INSECT SCIENCE, Issue 3 2002
LI Zheng-xi
Abstract The rDNA-ITS2 regions of T. dendrolimi Matsumura and T. ostriniae Pang et Chen (Hymenoptera: Trichogrammatidae) were cloned and sequenced. The homologous sequences available in GenBank were retrieved and analyzed, and then specific primers were designed for molecular identification and detection of T. dendrolimi. Repeated screening showed that PCR amplification by the diagnostic primers enabled the differentiation of not only bulk samples and single adult (male or female), but also eggs and juveniles, which was not possible by conventional methods. The advantage of this system over morphology-based systems is that non-specialists are able to identify individuals or trace specimens efficiently. The derived molecular detection technique was then used to identify 12 specimens collected from different localities on the Chinese mainland; the results showed that this protocol could be applied to molecular monitoring of Trichogramma species in the field. Finally, 1132s of 6 geographical populations of T. dendrolimi (TdCHA, TDJL, TdXZ, TdKH, TdCZ and TdYBL) were cloned and sequenced. The multialignment analysis of intraspecific ITS2 sequences showed that the diagnostic primers have their own theoretical bases. [source]

PRESENCE OF SPOROPHYLLS IN FLOATING KELP RAFTS OF MACROCYSTIS SPP. (PHAEOPHYCEAE) ALONG THE CHILEAN PACIFIC COAST,

JOURNAL OF PHYCOLOGY, Issue 5 2005
Erasmo C. Macaya
Some species of macroalgae continue to live for extended periods of time after detachment and may even maintain reproductive structures, yet very little is known about this process. Here, we describe the presence of sporophylls (with sporogenous tissues) on floating kelp rafts of Macrocystis spp. along the coast of Chile. Surveys were conducted at nine sites (18,50° S) during austral summer 2002, and floating kelp rafts were seen and collected at seven of these nine sites (between 22 and 50° S). Fifteen (26.8%) of the 56 samples had sporophylls, indicating maintenance of sporophylls after detachment. Some of the kelp sporophytes with reproductive blades showed signs of having been afloat for long periods (indicated by the large size of attached stalked barnacles). Additionally, experiments showed that floating kelps released viable zoospores. To understand the reproductive dynamics of floating kelps, we compared these results with information from attached populations of Macrocystis spp. at nearby coastal sites. In general, attached kelp had higher proportions of sporophylls than floating rafts, suggesting that detachment may negatively affect reproductive status. Nevertheless, floating kelps remained functionally reproductive, suggesting that zoospores may be dispersed via floating rafts. Published reports on other macroalgae indicate that some species (Lessoniaceae, Fucaceae, and Sargassaceae) are fertile and probably release zoospores or zygotes while floating or drifting in ocean currents. Because dispersal distances achieved by spores of most macroalgae are relatively short, release of spores from floating algae may be an alternative mechanism of long-distance dispersal. [source]

VARIABILITY IN THE ECOPHYSIOLOGY OF HALIMEDA SPP. (CHLOROPHYTA, BRYOPSIDALES) ON CONCH REEF, FLORIDA KEYS, USA,

JOURNAL OF PHYCOLOGY, Issue 4 2003
Kevin Beach
The photosynthetic performance, pigmentation, and growth of a Halimeda community were studied over a depth gradient on Conch Reef, Florida Keys, USA during summer,fall periods of 5 consecutive years. The physiology and growth of H. tuna (Ellis & Solander) Lamouroux and H. opuntia (L.) Lamouroux on this algal dominated reef were highly variable. Maximum rate of net photosynthesis (Pmax), respiration rate, and quantum efficiency (,) did not differ between populations of either species at 7 versus 21 m, even though the 21-m site received a 66% lower photon flux density (PFD). Physiological parameters, as well as levels of photosynthetic pigments, varied temporally. Pmax, saturation irradiance, compensation irradiance, and growth were greatest in summer months, whereas ,, chl a, chl b, and carotenoid concentrations were elevated each fall. Halimeda tuna growth rates were higher at 7 m compared with 21 m for only two of five growth trials. This may have arisen from variability in light and nutrient availability. Individuals growing at 7 m received a 29% greater PFD in August 2001 than in 1999. In August 1999 and 2001 seawater temperatures were uniform over the 14-m gradient, whereas in August 2000 cold water regularly intruded upon the 21-m but not the 7-m site. These results illustrate the potentially dynamic relationship between nutrients, irradiance, and algal productivity. This suggests the necessity of long-term monitoring over spatial and temporal gradients to accurately characterize factors that impact productivity. [source]

A NEW LARVAL FISH BIOASSAY FOR TESTING THE PATHOGENICITY OF PFIESTERIA SPP. (DINOPHYCEAE),

JOURNAL OF PHYCOLOGY, Issue 3 2003
Vincent J. Lovko
Water quality, microbial contamination, prior fish health, and variable results have been major impediments to identifying the cause and mechanism of fish mortality in standard aquarium-format Pfiesteria bioassays. Therefore, we developed a sensitive 96-h larval fish bioassay for assessing Pfiesteria spp. pathogenicity using six-well tissue culture plates and 7-day-old larval cyprinodontid fish. We used the assay to test pathogenicity of several clonal lines of Pfiesteria piscicida Steidinger and Burkholder and P. shumwayae Glasgow and Burkholder that had been cultured with algal prey for 2 to 36 months. The P. shumwayae cultures exhibited 80%,100% cumulative mortality in less than 96 h at initial zoospore densities of approximately 1000 cells·mL,1. No fish mortalities occurred with P. piscicida at identical densities or in controls. In a dose-response assay, we demonstrated a strong positive correlation between dinospore density and fish mortality in a highly pathogenic culture of P. shumwayae, generating a 96-h LD50 of 108 zoospores·mL,1. Additionally, we applied the assay to evaluate a 38-L P. shumwayae bioassay that was actively killing fish and compared results with those from exposures of juvenile tilapia (Oreochromis niloticus) in a 500-mL assay system. Water from the fish-killing 38-L assay was filtered and centrifuged to produce fractions dominated by dinoflagellates, bacteria, or presumed ichthyotoxin (cell-free fraction). After 96 h, the larval fish assay exhibited 50%,100% cumulative mortality only in fractions containing dinoflagellates, with no mortalities occurring in the other fractions. The 500-mL bioassay with tilapia produced inconsistent results and demonstrated no clear correlation between mortality and treatment. The new larval fish bioassay was demonstrated as a highly effective method to verify and evaluate dinoflagellate pathogenicity. [source]

Documenting Loss of Large Trophy Fish from the Florida Keys with Historical Photographs

