Hamilton D.P.,University of Waikato |
Carey C.C.,Virginia Polytechnic Institute and State University |
Arvola L.,Lammi Biological Station |
Arzberger P.,University of California at San Diego |
And 20 more authors.
Inland Waters | Year: 2015
A Global Lake Ecological Observatory Network (GLEON; www.gleon.org) has formed to provide a coordinated response to the need for scientific understanding of lake processes, utilising technological advances available from autonomous sensors. The organisation embraces a grassroots approach to engage researchers from varying disciplines, sites spanning geographic and ecological gradients, and novel sensor and cyberinfrastructure to synthesise high-frequency lake data at scales ranging from local to global. The high-frequency data provide a platform to rigorously validate processbased ecological models because model simulation time steps are better aligned with sensor measurements than with lower-frequency, manual samples. Two case studies from Trout Bog, Wisconsin, USA, and Lake Rotoehu, North Island, New Zealand, are presented to demonstrate that in the past, ecological model outputs (e.g., temperature, chlorophyll) have been relatively poorly validated based on a limited number of directly comparable measurements, both in time and space. The case studies demonstrate some of the difficulties of mapping sensor measurements directly to model state variable outputs as well as the opportunities to use deviations between sensor measurements and model simulations to better inform process understanding. Well-validated ecological models provide a mechanism to extrapolate high-frequency sensor data in space and time, thereby potentially creating a fully 3-dimensional simulation of key variables of interest. © International Society of Limnology 2014.
Korpelainen H.,University of Helsinki |
von Crautlein M.,University of Helsinki |
Laaka-Lindberg S.,Lammi Biological Station |
Huttunen S.,University of Turku
Evolutionary Ecology | Year: 2011
Fine-scale spatial genetic structure (SGS) of the liverwort, Barbilophozia attenuata, occupying an area characterized by a network of ant trails, was investigated using microsatellite markers. This is the first study investigating SGS in a liverwort. Significant genetic differentiation was detected among colonies along and outside ant trails, and the SGS pattern varied depending on the spatial scale. At short distances, kinship coefficients were significantly positive up to about eight meters, after which they approached zero and turned negative, while at distances greater than 25 m the values were about zero. Thus, nearby individuals are more closely related than expected, at mid-distances less related, and at great distances genotypes show a random distribution. We suggest that the reproductive mode strongly affects SGS in B. attenuata. Asexual propagation by relatively large gemmae allows more effective establishment than sexual reproduction by small-sized spores, and causes an aggregation of similar genotypes, although the inbreeding effect cannot be ruled out. In environments with small-scale disturbances, e.g., ant trails, gemmae are favoured over spores at establishment. Also, the diaspore bank of the forest floor can be activated by disturbances, which may affect SGS. At mid-distances, the isolation by distance effect, presumably related to comparatively ineffective gemma dispersal, is visible, while at greater distances, the role of spores as effective means of dispersal is evident. The Sp statistic values, which quantify the strength of SGS, indicate that outsider colonies possess less SGS than do plant colonies along ant trails, which relates to the more frequent spore production of outsider colonies. Moreover, dispersal from fallen logs or stumps may be more effective than dispersal from ground-level colonies along ant trails. Apparently, ants do not have much role as dispersal vectors, nor do the physical structures of ant trails as dispersal corridors, although they provide open areas for colonization. © 2010 Springer Science+Business Media B.V.
Olin M.,University of Helsinki |
Vinni M.,University of Helsinki |
Lehtonen H.,University of Helsinki |
Rask M.,Finnish Game And Fisheries Research Institute |
And 3 more authors.
Journal of Fish Biology | Year: 2010
In this study of 18 small boreal forest lakes, the effects of abiotic and biotic factors (roach Rutilus rutilus and pike Esox lucius) on various population variables of perch Perca fluviatilis were examined. As a single variable, the gillnet catch per unit effort (CPUE) of R. rutilus was negatively related to the mean mass of small (< 200 mm) and the growth rate of young (1-2 years) P. fluviatilis. The mean mass of large (≥ 200 mm) P. fluviatilis was the highest at intermediate CPUE of R. rutilus. Redundancy analysis including environmental factors and P. fluviatilis population variables suggested that 'predation-productivity-humus' gradient affected P. fluviatilis populations by decreasing the CPUE and mean mass of small individuals but increasing these variables of large individuals. The CPUE of R. rutilus and lake area had a negative effect on small and a positive effect on large P. fluviatilis growth rate. In small boreal forest lakes, P. fluviatilis populations are affected by the partially opposite forces of competition by R. rutilus and predation by E. lucius, and the intensity of these interactions is regulated by several environmental factors. © 2010 The Authors. Journal compilation © 2010 The Fisheries Society of the British Isles.
Rasilo T.,University of Helsinki |
Rasilo T.,University of Quebec at Montréal |
Ojala A.,University of Helsinki |
Huotari J.,Lammi Biological Station |
And 2 more authors.
