High temperature triggers latent variation among individuals: oviposition rate and probability for outbreaks

Background

It is anticipated that extreme population events, such as extinctions and outbreaks, will become more frequent as a consequence of climate change. To evaluate the increased probability of such events, it is crucial to understand the mechanisms involved. Variation between individuals in their response to climatic factors is an important consideration, especially if microevolution is expected to change the composition of populations.

Methodology/Principal Findings

Here we present data of a willow leaf beetle species, showing high variation among individuals in oviposition rate at a high temperature (20°C). It is particularly noteworthy that not all individuals responded to changes in temperature; individuals laying few eggs at 20°C continued to do so when transferred to 12°C, whereas individuals that laid many eggs at 20°C reduced their oviposition and laid the same number of eggs as the others when transferred to 12°C. When transferred back to 20°C most individuals reverted to their original oviposition rate. Thus, high variation among individuals was only observed at the higher temperature. Using a simple population model and based on regional climate change scenarios we show that the probability of outbreaks increases if there is a realistic increase in the number of warm summers. The probability of outbreaks also increased with increasing heritability of the ability to respond to increased temperature.

Conclusions/Significance

If climate becomes warmer and there is latent variation among individuals in their temperature response, the probability for outbreaks may increase. However, the likelihood for microevolution to play a role may be low. This conclusion is based on the fact that it has been difficult to show that microevolution affect the probability for extinctions. Our results highlight the urge for cautiousness when predicting the future concerning probabilities for extreme population events.     

Disentangling effects of uncertainties on population projections: climate change impact on an epixylic bryophyte

Assessment of future ecosystem risks should account for the relevant uncertainty sources. This means accounting for the joint effects of climate variables and using modelling techniques that allow proper treatment of uncertainties. We investigate the influence of three of the IPCC's scenarios of greenhouse gas emissions (special report on emission scenarios (SRES)) on projections of the future abundance of a bryophyte model species. We also compare the relative importance of uncertainty sources on the population projections. The whole chain global climate model (GCM)-regional climate model-population dynamics model is addressed. The uncertainty depends on both natural- and model-related sources, in particular on GCM uncertainty. Ignoring the uncertainties gives an unwarranted impression of confidence in the results. The most likely population development of the bryophyte Buxbaumia viridis towards the end of this century is negative: even with a low-emission scenario, there is more than a 65 per cent risk for the population to be halved. The conclusion of a population decline is valid for all SRES scenarios investigated. Uncertainties are no longer an obstacle, but a mandatory aspect to include in the viability analysis of populations.     

Plasma calcitonin response to a calcium clamp. Influence of sex and age

The influence of sex and age on basal and calcium stimulated immunoreactive plasma calcitonin (iCT) were studied in 36 healthy subjects. An identical calcium stimulus, "calcium clamp", was applied to 10 young males, 13 premenopausal females of similar ages and 13 postmenopausal females. A significantly greater iCT response was found in males compared with both female groups. No age correlation in basal or calcium stimulated iCT levels was observed despite 35 years difference in mean age between the pre- and postmenopausal groups. A positive correlation between the induced change in whole blood ionized calcium (B-Ca++) and the iCT response, recorded after 15 min, was seen in young subjects of both sexes. Basal iCT and B-Ca++ were similar in all three groups. No correlation between basal iCT and basal B-Ca++, or between basal iCT and age was found. The total amounts of infused calcium per kg body weight were equal. The results indicate that male subjects have a greater secretory capacity of the thyroid C-cell than females. No reduction of the secretory capacity was observed with increasing age in females, neither was any difference found between pre- and postmenopausal females of the iCT-response.     

Comorbidity among HHT patients and their controls in a 20 years follow-up period

Background

Hereditary Haemorrhagic Telangiectasia (HHT) is an autosomal dominant genetic disorder with a wide variety of clinical manifestations due to the presence of multiple arteriovenous malformations in various tissues and organs.

Objective

To study the need for hospital admittance in a group of HHT patients and matched controls during a 20?years follow-up period commencing in 1995.