CONSERVATION BIOLOGY, Issue 3 2009
LOREN McCLENACHAN
arrecifes de coral; ecología histórica; directrices cambiantes; peces de arrecife; sobrepesca Abstract:,A loss of large vertebrates has occurred in aquatic and terrestrial ecosystems, but data to measure long-term population changes are sparse. Historical photographs provide visual and quantitative evidence of changes in mean individual size and species composition for groups of marine fish that have been targeted by sport fishing. I measured such trends for 13 groups of recreationally caught "trophy" reef fish with photographs taken in Key West, Florida, from 1956 to 2007. The mean fish size declined from an estimated 19.9 kg (SE 1.5) to 2.3 kg (SE 0.3), and there was a major shift in species composition. Landings from 1956 to 1960 were dominated by large groupers (Epinephelus spp.), and other large predatory fish were commonly caught, including sharks with an average length of just <2 m. In contrast, landings in 2007 were composed of small snappers (Lutjanus spp. and Ocyurus chrysurus) with an average length of 34.4 cm (SE 0.62), and the average length of sharks declined by more than 50% over 50 years. Major declines in the size of fish caught were not reflected in the price of fishing trips, so customers paid the same amount for a less-valuable product. Historical photographs provide a window into a more pristine coral reef ecosystem that existed a half a century ago and lend support to current observations that unfished reef communities are able to support large numbers of large-bodied fish. Resumen:,Una pérdida de vertebrados mayores ha ocurrido en ecosistemas acuáticos y terrestres, pero los datos para medir los cambios poblaciones a largo plazo son escasos. Las fotografías históricas proporcionan evidencia visual y cuantitativa de cambios en el tamaño individual promedio y de la composición de especies en grupos de peces marinos que han sido blanco de la pesca deportiva. Medí esas tendencias en 13 grupos de peces de arrecife capturados recreativamente como "trofeos" mediante fotografías tomadas en Key West, Florida, desde 1956 a 2007. El peso promedio de los peces declinó de unos 19.9 kg (ES 1.5) a 2.3 kg (ES 0.3), y hubo un cambio mayor en la composición de especies. Las capturas entre 1956 y 1960 estuvieron dominadas por meros (Epinephelus spp.) grandes, y otros peces depredadores eran capturados comúnmente, incluyendo tiburones con una longitud promedio de poco menos de 2m. En contraste, las capturas en 2007 fueron compuestas de pargos (Lutjanus spp. y Ocyurus chrysurus) pequeños con una longitud promedio de 34.4 cm (ES 0.62), y la longitud promedio de los tiburones declinó más de 50% en 50 años. La gran declinación en el tamaño de los peces capturados no se reflejó en los precios de los viajes de pesca, así que los clientes pagaron la misma cantidad por un producto menos valioso. Las fotografías históricas proporcionan una visión de un ecosistema arrecifal coralino prístino que existió hace medio siglo y proporcionan soporte a los comentarios actuales de que las comunidades arrecifales no explotadas son capaces de soportar numerosos peces de talla grande. [source]

Modeled Effects of Sagebrush-Steppe Restoration on Greater Sage-Grouse in the Interior Columbia Basin, U.S.A.

CONSERVATION BIOLOGY, Issue 5 2002
Michael J. Wisdom
Consequently, managers of FS,BLM lands need effective strategies to recover sagebrush (Artemisia spp.) habitats on which this species depends. In response to this need, we evaluated the potential benefits of two restoration scenarios on Greater Sage-Grouse in the interior Columbia Basin and adjacent portions of the Great Basin of the western United States. Scenario 1 assumed a 50% reduction in detrimental grazing effects (through changes in stocking rates and grazing systems) and a six-fold increase in areas treated with active restoration (e.g., prescribed burning, native seedings, wildfire suppression) compared with future management proposed by the FS,BLM. Scenario 2 assumed a 100% reduction in detrimental grazing effects and the same increase in active restoration as scenario 1. To evaluate benefits, we estimated the risk of population extirpation for sage grouse 100 years in the future under the two scenarios and compared this risk with that estimated for proposed (100-year) FS,BLM management. We used estimates of extirpation risk for historical (circa 1850,1890) and current time periods as a context for our comparison. Under historical conditions, risk of extirpation was very low on FS,BLM lands, but increased to a moderate probability under current conditions. Under proposed FS,BLM management, risk of extirpation on FS,BLM lands increased to a high probability 100 years in the future. Benefits of the two restoration scenarios, however, constrained the future risk of extirpation to a moderate probability. Our results suggest that expansive and sustained habitat restoration can maintain desired conditions and reduce future extirpation risk for sage grouse on FS,BLM lands in western North America. The continued spread of exotic plants, however, presents a formidable challenge to successful restoration and warrants substantial research and management attention. Resumen: Los hábitats del urogallo (Centrocercus urophasianus) han disminuido a lo largo de la región occidental de Norteamérica, y la mayoría de los hábitats restantes ocurren en terrenos administrados por el Servicio Forestal de E.U.A. (SF) y el Buró de Administración de Tierras ( BAT ). Por lo tanto, los encargados de las tierras SF,BAT necesitan estrategias eficaces para recuperar los hábitats de artemisa (Artemisia spp.) de los cuales depende esta especie. En respuesta a esta necesidad, evaluamos los beneficios potenciales de dos escenarios de restauración sobre el urogallo en el interior de la Cuenca del Columbia y porciones adyacentes de la Gran Cuenca del occidente de los Estados Unidos. El escenario 1 supone una reducción del 50% en los efectos perjudiciales del pastoreo ( por medio de cambios en las tasas de aprovisionamiento y en los sistemas de pastoreo) y un incremento de seis veces en la superficie de las áreas tratadas con restauración activa ( por ejemplo, quemas prescritas, plántulas nativas, supresión de fuego no controlado) comparada con la administración futura propuesta por el SF,BAT. El escenario 2 supone una reducción del 100% en los efectos de pastoreo perjudiciales y el mismo aumento en la restauración activa que en el escenario 1. Para evaluar los beneficios, estimamos el riesgo de extirpación de la población de urogallos en 100 años bajo los dos escenarios y comparamos este riesgo con el riesgo estimado por la propuesta de manejo de SF,BAT (100-años). Utilizamos estimaciones del riesgo de extirpación en períodos históricos (entre 1850 y 1890) y actuales como contexto para nuestra comparación. Bajo condiciones históricas, el riesgo de extirpación fue muy bajo en los terrenos SF,BAT pero aumentó a una probabilidad moderada bajo condiciones actuales. Bajo la administración propuesta por SF,BAT, el riesgo de extirpación en los terrenos SF,BAT aumentó a una alta probabilidad 100 años en el futuro. Sin embargo, los beneficios de los dos escenarios de restauración constriñen el riesgo de extirpación a una probabilidad moderada. Nuestros resultados sugieren que la restauración expansiva y sostenida del hábitat puede mantener condiciones deseadas y reduce el riesgo de extirpación de urogallos en terrenos SF,BAT en la región occidental de Norteamérica. Sin embargo, la continua extensión de plantas exóticas representa un reto formidable para la restauración exitosa y justifica considerable investigación y atención de manejo. [source]

