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Complex Habitats (complex + habitat)
Selected AbstractsGrowth and mortality of prairie stream fishes: relations with fish community and instream habitat characteristicsECOLOGY OF FRESHWATER FISH, Issue 2 2001M. C. Quist Abstract , Few studies have been conducted to describe the age structure, growth rates and mortality of fishes in small stream ecosystems. The purpose of this study was therefore to determine age structure, growth rates and mortality (i.e., total annual mortality and, age-specific mortality) of central stonerollers Campostoma anomalum, creek chubs Semotilus atromaculatus, red shiners Cyprinella lutrensis and green sunfish Lepomis cyanellus from 13 streams on Fort Riley Military Reservation, Kansas, using incremental growth analysis. Further, we were interested in determining the influence of fish community and instream habitat characteristics on growth rates. The age structure of central stonerollers, creek chubs, and red shiners was dominated by young individuals (i.e., less than age 2); however, over 60% of the green sunfish were age 2 to age 4. Mean total annual mortality was >60% for cyprinids and averaged approximately 44% for green sunfish. The age-specific mortality of central stonerollers and red shiners was generally less than 45% between age 0 and 1 and increased to over 85% for fishes greater than age 1. Fish community characteristics (e.g., catch per unit effort of trophic guilds) and chemical habitat (e.g., total phosphorous) were not related to growth rates (P>0.05). Growth of central stonerollers was not significantly correlated with physical habitat (P>0.05). However, the growth increments of creek chubs, red shiners, and green sunfish were related to the amount of woody debris (e.g., total woody debris, log complex habitat; r>0.60; P,0.05). The results of this study provide important information on the population dynamic rate functions of cyprinid and green sunfish populations in small prairie streams. Furthermore, these data suggest that woody debris is important habitat influencing growth of stream fishes., [source] VISUAL BACKGROUND COMPLEXITY FACILITATES THE EVOLUTION OF CAMOUFLAGEEVOLUTION, Issue 6 2003Sami Merilaita Abstract., Cryptic animal coloration or camouflage is an adaptation that decreases the risk of detection. The study of the evolution of camouflage has strongly emphasized the minimization of visual information that predators receive from prey, by means of background matching. However, the evolutionary effects of information processing after its reception have been virtually ignored. I constructed a model that employs an artificial neural network and simulates the evolution of prey coloration in a visually complex and simple habitat. The model suggests: (1) the difficulty of a detection task is related to the visual complexity of the habitat; (2) it is easier to decrease the risk of detection by the means of camouflage in a visually complex habitat; (3) selection on camouflage can exploit limitations in predators information processing; and (4) there are shortcomings in using the degree of background matching as the measure of camouflage. [source] Hunger, light level and body size affect refuge use by post-settlement lingcod Ophiodon elongatusJOURNAL OF FISH BIOLOGY, Issue 4 2006M. E. Petrie Using experimental methods, body size, nutritional state (hunger) and light level were investigated as possible determinants of the extent to which juvenile lingcod Ophiodon elongatus used structural refuges. In the laboratory, older, larger individuals (134,162 mm total length, LT) exhibited a higher propensity for structure use than did smaller juvenile fish (78,103 mm LT). In fish of both body sizes, increasing hunger levels caused fish to emerge more readily from refuges than satiated individuals, with this effect most prominent for smaller fish. Diel patterns of ambient illumination were simulated in the laboratory, and refuge use by large individuals decreased significantly in response to lower nocturnal light levels, a pattern that was not observed in the smaller size class. These results indicate an ontogenetic shift in refuge use. During the summer, as post-settlement fish grew larger, they tended to increase affinity for structurally complex habitat, and also showed divergent patterns of behaviour in relation to hunger and light level. [source] Quorum sensing controls biofilm formation in Vibrio choleraeMOLECULAR MICROBIOLOGY, Issue 1 2003Brian K. Hammer Summary Multiple quorum-sensing circuits function in parallel to control virulence and biofilm formation in Vibrio cholerae. In contrast to other bacterial pathogens that induce virulence factor production and/or biofilm formation at high cell density in the presence of quorum-sensing autoinducers, V. cholerae represses these behaviours at high cell density. Consistent with this, we show here that V. cholerae strains ,locked' in the regulatory state mimicking low cell density are enhanced for biofilm production