CONSERVATION BIOLOGY, Issue 3 2007
SARAH B. YAKIMOWSKI
especies en riesgo; límites de distribución; poblaciones periféricas; reproducción sexual; Vaccinium stamineum Abstract:,Geographically peripheral populations of widespread species are often the focus of conservation because they are locally rare within political jurisdictions. Yet the ecology and genetics of these populations are rarely evaluated in a broader geographic context. Most expectations concerning the ecology and evolution of peripheral populations derive from the abundant-center model, which predicts that peripheral populations should be less frequent, smaller, less dense, and have a lower reproductive rate than central populations. We tested these predictions and in doing so evaluated the conservation value of peripheral populations for the clonal shrub Vaccinium stamineum L. (Ericaceae, deerberry), which is listed as threatened in Canada. Based on 51 populations sampled from the center to the northern range limits over 2 years, population frequency and size declined toward the range limit, but ramet density increased. Sexual reproductive output varied widely among populations and between years, with many populations producing very few seeds, but did not decline toward range margins. In fact seed mass increased steadily toward range limit, and this was associated with faster germination and seedling growth, which may be adaptive in seasonal northern environments. Our results did not support the prediction that clonal reproduction is more prevalent in peripheral populations or that it contributed antagonistically to the wide variation in seed production. Peripheral populations of V. stamineum are as productive as central populations and may be locally adapted to northern environments. This emphasizes the importance of a broad geographical perspective for evaluating the ecology, evolution, and conservation of peripheral populations. Resumen:,Las poblaciones geográficamente periféricas de una especie de amplia distribución a menudo son el foco de conservación porque son raras localmente dentro de jurisdicciones políticas. Sin embargo, la ecología y genética de estas poblaciones son evaluadas poco frecuentemente en un contexto geográfico más amplio. La mayoría de las expectaciones relacionadas con la ecología y evolución de las poblaciones periféricas se derivan del modelo centro-abundante, que predice que las poblaciones periféricas son menos frecuentes, más pequeñas, menos densas y menor tasa reproductiva que poblaciones centrales. Probamos estas predicciones y al hacerlo evaluamos el valor de conservación de poblaciones periféricas de una especie de arbusto clonal (Vaccinium stamineum L., Ericaceae), que está enlistada como amenazada en Canadá. Con base en 51 poblaciones muestreadas del centro hacia los límites norteños de su distribución durante 2 años, la frecuencia y tamaño poblacional declinó hacia los límites de su distribución, pero la densidad de rametos aumentó. La reproducción sexual varió ampliamente entre las poblaciones y entre años, con muchas poblaciones produciendo muy pocas semillas, pero no declinó hacia los límites de su distribución. De hecho, la masa de semillas incrementó sostenidamente hacia los límites, y esto se asoció a una acelerada germinación y crecimiento de plántulas, lo cual puede ser adaptativo en ambientes norteños estacionales. Nuestros resultados no sustentaron la predicción de que la reproducción clonal es más prevaleciente en poblaciones periféricas o que contribuye antagónicamente a la amplia variación en la producción de semillas. Las poblaciones periféricas de V. stamineum son tan productivas como las poblaciones centrales y pueden estar adaptadas localmente a ambientes norteños. Esto enfatiza la importancia de una perspectiva geográfica amplia cuando se evalúa la ecología, evolución y conservación de poblaciones periféricas. [source]

Role of Corridors in Plant Dispersal: an Example with the Endangered Ranunculus nodif lorus

CONSERVATION BIOLOGY, Issue 2 2003
Florian Kirchner
But the few experimental studies supporting the usefulness of corridors have all concerned animal species. We investigated the role of corridors in seed dispersal, studying population genetic and demographic structure in metapopulations of the rare, pond-dwelling, autogamous plant species Ranunculus nodiflorus L. in the Fontainebleau Forest ( France ). Differentiation on three polymorphic isozyme markers was strong among local populations ( ponds ) within metapopulations ( sites ) and moderate among metapopulations. Partial Mantel tests revealed that the connection of ponds through temporarily flooded natural corridors, facilitating seed migration, had a strong negative effect on genetic differentiation between local populations and that a pond was more likely to be colonized when connected by corridors to other occupied ponds. Thus, corridors are probably a key element of landscape structure for metapopulation dynamics in R. nodiflorus. From a conservation perspective, our results suggest that corridors could increase the chance of persistence of plant species living in fragmented habitats by promoting seed dispersal between habitat patches. Resumen: La propuesta de que la migración de organismos entre parches de hábitat puede ser incrementada por corredores ha sido muy discutida en biología de la conservación. Pero los pocos estudios experimentales que apoyan la utilidad de los corredores han sido enfocados hacia especies de animales. Investigamos el papel de los corredores en la dispersión de semillas, estudiando la genética poblacional y la estructura demográfica en metapoblaciones de la especie de planta rara, autógama, habitante de estanques Ranunculus nodiflorus L. en el bosque Fontainebleau ( Francia ). La diferenciación de tres isozimas polimórficas marcadoras fue fuerte entre las poblaciones locales ( estanques ) dentro de metapoblaciones ( sitios ) y fue moderada entre metapoblaciones. Las pruebas parciales de Mantel revelaron que la conexión de estanques a través de corredores naturales inundados facilitando la migración de semillas, tuvo un efecto negativo fuerte en la diferenciación genética entre poblaciones locales y que un estanque fue más probable de ser colonizado cuando se conectaba por corredores con otros estanques ocupados. Por lo tanto, los corredores probablemente son un factor clave de la estructura del paisaje para dinámicas metapoblacionales en R. nodiflorus. Desde una perspectiva de conservación, nuestros resultados sugieren que los corredores podrían incrementar la probabilidad de persistencia de especies de plantas que viven en hábitats fragmentados al promover la dispersión de semillas entre parches de hábitats. [source]

