1,720,981 research outputs found
Temperature and predator cues interactively affect ontogenetic metabolic scaling of aquatic amphipods: T and P effect on metabolic scaling
No full textA common belief is that body mass scaling of metabolic rate results chiefly from intrinsic body-design constraints. However, several studies have shown that multiple ecological factors affect metabolic scaling. The mechanistic basis of these effects is largely unknown. Here, we explore whether abiotic and biotic environmental factors have interactive effects on metabolic scaling. To address this question, we studied the simultaneous effects of temperature and predator cues on the ontogenetic metabolic scaling of amphipod crustaceans inhabiting two different aquatic ecosystems, a freshwater spring and a saltwater lagoon. We assessed effects of phenotypic plasticity on metabolic scaling by exposing amphipods in the laboratory to water with and without fish cues at multiple temperatures. Temperature interacts significantly with predator cues to affect metabolic scaling. Our results suggest that metabolic scaling is highly malleable in response to short-term acclimation. The interactive effects of temperature and predators show the importance of studying effects of global warming in realistic ecological contexts
Size dependency of patch departure behavior: evidence from granivorous rodents
No full textIndividual size is a major determinant of mobile organisms\u27 ecology and behavior. This study aims to explore whether allometric scaling principles can provide an underlying framework for general patterns of resource patch use. To this end, we used giving-up densities (GUDs), that is, the amount of resources remaining in a patch after a forager has quit feeding, as a comparative measure of the amount of resources exploited by a forager of any given size. We specifically tested the hypothesis that size-dependent responses to both internal (energy requirement) and external (risk management) forces may have an effect on GUDs. We addressed this topic by conducting an extensive meta-analysis of published data on granivorous rodents, including 292 GUD measurements reported in 25 papers. The data set includes data on 22 granivorous rodent species belonging to three taxonomic suborders (Castorimorpha, Myomorpha, and Sciuromorpha) and spans three habitat types (desert, grassland, and forest). The observations refer to both patches subject to predation risk and safe patches. Pooling all data, we observed positive allometric scaling of GUDs with average forager size (scaling exponent = 0.45), which explained 15% of overall variance in individual GUDs. Perceived predation risk during foraging led to an increase in GUDs independently of forager size and taxonomy and of habitat type, which explained an additional 12% of overall GUD variance. The size scaling exponent of GUDs is positive across habitat types and taxonomic suborders of rodents. Some variation was observed, however. The scaling coefficients in grassland and forest habitat types were significantly higher than in the desert habitat type. In addition, Sciuromorpha and Myomorpha exhibited a more pronounced size scaling of GUDs than Castorimorpha. This suggests that different adaptive behaviors may be used in different contexts and/or from different foragers. With body size being a fundamental ecological descriptor, research into size scaling of GUDs may help to place patch-use observations in a broader allometric framework
Cross-community scaling of benthic macroinvertebrate guilds: a functional approach to community organisation in inland waters of Southern Italy
No full textThe search for simple and effective descriptors of biological ecosystem components is a major challenge of
monitoring aquatic ecosystem health. There have been discussed the relevance of body-size-related
descriptors of benthic invertebrate guilds in monitoring the health of aquatic ecosystems. The rationale is that
macroinvertebrate body-size relates individual responses to disturbance pressures through individual energetic,
population dynamics and species coexistence responses.
The mechanistic relevance of individual body-size on coexistence relationships still requires field and laboratory
tests and community level scaling-up. The different proposed models of size abundance distributions offer
promising approaches to scale-up and address the overall role of individual body size in community
organisation.
One of the relationships between body-size and abundance in ecology is the cross-community scaling
relationship (CCSR), which use ecological energetics to evaluate the overall body size based responses to
actors affecting energy flow in ecosystems; external perturbations and pollution are main anthropogenic-based
factors acting on energy flow.
