Hydrology is reflected in the functioning and community composition of methanotrophs in the littoral wetland of a boreal lake

In lake ecosystems a major proportion of methane (CH(4) ) emissions originate from the littoral zone, which can have a great spatial variability in hydrology, soil quality and vegetation. Hitherto, spatial heterogeneity and the effects it has on functioning and diversity of methanotrophs in littoral wetlands have been poorly understood. A diagnostic microarray based on the particulate methane monooxygenase gene coupled with geostatistics was used to analyse spatial patterns of methanotrophs in the littoral wetland of a eutrophic boreal lake (Lake Kev?t?n, Eastern Finland). The wetland had a hydrology gradient with a mean water table varying from -8 to -25 cm. The wettest area, comprising the highest CH(4) oxidation, had the highest abundance and species richness of methanotrophs. A high water table favoured the occurrence of type Ib methanotrophs, whereas types Ia and II were found under all moisture conditions. Thus the spatial heterogeneity in functioning and diversity of methanotrophs in littoral wetlands is highly dependent on the water table, which in turn varies spatially in relation to the geomorphology of the wetland. We suggest that changes in water levels resulting from regulation of lakes and/or global change will affect the abundance, activity and diversity of methanotrophs, and consequently CH(4) emissions from such systems.     

Chloroplast DNA variation inAnemone s. lato (Ranunculaceae)

Chloroplast DNA of seven species belonging toAnemone (sectt.Omalocarpus, Anemonidium, andAnemonanthea),Hepatica, andPulsatilla have been analyzed by restriction enzymes. According to the dendrogram constructed, the sections ofAnemone and the generaHepatica andPulsatilla seem to be evolutionary approximately equidistant to each others. This supports the concept that these groups should be treated on a similar taxonomic level, either as genera or subgenera.     

Multiple paternity in the common frog (Rana temporaria): genetic evidence from tadpole kin groups

Very few studies have investigated the occurrence of multiple paternity and sperm competition in amphibians. We studied genetic relatedness within kin groups of tadpoles of an aquatically breeding anuran Rana temporaria using allozymes. We collected samples from 52 naturally fertilized spawn clumps produced by single females at three breeding sites in two populations. We estimated relatedness (r) within kin groups, and compared the observed genotype distributions of the tadpoles (on average 23 individuals in each group) with the expected distributions based on single mating. Average relatedness over five polymorphic loci was 0.44 and 0.43 in the two populations, the latter being significantly smaller than that expected by single mating (0.5). The number of patrilines, calculated from relatedness estimates, was 1.3 in one population and 1.4 in the other. Genotype distributions deviated significantly from the expected in half of the kin groups and at all breeding sites. The results show that egg clutches of R. temporaria commonly contain multiply sired offspring. We suggest that communal breeding may affect paternity patterns in R. temporaria as well as in anurans in general.     

Larval life history and anti-predator strategies are affected by breeding phenology in an amphibian

Seasonal time constraints can pose strong selection on life histories. Time-constrained animals should prioritise fast development over predation risk to avoid unfavourable growing conditions. However, changes in phenology could alter the balance between anti-predator and developmental needs. We studied variation of anti-predator strategies in common frog (Rana temporaria) tadpoles in four populations from the two extremes of a latitudinal gradient across Sweden. We examined, under common conditions in the laboratory, the anti-predator responses and life histories of tadpoles raised with predatory Aeshna dragonfly larvae in two consecutive years with a difference of 20 days in breeding time in the north, but no difference in breeding time in the nouth. In a year with late breeding, northern tadpoles did not modify their behaviour and morphology in the presence of predators, and metamorphosed faster and smaller than tadpoles born in a year with early breeding. In the year with early breeding, northern tadpoles showed a completely different anti-predator strategy by reducing activity and developing morphological defences in the presence of predators. We discuss the possible mechanisms that could activate these responses (likely a form of environmentally-mediated parental effect). To our knowledge, this is the first study to show that a vertebrate modifies the anti-predator strategy of its offspring in response to natural variation in reproductive phenology, which highlights the need to consider phenology in studies of life-history evolution.     

Pyrophosphate-Fueled Na+ and H+ Transport in Prokaryotes

SUMMARY

In its early history, life appeared to depend on pyrophosphate rather than ATP as the source of energy. Ancient membrane pyrophosphatases that couple pyrophosphate hydrolysis to active H⁺ transport across biological membranes (H⁺-pyrophosphatases) have long been known in prokaryotes, plants, and protists. Recent studies have identified two evolutionarily related and widespread prokaryotic relics that can pump Na⁺ (Na⁺-pyrophosphatase) or both Na⁺ and H⁺ (Na⁺,H⁺-pyrophosphatase). Both these transporters require Na⁺ for pyrophosphate hydrolysis and are further activated by K⁺. The determination of the three-dimensional structures of H⁺- and Na⁺-pyrophosphatases has been another recent breakthrough in the studies of these cation pumps. Structural and functional studies have highlighted the major determinants of the cation specificities of membrane pyrophosphatases and their potential use in constructing transgenic stress-resistant organisms.     