The coumarin herniarin as a sensitizer in German chamomile [Chamomilla recutita (L.) Rauschert, Compositae]

CONTACT DERMATITIS, Issue 6 2010
Evy Paulsen
Background: Although German chamomile (Chamomilla recutita) is considered a weak sensitizer, recent studies have shown several possible non-sesquiterpene lactone allergens in tea (infusions) from the plant. Objective: The aim of this study was to report the results of patch testing with herniarin (7-methoxycoumarin), which is one of the possible coumarin allergens in chamomile. Patients/materials/methods: Between 1991 and 2009, selected patients with known or suspected Compositae contact allergy were patch tested with herniarin 1% petrolatum. Results: Among 36 patients tested, there was one positive and three doubtful positive reactions to herniarin. All 4 patients had a relevant contact allergy to German chamomile, whereas the majority of the remaining 32 patients had chamomile allergy of unknown relevance. Conclusions: The clinical results suggest that herniarin indeed is one of the non-sesquiterpene lactone sensitizers in German chamomile and that sensitization may occur through, for example, external use of chamomile tea or use of chamomile-containing topical herbal remedies. [source]

The evolution of depression and suicidality in first episode psychosis

ACTA PSYCHIATRICA SCANDINAVICA, Issue 3 2010
R. Upthegrove
Upthegrove R, Birchwood M, Ross K, Brunett K, McCollum R, Jones L. The evolution of depression and suicidality in first episode psychosis. Objective:, To have a clearer understanding of the ebb and flow of depression and suicidal thinking in the early phase of psychosis, whether these events are predictable and how they relate to the early course of psychotic symptoms. Method:, Ninety-two patients with first episode psychosis (FEP) completed measures of depression, including prodromal depression, self-harm and duration of untreated psychosis. Follow-up took place over 12 months. Results:, Depression occurred in 80% of patients at one or more phases of FEP; a combination of depression and suicidal thinking was present in 63%. Depression in the prodromal phase was the most significant predictor of future depression and acts of self-harm. Conclusion:, Depression early in the emergence of a psychosis is fundamental to the development of future depression and suicidal thinking. Efforts to predict and reduce depression and deliberate self-harm in psychosis may need to target this early phase to reduce later risk. [source]

Ultrastructural features of the process of wound healing after tail and limb amputation in lizard

ACTA ZOOLOGICA, Issue 3 2010
L. Alibardi
Abstract Alibardi, L. 2010. Ultrastructural features of the process of wound healing after tail and limb amputation in lizard.,Acta Zoologica (Stockholm) 91: 306,318 Wound healing and re-epitelization after amputation of tail and limb in lizard have been studied by electron microscopy to understand the cytological base of immunity to infection in this species. After 2 days post-amputation in both limb and tail stumps, numerous granulocytes are accumulated over the stump, and participate to the formation of the scab. Bacteria remain confined to the scab or are engulfed by leukocytes and migrating keratinocytes located underneath the scab. Bacteria are degraded within lysosomes present in these cells and are not observed among mesenchymal cells or in blood vessels of the regenerative blastema. Granulocytes, migrating keratinocytes, and later macrophages form an effective barrier responsible for limiting microbe penetration. The innate immunity in lizard is very effective in natural (dirty) condition and impedes the spreading of infection to inner tissues. While the complete re-epitelization of the tail stump underneath the scab requires 4,7 days, the same process in the limb requires 8,18 or more days post-amputation, depending from the level of amputation and the persistence of a protruding humerus or femurs on the stump surface. This delay produces the permanence of inflammatory cells such as granulocytes and macrophages in the limb stump for a much longer period than in the tail stump, a process that stimulates scarring. [source]

Autoradiographic observations on developing and growing claws of reptiles

ACTA ZOOLOGICA, Issue 2 2010
Lorenzo Alibardi
Abstract Alibardi, L. 2010. Autoradiographic observations on developing and growing claws of reptiles. ,Acta Zoologica (Stockholm) 91: 233,241 The present qualitative autoradiographic analysis aims to present the main features of morphogenesis and growth of claws in reptiles. Lizard embryos treated with tritiated thymidine reveal that epidermal cell proliferation in terminal digits is prevalent in the dorsal side and gives origin to the curved unguis of the claw. Less proliferation occurs in the ventral side of the digit tip where the concave sub-unguis is derived. Adult claws of a turtle show that thymidine-labelled cells are present along most of the epidermis of the claw, especially at the claw tip. Also, injection of tritiated histidine and proline, indicating active protein synthesis, confirm autoradiographic labelling along most of the epidermis of claws, in particular at the apical tip. The present study indicates that proximal matrix regions, as have been described in mammalian nails, are absent in reptiles. This pattern of claw growth probably derives from that of terminal digital scales. In fact reptilian (and avian) claws are formed from a modification of scales, a different condition from that present in mammals. [source]

A shortening of the manus precedes the attenuation of other wing-bone elements in the evolution of flightlessness in birds

ACTA ZOOLOGICA, Issue 1 2010
R. L. Nudds
Abstract Nudds, R. L. and Slove Davidson, J. 2010. A shortening of the manus precedes the attenuation of other wing-bone elements in the evolution of flightlessness in birds. ,Acta Zoologica (Stockholm) 91: 115,122 This is the first study to present evidence for a general pattern of wing-bone attenuation during the early stages of the evolution of flightlessness. A comparative analysis using phylogenetic independent contrasts showed that in families that contain both flighted (volant) and flightless species, the volant species have shorter wings and total-arm (humerus + ulna + manus) lengths relative to their body masses than the species within their wholly volant sister families. A shortening of the manus may typify the early stages of the evolution of flightlessness, with the humerus and ulna attenuating later, perhaps because of their role in maintaining the position of the aerodynamically important alula. A shorter wing relative to body mass was not the result of the inverse (i.e. heavier body mass relative to wing length) because mean body masses of volant members of flightless families were similar to or lower than those of their wholly volant sister families. Despite finding a common trend in the wing morphologies of volant members of flightless families, it seems unlikely that a general model of selection pressures driving the evolution of flightlessness exists. At the very least, a dichotomy between those birds that have lost the ability to fly in order to gain the ability to swim and terrestrial forms, may persist. [source]