whereas mutants ,locked' in the regulatory state mimicking high cell density are incapable of producing biofilms. The quorum-sensing cascade we have identified in V. cholerae regulates the transcription of genes involved in exopolysaccharide production (EPS), and variants that produce EPS and form biofilms arise at high frequency from non-EPS, non-biofilm producing strains. Our data show that spontaneous mutation of the transcriptional regulator hapR is responsible for this effect. Several toxigenic strains of V. cholerae possess a naturally occurring frameshift mutation in hapR. Thus, the distinct environments occupied by this aquatic pathogen presumably include niches where cell-cell communication is crucial, as well as ones where loss of quorum sensing via hapR mutation confers a selective advantage. Bacterial biofilms could represent a complex habitat where such differentiation occurs. [source] Geophysical study of a Pre-Hispanic lakeshore settlement, Chiconahuapan Lake, MexicoARCHAEOLOGICAL PROSPECTION, Issue 1 2010R. E. Chávez Abstract Results of a combined geophysical survey carried out along the northern shore of Lake Chiconahuapan in central Mexico are presented. The site contains a series of mounds found between the lakeshore and the ceremonial centre named La Campana-Tepozoco Hill. Those features are the remains of habitation complexes built by the lake residents about 1100 years ago. Archaeological excavations performed towards the northeastern margins of the lake uncovered rectangular clusters of basaltic rocks forming the foundations of ancient dwellings, surrounded by a barrier (,bordo'), built to prevent floods. A mound located close to the ceremonial centre was studied using the vertical magnetic gradient (VMG), ground-penetrating radar (GPR) and electric tomography (ET) methods. Interesting magnetic anomalies were found towards the central portion of the mound and one of these was modelled with a three-dimensional magnetic polygon. The GPR studies unveiled a circular feature in the central portion of the mound that could be associated with a bordo. A rectangular structure was also interpreted within the limits of that structure, which is probably the location of ancient dwelling foundations. Electric tomography profiles were collected in the area, around the VMG anomaly. The resistivity model computed shows the presence of a high-resistivity layer, which displays discontinuities within the area defined by the bordo. Presumably, the ancient settlers built their constructions on top of this horizon. The geophysical results reveal a rather complex habitat within the mound. The larger size of the bordo (ca. 30,m in diameter) compared with others already studied by archaeologists makes us believe that the purpose of the site was of administrative use or hosted a wealthy group of people. Dwelling foundations are found within the limits of the barrier. Copyright © 2009 John Wiley & Sons, Ltd. [source] Densities of polychaetes in habitat fragments depend on the surrounding matrix but not the complexity of the remaining fragmentAUSTRAL ECOLOGY, Issue 4 2009VICTORIA J. COLE Abstract Biogenically engineered habitats are constantly changing in space and time, resulting in changes to the landscape and the ecology of associated taxa. Using patchily distributed biogenic habitats on intertidal rocky shores the influences of different aspects of the landscape were investigated, that is, the surrounding matrix and the habitat itself. Experiments to test the effect of the matrix were carried out by transplanting assemblages in artificial habitats from one type of biogenically engineered matrix (created by the tubeworm Galeolaria caespitosa) to another (created by the oyster Saccostrea glomerata). Change to the surrounding matrix resulted in the densities of polychaete worms in central fragments of habitat changing to become more similar to their new surroundings. To test how the habitat influenced predator,prey interactions, polychaetes were transplanted from a complex habitat (created by the turfing alga Corallina officinalis) to less complex habitat (created by the tubeworm G. caespitosa), with or without the presence of the predatory polychaete, Perinereis amblyodonta. This experiment also tested the influence of habitat replacement on densities of polychaetes, regardless of any new interactions between species. Despite coralline turf being a much more complex habitat than Galeolaria, P. amblyodonta successfully preyed on other species of polychaetes in both habitats. Furthermore, in the absence of P. amblyodonta, survival of polychaetes did not differ between the habitats. These types of experiments will be useful for testing similar hypotheses in different landscapes and will assist in gaining a more general understanding of habitat modification. [source] Effects of radio-transmitter antenna length on swimming performance of juvenile rainbow troutECOLOGY OF FRESHWATER FISH, Issue 4 2004K. J. Murchie Abstract,,, Technological advances have lead to