bluuebunny/crossref_metadata_2025 huggingface dataset:
Constraints on the reproductive value of vertical transmission for a microsporidian parasite and its female‐killing behaviour
Authors: Agnew Philip , Koella Jacob C.
Published: March 2003

1. Several species of microsporidian parasites use a mixture of vertical and horizontal transmission among their respective mosquito host species. These relationships vary in how hosts are exploited for either vertical or horizontal transmission. An important factor is that only females can provide vertical transmission. Two types of relationship have particularly been contrasted; those where vertically infected larvae of both sexes are killed late in their development and contribute towards the parasite's horizontal transmission, and those where only male larvae are killed while females experience benign infections, become adults, and contribute towards the parasite's vertical transmission success. The selective killing of males in these latter relationships leads to female‐biased adult sex ratios. These differences among relationships have been suggested to depend on the environmental conditions they experience and on the relative efficiency of vertical or horizontal transmission.

2. The transmission behaviour of the microsporidian parasiteEdhazardia aedis(Becnel, Fukuda & Sprague) following vertical transmission was studied as a function of larval food availability to its host, the mosquitoAedes aegypti(L.). The number of vertically infected mosquitoes dying before reaching adulthood increased as larval food availability became less. However, proportionately more females died as food availability decreased and adult mosquito populations became increasingly male‐biased.

3. The fate of vertically infected mosquitoes was closely related to their larval growth rate. As food availability decreased and larval growth rates slowed, the parasite's infection had more time to produce its spores and induce the host's mortality before emergence. This disproportionately affected female mosquitoes as they pupate later than males, especially as larval growth rates slow. As late ages at pupation are associated with smaller adult size (≈ lower fecundity), the potential vertical transmission offered by slowly growing female larvae is limited and more success may be gained by exploiting them for horizontal transmission.

4. Our results indicate that the relative reproductive value of vertical or horizontal transmission altered with an ecological parameter (larval food availability). Constraints in the life‐history traits of each organism helped to explain why the observed sex ratio was biased towards males rather than females.
Alternative perspectives on consumer–resource dynamics: a reply to Ginzburg
Authors: Berryman Alan A.
Published: March 2003

1.
Ginzburg (1998) proposes that models of predator–prey interactions should conform to what he calls the ‘biomass conversion principle’, that consumer reproduction should be directly linked to resource consumption.

2. I argue that consumer–resource models can be built from two different perspectives – biomass conversion or individual survival – and that, as Ginzburg's principle only applies to the first, it should not be used to judge the plausibility of individual survival models.

3. I also suggest that a failure to understand and preserve the distinction between biomass consumption and individual survival may be responsible for much of the confusion and controversy in predator–prey theory.
A method for validating stochastic models of population viability: a case study of the mountain pygmy‐possum (Burramys parvus)
Authors: McCarthy Michael A. , Broome Linda S.
Published: March 2003

1. A method of validating stochastic models of population viability is proposed, based on assessing the mean and variance of the predicted population size.

2. The method is illustrated with a model of the population dynamics of the mountain pygmy‐possum (Burramys parvus Broom 1895), based on annual census data collected from a single population in the Snowy Mountains of New South Wales, Australia between 1986 and 1997. The model incorporates density‐dependence in survivorship and recruitment, and demographic and environmental stochasticity.

3. The model appeared to make reasonable predictions for the three populations that were used for validation, provided the equilibrium population size was estimated accurately. This may require that differences in habitat quality between populations be taken into account.

4. Following validation, the model was given new parameters using the additional data from the three populations, and the risk of population decline within the next 100 years was assessed. Although populations as small as 15 females are predicted to be relatively safe from extinction caused by stochastic processes, B. parvus appears vulnerable to loss of habitat and reductions in the population growth rate.

5. The approach used in this paper is one of few attempts to validate a model of population viability using field data, and demonstrates that some aspects of stochastic population models can be tested.
When time is of the essence: choosing a currency for prey‐handling costs
Authors: Rovero Francesco , Hughes Roger N. , Chelazzi Guido
Published: March 2003

1. Heartbeat rate was measured in shore crabs Carcinus maenas (L.) feeding on mussels Mytilus edulis L. in order to estimate the energetic cost of handling prey and to assess the relative importance of energy and time as costing currencies.

2. Energetic handling costs represented approximately 2% of corresponding gains.

3. The tendency of profitability (gain per unit handling time) to increase with prey size was weakened by including energetic handling costs.