Migratory connectivity in a declining bird species: using feather isotopes to inform demographic modelling

DIVERSITY AND DISTRIBUTIONS, Issue 4 2010
Thomas S. Reichlin
Abstract Aim, Conservation programmes for endangered migratory species or populations require locating and evaluating breeding, stopover and wintering areas. We used multiple stable isotopes in two endangered European populations of wrynecks, Jynx torquilla L., to locate wintering regions and assess the degree of migratory connectivity between breeding and wintering populations. Location, Switzerland and Germany. Methods, We analysed stable nitrogen (,15N), carbon (,13C) and hydrogen (,D) isotopes from wing feathers from two populations of wrynecks to infer their wintering origins and to assess the strength of migratory connectivity. We tested whether variation in feather isotopic values within the Swiss population was affected by bird age and collection year and then considered differences in isotopic values between the two breeding populations. We used isotopic values of summer- and winter-grown feathers to estimate seasonal distributions. Finally, we calculated a species-specific ,D discrimination factor between feathers and mean annual ,D values to assign winter-grown feathers to origin. Results, Bird age and collection year caused substantial isotopic variation in winter-grown feathers, which may be because of annually variable weather conditions, movements of birds among wintering sites and/or reflect asynchronous moulting or selection pressure. The large isotopic variance in winter-grown feathers nevertheless suggested low migratory connectivity for each breeding population, with partially overlapping wintering regions for the two populations. Main conclusions, Isotopic variance in winter-grown feathers of two breeding populations of wrynecks and their geographical assignment point to defined, albeit overlapping, wintering areas, suggesting both leapfrog migration and low migratory connectivity. On this basis, integrative demographic models can be built looking at seasonal survival patterns with links to local environmental conditions on both breeding and wintering grounds, which may elucidate causes of declines in migratory bird species. [source]

Landscape composition influences patterns of native and exotic lady beetle abundance

DIVERSITY AND DISTRIBUTIONS, Issue 4 2009
M. M. Gardiner
Abstract Aim, Coccinellid beetles are important predators that contribute to pest suppression in agricultural landscapes. Since the introduction of the exotic coccinellids Coccinella septempunctata L. and Harmonia axyridis Pallas into the USA, several studies have reported a decline of native Coccinellidae in agroecosystems. We aimed to investigate the influence of landscape composition on native and exotic coccinellid abundance within soybean fields. Location, Iowa, Michigan, Minnesota and Wisconsin. Methods, As part of a 2-year study (2005,06) on the biological control of the soybean aphid, Aphis glycines Matsumura, we examined coccinellid communities in 33 soybean fields using yellow sticky card traps. Landscape heterogeneity and composition were measured at multiple spatial scales ranging 1,3.5 km from focal soybean fields where coccinellid sampling took place. Results, Exotic species made up 90% of the total coccinellid community in Michigan soybean fields followed by Wisconsin (84%), Minnesota (66%) and Iowa (57%). Harmonia axyridis was the dominant exotic coccinellid in all states comprising 45,62% of the total coccinellid community, followed by C. septempunctata (13,30%). Two additional exotic species, Hippodamia variegata (Goeze) and Propylea quatuordecimpunctata (L.) were also found in the region. Overall, the most abundant native coccinellid was Hippodamia convergens Guerin-Meneville; however, its abundance varied across the region, comprising 0% (Michigan) to 28% (Iowa) of the total coccinellid community. Landscape structure significantly influenced the composition of coccinellid communities in soybean agroecosystems. We found that native coccinellids were most abundant in low-diversity landscapes with an abundance of grassland habitat while exotic coccinellids were associated with the abundance of forested habitats. Main conclusion, We propose that grassland dominated landscapes with low structural diversity and low amounts of forested habitat may be resistant to exotic coccinellid build-up, particularly H. axyridis and therefore represent landscape-scale refuges for native coccinellid biodiversity. [source]

Grazing and community structure as determinants of invasion success by Scotch broom in a New Zealand montane shrubland

DIVERSITY AND DISTRIBUTIONS, Issue 1 2003
P. J. Bellingham
Abstract. Scotch broom (Cytisus scoparius (L.) Link; Fabaceae) is a problematic invasive plant in many countries, and while attention has been paid to traits that make it a successful invader, there has been less focus on the properties of ecosystems that it invades. We conducted an experiment in a New Zealand montane shrubland with tussock grasses that has been invaded by Scotch broom to determine features that rendered it susceptible to invasion. We planted broom seedlings into the shrubland (control) and into three treatments: (1) resident shrubs removed, (2) tussocks removed and (3) shrubs and tussocks removed. We measured broom seedling mortality and growth over two growing seasons. The site was grazed by sheep in the first season, and scarcely grazed in the second, wetter season. Survivorship across all treatments after 19 months was 42%, and was lowest where shrubs were retained but tussocks removed. Broom seedlings grew taller and had greater leaf areas in treatments that retained shrubs. Neighbouring (within 49 cm) shrubs had no effects on survivorship or growth of broom seedlings. Neighbouring tussocks increased survivorship of broom seedlings but depressed their growth. Grazing by sheep was the most important determinant of survivorship and growth of broom seedlings, and effects were uniform regardless of experimental treatments. Initial high mortality of seedlings (48% in the first 3 months) was due to grazing, and height growth was often negative during periods of grazing. In the second growing season when the site was less grazed and there was greater rainfall, there was a rapid increase in height across all treatments. Continued grazing of the site by sheep is likely to be the chief means of retarding the invasion. [source]

Spatial, environmental and human influences on the distribution of otter (Lutra lutra) in the Spanish provinces