Prescribed Burning to Restore Mixed-Oak Communities in Southern Ohio: Effects on Breeding- Bird Populations

CONSERVATION BIOLOGY, Issue 5 2001
Vanessa L. Artman
We studied the effects of repeated burning (1,4 years of annual burning) and recovery (1 year after burning,) on the breeding bird community. Burning resulted in incremental but temporary reductions in the availability of leaf litter, shrubs, and saplings, but it did not affect trees, snags, or understory vegetation cover. Of 30 bird species monitored, 4 were affected negatively and 2 were affected positively by burning. Population densities of Ovenbirds ( Seiurus aurocapillus), Worm-eating Warblers ( Helmitheros vermivorus), and Hooded Warblers ( Wilsonia citrina) declined incrementally in response to repeated burning and did not recover within 1 year after burning, suggesting a lag time in response to the changes in habitat conditions. Densities of Northern Cardinals ( Cardinalis cardinalis) fluctuated among years in the control units, but remained low in the burned units. Densities of American Robins ( Turdus migratorius) and Eastern Wood-Pewees ( Contopus virens) increased in response to burning, but these increases were apparent only after several years of repeated burning. In general, burning resulted in short-term reductions in the suitability of habitat for ground- and low-shrub-nesting birds, but it improved habitat for ground- and aerial-foraging birds. Overall, there were no changes in the composition of the breeding-bird community. Total breeding bird population levels were also unaffected by burning. Our results suggest that prescribed burning applied on a long-term basis or across large spatial scales is likely to have adverse effects on ground- and low-shrub-nesting bird species, but other changes in the composition of the breeding-bird community are likely to be minimal as long as the closed-canopy forest structure is maintained within the context of prescribed burning. Resumen: Se está reintroduciendo fuego artificialmente en los bosque del sur de Ohio para determinar su efectividad para restaurar y mantener comunidades de bosques mixtos de encino ( Quercus spp.). Estudiamos los efectos de quemas repetidas (1,4 años de quema anual,) y de recuperación (1 año después de la quema) sobre la comunidad de aves reproductivas. La quema resultó en reducciones temporales en la disponibilidad de hojarasca, arbustos y renuevos, pero no afectó a los árboles, tocones o la cubierta vegetal del sotobosque. De 30 especies de aves monitoredas, 4 fueron afectadas negativamente por la quema y 2 fueron afectadas positivamente. Las densidades de población de Seiurus aurocapillus, de Helmitheros vermivorus y de Wilsonia citrina declinaron incrementalmente en respuesta a quemas repetidas y no se recuperaron en un año después de la quema, sugiriendo un retraso en el tiempo de respuesta a los cambios en las condiciones del hábitat. Las densidades de Cardinalis cardinalis fluctuaron entre años en las unidades control, pero permanecieron bajas en las unidades quemadas. Las densidades de Turdus migratorius y de Contopus virens aumentaron en respuesta a la quema, pero estos incrementos fueron evidentes sólo hasta varios años después de quemas repetidas. En general, en el corto plazo la quema resultó en reducciones en la calidad del hábitat para aves que anidan sobre el suelo y en arbustos bajos, pero mejoró el hábitat para aves que forrajean en el suelo y el aire. En general, no hubo cambios en la composición de la comunidad de aves reproductivas. Los niveles totales de poblaciones de aves reproductivas tampoco fueron afectados por la quema. Nuestros resultados sugieren la posibilidad de que la quema prescrita aplicada a largo plazo o en escalas espaciales grandes tenga efectos adversos sobre especies de aves que anidan sobre el suelo y en arbustos bajos, pero la posibilidad de cambios en la composición de la comunidad de aves reproductivas es mínima. [source]

Application of the New Keystone-Species Concept to Prairie Dogs: How Well Does It Work?

CONSERVATION BIOLOGY, Issue 6 2000
Natasha B. Kotliar
This prompted Power et al. (1996) to refine the definition: keystone species have large effects on community structure or ecosystem function (i.e., high overall importance), and this effect should be large relative to abundance (i.e., high community importance). Using prairie dogs (Cynomys spp.) as an example, I review operational and conceptual difficulties encountered in applying this definition. As applied to prairie dogs, the implicit assumption that overall importance is a linear function of abundance is invalid. In addition, community importance is sensitive to abundance levels, the definition of community, and sampling scale. These problems arise largely from the equation for community importance, as used in conjunction with removal experiments at single abundance levels. I suggest that we shift from the current emphasis on the dualism between keystone and nonkeystone species and instead examine how overall and community importance vary (1) with abundance, (2) across spatial and temporal scales, and (3) under diverse ecological conditions. In addition, I propose that a third criterion be incorporated into the definition: keystone species perform roles not performed by other species or processes. Examination of how these factors vary among populations of keystone species should help identify the factors contributing to, or limiting, keystone-level functions, thereby increasing the usefulness of the keystone-species concept in ecology and conservation. Although the quantitative framework of Power et al. falls short of being fully operational, my conceptual guidelines may improve the usefulness of the keystone-species concept. Careful attention to the factors that limit keystone function will help avoid misplaced emphasis on keystone species at the expense of other species. Resumen: Se ha sugerido que el concepto de especie pilar no sea usado más en ecología y conservación, principalmente debido a que el concepto ha sido pobremente definido. Esto instigó a Power et al. (1996) a refinar la definición: las especies pilar tienen grandes efectos en la estructura de una comunidad o la función de un ecosistema (alta importancia en lo general), y este efecto debe ser grande en relación con la abundancia (alta importancia en la comunidad). Usando los perros de pradera (Cynomys spp) como ejemplo, revisé las dificultades operativas y conceptuales encontradas durante la aplicación de esta definición. Al aplicarse a perros de pradera, la suposición implícita de que la importancia en lo general es una función lineal de la abundancia es inválida. Además, la importancia en la comunidad es sensible a los niveles de abundancia, a la definición de comunidad y a la escala de muestreo. Estos problemas surgen, en gran medida, de la ecuación para la importancia en la comunidad, al ser usada conjuntamente con experimentos de remoción a un solo nivel de abundancia. Sugiero que el énfasis actual en la dualidad sobre especies pilares/no pilares cambie para examinar cómo varía la importancia en lo general y en la comunidad; (1) con la abundancia, (2) a lo largo de escalas espaciales y temporales, y (3) bajo diversas condiciones ecológicas. Además, propongo que sea incorporado un tercer criterio en la definición: las especies pilar llevan a cabo funciones no llevadas a cabo por otras especies o procesos. El análisis de cómo varían estos factores entre poblaciones de especies pilar ayudará a identificar los factores que contribuyen, o limitan las funciones a nivel pilar, incrementando con ello la utilidad del concepto de especie pilar en ecología y conservación. Aunque el marco de trabajo cuantitativo de Power et al. no llega a ser completamente operacional, mis guías conceptuales pueden mejorar la utilidad de este concepto. Una atención especial a los factores que limitan el funcionamiento pilar ayudaría a evitar un énfasis mal ubicado en especies pilar a costa de otras especies. [source]