Epizootic cutaneous papillomatosis, cortisol and male ornamentation during and after breeding in the roach Rutilus rutilus

The prevalence of epidermal papillomatosis in roach is known to peak during the spawning period and to be higher in males than in females. The high occurrence of papillomatosis in polluted waters suggests that stress may contribute to the outbreak of the disease. However, little is known about breeding-induced stress in fish and its relationship with diseases. In this study, plasma cortisol concentration, hematocrit and the relative size of the spleen were determined in healthy and diseased male and female roach Rutilus rutilus during and shortly after spawning in a wild population. In addition, the sexual ornamentation (breeding tubercles on the lateral sides and on the frontal) of male roach during spawning was examined. Plasma cortisol concentration was higher during than after the spawning period, and higher in males than in females during spawning, indicating a spawning-induced stress and higher spawning stress among males. There was no correlation between cortisol concentration and the intensity of papillomatosis (number of scales under papilloma tumors) among the diseased fish. However, the significant interaction sex x disease status revealed by ANCOVA suggested that diseased males could be more prone to increased cortisol levels than diseased females or healthy males. Hematocrit values (ratio of the volume of red blood cells to total volume of blood) but not condition factor were lowered in papilloma-diseased fish after spawning. The relative size of the spleen was greater in males than in females. The number of frontal breeding tubercles correlated negatively with the intensity of papillomatosis. Experimental studies are needed to investigate the association of papillomatosis with stress and cortisol.     

Heat waves trigger swift changes in the diet and life-history of a freshwater snail

Hydrobiologia - Extreme climatic events, such as heat waves, may induce changes in nutrient acquisition by omnivorous ectotherms. Likely modulated by the intensity, frequency and duration of these...     

Compensating for delayed hatching reduces offspring immune response and increases life‐history costs

Organisms are exposed to multiple sources of stress in nature. When confronted with a stressful period affecting growth and development, compensatory responses allow the restoration of individual fitness, providing an important buffering mechanism against climatic and other environmental variability. However, tradeoffs between increased growth/development and other physiological traits are predicted to prevent these high growth and development rates from becoming constitutive. Here, we investigated how compensatory responses in growth and development affect immune responses. By using low temperature to stop embryonic development, we exposed moor frog Rana arvalis tadpoles to two levels of time‐constraints: non‐delayed hatching and 12‐day delayed hatching. In a common garden experiment, we recorded larval growth and development, as well as their immune response, measured as the inflammatory reaction after the injection of phytohaemagglutinin (PHA). Tadpoles originating from delayed hatching treatments had a lower immune response to PHA challenge than those from the non‐delayed hatching treatment. In general, tadpoles from the delayed hatching treatment reached metamorphosis faster and at a smaller size than control tadpoles. However, immune‐challenged tadpoles were not able to accelerate their development in response to delayed hatching. Our results indicate that 1) the innate immune response can be reduced in organisms undergoing compensatory developmental responses in growth and development and 2) compensatory capacity can be reduced when organisms are immunologically challenged. These dual findings reveal the complexity of handling multiple stressors and highlight the importance of examining the costs and limits of mounting an immune response in the context of increasing phenological instability ascribed to climate change.     

Are high-latitude individuals superior competitors? A test with <Emphasis Type="Italic">Rana temporaria</Emphasis> tadpoles

Species with a wide distribution over latitudinal gradients often exhibit increasing growth and development rates towards higher latitudes. Ecological theory predicts that these fast-growing genotypes are, in the absence of trade-offs with fast growth, better competitors than low-latitude conspecifics. While knowledge on key ecological traits along latitudinal clines is important for understanding how these clines are maintained, the relative competitive ability of high latitude individuals against low latitude conspecifics has not been tested. Growth and development rates of the common frog Rana temporaria increase along the latitudinal gradient across Scandinavia. Here we investigated larval competition over food resources within and between two R. temporaria populations originating from southern and northern Sweden in an outdoor common garden experiment. We used a factorial design, where southern and northern tadpoles were reared either as single populations or as mixes of the two populations at two densities and predator treatments (absence and non-lethal presence of Aeshna dragonfly larvae). Tadpoles from the high latitude population grew and developed faster and in the beginning of the experiment they hid less and were more active than tadpoles from the low latitude population. When raised together with high latitude tadpoles the southern tadpoles had a longer larval period, however, the response of high latitude tadpoles to the competition by low latitude tadpoles did not differ from their response to intra-population competition. This result was not significantly affected by density or predator treatments. Our results support the hypothesis that high latitude populations are better competitors than their low latitude conspecifics, and suggest that in R. temporaria fast growth and development trade off with other fitness components along the latitudinal gradient across Scandinavia.