DIVERSITY AND DISTRIBUTIONS, Issue 3 2001
Ana Márcia Barbosa
Abstract In a previous survey of otters (Lutra lutra L. 1758) in Spain, different causes were invoked to explain the frequency of the species in each province. To find common causes of the distribution of the otter in Spain, we recorded a number of spatial, environmental and human variables in each Spanish province. We then performed a stepwise linear multiple regression of the proportion of positive sites of otter in the Spanish provinces separately on each of the three groups of variables. Geographic longitude, January air humidity, soil permeability and highway density were the variables selected. A linear regression of the proportion of otter presence on these variables explained 62.4% of the variance. We then used the selected variables in a partial regression analysis to specify which proportions of the variation are explained exclusively by spatial, environmental and human factors, and which proportions are attributable to interactions between these components. Pure environmental effects accounted for only 5.5% of the variation, while pure spatial and pure human effects explained 18% and 9.7%, respectively. Shared variation among the components totalled 29.2%, of which 10.9% was explained by the interaction between environmental and spatial factors. Human factors explained globally less variance than spatial and environmental ones, but the pure human influence was higher than the pure environmental one. We concluded that most of the variation in the proportion of occurrences of otter in Spanish provinces is spatially structured, and that environmental factors have more influence on otter presence than human ones; however, the human influence on otter distribution is less structured in space, and thus can be more disruptive. This effect of large infrastructures on wild populations must be taken into account when planning large-scale conservation policies. [source]

Effects of physical disturbance and granivory on establishment of native and alien riparian trees in Colorado, U.S.A.

DIVERSITY AND DISTRIBUTIONS, Issue 1-2 2001
Gabrielle L. Katz
In western North America, the alien Elaeagnus angustifolia L. invades riparian habitats usually dominated by pioneer woody species such as Populus deltoides Marshall ssp. monilifera (Aiton) Eckenwalder. We conducted manipulative field experiments to compare the importance of physical disturbance and granivory for seedling establishment of these two species. We planted seeds of both species in disturbed and undisturbed study plots, and used exclosures, seed dish trials and live-trapping to assess the role of granivory. Seedling establishment of both species was increased by physical disturbance and seeds of both species were subject to granivory. However, the relative importance of these two factors differed between species. For P. deltoides, lack of physical disturbance prevented seedling establishment in uncleared subplots, but granivory did not prevent seedling establishment outside of exclosures. For E. angustifolia, granivory prevented seedling establishment outside of exclosures, but lack of physical disturbance did not prevent establishment in uncleared subplots. The lesser dependence on disturbance may enable E. angustifolia to invade areas characterized by low levels of fluvial disturbance, such as floodplains along regulated rivers, where P. deltoides recruitment does not occur. Populations of granivorous rodents may affect the susceptibility of riparian ecosystems to invasion by E. angustifolia. [source]

A PCA-based modelling technique for predicting environmental suitability for organisms from presence records

DIVERSITY AND DISTRIBUTIONS, Issue 1-2 2001
M. P. Robertson
We present a correlative modelling technique that uses locality records (associated with species presence) and a set of predictor variables to produce a statistically justifiable probability response surface for a target species. The probability response surface indicates the suitability of each grid cell in a map for the target species in terms of the suite of predictor variables. The technique constructs a hyperspace for the target species using principal component axes derived from a principal components analysis performed on a training dataset. The training dataset comprises the values of the predictor variables associated with the localities where the species has been recorded as present. The origin of this hyperspace is taken to characterize the centre of the niche of the organism. All the localities (grid-cells) in the map region are then fitted into this hyperspace using the values of the predictor variables at these localities (the prediction dataset). The Euclidean distance from any locality to the origin of the hyperspace gives a measure of the ,centrality' of that locality in the hyperspace. These distances are used to derive probability values for each grid cell in the map region. The modelling technique was applied to bioclimatic data to predict bioclimatic suitability for three alien invasive plant species (Lantana camara L., Ricinus communis L. and Solanum mauritianum Scop.) in South Africa, Lesotho and Swaziland. The models were tested against independent test records by calculating area under the curve (AUC) values of receiver operator characteristic (ROC) curves and kappa statistics. There was good agreement between the models and the independent test records. The pre-processing of climatic variable data to reduce the deleterious effects of multicollinearity, and the use of stopping rules to prevent overfitting of the models are important aspects of the modelling process. [source]

The use of drug detection dogs in Sydney, Australia

DRUG AND ALCOHOL REVIEW, Issue 6 2009
MATTHEW DUNN
Abstract Introduction and Aims. At present there is little research into the use of drug detection dogs. The present study sought to explore the use of detection dogs in Sydney, Australia, utilising multiple data sources. Design and Methods. Data were taken from interviews with 100 regular ecstasy users and 20 key experts as part of the 2006 New South Wales arm of the Ecstasy and Related Drugs Reporting System, and secondary data sources. Results. The majority of regular ecstasy users reported taking some form of precaution if made aware that dogs would be at an event they were attending. A small proportion of the sample reported consuming their drugs when coming into contact with detection dogs. One group of key experts viewed the use of detection dogs as useful; one group disliked the use of detection dogs though cooperated with law enforcement when dogs were used; and one group considered that detection dogs contribute to greater harm. Secondary data sources further suggested that the use of detection dogs do not significantly assist police in identifying and apprehending drug suppliers. Discussion and Conclusions. The present study suggests that regular ecstasy users do not see detection dogs as an obstacle to their drug use. Future research is necessary to explore in greater depth the experiences that drug users have with detection dogs; the effect detection dogs may have on deterring drug consumption; whether encounters with detection dogs contribute to drug-related harm; and the cost,benefit analysis of this law enforcement exercise. [Dunn M, Degenhardt L. The use of drug detection dogs in Sydney, Australia. Drug Alcohol Rev 2009] [source]