Widespread resistance of Mediterranean island ecosystems to the establishment of three alien species

DIVERSITY AND DISTRIBUTIONS, Issue 5 2008
Montserrat Vilà
ABSTRACT Although some invasive plants are cosmopolitan, not all ecosystems are invaded to the same degree. Yet there is little experimental work on how ecosystem resistance to invasion at the establishment phase differs among ecosystems. We conducted two field sowing experiments in two consecutive years to examine establishment of the deciduous tree Ailanthus altissima, the succulent subshrub Carpobrotus spp. and the annual geophyte Oxalis pes-caprae in coastal dunes, shrublands and oldfields in more than 200 sites across six Mediterranean Basin islands differing in climatic conditions and local species richness. Establishment success (i.e. percentage of plots with at least one seedling) and rates (i.e. seedling to sown seed ratio) were low, especially for Ailanthus even when accounting for differences in seed viability. Oxalis was capable of producing a new cohort of seedlings the year following planting. By contrast, all Ailanthus seedlings and half the Carpobrotus seedlings died following the first summer. Differences in establishment success and rates among ecosystems were species-, island- and year-dependent. Differences in precipitation and mean temperature were associated with differences in establishment rates across sites. Establishment rates tended to be positively correlated with cumulative precipitation and negatively with mean Ta. Unexpectedly, native species richness was not a good predictor of seedling establishment, except for higher Oxalis establishment success in species rich habitats. By conducting field sowing tests at multiple sites across a region we found that except for Oxalis, Mediterranean island ecosystems are quite resistant to invader establishment. These results suggest that differences in the degree of invasion between ecosystems and islands might be more dependent upon the influence of invasion event factors (e.g. propagule pressure) or factors acting at a later life-history stages rather than differences in the resistance imposed by ecosystems to invader recruitment. Moreover, our results support the notion that in Mediterranean ecosystems invasions are highly idiosyncratic events and strongly dependent on water availability conditions. [source]

Impacts of Dreissena invasions on benthic macroinvertebrate communities: a meta-analysis

DIVERSITY AND DISTRIBUTIONS, Issue 2 2007
Jessica M. Ward
ABSTRACT Dreissenid mussels (the zebra mussel Dreissena polymorpha and the quagga mussel Dreissena bugensis) have invaded lakes and rivers throughout North America and Europe, where they have been linked to dramatic changes in benthic invertebrate community diversity and abundance. Through a meta-analysis of published data from 47 sites, we developed statistical models of Dreissena impact on benthic macroinvertebrates across a broad range of habitats and environmental conditions. The introduction of Dreissena was generally associated with increased benthic macroinvertebrate density and taxonomic richness, and with decreased community evenness (of taxa excluding Dreissena). However, the strength of these effects varied with sediment particle size across sites. The effects of Dreissena differed among taxonomic and functional groups of macroinvertebrates, with positive effects on the densities of scrapers and predators, particularly leeches (Hirudinea), flatworms (Turbellaria), and mayflies (Ephemeroptera). Gastropod densities increased in the presence of Dreissena, but large-bodied snail taxa tended to decline. Dreissena was associated with declines in the densities sphaeriid clams and other large filter-feeding taxa, as well as burrowing amphipods (Diporeia spp.), but had strong positive effects on gammarid amphipods. These patterns are robust to variation in the methodology of primary studies. The effects of Dreissena are remarkably concordant with those of ecologically similar species, suggesting universality in the interactions between introduced byssally attached mussels and other macroinvertebrates. [source]

Conifers as invasive aliens: a global survey and predictive framework

DIVERSITY AND DISTRIBUTIONS, Issue 5-6 2004
David M. Richardson
ABSTRACT We summarize information on naturalized and invasive conifers (class Pinopsida) worldwide (data from 40 countries, some with remote states/territories), and contrast these findings with patterns for other gymnosperms (classes Cycadopsida, Gnetopsida and Ginkgoopsida) and for woody angiosperms. Eighty conifer taxa (79 species and one hybrid; 13% of species) are known to be naturalized, and 36 species (6%) are ,invasive'. This categorization is based on objective and conservative criteria relating to consistency of reproduction, distance of spread from founders, and degree of reliance on propagules from the founder population for persistence in areas well outside the natural range of species. Twenty-eight of the known invasive conifers belong to one family (Pinaceae) and 21 of these are in one genus (Pinus). The Cupressaceae (including Taxodiaceae) has six known invasive species (4%) in four genera, but the other four conifer families have none. There are also no known invasive species in classes Cycadopsida, Gnetopsida or Ginkgoopsida. No angiosperm family comprising predominantly trees and shrubs has proportionally as many invasive species as the Pinaceae. Besides the marked taxonomic bias in favour of Pinaceae, and Pinus in particular, invasiveness in conifers is associated with a syndrome of life-history traits: small seed mass (< 50 mg), short juvenile period (< 10 year), and short intervals between large seed crops. Cryptomeria japonica, Larix decidua, Picea sitchensis, Pinus contorta, Pinus strobus, and Pseudotsuga menziesii exemplify this syndrome. Many rare and endangered conifer species exhibit opposite characters. These results are consistent with earlier predictions made using a discriminant function derived from attributes of invasive and noninvasive Pinus species. Informative exceptions are species with small seeds (< 4 mg, e.g. Chamaecyparis spp., Pinus banksiana, Tsuga spp. , mostly limited to wet/mineral substrates) or otherwise ,non-invasive' characters (e.g. large seeds, fleshy fruits, e.g. Araucaria araucana, Pinus pinea, Taxus baccata that are dependent on vertebrates for seed dispersal). Most conifers do not require coevolved mutualists for pollination and seed dispersal. Also, many species can persist in small populations but have the genetic and reproductive capacity to colonize and increase population size rapidly. The underlying mechanisms mediating conifer invasions are thus easier to discern than is the case for most angiosperms. Further information is needed to determine the extent to which propagule pressure (widespread dissemination, abundant plantings, long history of cultivation) can compensate for low ,inherent invasiveness'. [source]