the production of micro radio-transmitters capable of being implanted in fish as small as c. 5 g. Although the actual tags are small, transmitters are equipped with long antennas that can increase drag and tangle in debris. We examined the effects of radio-transmitter antenna length on the swimming performance of juvenile rainbow trout, Oncorhynchus mykiss, (N = 156, mean mass = 34 g, mean fork length = 148 mm). Although we tested a variety of different antenna lengths up to a maximum of 300 mm, only the longest antenna significantly impaired swimming performance relative to control fish (P < 0.001). There was no difference in swimming performance between the sham (surgery, but no transmitter) and the control fish (handled, but no surgery), suggesting that the surgical procedure itself did not negatively affect the fish. Regression analysis, however, indicated that there was a significant decrease in swimming performance associated with increased antenna length (R2 = 0.11, P < 0.001). In addition, when held in laboratory tanks, fish with the three longest antennas (150, 225 and 300 mm) frequently became entangled with the standpipe. We suggest that researchers, under the guidance of the tag manufacturer, trim antennas to the shortest possible length required to detect fish in their specific study area. Antenna length is clearly an important issue for small fish, especially for species that inhabit complex habitats where antennas may become entangled, and where fish must attain speeds near limits of their swimming capacity. Resumen 1. Los avances tecnológicos han llevado a producir micro radio-trasmisores capaces de ser implantados en peces de muy pequeño tamaño (,5 g). Aunque las marcas actuales son pequeñas, los trasmisores están equipados con antenas largas que pueden llegar a enredarse en los restos de vegetación. Examinamos los efectos de la longitud de la antena sobre la rutina natatoria de juveniles de Oncorhynchus mykiss (n = 156, peso medio = 34 g, longitud furcal media = 148 mm). 2. Aunque analizamos varias longitudes de antena, hasta 300 mm, solamente las de mayor longitud alteraron la rutina natatoria en relación a los peces control (P < 0.001). No hubo diferencia en la rutina natatoria entre individuos bajo cirugía pero sin trasmisores respecto de los individuos control (manipulados pero sin cirugía) lo que sugiere que los procedimientos de cirugía no afectaron negativamente a los peces. Sin embargo, análisis de regresión indicaron un declive significativo en la rutina natatoria asociado a la longitud de la antena (R2 = 0.11, P < 0.001). Además, al ser mantenidos en tanques, los individuos con las tres antenas mas largas (150, 225, y 300 mm) frecuentemente se enredaron con las tuberías. 3. Sugerimos a los investigadores que, bajo la dirección de los productores de marcas y antenas, consideren el uso de las antenas más pequeñas que permitan detectar a los peces en sus respectivas áreas de estudio. La longitud de la antena es una cuestión importante para los pequeños peces, especialmente para especies en hábitats complejos donde las antenas pueden llegar a enredarse y donde los peces pueden alcanzar velocidades casi al limite de su capacidad natatoria. [source] Habitat use and foraging success of 0+ pike (Esox lucius L.) in experimental ponds related to prey fish, water transparency and light intensityECOLOGY OF FRESHWATER FISH, Issue 2 2002C. Skov Abstract ,,,This study investigated the habitat use of 0+ pike (9,17 cm) in relation to two different water transparency regimes (clear water/chlorophyll water), two different light regimes (day/night) and the presence/absence of prey using 16 m2 experimental ponds. Pike could freely choose between two structured habitats (a simple structured and a complex structured), an interface habitat (between the structured habitats and open water) and an open water habitat. Foraging success of the pike in relation to water transparency was investigated by comparing mean condition (Fultons K) of the pike as well as the number of surviving prey fish. Habitat use was influenced by the presence/absence of prey and varied between waters with different transparency. The presence of prey intensified the use of structural habitats of 0+ pike in both clear and chlorophyll waters. A preference for complex habitats was found in clear water and was presumably related to foraging. The pike in chlorophyll water, in contrast, appeared more evenly distributed among all habitats, as illustrated by a more intensive use of open water in chlorophyll water compared to the clear water. No detectable impact of water transparency on the foraging success of 0+ pike was found. [source] Microbial biodiversity in groundwater ecosystemsFRESHWATER BIOLOGY, Issue 4 2009C. GRIEBLER Summary 1. Groundwater ecosystems offer vast and complex habitats for diverse microbial communities. Here we review the current status of groundwater microbial biodiversity research with a focus on Bacteria and Archaea and on the prospects of modern techniques for enhancing our understanding of microbial biodiversity patterns and their relation to environmental conditions. 