Light and scanning microscopic studies of integument differentiation in the grass snake Natrix natrix L. (Lepidosauria, Serpentes) during embryogenesis

ACTA ZOOLOGICA, Issue 1 2009
Elwira Swad
Abstract We analysed the differentiation of body cover in the grass snake (Natrix natrix L.) over the full length of the embryo's body at each developmental stage. Based on investigations using both light and scanning electron microscopes, we divided the embryonic development of the grass snake integument into four phases. The shape of the epidermal cells changes first on the caudal and ventral parts of the embryo, then gradually towards the rostral and dorsal areas. In stage V on the ventral side of the embryo the gastrosteges are formed from single primordia, but on the dorsal side the epidermis forms the scale primordia in stage VII. This indicates that scalation begins on the ventral body surface, and spreads dorsally. The appearance of melanocytes between the cells of the stratum germinativum in stage VII coincides with changes in embryo colouration. The first dermal melanocytes were detected in stage XI so in this stage the definitive skin pattern is formed. In the same stage the epidermis forms the first embryonic shedding complex and the periderm layer begins to detach in small, individual flakes. This process coincides with rapid growth of the embryos. [source]

Functional morphology of the postpharyngeal gland of queens and workers of the ant Monomorium pharaonis (L.)

ACTA ZOOLOGICA, Issue 2 2006
Dieter Eelen
Abstract Eelen D., Børgesen L.W. and Billen J. 2006. Functional morphology of the postpharyngeal gland of queens and workers of the ant Monomorium pharaonis (L.). ,Acta Zoologica (Stockholm) 87: 101,111 The postpharyngeal gland (PPG) is unique to ants and is the largest exocrine gland in their head. In queens of the pharaoh's ant, Monomorium pharaonis, the gland contains approximately 15 finger-like epithelial extensions on each side and opens dorsolaterally in the posterior pharynx. In these ants the PPG morphology varies considerably according to age and mating status. The epithelial thickness increases with age and reaches a maximum at 3 weeks in both virgin and mated queens. A considerable expansion of the lumen diameter occurs in both groups between 4 and 7 days. Virgin queens release their secretion into the gland lumen from an age of 7 days, whereas mated queens accumulate large amounts of secretion in their epithelium. The increasing epithelial thickness, together with the increasing lumen diameter, the presence of numerous inclusions in the epithelium and the release of secretion, are indicative for increasing gland activity. The gland ultrastructure indicates involvement in lipid metabolism and de novo synthesis of lipids. The PPG of workers consists of 12 finger-like tubes at each side. There is a significant difference in epithelial thickness between nurses and repletes and between nurses and foragers. We suggest the PPG serves different purposes in pharaoh's ants: it is likely that the PPG of workers and virgin queens is used to feed larvae. In mated queens the gland probably plays a role in providing the queen with nutritious oils for egg production. The PPG may also function in signalling species nestmate and caste identity, as well as in the reproductive capacity of the queens. [source]

Dendrogeomorphic reconstruction of past debris-flow activity using injured broad-leaved trees

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2010
Estelle Arbellay
Abstract Tree-ring records from conifers have been regularly used over the last few decades to date debris-flow events. The reconstruction of past debris-flow activity was, in contrast, only very rarely based on growth anomalies in broad-leaved trees. Consequently, this study aimed at dating the occurrence of former debris flows from growth series of broad-leaved trees and at determining their suitability for dendrogeomorphic research. Results were obtained from gray alder (Alnus incana (L.) Moench), silver birch and pubescent birch (Betula pendula Roth and Betula pubescens Ehrh.), aspen (Populus tremula L.), white poplar, black poplar and gray poplar (Populus alba L., Populus nigra L. and Populus x canescens (Ait.) Sm.), goat willow (Salix caprea L.) and black elder (Sambucus nigra L.) injured by debris-flow activity at Illgraben (Valais, Swiss Alps). Tree-ring analysis of 104 increment cores, 118 wedges and 93 cross-sections from 154 injured broad-leaved trees allowed the reconstruction of 14 debris-flow events between AD 1965 and 2007. These events were compared with archival records on debris-flow activity at Illgraben. It appears that debris flows are very common at Illgraben, but only very rarely left the channel over the period AD 1965,2007. Furthermore, analysis of the spatial distribution of disturbed trees contributed to the identification of six patterns of debris-flow routing and led to the determination of preferential breakout locations of events. The results of this study demonstrate the high potential of broad-leaved trees for dendrogeomorphic research and for the assessment of the travel distance and lateral spread of debris-flow surges. Copyright © 2010 John Wiley & Sons, Ltd. [source]

The male postabdomen of Stolotermes inopinus: a termite with unusually well-developed external genitalia (Dictyoptera: Isoptera: Stolotermitinae)

ACTA ZOOLOGICA, Issue 2 2000
Klaus-Dieter Klass
Abstract Klass, K.-D., Thorne, B. L. and Lenz, M. 2000. The male postabdomen of Stolotermes inopinus: a termite with unusually well-developed external genitalia (Dictyoptera: Isoptera: Stolotermitinae). ,Acta Zoologica (Stockholm) 81: 121,130 Stolotermes inopinus has large external male genitalia (phallic lobe), which contrast with the small genital papillae or lack of external genitalia of other Isoptera. As in the genital papilla of Mastotermesdarwiniensis, a ventral sclerite pair is present, the gonopore is located ventroterminally on the phallic lobe, and the genital area is entirely symmetrical , suggesting that this may be the groundplan condition of Isoptera. The relations of the phallic lobe to surrounding components like the subgenital plate, paraprocts, and certain muscles and nerves indicate that the lobe of S. inopinus is homologous with the phallomeres of other Dictyoptera. The bilateral symmetry and simple structure, however, are in strong contrast to the asymmetry and high complexity found in male genitalia of Blattaria and Mantodea. The postabdominal nervous system of S. inopinus resembles that of the cockroach Periplaneta americana. Indications are given that the Stolotermitinae are related to the Kalotermitidae, Rhinotermitidae, and Termitidae rather than to the Termopsinae. [source]