Autopodial skeleton evolution in side-necked turtles (Pleurodira)

ACTA ZOOLOGICA, Issue 3 2007
Marcelo R. Sánchez-Villagra
Abstract Carpal and tarsal anatomy was documented based on the observation of dry skeletons of adult specimens representing 25 species in 15 genera and on data taken from the literature. In addition, histological sections and cleared and double-stained autopodia of recently hatched and juvenile specimens representing seven chelid and pelomedusoid species were studied. There is much more morphological diversity in the manus than in the pes. Variation in autopodial skeletons includes: the astragalus and calcaneum are either separated or fused; fusion of distal carpals 3,4,5 or just 4,5; number of centralia in the carpus; and presence/absence of a pisiform and of an accessory radial element. The widespread and probably basal phalangeal formula for Pleurodira is 2.3.3.3.3. Deviations are Pelomedusa subrufa, exhibiting a reduction to 2.2.2.2.2, Pelusios spp. with one phalanx less in digit I and for one species in digit V as well, and Acanthochelys pallidipectoris with an additional phalanx in the fourth finger. Six discrete characters itemizing some of the morphological variation observed were plotted on a composite pleurodire phylogeny, revealing not only homoplastic patterns but also the utility of some characters in supporting the monophyly of several clades. The pisiform is the last carpal element to ossify in Chelus fimbriatus. We hypothesize that the so-called fifth hooked metatarsal represents the fusion of distal tarsal 5 with metatarsal V. The accessory radial element that was occasionally present in the turtles examined may represent an atavism of the otherwise lost radiale of turtles. [source]

Assessing ecosystem threats from global and regional change: hierarchical modeling of risk to sagebrush ecosystems from climate change, land use and invasive species in Nevada, USA

ECOGRAPHY, Issue 1 2010
Bethany A. Bradley
Global change poses significant challenges for ecosystem conservation. At regional scales, climate change may lead to extensive shifts in species distributions and widespread extirpations or extinctions. At landscape scales, land use and invasive species disrupt ecosystem function and reduce species richness. However, a lack of spatially explicit models of risk to ecosystems makes it difficult for science to inform conservation planning and land management. Here, I model risk to sagebrush (Artemisia spp.) ecosystems in the state of Nevada, USA from climate change, land use/land cover change, and species invasion. Risk from climate change is based on an ensemble of 10 atmosphere-ocean general circulation model (AOGCM) projections applied to two bioclimatic envelope models (Mahalanobis distance and Maxent). Risk from land use is based on the distribution of roads, agriculture, and powerlines, and on the spatial relationships between land use and probability of cheatgrass Bromus tectorum invasion in Nevada. Risk from land cover change is based on probability and extent of pinyon-juniper (Pinus monophylla; Juniperus spp.) woodland expansion. Climate change is most likely to negatively impact sagebrush ecosystems at the edges of its current range, particularly in southern Nevada, southern Utah, and eastern Washington. Risk from land use and woodland expansion is pervasive throughout Nevada, while cheatgrass invasion is most problematic in the northern part of the state. Cumulatively, these changes pose major challenges for conservation of sagebrush and sagebrush obligate species. This type of comprehensive assessment of ecosystem risk provides managers with spatially explicit tools important for conservation planning. [source]

Postfledging habitat selection of juvenile middle spotted woodpeckers: a multi-scale approach

ECOGRAPHY, Issue 4 2009
Carlos Ciudad
Despite its relevance for the persistence of populations, the ecological mechanisms underlying habitat use decisions of juvenile birds are poorly understood. We examined postfledging habitat selection of radio-tracked juvenile middle spotted woodpeckers Dendrocopos medius at multiple hierarchically-nested spatial scales in NW Spain. At the landscape and home range scales, old oak forest was the most used and selected habitat, young oak forests and pine plantations were avoided, and riverside forests were used as available. At a lower scale, birds selected larger diameter trees for foraging. Home ranges had higher densities of large deciduous trees (mainly oaks Quercus spp., but also poplars Populus spp. and willows Salix spp. >22,cm and >33,cm DBH) selected for foraging by juveniles than non-used areas. These results suggest that foraging conditions may drive, at least partly, habitat use decisions by juvenile birds. We also discuss the potential influence of intraspecific competition, the search for a future breeding territory in the early postfledging period and predation avoidance on habitat use decisions by juvenile birds. Contrary to previous studies on migrant forest birds, postfledging juvenile woodpeckers selected the same habitat as for the breeding adults (i.e. old oak forest), indicating that migrant and resident specialist avian species may require different conservation actions. Conservation strategies of woodpecker populations should consider the protection of old oak forests with high densities of large trees to provide suitable habitat to breeding adults and postfledging juveniles. The habitat improvement for this indicator and umbrella species would also favour other organisms that depend on characteristics of old-growth oak forests. [source]

Numerical and dietary responses of a predator community in a temperate zone of Europe

ECOGRAPHY, Issue 2 2009
Gilles Dupuy
The generalist predation hypothesis predicts that the functional responses of generalist predator species should be quicker than those of specialist predators and have a regulating effect on vole populations. New interpretations of their role in temperate ecosystems have, however, reactivated a debate suggesting generalist predators may have a destabilizing effect under certain conditions (e.g. landscape homogeneity, low prey diversity, temporary dominance of 1 prey species associated with a high degree of dietary specialization). We studied a rich predator community dominated by generalist carnivores (Martes spp., Vulpes vulpes, Felis catus) over a 6 yr period in farmland and woodland in France. The most frequent prey were small rodents (mostly Microtus arvalis, a grassland species, and Apodemus spp., a woodland species). Alternative prey were diverse and dominated by lagomorphs (Oryctolagus cuniculus, Lepus europeus). We detected a numerical response among specialist carnivores but not among generalist predators. The dietary responses of generalist predators were fairly complex and most often dependent on variation in density of at least 1 prey species. These results support the generalist predation hypothesis. We document a switch to alternative prey, an increase of diet diversity, and a decrease of diet overlap between small and medium-sized generalists during the low density phase of M. arvalis. In this ecosystem, the high density phases of small mammal species are synchronous and cause a temporary specializing of several generalist predator species. This rapid functional response may indicate the predominant role of generalists in low amplitude population cycles of voles observed in some temperate areas. [source]

The relationships between habitat topology, critical scales of connectivity and tick abundance Ixodes ricinus in a heterogeneous landscape in northern Spain