Field experiments on freshwater and transitional water benthic macroinvertebrate guilds from perturbed and
unperturbed ecosystems of Southern Italy (Apulia and Sardinia areas) were designed to test: i. the crosscommunity
scaling relationship relevance of body-size-related constraints on the organization of detritus-based
benthic guilds through the relationship between the average size of an individual in an assemblage and the
total community density; ii. the sensibility of statistical CCSR descriptors to perturbed conditions, compared to
unperturbed ones
Size–Abundance Relationships of Freshwater Macroinvertebrates in Two Contrasting Floodplain Channels of Rhone River
Full text linkBody size is perhaps the most fundamental property of an organism and its relationship with abundance is one of the most studied relationships in ecology. Although numerous studies have examined these relationships in local communities, few have investigated how they vary at different temporal and spatial scales. We investigated the relationship between body size and abundance of local macroinvertebrate communities in two floodplain channels of the French upper Rhone River. The two channels differ in their vegetation coverage (high vs. low vegetation) and hydrological regimes. The shapes of the size–abundance relationship were similar between channels on a yearly basis but differed when compared between months. The variation in local size–abundance relationships between months was related to variation in the functional diversity across time. Our findings suggest that local size–abundance relationships are able to quantitatively describe temporal changes in community structure, showing the importance of relating diversity with ecosystem function in a more realistic context
The Lagoons of Corfu: multiple impacts, conservation strategies and economic exploitations
Full text linkIn the Island of Corfu there are seven lagoons which have different biological and
chemical characteristics and also different impacts and human interventions. In this research, a
preliminary description of the lagoons is reported using available data from the literature.
The lagoons of Corfu have been poorly studied from the point of view of ecological functuins and
biodiversity. Specifically the lagoons are: 1.Lagoon Korission, it is the largest lagoon of Corfu.
Located in the southwest of the island has an area of 600hectares approximately. Works like a fish
farm and is protected area Natura 2000. The main intervention of the lagoon is the increasing of
the human activities in the area of the lagoon; 2. Lagoon Chalkiopoulou, the second largest lagoon
of Corfu, it has a total size of 180 hectares. There was a fish farm fifteen years ago. It is estimated
that the last seventy years the lagoon has lost about 1/3 of its extent. This lagoon has received
the most and the major intervention is the reduction in the area in order to create the Airport of
Corfu; 3.Lagoon Antinioti, it is located northeast of Corfu and it has a total size of 100 hectares
with the marshland Kounoufadi which is part of the lagoon. Works like a fish farm and is included
in the protected areas Natura 2000. The main interference of the area has been done on the part of
the marshland Kounoufadi where twenty years ago have been put polders by the municipality of
Corfu in order to build a Municipal Stadium; 4. Lagoon Alykes Lefkimmis, it is a small lagoon of about 30 hectares in the southeast of Corfu. Along with former Alykes Lefkimmis is included in
the protected areas Natura 2000. There is not significant human intervention in the lagoon
in addition with the former Saline of Lefkimmi (which forms a single ecosystem) for which the
area has decreased due to residential use. Three small lagoons in the area of Erimitis
which is in the northeast part of Corfu, there are 3 small lagoon ecosystems (Akoli, Vromolimni
and Avlaki) located on the northeast coast of Corfu. Each of these has a size of 2-4hectares. The
most remarkable is that the lagoon Akoli in the past served as a fish farm and had an artificial
orifice communicating with the sea. Such abandonment of this orifice it is noticed a decrease in
the depth of the lagoon
The expansion of the Atlantic–Mediterranean ghost crab Ocypode cursor (Linnaeus, 1758): Distribution, environmental niches and future perspectives
Full text linkThe tufted ghost crab Ocypode cursor (Linnaeus, 1758) found in the Mediterranean Sea and the Atlantic Ocean is currently a great example that elucidates concerns within scientific and conservation communities. This species, native to the subtropical Atlantic Ocean and the warmest southeastern Mediterranean Sea (Egypt), has been extending its distribution in both regions since the 1980s, likely due to the warming sea temperatures. These small nocturn crabs are typically found inhabiting sandy beaches and dune environments. This species is an opportunistic predator eating terrestrial and marine prey, especially on sea turtle eggs. Despite its status as a threatened species by two European conventions, there is a lack of knowledge of its ecology and biology. Sometimes considered as an indicator of good ecological status of beaches where it lives, this ghost crab could nevertheless benefit from climate change to extend its distribution range. This review aims to create a baseline on the current knowledge and gaps in the published scientific literature on the ghost crab. Additionally, through an analysis of the existing literature, we also offer insights into the potential risk of beach erosion associated with the expansion of this species