Direct and indirect effects of the introduced toad Bufo marinus (Anura: Bufonidae) on populations of native anuran larvae in Australia

ECOGRAPHY, Issue 3 2000
Michael R. Crossland
Introduced species are frequently believed to have adverse effects on native biota and ecosystems. However, much of our knowledge of the ecological impacts of introduced species is anecdotal, and the mechanisms controlling these effects are often poorly understood. I used replicated artificial pond experiments to investigate the impact of eggs and hatchlings of the introduced toad Bufo marinus on populations of native anuran larvae (Limnodynastes ornatus and Litoria rubella) in Australia. Bufo marinus eggs and hatchlings are highly toxic to predatory native tadpoles. Under naturalistic conditions, populations of predatory L. ornatus tadpoles experienced significantly reduced survival when exposed to Bufo eggs and hatchlings. The impact of Bufo on L. ornatus survival was positively correlated with Bufo density. However, the toxic effects of Bufo on L. ornatus indirectly facilitated the survival of later-breeding L. rubella by altering predator-prey interactions between L. ornatus and L. rubella. Limnodynastes ornatus tadpoles are voracious predators of L. rubella eggs and hatchlings. Consequently, the negative impact of Bufo on populations of L. ornatus tadpoles reduced the intensity of predation by L. ornatus tadpoles on L. rubella eggs and hatchlings, thereby increasing L. rubella survival. The results demonstrate that B. marinus plays an important role in structuring native larval anuran communities via direct and indirect mechanisms, and that Bufo may have both negative and positive effects on populations of native anuran larvae. As far as I am aware, these are the first quantitative data to demonstrate that introduced fauna may affect populations of native biota via toxic effects. [source]

Inter- and intraspecific variation of stemflow production from Fagus grandifolia Ehrh. (American beech) and Liriodendron tulipifera L. (yellow poplar) in relation to bark microrelief in the eastern United States,

ECOHYDROLOGY, Issue 1 2010
J. Toland Van Stan II
Abstract Stemflow is a spatially concentrated hydrologic input at the tree base. Prior work has documented the differential effects of stemflow from a wide range of plant species on ecohydrological processes, such as the alteration of soil pH and spatial patterning of understory vegetation. No known work has coupled stemflow yield with high resolution measurements of bark microrelief that definitively ascribe differential stemflow yield to bark microrelief. As such, our research objectives were to: (1) correlate inter- and intraspecific variation in stemflow yield to a quantitative bark microrelief scale and (2) compare and contrast stemflow for two co-occurring deciduous species,Fagus grandifolia Ehrh. (American beech) and Liriodendron tulipifera L. (yellow poplar). Using a newly developed instrument to measure bark microrelief, namely the LaserBarkÔ automated tree measurement system, in combination with an 11-month stemflow database for a broadleaved deciduous forest in eastern North America, it was found that bark microrelief values significantly differed between the two species [P = 0·000, F (1,19) = 49·32]. Funneling ratios [P = 0·000, H (1, 990) = 339·20] and stemflow generation [P = 0·000, H (1, 990) = 146·75] also significantly differed between the two species. Our results indicate that bark microrelief exerts a considerable effect on stemflow yield from F. grandifolia and L. tulipifera, possibly affecting water and solute flux to the forest floor. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Phenology determines seasonal variation in ectoparasite loads in a natural insect population

ECOLOGICAL ENTOMOLOGY, Issue 4 2010
CHRISTOPHER HASSALL
1. The extent to which individuals are parasitised is a function of exposure to parasites and the immune response, which in ectotherms may be associated with temperature. 2. We test the hypothesis that seasonal variation in ectoparasite burden is driven by temperature using an extensive mark-release-recapture study of adult Coenagrion puella (L.) (Zygoptera) as a model system. Mite counts were taken both at capture and on a subset of subsequent recaptures over two entire, consecutive breeding seasons. 3. Emergence date was the most significant factor in determining individual differences in mite burden, and mean counts for individuals emerging on the same days showed strong unimodal relationships with time of season. Subsequent recounting of mites on a subset of individuals showed that patterns of loss of mites were similar between seasons. 4. While temperature did not significantly affect mite burdens within seasons and ectoparasite prevalence was very similar across the two seasons, intensity of infection and rate of mite gain in unparasitised individuals were significantly higher in the cooler season. 5. We demonstrate that, while temperature may modulate the invertebrate immune response, this modulation does not manifest in variations in mite burdens in natural populations. [source]

Post-gall induction performance of Adelges Abietis (L.) (Homoptera: Adelgidae) is influenced by clone, shoot length, and density of colonising gallicolae

ECOLOGICAL ENTOMOLOGY, Issue 1 2010
LEAH FLAHERTY
1. We evaluated the effect of clone (one susceptible and one resistant clone), shoot length, crown level, and gallicola density on post-gall induction performance of Adelges abietis. Galls that had been successfully induced by one fundatrix on a range of shoot sizes were selected, and the number of gallicolae that could colonise the gall was manipulated. 2. Post-induction gall development success was inversely related to shoot length and was higher on the susceptible clone than on the resistant clone. As gallicola density did not influence the proportion of galls that successfully completed development, reduced post-induction gall development on large shoots was not likely to be result of an insufficient stimulus from gallicolae. 3. Clone was the only factor that significantly influenced gall volume and galls were larger on the susceptible clone than on the resistant clone. As gall volume did not increase when more gallicolae attempted to colonise a gall, competition within a gall increased. Gallicola survival was inversely related to the number of colonising gallicolae. Our results suggest that gall size may be limiting at natural densities. 4. Previous studies report positive relationships between gall induction success and fundatrix density, and between gall size and fundatrix density. As each fundatrix produces one egg mass of gallicolae, this study suggests that there may be a trade-off between the successful induction of a large gall and subsequent survival of gallicolae. 5. In the present study, clone influenced all measures of post-gall induction performance. Performance was always higher on the susceptible than on the resistant clone. [source]