Methods

All HHT patients in the County of Funen, Denmark, were included. For each patient, three age and sex matched controls were identified at the time of enrolment. Data on all hospitalisations were extracted from the national health registers and compared with clinical records. The hospitalisations were grouped as HHT relevant or not HHT relevant based on the discharge diagnosis (International Classification of Diseases, ICD10) and with particular focus on infections, bleedings and thromboembolic events.Patients with HHT were compared with controls concerning the first time incidence of each discharge diagnosis.

Results

We included 73 HHT patients and 219 controls of which one control was lost to follow-up. HHT-patients had significantly more hospitalisations per person caused by infections in joints and bones, but not caused by infections in general. Bleeding episodes were, as expected, more frequent among the HHT-patients. The study revealed a similar incidence of abscesses and thromboembolisms, including in the central nervous system, among the HHT patients and controls.

Conclusions

Based on this study Danish HHT patients had an increased comorbidity of infections in joints and bones and of bleeding episodes. However, the incidence of thromboembolisms, cerebral abscesses and other conditions commonly considered related to HHT was comparable between the patients and the controls. The patients included in this study were closely monitored at a highly specialised HHT Centre where they received relevant diagnostic evaluation, treatment and counselling. Since this is assumed to benefit the overall health of the patients, it may explain why these patients were less prone to comorbidity than other studies have suggested.

     

Multiple infections: relatedness and time between infections affect the establishment and growth of the cestode Schistocephalus solidus in its stickleback host

We studied experimental double infections of the cestode Schistocephalus solidus in its stickleback host. In particular, we were interested in how two important components of the cestode's transmission success-establishment and growth within the fish host-were affected by the relatedness of the two parasites in a double exposure and by the timing of the two exposures, that is, whether they occurred simultaneously or sequentially. We found that male sticklebacks more often became infected (singly or doubly) if the two cestodes in the exposures were related, whereas female sticklebacks were more easily infected (singly or doubly) when exposed to two unrelated cestodes. Irrespective of the fish's gender, successful infections more often contained both cestodes when they were related. In sequential exposures with related as well as unrelated cestodes, the cestode in the later exposure survived better and also grew larger than the cestode from the first exposure, despite being one week younger. Our results emphasize that within-host dynamics and factors acting at this level can play an important role in determining a parasite's transmission success.     

Eutrophication and agriculture in Denmark: 20 years of experience and prospects for the future

During the past two decades there has been growing public and political awareness of the consequences of eutrophication in Denmark. By the mid-1980s, the environmental status of inland and coastal waters had deteriorated due to high nutrient loads. Consequently, a number of different Action Plans against water pollution were introduced. In the agricultural sector, focus has been on reductions in nitrogen leaching obtained by the introduction of various measures: a maximum limit to the density of livestock, 9 months’ storage capacity for manure, catch crops for at least 6% of the land, enhanced utilization (up to 75%) of nitrogen in manure, etc. The agricultural sector in Denmark has implemented all of these measures, and as a result of the effort, the target for reductions in nitrogen leaching will be reached. Currently, the total loss of nitrogen from farmland is likely to be reduced by approximately 50% compared to the level in the mid-1980s. Some of the measures have been fair and based on sound arguments, and have been implemented with only minor difficulties, whereas others have proved troublesome and in our opinion disproportionately expensive. Today, further general regulation with equal restrictions toward all farmers regardless of differences in environmental impacts is no longer an acceptable path to follow. In the future, it will be necessary to pinpoint new measures in the most sensitive areas, where the potential for further reductions in nutrient loads is large. Danish Agriculture calls for specific actions—and consequently a shift in environmental management and policy making. Such a revised management strategy is the only path to follow in order to obtain further improvements in environmental conditions. Meanwhile, future development in the agricultural sector will be possible and a win–win situation can be reached. Guest editors: J. H. Andersen & D. J. Conley Eutrophication in Coastal Ecosystems: Selected papers from the Second International Symposium on Research and Management of Eutrophication in Coastal Ecosystems, 20–23 June 2006, Nyborg, Denmark