ECOGRAPHY, Issue 5 2003
Agustin Estrada-Peña
The habitat mosaic was used to quantify connectivity between patches of different tick density of the notorious tick species Ixodes ricinus in an attempt to determine the cause of variations in tick abundance among apparently homogeneous sites in northern Spain. The analysis revealed that patches with high tick abundance are "stepping-stone" territories that, when removed from the landscape, cause large changes in connectivity. Sites with medium tick abundance do not cause such a critical transition in connectivity. Patches with low tick abundance, but optimal abiotic conditions for survival, are located within the minimum cost corridors network joining the patches, while those sites where the tick has been intermittently collected are located at variable distances from this network. Sites where the tick is consistently absent, but where the habitat is predicted to be suitable (old, heterogeneous forests of Quercus spp.) for the tick, are very separated from this main network of connections. These results suggest that tick distribution in a zone is highly affected not only by abiotic variables (vegetation and weather) but also by host movements. Dispersal of the tick is a function of how the hosts perceive the habitat, and the habitat's permeability to host movement. Permanent tick populations seem to be supported by the existence of these critical, high density patches, located at significant places within the habitat network. [source]

Soil water dynamics along a tree diversity gradient in a deciduous forest in Central Germany

ECOHYDROLOGY, Issue 3 2010
Inga Krämer
Abstract This study aimed to investigate whether soil water dynamics differ along a tree species diversity gradient. The 12 study plots in the Hainich National Park, Germany, were composed of up to 11 tree species. Fagus sylvatica formed the monospecific plots. Mixed forest plots consisted of a variable admixture of other broad-leaved deciduous tree species such as Tilia spp., Fraxinus excelsior, Carpinus betulus, and Acer pseudoplatanus. Volumetric soil water content and soil water potential were measured for about two and a half years. Overall patterns of soil water dynamics were similar in all study plots. However, during a desiccation period in summer 2006, significant correlations between soil water in the upper soil and tree species diversity of the 12 study plots were observed. At the beginning of this period, soil water was extracted at higher rates in the species-rich plots than in the beech-dominated plots. However, later during the desiccation period, when atmospheric evaporative demand was higher, only the beech-dominated stands were able to increase soil water extraction. In plots of high tree species diversity, soil water reserves were already low and soil water extraction reduced. Possible explanations for high water extraction rates in mixed species plots at the beginning of the desiccation period include species-specific characteristics such as high maximum water use rate of some species, enhanced exploitation of soil water resources in mixed stands (complementarity effect), and additional water use of the herb layer, which increased along the tree species diversity gradient. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Wide-area estimates of saltcedar (Tamarix spp.) evapotranspiration on the lower Colorado River measured by heat balance and remote sensing methods,,

ECOHYDROLOGY, Issue 1 2009
Pamela L. Nagler
Abstract In many places along the lower Colorado River, saltcedar (Tamarix spp) has replaced the native shrubs and trees, including arrowweed, mesquite, cottonwood and willows. Some have advocated that by removing saltcedar, we could save water and create environments more favourable to these native species. To test these assumptions we compared sap flux measurements of water used by native species in contrast to saltcedar, and compared soil salinity, ground water depth and soil moisture across a gradient of 200,1500 m from the river's edge on a floodplain terrace at Cibola National Wildlife Refuge (CNWR). We found that the fraction of land covered (fc) with vegetation in 2005,2007 was similar to that occupied by native vegetation in 1938 using satellite-derived estimates and reprocessed aerial photographs scaled to comparable spatial resolutions (3,4 m). We converted fc to estimates of leaf area index (LAI) through point sampling and destructive analyses (r2 = 0·82). Saltcedar LAI averaged 2·54 with an fc of 0·80, and reached a maximum of 3·7 with an fc of 0·95. The ranges in fc and LAI are similar to those reported for native vegetation elsewhere and from the 1938 photographs over the study site. On-site measurements of water use and soil and aquifer properties confirmed that although saltcedar grows in areas where salinity has increased much better than native shrubs and trees, rates of transpiration are similar. Annual water use over CNWR was about 1·15 m year,1. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Effects of temperature and elevation on habitat use by a rare mountain butterfly: implications for species responses to climate change

ECOLOGICAL ENTOMOLOGY, Issue 4 2009
SARAH ASHTON
Abstract 1.,The present study used the mountain specialist butterfly Parnassius apollo as a model system to investigate how climate change may alter habitat requirements for species at their warm range margins. 2.,Larval habitat use was recorded in six P. apollo populations over a 700 m elevation gradient in the Sierra de Guadarrama (central Spain). Larvae used four potential host species (Sedum spp.) growing in open areas amongst shrubs. 3.,Parnassius apollo host-plant and habitat use changed as elevation increased: the primary host shifted from Sedum amplexicaule to Sedum brevifolium, and larvae selected more open microhabitats (increased bare ground and dead vegetation, reduced vegetation height and shrub cover), suggesting that hotter microhabitats are used in cooler environments. 4.,Larval microhabitat selection was significantly related to ambient temperature. At temperatures lower than 27 °C, larvae occupied open microhabitats that were warmer than ambient temperature, versus more shaded microhabitats that were cooler than ambient conditions when temperature was higher than 27 °C. 5.,Elevational changes in phenology influenced the temperatures experienced by larvae, and could affect local host-plant favourability. 6.,Habitat heterogeneity appears to play an important role in P. apollo larval thermoregulation, and may become increasingly important in buffering populations of this and other insect species against climatic variation. [source]

Genetic divergence and ecological specialisation of seed weevils (Exapion spp.) on gorses (Ulex spp.)

ECOLOGICAL ENTOMOLOGY, Issue 3 2008
MYRIAM BARAT
Abstract 1.,Reproductive isolation of sympatric populations may result from divergent selection of populations in different environments, and lead to ecological specialisation. In Brittany (France), the gorse Ulex europaeus (Fabaceae, Genisteae), may be encountered in sympatry with one of the two other gorse species present: U. gallii and U. minor. A recent study based on morphological identification of seed predators of gorse has shown that two weevil species (Curculionoidea, Apionidae) infest gorse pods at different seasons and have different host ranges: Exapion ulicis infests U. europaeus in spring, whereas E. lemovicinum infests U. gallii and U. minor in autumn. Weevil populations may thus have diverged in sympatry. 2.,As morphological identification of weevils is often difficult and some of the characters used may exhibit individual or environmental variation, mitochondrial and nuclear sequences of weevils collected within pods of the three gorse species in 10 populations of Brittany were used to reconstruct their phylogeny. 3.,The results reveal that species differentiation based on morphological characters is confirmed by the two molecular data sets, showing that E. ulicis and E. lemovicinum are distinct species, and suggesting the absence of host races. Finally, E. ulicis was able to use U. gallii and U. minor pods in spring in some years in some populations, which appeared to depend on the availability of pods present during its reproductive period. 4.,Divergence between E. ulicis and E. lemovicinum may have resulted from temporal isolation of reproductive periods of weevil populations followed by specialisation of insects to host phenology. [source]