Dropping behaviour of larvae of aphidophagous ladybirds and its effects on incidence of intraguild predation: interactions between the intraguild prey, Adalia bipunctata (L.) and Coccinella septempunctata (L.), and the intraguild predator, Harmonia axyridis Pallas

ECOLOGICAL ENTOMOLOGY, Issue 2 2005
Satoru Sato
Abstract., 1.,Two experiments were performed in the laboratory to assess the behaviour of dropping from a host plant as a defence against intraguild predation in aphidophagous ladybird larvae. 2.,In the first experiment, encounters were observed on bean plants between fourth instars of the intraguild predator species, Harmonia axyridis, and first instars of two other ladybird species, Adalia bipunctata (L.) and Coccinella septempunctata (L.). The percentages of first instars of the latter two species that dropped from the plant in response to attack differed dramatically, with 47.5% of C. septempunctata first instars dropping vs. 0% of A. bipunctata. 3.,In the second experiment, first instars of A. bipunctata or C. septempunctata and a fourth instar of H. axyridis were allowed to forage together on bean plants for 3 h. During this time, 44.3% of C. septempunctata larvae dropped from the plant, but less than 2% of A. bipunctata larvae did so. In contrast, 95.0% of A. bipunctata larvae fell victim to intraguild predation by H. axyridis vs. only 54.5% of C. septempunctata larvae. 4.,The significance of dropping behaviour of ladybird larvae as a defence against intraguild predation, and the relationship of dropping behaviour to species-specific habitat affinity of ladybirds, is discussed. [source]

Tracking larval insect movement within soil using high resolution X-ray microtomography

ECOLOGICAL ENTOMOLOGY, Issue 1 2004
Scott N. Johnson
Abstract., 1. In contrast to above-ground insects, comparatively little is known about the behaviour of subterranean insects, due largely to the difficulty of studying them in situ. 2. The movement of newly hatched (neonate) clover root weevil (Sitona lepidus L. Coleoptera: Curculinidae) larvae was studied non-invasively using recently developed high resolution X-ray microtomography. 3. The movement and final position of S. lepidus larvae in the soil was reliably established using X-ray microtomography, when compared with larval positions that were determined by destructively sectioning the soil column. 4. Newly hatched S. lepidus larvae were seen to attack the root rhizobial nodules of their host plant, white clover (Trifolium repens L.). Sitona lepidus larvae travelled between 9 and 27 mm in 9 h at a mean speed of 1.8 mm h,1. 5. Sitona lepidus larvae did not move through the soil in a linear manner, but changed trajectory in both the lateral and vertical planes. [source]

Impact of avian and arthropod predation on lepidopteran caterpillar densities and plant productivity in an ephemeral agroecosystem

ECOLOGICAL ENTOMOLOGY, Issue 5 2003
Cerruti R. R. Hooks
Abstract., 1.,Most studies evaluating the combined impact of spiders and other predators on herbivore densities in agroecosystems have focused primarily on their trophic connections with invertebrate predators (e.g. carabids, chrysopids); however linkages among spiders and vertebrate predators may also help structure the population dynamics of insect herbivores. A field experiment was conducted to examine the impact of avian and spider predation on lepidopteran caterpillar densities and plant productivity within a Brassica agroecosystem. 2.,Arthropod abundance, leaf-chewing damage, and final plant productivity associated with broccoli, Brassica oleracea L. (var. italica), were recorded for four treatments: (1) bird present but spiders removed; (2) both birds and spiders present; (3) birds excluded, spiders present; and (4) birds and spiders both excluded. 3.,Densities of Artogeia rapae L. (Lepidoptera: Pieridae) and Trichoplusia ni Hübner (Lepidoptera: Noctuidae) large caterpillars and post feeding stages were reduced significantly by bird predation. The abundance of large caterpillars was also reduced on spider-inhabited plants during early plant growth; however the assemblage of birds and spiders did not suppress caterpillar densities more significantly than either predator alone. 4.,Plants protected by birds, spiders, and birds plus spiders sustained less folivory attributable to leaf chewing caterpillars than check plants. Plant productivity was also greater for predator-protected plants than check plants. 5.,Although spiders and parasitoids were responsible for some of the mortality inflicted upon lepidopteran caterpillars, it was concluded that in this study system, birds are the most important natural enemies of folivores. [source]

Host shifting by Operophtera brumata into novel environments leads to population differentiation in life-history traits

ECOLOGICAL ENTOMOLOGY, Issue 5 2003
Adam J. Vanbergen
Abstract., 1. Operophtera brumata L. (Lepidoptera: Geometridae), a polyphagous herbivore usually associated with deciduous trees such as oak Quercus robur L., has expanded its host range to include the evergreen species heather Calluna vulgaris (L.) Hull and, most recently, Sitka spruce Picea sitchensis (Bong.) Carrière. 2. Phenology, morphology, and survival of O. brumata were measured at several life-history stages in populations from the three different host plant communities sampled from a range of geographical locations. The data were used to test for population differences, reflecting the marked differences in host-plant secondary chemistry, growth form, and site factors such as climate. The hypothesis that spruce-feeding populations originated from populations feeding on moorland, commonly sites of coniferous afforestation, was also tested. 3. Altitude, not host plant species, was the major influence on the timing of adult emergence. An effect of insect population independent of altitude was found, implying that additional unidentified factors contribute to this phenological variation. Larval survival and adult size varied between populations reared on different host plant species. Survival of larvae was affected negatively when reared on the novel host plant, Sitka spruce, versus the natal plant (oak or heather) but oak and heather-sourced insects did not differ in survivorship on Sitka spruce. 4. Host range extension into novel environments has resulted in population differentiation to the local climate, demonstrating that host shifts pose challenges to the herbivore population greater than those offered by the host plant alone. The hypothesis that Sitka spruce feeding populations have arisen predominantly from moorland feeding populations was not supported. [source]