2. The enormous volume of the saturated terrestrial underground forms the largest habitat for microorganisms on earth. Up to 40% of prokaryotic biomass on earth is hidden within this terrestrial subsurface. Besides representing a globally important pool of carbon and nutrients in organisms, these communities harbour a degree of microbial diversity only marginally explored to date. 3. Although first observations of groundwater microbiota date back to Antonie van Leeuwenhoek in 1677, the systematic investigation of groundwater microbial biodiversity has gained momentum only within the last few decades. These investigations were initiated by an increasing awareness of the importance of aquifer microbiota for ecosystem services and functioning, including the provision of drinking water and the degradation of contaminants. 4. The development of sampling techniques suitable for microbiological investigations as well as the application of both cultivation-based and molecular methods has yielded substantial insights into microbial communities in contaminated aquifers, whereas knowledge of microbial biodiversity in pristine habitats is still poor at present. 5. Several novel phylogenetic lineages have been described from groundwater habitats, but to date no clearly ,endemic' subsurface microbial phyla have been identified. The future will show if the rather low diversity generally found in pristine oligotrophic aquifers is a fact or just a result of low abundances and insufficient resolution of today's methods. Refined approaches complemented by statistically rigorous applications of biodiversity estimates are urgently needed. 6. Factors identified to control microbial diversity in aquifers include spatial heterogeneity, temporal variability and disturbances such as pollution with chemical anthropogenic contaminants. Although first insights into the importance of individual biogeochemical processes may be obtained from surveys of microbial diversity within functional groups, direct links to groundwater ecosystem functioning have rarely been established so far. [source] The impact of an introduced predator on a threatened galaxiid fish is reduced by the availability of complex habitatsFRESHWATER BIOLOGY, Issue 8 2007RICK D. STUART-SMITH Summary 1. The availability of complex habitats such as macrophytes may be vital in determining the outcomes of interactions between introduced predators and native prey. Introduced brown trout (Salmo trutta) have impacted numerous small native freshwater fishes in the southern hemisphere, but the potential role of complex habitats in determining the direct outcomes of brown trout , native fish interactions has not been experimentally evaluated. 2. An in-lake enclosure experiment was used to evaluate the importance of structurally complex habitats in affecting the direct impacts of brown trout on a threatened galaxiid fish. Five Galaxias auratus and a single brown trout were added to enclosures containing one of three different habitat types (artificial macrophytes, rocks and bare silt substrate). The experiment also had control enclosures without brown trout. Habitat-dependence of predation risk was assessed by analysis of G. auratus losses to predation, and stomach contents of remaining fish were analysed to determine if brown trout directly affect the feeding of G. auratus and whether this is also habitat-dependent. 3. Predation risk of G. auratus differed significantly between habitat types, with the highest mortality in enclosures with only bare silt substrate and the lowest in enclosures containing artificial macrophytes. This result highlights the importance of availability of complex habitats for trout , native fish interactions and suggests that increasing habitat degradation and loss in fresh waters may exacerbate the direct impacts of introduced predators. 4. Stomach contents analyses were restricted to fish in enclosures with artificial macrophytes and rocks, as most fish were consumed in enclosures with brown trout and only bare silt substrate. These analyses suggest that brown trout do not directly affect the feeding of G. auratus in complex habitats, but it is still unknown whether its feeding is reduced if complex habitats are unavailable. [source] Time allocation of a parasitoid foraging in heterogeneous vegetation: implications for host,parasitoid interactionsJOURNAL OF ANIMAL ECOLOGY, Issue 5 2007TIBOR BUKOVINSZKY Summary 1Changing plant composition in a community can have profound consequences for herbivore and parasitoid population dynamics. To understand such effects, studies are needed that unravel the underlying behavioural decisions determining the responses of parasitoids to complex habitats. 