Interactions between cottonwood and beavers positively affect sawfly abundance

ECOLOGICAL ENTOMOLOGY, Issue 4 2006
JOSEPH K. BAILEY
Abstract 1.,Cottonwood (Populus spp.) are the dominant tree type in riparian forests of the western U.S.A. In these riparian forests, the beaver (Castor canadensis) is a major ecosystem engineer that commonly browses cottonwood, resulting in distinct changes to plant architecture. Here the hypothesis that beaver herbivory indirectly affects the distribution of a keystone leaf-galling sawfly through architectural changes in cottonwood was examined. 2.,It was found that: (a) beaver herbivory of cottonwood results in an increase in average shoot length over unbrowsed cottonwood; (b) sawfly galls were up to 7,14 times more abundant on browsed cottonwood than unbrowsed cottonwood; and (c) sawfly gall abundance was correlated positively with changes in shoot length after beaver herbivory. Together these data show that the individual and combined effects of cottonwood and beaver herbivory increase shoot length, positively affecting sawfly abundance. 3.,Because herbivores are a ubiquitous component of most ecosystems, we argue that the indirect effects of herbivory on plant quality, and subsequently other herbivores, may be as important as environmental variation. [source]

Burying beetle Nicrophorus investigator reproduction on Pacific salmon carcasses

ECOLOGICAL ENTOMOLOGY, Issue 1 2006
M. D. Hocking
Abstract., 1.,In many undisturbed watersheds along the Pacific Rim, anadromous salmon (Oncorhynchus spp.) provide a predictable source of carrion to the riparian zone, largely due to horizontal transfer of salmon carcasses by bears (Ursus spp.) and other vertebrates. 2.,Burying beetles are important members of the north-temperate carrion fauna, and may utilise salmon carcasses and remnants for breeding. In this study, isotopic and observational data are reported that demonstrate previously unrecognised Nicrophorus investigator (Zetterstedt) reproduction on large salmon carcasses from five watersheds in coastal British Columbia. 3.,Stable isotope signatures (,15N and ,13C) of adult beetles collected in autumn indicate a diet of salmon origin in all but one individual from all watersheds, suggesting that this beetle,salmon association is widespread. Comparison of autumn isotope signatures to individuals collected randomly in summer suggests that isotope signatures represent the larval carrion source from the previous autumn rather than immediate adult diet. 4.,In a survey of N. investigator use of salmon carcasses from two watersheds, 35 broods were observed on chum and pink salmon carcasses, including 16 natural brood complexes containing over 100 larvae, and five ranging from 250 to 750 larvae. 5.,Overall, north-coastal populations of N. investigator breed on the rich and reliable salmon resource and may exhibit a system of communal breeding on these carcasses. This is most relevant when the dramatic reduction in salmon spawning biomass over the last century is considered. [source]

The community-wide and guild-specific effects of pubescence on the folivorous insects of manzanitas Arctostaphylos spp.

ECOLOGICAL ENTOMOLOGY, Issue 4 2003
Melissa R. Andres
Abstract., 1.,Insect communities on 26 species of manzanita Arctostaphylos spp. (Ericaceae) were sampled in order to examine the effects of variation in foliar pubescence traits on a community of folivorous insects. Manzanitas vary widely in pubescence density, length, and glandularity both within and between species. 2.,Linear models were fitted and evaluated to determine whether pubescence traits are associated with the species richness and abundance of folivorous insects after accounting for the effects of other relevant habitat and host-plant related characteristics. 3.,Pubescence traits were clearly associated with both community-wide and guild-specific variation in the structure of the folivorous insect community of manzanitas, however the effects of pubescence were manifested primarily as effects on the abundance of folivores not on species richness. The species richness of folivorous insects on manzanitas was not associated with pubescence density or length but was associated positively with glandularity. 4.,The abundance of all guilds except leaf-mining insects was lower on manzanitas having longer pubescence. In contrast, the abundance of external-chewing insects was higher on plants having denser pubescence and on plants having glandular pubescence. 5.,Overall, the results suggest that both longer pubescence and the amount of contact between an insect and pubescence act quantitatively to decrease the abundance of external-feeding guilds of folivorous insects. The abundance of species in internal-feeding guilds that oviposit directly on leaves is unrelated to foliar pubescence traits in the host plant. [source]

Nutrients, diversity, and community structure of two phytotelm systems in a lower montane forest, Puerto Rico

ECOLOGICAL ENTOMOLOGY, Issue 3 2000
Barbara A. Richardson
Summary 1. Bromeliad and heliconia phytotelmata in the same forest area were compared in terms of their animal assemblages, nutrient inputs, and plant architecture. 2. For all major elements, nutrient inputs from canopy-derived debris and rainfall in bromeliads were significantly lower than those derived from decaying flower parts and plant secretions in heliconia bracts. Bromeliads contained significantly fewer organisms per unit volume of water and unit dry weight of organic matter than did heliconia inflorescences. They also contained a significantly lower animal biomass (199 mg DW from 15 bromeliads, 527 mg DW from 15 heliconia inflorescences). 3. Species richness was independent of abundance, demonstrating that, at least for small container habitats, higher abundance does not necessarily lead to a greater species richness. Communities were remarkably similar in patterns of relative abundance and species richness (23 spp. in bromeliads, 21 spp. in heliconia), probably due to functional similarities in plant architecture, with the two most abundant species comprising 60,62% of the total community. Coefficients of similarity were low because of marked differences in species assemblages. 4. Some taxa were phytotelm generalists but most showed a preference for one particular habitat, indicating differential selection in the choice of oviposition sites and larval development within the forest ecosystem. In common with many island communities, species richness was lower than that reported for these phytotelm habitats in mainland central and south America. [source]

The underestimated importance of belowground carbon input for forest soil animal food webs

ECOLOGY LETTERS, Issue 8 2007
Melanie M. Pollierer
Abstract The present study investigated the relative importance of leaf and root carbon input for soil invertebrates. Experimental plots were established at the Swiss Canopy Crane (SCC) site where the forest canopy was enriched with 13C depleted CO2 at a target CO2 concentration of c. 540 p.p.m. We exchanged litter between labelled and unlabelled areas resulting in four treatments: (i) leaf litter and roots labelled, (ii) only leaf litter labelled, (iii) only roots labelled and (iv) unlabelled controls. In plots with only 13C-labelled roots most of the soil invertebrates studied were significantly depleted in 13C, e.g. earthworms, chilopods, gastropods, diplurans, collembolans, mites and isopods, indicating that these taxa predominantly obtain their carbon from belowground input. In plots with only 13C-labelled leaf litter only three taxa, including, e.g. juvenile Glomeris spp. (Diplopoda), were significantly depleted in 13C suggesting that the majority of soil invertebrates obtain its carbon from roots. This is in stark contrast to the view that decomposer food webs are based on litter input from aboveground. [source]