4. Time was judged to be a more appropriate currency than energy for costing prey‐handling behaviour.

5. The importance of time as a costing currency, either through the principle of lost opportunity or through exposure to mortality risk, may extend to other behavioural systems, including aggression.
Flippers versus feet: comparative trends in aquatic and non‐aquatic carnivores
Authors: Bininda‐Emonds Olaf R.P. , Gittleman John L. , Kelly Colleen K.
Published: March 2003

It is commonly accepted that many adaptations characterize carnivores that live in water. However, no comparative tests have ever shown systematic differences between aquatic and terrestrial carnivore species as a whole. We examine numerous hypotheses that purport to distinguish aquatic and terrestrial carnivores using 20 morphological, life history, physiological and ecological traits.

 Using the method of independent contrasts with a complete species‐level phylogeny of extant carnivores, we found few differences between aquatic and terrestrial species. Compared to terrestrial sister taxa, aquatic carnivores are streamlined (increased head and body length for a given body weight), have larger brains, smaller litter sizes, shorter interbirth intervals, and shorter lifespans.

 Some of these differences are important functionally. Larger brain size may be related to increased cognitive and sensory needs required for an amphibious lifestyle; smaller litters are likely associated with increased neonatal survival amidst competition for suitable breeding sites and advantages accruing to increased precociality.

 We conclude that broad differentiation of carnivores into aquatic and terrestrial ecotypes is not useful given that adaptive differences between these groups are limited and seemingly no more numerous than those that occur within each ecological group.
Metapopulation structures affect persistence of predator–prey interactions
Authors: Bonsall Michael B. , French David R. , Hassell Michael P.
Published: March 2003

We investigate the metapopulation dynamics of an extinction‐prone host–parasitoid interaction.

Single cell host–parasitoid interactions show diverging oscillations resulting in rapid extinction of both host and parasitoid. By linking cells together into metapopulations and controlling for increased availability of resource, persistence time of the trophic interaction is enhanced.

Metapopulation persistence is influenced by spatial structure and local demographics. Using nonlinear mixed models, we show that the persistence time of these host–parasitoid metapopulations is determined by habitat size and local within‐patch population dynamics.

We use a metapopulation model to show how the role of local demographic population structure and habitat size act concomitantly to affect persistence.
Denning ecology of the striped skunk in the Canadian prairies: implications for waterfowl nest predation
Authors: LariviÈre Serge , Messier FranÇois
Published: March 2003

1.  From 1993 to 1995, we studied the summer denning ecology of 40 radio‐collared striped skunks Mephitis mephitis (32 females, eight males) during the waterfowl nesting season in Saskatchewan, Canada.

2.  Forty‐seven natal dens were used by 30 females. Natal den sites were either underground burrows (55%) or holes underneath buildings (45%), and were preferably located in farmsteads.

3.  Male and female striped skunks used similar resting sites which consisted of above‐ground retreats (57%), underground burrows (23%), buildings (17%) and culverts (3%).

4.  Habitat preferences for resting sites did not differ between males and females: both sexes preferred farmsteads and wetlands, whereas managed waterfowl nesting areas, woodland and miscellanous habitats were avoided. Cropland was avoided for both natal dens and resting sites.

5.  Females did not simultaneously share natal dens or resting sites, but both types of retreats were occupied by different females over time. Natal dens were occupied for 47 ± 3 days for females using a single den vs. 60 ± 3 days for females using >1 natal dens. Den switching may have been induced by a build‐up of faeces.

6.  Management of natal den sites such as abandoned farmsteads and buildings may provide an avenue of non‐destructive predator management that is less expensive and controversial than exclusion or control.
How does temporal variability affect predictions of weed population numbers?
Authors: Freckleton R.P. , Watkinson A.R.
Published: March 2003

1.  Population models that are used to predict weed population dynamics or the impact of control measures on weed abundance typically ignore temporal variability in life‐history parameters and control measures, and utilize mean arithmetic population growth rates to predict population abundance.

2.  We demonstrate that the persistence of weeds in a stochastically varying environment depends on the geometric mean population growth rate being greater than zero, rather than the arithmetic mean population growth rate being greater than zero.