2The searching behaviour of the parasitoid Diadegma semiclausum was followed in environments with different plant species composition. In the middle of these environments, two Brassica oleracea plants infested by the host Plutella xylostella were placed. The control set-up contained B. oleracea plants only. In the more complex set-ups, B. oleracea plants were interspersed by either Sinapis alba or Hordeum vulgare. 3Parasitoids did not find the first host-infested plant with the same speed in the different environments. Sinapis alba plants were preferentially searched by parasitoids, resulting in fewer initial host encounters, possibly creating a dynamic enemy-free space for the host on adjacent B. oleracea plants. In set-ups with H. vulgare, also, fewer initial host encounters were found, but in this case plant structure was more likely than infochemicals to interfere with the searching behaviour of parasitoids. 4On discovering a host-infested plant, parasitoids located the second host-infested plant with equal speed, demonstrating the effect of experience on time allocation. Further encounters with host-infested plants that had already been visited decreased residence times and increased the tendency to leave the environment. 5Due to the intensive search of S. alba plants, hosts were encountered at lower rates here than in the other set-ups. However, because parasitoids left the set-up with S. alba last, the same number of hosts were encountered as in the other treatments. 6Plant composition of a community influences the distribution of parasitoid attacks via its effects on arrival and leaving tendencies. Foraging experiences can reduce or increase the importance of enemy-free space for hosts on less attractive plants. [source] Evidence that dingoes limit abundance of a mesopredator in eastern Australian forestsJOURNAL OF APPLIED ECOLOGY, Issue 3 2009Chris N. Johnson Summary 1Aggressive behaviour of top predators may have strong effects on the distribution and abundance of mesopredator species. Such interactions between predator species can reduce the intensity of predation on vulnerable prey. Suppression of mesopredators by top predators is a potentially important process that could protect small prey species from unsustainable predation. 2There is some evidence that in Australia, the dingo Canis lupus suppresses populations of the red fox Vulpes vulpes. This interaction could be significant to biodiversity conservation because while dingoes have been in Australia for several thousand years and coexist with a wide range of small mammals, the fox is a recent arrival which has caused declines and extinctions, and continues to threaten many prey species. 3However the strength of the effect of dingoes on foxes is unclear, and some published data have been interpreted as demonstrating no relationship between abundance of the two species. These data come from forested habitats in eastern Australia, and may suggest that negative relationships of dingoes and foxes do not occur in complex habitats. 4We re-analyse published data on fox vs. wild dog (i.e. dingoes plus, potentially, feral dogs and hybrids) abundance in eastern forests. These data reveal a triangular relationship of fox to wild dog density: when wild dogs are abundant, foxes are consistently rare, while when wild dogs are rare, foxes may be abundant but are not always so. This suggests that the abundance of wild dogs sets an upper limit on the abundance of foxes, but does not fully determine fox abundance. 5Standard regression and correlation methods are not appropriate for analysing such triangular relationships. We apply two statistical methods that can be used to characterize the edges of data distributions, and use these to demonstrate a negative relationship of maximum fox abundance to the abundance of wild dogs. 6Synthesis and applications. Our analysis adds to evidence that dingoes may have negative effects on red foxes in a wide range of habitats, and therefore, that dingoes may be significant to conservation of mammal biodiversity in Australia. It also illustrates problems and solutions in the statistical analysis of abundance of one species as a function of the abundance of another species with which it has a strong interaction. [source] The effect of habitat management on home-range size and survival of rural Norway rat populationsJOURNAL OF APPLIED ECOLOGY, Issue 6 2008M. S. Lambert Summary 1Norway rat Rattus norvegicus populations are usually controlled with toxic baits, but this approach is increasingly recognized as having negative welfare and environmental impacts. An integrated strategy that relies less on rodenticides is therefore required. Here we investigate the possibility of using a resource-based approach to rat population management. 2Structurally complex habitats provide rat populations with nest sites and opportunities to avoid predators; modifying habitats to reduce structural complexity might reduce their potential to support rat populations. As part of an integrated approach, this could be more sustainable than relying exclusively on lethal control. However, in order to target habitat management efforts most effectively with minimum impact on other species, an understanding of habitat utilization by Norway rats is required. 