Parasites in the food web: linking amphibian malformations and aquatic eutrophication

ECOLOGY LETTERS, Issue 7 2004
Pieter T. J. Johnson
Abstract Emerging diseases are an ever-growing affliction of both humans and wildlife. By exploring recent increases in amphibian malformations (e.g. extra or missing limbs), we illustrate the importance of food web theory and community ecology for understanding and controlling emerging infections. Evidence points to a native parasite, Ribeiroia ondatrae, as the primary culprit of these malformations, but reasons for the increase have remained conjectural. We suggest that the increase is a consequence of complex changes to aquatic food webs resulting from anthropogenic disturbance. Our results implicate cultural eutrophication as a driver of elevated parasitic infection: (1) eutrophication causes a predator-mediated shift in snail species composition toward Planorbella spp., (2) Planorbella are the exclusive first intermediate hosts of R. ondatrae and (3) Ribeiroia infection is a strong predictor of amphibian malformation levels. Our study illustrates how the effects of anthropogenic disturbance on epidemic disease can be mediated through direct and indirect changes in food web structure. [source]

How 17-year cicadas keep track of time

ECOLOGY LETTERS, Issue 4 2000
R. Karban
Seventeen-year periodical cicadas (Magicicada spp.) require 17 years to develop underground and all individuals at any location emerge synchronously within several days. The mechanisms that animals use to keep track of time are poorly understood and nothing is known about how cicada nymphs emerge after precisely 17 years. We altered the seasonal cycles of trees supporting cicada nymphs and thereby induced premature metamorphosis of the associated cicadas. This indicates that cicadas accomplish a consistently accurate 17-year preadult development time by counting host seasonal cycles and not either by the passage of real time or by the accumulation of degree days. [source]

Effects of stocked trout on native fish communities in boreal foothills lakes

ECOLOGY OF FRESHWATER FISH, Issue 2 2010
Leslie E. Nasmith
Nasmith LE, Tonn WM, Paszkowski CA, Scrimgeour GJ. Effects of stocked trout on native fish communities in boreal foothills lakes. Ecology of Freshwater Fish 2010: 19: 279,289. © 2010 John Wiley & Sons A/S Abstract,,, Ecological effects of stocking nonnative trout into lakes are receiving increased attention, especially in alpine environments. We assessed effects of stocked trout on native forage fishes in the boreal foothills of Alberta (Canada) by comparing fish density, population size structure and spatial and temporal activities in stocked and unstocked lakes over 3 years (2005,2007). The numerically dominant dace (primarily Phoxinus spp.) were larger in stocked lakes, consistent with size-limited predation. Dace were also more crepuscular and concentrated on the lake-bottom in stocked lakes, compared to more daytime activity in the water column in unstocked lakes. There were, however, no demonstrable effects of trout on the abundance of forage fish. The lack of major population-level impacts of stocked trout suggests that current stocking practices, characteristics of boreal foothill lakes (e.g. thermal structure, abundant invertebrates, dense macrophytes) and/or behavioural adjustments of forage fish contribute to healthy native fish populations in our stocked lakes. [source]

Relationship between stream temperature, thermal refugia and rainbow trout Oncorhynchus mykiss abundance in arid-land streams in the northwestern United States

ECOLOGY OF FRESHWATER FISH, Issue 1 2001
J. L. Ebersole
Abstract , Warm stream temperatures may effectively limit the distribution and abundance of Pacific salmon Oncorhynchus spp. in streams. The role of cold thermal refugia created by upwelling groundwater in mediating this effect has been hypothesized but not quantitatively described. Between June 21 and September 15, 1994, rainbow trout O. mykiss abundance within 12 northeast Oregon (USA) stream reaches was inversely correlated with mean ambient maximum stream temperatures (r=,0.7, P<0.05). Some rainbow trout used thermal refugia (1,10 m2 surface area) that were on average 3,8°C colder than ambient stream temperatures. Within the warmest reaches, high ambient stream temperatures (>22°C) persisted from mid-June through August, and on average 10,40% of rainbow trout were observed within thermal refugia during periods of midday maximum stream temperatures. Frequency of cold-water patches within reaches was not significantly associated with rainbow trout density after accounting for the influence of ambient stream temperature (P=0.06; extra sum of squares F -test). Given prolonged high ambient stream temperatures in some reaches, the thermal refugia available in the streams we examined may be too small and too infrequent to sustain high densities of rainbow trout. However, these refugia could allow some rainbow trout to persist, although at low densities, in warm stream reaches. [source]

Sequence-related amplified polymorphism, an effective molecular approach for studying genetic variation in Fasciola spp. of human and animal health significance

ELECTROPHORESIS, Issue 2 2009
Qiao-Yan Li
Abstract In the present study, a recently described molecular approach, namely sequence-related amplified polymorphism (SRAP), which preferentially amplifies ORFs, was evaluated for the studies of genetic variation among Fasciola hepatica, Fasciola gigantica and the "intermediate" Fasciola from different host species and geographical locations in mainland China. Five SRAP primer combinations were used to amplify 120 Fasciola samples after ten SRAP primer combinations were evaluated. The number of fragments amplified from Fasciola samples using each primer combination ranged from 12 to 20, with an average of 15 polymorphic bands per primer pair. Fifty-nine main polymorphic bands were observed, ranging in size from 100 to 2000,bp, and SRAP bands specific to F. hepatica or F. gigantica were observed. SRAP fragments common to F. hepatica and the "intermediate" Fasciola, or common to F. gigantica and the "intermediate" Fasciola were identified, excised and confirmed by PCR amplification of genomic DNA using primers designed based on sequences of these SRAP fragments. Based on SRAP profiles, unweighted pair-group method with arithmetic averages clustering algorithm categorized all of the examined representative Fasciola samples into three groups, representing the F. hepatica, the "intermediate" Fasciola, or the F. gigantica. These results demonstrated the usefulness of the SRAP technique for revealing genetic variability between F. hepatica, F. gigantica and the "intermediate" Fasciola, and also provided genomic evidence for the existence of the "intermediate" Fasciola between F. hepatica and F. gigantica. This technique provides an alternative and a useful tool for the genetic characterization and studies of genetic variability in parasites. [source]