenic system in
T. repens
(amphidiploid),
T. nigrescens
(diploid) and their reciprocal hybrids. A comparison of the enzyme linamarase in the species and hybrids shows that there is a general resemblance between their linamarases. Immunological studies indicate that the linamarases must have a somewhat different three‐dimensional structure. These facts are consistent with the view that
T. nigrescens
(or an ancestral form of this species) has donated the
Li
gene of
T. repens
. The other putative parent,
T. occidentale
has probably not donated an active
Li
gene. The hypothesis of the origin of the
Li
gene does not explain its polymorphism in European populations of
T. repens
, as
T. nigrescens
is monomorphic for cyanogenesis and amphidiploids do not segregate for genes which are homozygous dominant in one of the parents. Segregation for
Li
could be caused by a gene mutation or a small exchange between homeologous chromosomes. The latter event is more probable. A nigrescens‐repens exchange would give rise to a chromosomal region with reduced homology to both parental chromosomes. The genes in the region of exchange will be tightly linked due to diminished cross‐over frequency. It has been known for years that
Li
has effects on the vegetative and reproductive characters in
T. repens
and we have recently shown that these effects must be the result of genes linked to
Li
. As the associated characters influence the fitness of the cyanotypes, not only the origin but also the maintenance of the cyanogenic polymorphism is closely related to the evolutionary history of
T. repens .
Relationships between plant density, outcrossing rates and seed set in natural and experimental populations of Scabiosa columbaria
Authors: Van Treuren R. , Bijlsma R. , Ouborg N. J. , Kwak M. M.
Published: December 2004

Outcrossing rates were estimated in both natural and experimental populations of Scabiosa columbaria, a self‐compatible, entomophilous, gynodioecious, protandrous perennial. In natural populations, estimates of the outcrossing rate in hermaphrodites were near to one and ranged from 0.84 ± 0.07 to 1.12 ± 0.11. The effect of plant density on outcrossing rates was studied in two experimental populations of 27 individuals. Contrary to expectation the estimates of the outcrossing rate in hermaphrodites were about 100% for both densities. However, in the sparse population, the fraction of developed seeds of plants used to estimate outcrossing rates was significantly lower than of plants in the dense population (0.41 ± 0.06 and 0.68 ± 0.08, respectively). Artificial pollinations of these plants in the greenhouse showed that the fraction of developed seeds was 0.60 ± 0.01 and 0.83 ± 0.05 after self‐ and cross‐pollination, respectively. The combined results suggested that the differential success of self‐ and cross‐pollination might have caused equalization of the outcrossing rates in the experimental populations, despite different plant densities. The implications of the results for conservation biology are discussed.
Mitochondrial DNA phylogeny of North American field crickets: perspectives on the evolution of life cycles, songs, and habitat associations
Authors: Harrison Richard G. , Bogdanowicz Steven M.
Published: December 2004

North American field crickets (genus Gryllus) exhibit a diversity of life cycles, habitat associations, and calling songs. However, patterns of evolution for these ecological and behavioral traits remain uncertain in the absence of a robust phylogenetic framework. Analyses of morphological variation have provided few clues about species relationships in the genus Gryllus. Here we use comparisons of mitochondrial DNA restriction site maps for 29 individuals representing 11 species (including potential outgroups) to examine relationships among eastern North American field crickets. Initially chosen as likely outgroup taxa, the two European species of Gryllus do not obviously fall outside of an exclusively North American clade and (based on amount of sequence divergence) appear to have diverged from North American lineages at about the same time that major North American lineages diverged from each other. The egg‐overwintering crickets comprise a strongly supported monophyletic group, but relationships among these three closely related species cannot be resolved. The mtDNA data are consistent with a single origin of egg diapause and do not support a model of recent life cycle divergence and allochronic speciation for Gryllus pennsylvanicus and G. veletis. The two crickets are not sister species, despite remarkable similarity in morphology, habitat, and calling song. This conclusion is consistent with published data on allozyme variation in North American field crickets. The habitat associations of eastern North American field crickets have been labile, but calling songs sometimes have remained virtually unchanged across multiple speciation events.
Diverse, endemic and polyphyletic clones in mixed populations of a freshwater snail (Potamopyrgus antipodarum)
Authors: Dybdahl Mark F. , Lively Curtis M.
Published: December 2004

Understanding the source and diversity of clones is necessary to resolve the complicated issues surrounding the apparent evolutionary stability of sexual reproduction. The source of clones is important because present theory is based on an “all else equal” assumption, which is predicated on the idea that clonal mutants are derived from and compete with local sexual populations. Clonal diversity is important because it reduces the advantage of sexual reproduction under either soft selection (the Tangled Bank Hypothesis) or under strict frequency‐dependent selection (the Red Queen Hypothesis). In the present study, protein electrophoresis was used to determine the source and diversity of clones in a freshwater snail (Potamopyrgus antipodarum) in four glacial lakes in which sexual and clonal females were thought to coexist. The results showed (1) that the populations were mixtures of diploid sexual and triploid asexual individuals, (2) that genotypic diversity of clonal populations is very high in all four lakes (but lower than in the sympatric sexual populations), and (3) that the clones are polyphyletically derived from their sympatric sexual populations. Consequently, repeated mutation to parthenogenetic reproduction since the Pleistocene has introduced a different and diverse set of clones in all four lakes. Such diversity may provide a challenge for the ecological theories of sex that rely on frequency‐dependent selection.