A new approach to assessing the space use behavior of macroinvertebrates by automated video tracking
No full textIndividual space and resource use are central issues in ecology and conservation. Recent technological advances such as automated tracking techniques are boosting ecological research in this field. However, the development of a robust method to track space and resource use is still challenging for at least one important ecosystem component: motile aquatic macroinvertebrates. The challenges are mostly related to the small body size and rapid movement of many macroinvertebrate species and to light scattering and wave signal interference in aquatic habitats. We developed a video tracking method designed to reliably assess space use behavior among individual aquatic macroinvertebrates under laboratory (microcosm) conditions. The approach involves the use of experimental apparatus integrating a near infrared backlight source, a Plexiglas multi-patch maze, multiple infrared cameras, and automated video analysis. It allows detection of the position of fast-moving (~ 3 cm/s) and translucent individuals of small size (~ 5 mm in length, ~1 mg in dry weight) on simulated resource patches distributed over an experimental microcosm (0.08 m2). To illustrate the adequacy of the proposed method, we present a case study regarding the size dependency of space use behavior in the model organism Gammarus insensibilis, focusing on individual patch selection, giving-up times, and cumulative space used. In the case study, primary data were collected on individual body size and individual locomotory behavior, for example, mean speed, acceleration, and step length. Individual entrance and departure times were recorded for each simulated resource patch in the experimental maze. Individual giving-up times were found to be characterized by negative size dependency, with patch departure occurring sooner in larger individuals than smaller ones, and individual cumulative space used (treated as the overall surface area of resource patches that individuals visited) was found to scale positively with body size. This approach to studying space use behavior can deepen our understanding of species coexistence, yielding insights into mechanistic models on larger spatial scales, for example, home range, with implications for ecological and evolutionary processes, as well as for the management and conservation of populations and ecosystems. Despite being specifically developed for aquatic macroinvertebrates, this method can also be applied to other small aquatic organisms such as juvenile fish and amphibians
Relationship between individual metabolic rate and patch departure behaviour: evidence from aquatic gastropods
No full textIndividual energy requirements are tightly related to individual resource use and by extension of space-use patterns and other traits at higher levels of the ecological hierarchy. However, there is still little experimental evidence linking individual energetics and space-use behaviour. Individual energy requirements scale mainly with body size and temperature, but these do not explain all individual variation. Therefore, studies focused on inter individual variation in resource and space use behaviour can be used to frame foraging dynamics in an energy perspective. We empirically tested the hypothesis of a relationship between individual energetics and patch departure behaviour using as model organisms four small species (body mass ranging from 0.4 to 14 mg AFDW) of aquatic gastropods strongly differing in adult size: Galba truncatula, Bithynia tentaculata, Theodoxus fluviatilis and Ecrobia ventrosa (in descending order of size). Motility tests were performed in controlled microcosm conditions. The tests were designed to classify the specimens as either low motility (not inclined to abandon the patch) or high motility (likely to abandon the patch). The tests entailed measuring the propensity of the individuals to abandon a limited resource patch (2 g DW of conditioned Phragmites australis leaves) within a given amount of time (24 h) when foraging with conspecifics under conditions where competition for food is expected to increase over time due to resource depletion. The individual standard metabolic rate of the tested specimens was measured via open flow respirometry and compared across motility classes at intra- and interspecific level. At both levels, we observed that individuals with higher standard metabolic rates were more inclined to abandon the patch. This finding establishes a link between foraging theory and competitive coexistence mechanisms
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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