Clutch size in frugivorous insects as a function of host firmness: the case of the tephritid fly Anastrepha ludens

ECOLOGICAL ENTOMOLOGY, Issue 3 2003
Francisco Díaz-Fleischer
Abstract. 1.,Optimal clutch size theory predicts that individuals will oviposit the number of eggs that increases their fitness. In Anastrepha ludens Loew (Diptera: Tephritidae), females oviposit larger clutches in unripe (firm) fruits than in ripe (soft) fruits. The following hypotheses were tested: (1) Using fruit firmness as an indicator of fruit quality, A. ludens females vary the number of eggs per clutch every time they reach an oviposition decision. (2) Maximising offspring survival with respect to either unripe or ripe fruit requires placing large clutches in firm fruit and smaller clutches in soft fruit. 2.,Agar spheres were used as artificial hosts. Three agar concentrations resulted in three degrees of firmness. Mango fruits Mangifera indica L. served as natural hosts. Ripe and unripe fruits were used to test soft and firm host conditions respectively. Females laid significantly larger clutches in the firmer artificial hosts than in the softer hosts. They also laid significantly more eggs in artificial hosts without sugar than in hosts with sugar. Firm (unripe) mangoes also received significantly larger clutches than soft (ripe) mangoes. 3.,When an individual female was first presented with a firm artificial host, it laid a large clutch. If subsequently offered a soft host, the female laid a significantly smaller clutch. Finally, if again offered a firm host, clutch size was increased significantly. 4.,Possible trade-offs in offspring fitness were explored in ripe and unripe mangoes by measuring offspring egg-to-adult survival, pupal weight, mean adult longevity, and fecundity. Despite the fact that larval survival was greater in soft fruit than in firm fruit, parameters such as pupal weight, mean longevity, and fecundity of adults stemming from both fruit types did not differ significantly. 5.,A probable trade-off between high offspring mortality caused by host unsuitability and low offspring and adult mortality caused by parasitism and predation is discussed as the reason for the exploitation of sub-optimal hosts. [source]

Movement of two grassland butterflies in the same habitat network: the role of adult resources and size of the study area

ECOLOGICAL ENTOMOLOGY, Issue 2 2003
Christine Schneider
Abstract. 1., Movement patterns of two butterfly species (meadow brown Maniola jurtina L. and scarce copper Lycaenae virgaureae L.) were studied in a 172 ha area within a landscape with a high percentage of suitable habitats for mark,release,recapture experiments. 2., Adult resource density, but not patch size or larval food plant abundance, influenced the numbers and the fractions of residents, emigrants, and immigrants. 3., Differences between species were observed in movement frequency and maximum distances moved but not in mean distances moved. 4., The scarce copper showed much greater movement ability than expected from the results of published studies. This is believed to be a result of the comparatively large size of the study area and the high cover of suitable habitat (>50%). 5., The mean and maximum distances travelled by butterflies reflected differences in the size of the study area. [source]

Using age grading by wing injuries to estimate size-dependent adult survivorship in the field: a case study of the yellow dung fly Scathophaga stercoraria

ECOLOGICAL ENTOMOLOGY, Issue 5 2002
Dieter U. Burkhard
Abstract 1. Studies of natural selection depend on estimates of longevity and mortality in the wild. In small and mobile species such as insects, direct, mark,recapture (resight), studies are difficult to perform because individuals cannot be tracked easily. 2. It was investigated whether age grading based on wing injuries alone can be used to estimate size-specific survivorship in the field in the yellow dung fly Scathophaga stercoraria (L.) (Diptera: Scathophagidae). 3. The accumulation of different types of wing injury throughout the spring and autumn flight seasons for both sexes was recorded: tears, notches (both reflecting regular wear), and large missing areas (probably due to intra- and inter-specific interactions). 4. Female longevity increased with body size in both spring and autumn, whereas male longevity increased slightly with size in spring but decreased in autumn. 5. The two sexes and males of different size classes accumulated the various types of wing injury differentially, presumably due to differential patterns of intraspecific interactions. Additionally, body size exhibited a seasonal pattern, complicating interpretation of the relationship between body size and wing injuries. 6. It is therefore concluded that estimating adult viability selection on body size using wing injuries is problematic in dung flies, and potentially also in other species. It is suggested that before this method is applied in any particular species, pilot studies should be conducted to verify whether wing injuries accumulate equally in all classes of individuals of interest. In addition, it is necessary to investigate the causes of different types of wing injury. [source]

Gamete production and sexual size dimorphism in an insect (Orchesella cincta) with indeterminate growth

ECOLOGICAL ENTOMOLOGY, Issue 2 2002
G. Ernsting
Abstract 1. The relationship of growth and body size with reproductive effort in animal species has been studied much less for males than for females. This imbalance applies to Orchesella cincta (L.) (Collembola), an insect with indeterminate growth, in which egg production is related positively to body size and negatively to growth. 2. To allow a comparison of the reproductive effort of male and female O. cincta, development and growth in immature stages of both sexes, and growth and spermatophore production for adult males were studied. 3. Embryonic development time and hatchling size did not differ between prospective males and females, but from hatching on the trajectories diverged, with males growing more slowly and maturing earlier and at a much smaller body size than females. 4. Neither the number of spermatophores deposited in the first adult instar (= inter-moult period) nor the total number of spermatophores deposited during seven instars was related to body size or growth. 5. Differences in growth rate between instars with and without spermatophore deposition indicated that the physiology of spermatophore production inhibits growth, which, however, was compensated for during the next instar. 6. The difference in the relationship of gamete production with body size and growth between males and females explains the divergence of their size at maturity. [source]