3In this study, rat populations on farms in the north-east of England were monitored by radio-tracking and population counts before and after a single phase of habitat modification. Rats living near farm buildings utilized areas with high levels of cover; habitat modification reduced the survival rate and size of these rat populations. Rats living in field margins also preferred areas with high levels of cover, but they had significantly bigger home ranges than rats living near farm buildings and were largely unaffected by small-scale habitat management. 4Synthesis and applications. Our results indicate that habitat management near farm buildings has the potential to reduce the size of rat populations. As part of an integrated approach, this technique offers a way of reducing reliance on rodenticides. Habitat use by rats within the wider farm landscape suggests that land management practices have the potential to influence the size and distribution of rat populations; many game-rearing practices and environmental policies designed to create habitats for ,desirable' farm wildlife, inadvertently create desirable habitats for rats. [source] A conservation trade-off?AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 5 2007Interspecific differences in seahorse responses to experimental changes in fishing effort Abstract 1.A 2-year experimental seining programme and underwater visual censuses were undertaken to quantify the direct effects of active demersal fishing on the population structure and relative abundance of two sympatric seahorse species of conservation concern: the European long-snouted seahorse, Hippocampus guttulatus Cuvier 1829 and the short-snouted seahorse, Hippocampus hippocampus L. The influence of habitat preference on population-level responses to changes in habitat structure following a reduction in fishing effort was also investigated. 2.It was predicted that the benthic habitat would be more structurally complex after fishing ceased and that seahorse densities would increase in response to reduced fishing mortality. Furthermore, it was predicted that the magnitude of the increase in density would be greater for H. guttulatus than for H. hippocampus, because the former species prefers complex vegetated habitats while the latter species uses sparsely vegetated habitats. 3.As predicted, the amount of habitat cover increased significantly when seining ceased, primarily through increases in the abundance of drifting macroalgae and unattached invertebrates. Despite similarities in life histories, the two seahorse species responded differently in terms of magnitude and direction to reduced fishing effort: the abundance of H. guttulatus increased significantly while H. hippocampus decreased in abundance. 4.Results suggest that active demersal fishing may influence the magnitude and direction of the responses of benthic marine fishes to exploitation through its impacts on habitat structure. An increase in habitat cover appeared to favour higher densities of H. guttulatus when seining effort was reduced. By contrast, repeated seining, which maintained less complex habitats, appeared to favour greater abundances of H. hippocampus. 5.Given differences in habitat preference among benthic marine fishes subject to incidental capture in fisheries, simultaneous attempts to manage populations of sympatric species may require complementary strategies that support the persistence of diverse habitat types. Copyright © 2006 John Wiley & Sons, Ltd. [source] Grassland invertebrate assemblages in managed landscapes: Effect of host plant and microhabitat architectureAUSTRAL ECOLOGY, Issue 6 2007ADELE M. REID Abstract Grasslands are often considered as two-dimensional habitats rather than complex, multilayered habitats. However, native grasslands are complex habitats, with multiple layers of annual and perennial grasses, sedges, shrubs and mosses. Vegetation complexity, including plant type, quality and three-dimensional structure is important for providing a variety of food and habitat resources for insects. Grazing by domestic livestock can affect these processes through the loss or fragmentation of habitats, as well as altering the vertical and horizontal vegetation structure. This study aimed to investigate the role of host plants and microhabitat architecture for determining foliage invertebrate assemblages. Different plant species supported distinct invertebrate assemblages and less complex host plants supported fewer invertebrate individuals and species. Manipulations of plant architecture changed the species composition of invertebrates, with most species found in more complex vegetation. This study illustrates the importance of host diversity and pasture complexity for invertebrate communities. Management practices that encourage a heterogeneous environment with diverse and structurally complex pastures should also sustain a more diverse and functional invertebrate assemblage. [source] | |||||||||||||