Freshwater Science | Year: 2015
C cycling and dissolved organic C (DOC) inputs to boreal aquatic systems probably will change substantially with climate change. DOC concentrations already are increasing in surface waters. Terrestrial C is a major source of C to boreal freshwater ecosystems, but the interface between these 2 ecosystems, the riparian zone, has not been studied often. To improve our understanding of the importance of terrestrial inputs of DOC to aquatic systems from surrounding forests, we followed the changes of DOC concentration along a continuum of precipitation, throughfall, soil water, ground water, lake, and brook water in a pristine, boreal, forested headwater catchment and developed a lake C balance based on terrestrial and lacustrine C fluxes. We also examined DOC quality changes using the ratio of absorbance at 465 and 665 nm (E4/E6). DOC concentrations increased from 2.4 mg/L in precipitation to 132.3 mg/L in soil water as water passed through the terrestrial ecosystem. DOC concentrations in the riparian zone were correlated with DOC concentrations in the adjacent outflowing brook but not in the headwater lake. E4/E6 ratios indicated that the DOC in precipitation and throughfall was dominated by higher molecular weight compounds and that the DOC in soil and ground water was dominated by lower molecular weight compounds. The input of terrestrial DOC to the aquatic ecosystem was estimated to be 5 to 13 g C m-2 y-1, which is small compared with the C fluxes between atmosphere and vegetation, but can significantly decrease the net ecosystem exchange of an old-growth forest catchment. Terrestrial DOC was a major source of C in the lake, rendering it heterotrophic. The DOC export (3 g DOC m-2 y-1) made up almost 70% of total C export. © 2015 by The Society for Freshwater Science.
Duplouy A.,University of Helsinki |
Ikonen S.,Lammi Biological Station |
Hanski I.,University of Helsinki
Ecology and Evolution | Year: 2013
Habitat loss and fragmentation threaten the long-term viability of innumerable species of plants and animals. At the same time, habitat fragmentation may impose strong natural selection and lead to evolution of life histories with possible consequences for demographic dynamics. The Baltic populations of the Glanville fritillary butterfly (Melitaea cinxia) inhabit regions with highly fragmented habitat (networks of small dry meadows) as well as regions with extensive continuous habitat (calcareous alvar grasslands). Here, we report the results of common garden studies on butterflies originating from two highly fragmented landscapes (FL) in Finland and Sweden and from two continuous landscapes (CL) in Sweden and Estonia, conducted in a large outdoor cage (32 by 26 m) and in the laboratory. We investigated a comprehensive set of 51 life-history traits, including measures of larval growth and development, flight performance, and adult reproductive behavior. Seventeen of the 51 traits showed a significant difference between fragmented versus CL. Most notably, the growth rate of postdiapause larvae and several measures of flight capacity, including flight metabolic rate, were higher in butterflies from fragmented than CL. Females from CL had shorter intervals between consecutive egg clutches and somewhat higher life-time egg production, but shorter longevity, than females from FL. These results are likely to reflect the constant opportunities for oviposition in females living in continuous habitats, while the more dispersive females from FL allocate more resources to dispersal capacity at the cost of egg maturation rate. This study supports theoretical predictions about small population sizes and high rate of population turnover in fragmented habitats selecting for increased rate of dispersal, but the results also indicate that many other life-history traits apart from dispersal are affected by the degree of habitat fragmentation. © 2013 The Authors.
Lepparanta M.,University of Helsinki |
Heini A.,University of Helsinki |
Jaatinen E.,University of Helsinki |
Arvola L.,Lammi Biological Station
Water Quality Research Journal of Canada | Year: 2012
The results from a winter field study in 2009-2010 in Lake Vanajanselkä are presented. This lake is shallow, eutrophic, and annually ice-covered on average for 5 months. The ice sheet was 41-55 cm thick at the annual maximum, consisting of snow-ice and congelation ice. The e-folding depth of light intensity was 50-100 cm for congelation ice and 5-10 cm for snow. The water body had a 4-m thick upper mixed layer and lower continuously stratified layer. Fall cooling process was crucial to determine the temperature of the lower layer at freeze-up, anything within 0-4 °C. Oxygen concentration decreased in winter, especially close to the bottom sediments, and carbon dioxide concentration increased due to respiration activity. Phytoplankton production and biomass level were low or very low and, therefore, heterotrophic and mixotrophic species were abundant. Oxygen depletion in the hypolimnium had several chemical and ecological consequences, such as release of phosphorus from the bottom sediments. In spring, just before the ice-out, photosynthesis was at a high level beneath the ice due to improved light conditions and started to elevate the oxygen concentration in the topmost water layer. © IWA Publishing 2012.
Vihervaara H.,University of Helsinki |
Sundell J.,Lammi Biological Station |
Ylonen H.,University of Jyväskylä
Ethology | Year: 2010
Infanticide, the killing of conspecific young, is commonly recognized as an adaptive behavioural strategy enhancing the fitness of the perpetrator. Infanticide is supposed to be inhibited in several male rodent species after mating with a time lag to the time when perpetrators own offspring would be born. This is because males with no parental care do not recognize their own offspring. It has been suggested that copulation alone is enough to inhibit infanticidal behaviour in male rodents. Infanticidal behaviour occurs in more than 50% of male bank voles (Myodes glareolus), and offspring loss because of infanticide may have a great effect on breeding success and population recruitment. In a laboratory experiment, we studied whether infanticidal male bank voles after successful mating stop the killing of pups. Infanticidal males were paired with a female until successful copulation. After the young were born, the males' infanticidal behaviour was studied from the time of expected birth of own pups until their post-weaning age. We predicted that mated infanticidal males are inhibited from committing infanticide especially during the time period when pups are less than 10 d old. Against our prediction, 67% of the infanticidal males continued the killing of pups in the age of 3 d. Infanticidal behaviour remained stable, and half of the males were infanticidal still at the age of weaning of pups. Our results are contradictory to previous studies, as we observed no inhibition of infanticide during early life of pups nor increase in infanticide again when their own offspring would have reached the 'safe' age and size after weaning. We suggest that mating alone is not sufficient to inhibit infanticide. Thus, we suggest that other cues of the female with whom the male mated with or on her territory are needed for inhibition to occur. © 2010 Blackwell Verlag GmbH.