3.  In a stochastically varying environment we show that temporal variability in fecundity, germination and survivorship will tend to decrease population size, relative to predictions based on arithmetic means. Conversely, variability in competitive effects and weed control will tend to increase population size, relative to predictions based on arithmetic mean values. The distinction between these two sets of parameters is that increases in the former will increase population growth rate, whereas increases in the latter will decrease it.

4.  We argue that population models based on arithmetic mean population growth rates will tend to over‐estimate population size. Numerical simulations indicate that this bias may be considerable.

5.  Since short‐term studies cannot, in general, estimate the geometric mean growth rate of a population we suggest several approaches for estimating the degree of bias in the predictions of models owing to the effects of variability. Accounting for such variability is necessary since current models for the dynamics of weed populations are based on arithmetic mean measures of population growth and hence likely to be biased.
Effects of supplementary feeding on territoriality, breeding success and survival of pheasants
Authors: Hoodless A. N. , Draycott R. A. H. , Ludiman M. N. , Robertson P. A.
Published: March 2003

1. The effects of supplementary food in spring on subsequent pheasant breeding in an intensively farmed area in southern England were assessed by a large‐scale, replicated field experiment.

2. Territorial cock pheasants were counted in April, and the breeding success and survival of radio‐tagged hens were monitored in six 1‐km2 plots during 1994 and 1995. Total numbers of young reared and post‐breeding pheasant densities were found by August counts. In 1994, three randomly selected plots were supplied with wheat grains via hoppers along woodland edges and hedgerows. The other three plots acted as controls and the treatments were reversed in 1995.

3. The density of cock territories increased significantly in food‐supplemented plots (44 ± 8 km−2) in relation to control plots (29 ± 8 km−2), and the presence of hoppers significantly affected the locations of territories. However, similar proportions of territorial males acquired harems in the control and food‐supplemented plots. Hen density did not increase and, consequently, the mean harem size was significantly lower with supplementary feeding.

4. Hens given supplementary food did not nest earlier and the number of nests initiated, clutch sizes and the proportion of successful nests did not differ significantly from those of controls. However, hens supplied with supplementary food re‐nested significantly more quickly following the loss of a nest or brood.

5. Radio‐tagged hens did not rear significantly more young with supplementary feeding. Hen survival was unchanged and post‐breeding pheasant densities were no higher.

6. On present evidence, spring feeding cannot be advocated as a management technique to improve the breeding success of pheasants surviving the winter.
A comparison of regeneration dynamics following gap creation at two geographically contrasting heathland sites
Authors: Britton A.J. , Carey P.D. , Pakeman R.J. , Marrs R.H.
Published: March 2003

1. Lowland Calluna‐dominated heathlands are a high priority for conservation in Europe. As an anthropogenic subclimax community they require regular management intervention to maintain their conservation interest.

2. Increasingly, Calluna is disappearing from lowland heathlands and being replaced by grasses, especially in the Netherlands and more recently in south‐east England. While Calluna is highly competitive over much of its life cycle, its competitive ability is reduced during the regeneration phase that follows the death of stands or results from management activity.

3. We examined the influence of five factors on regeneration of vegetation in gaps in two broadly similar lowland dry heaths over a 3‐year period. These were: geographical location (combining a variety of environmental contrasts); dominant species (Calluna or grasses); management techniques; gap size; and seed source availability.

4. Site location had the greatest effect on patterns of regeneration. Regeneration on the Wirral (north‐west England) was faster and more dominated by Calluna than regeneration in Breckland (south‐east England), which was dominated by other species including grasses and annual plants. Addition of Calluna seed at the Breckland site failed to increase Calluna cover. It was concluded that climatic or other environmental factors were the most probable cause of poor regeneration.

5. Cover of grasses in regenerating areas was greatest in Breckland, where Deschampsia was able to establish in all gaps where there was a seed source (either in the surrounding vegetation or applied as a treatment). On the Wirral, Deschampsia establishment was limited, even in gaps where a seed source was applied.

6. This work has implications for the conservation management of heathlands, which currently follows a standard prescription throughout the UK. It is suggested that management regimes should be tailored to suit the conditions prevailing at individual sites as regeneration dynamics may be extremely variable.
Fire and biodiversity: responses of grass‐layer beetles to experimental fire regimes in an Australian tropical savanna
Authors: JÉrôme Orgeas , Andersen Alan N.
Published: March 2003

Up to 50% or more of the savanna landscapes of northern Australia are burnt each year, but the effects of these fires on savanna faunas are poorly known, especially for arthropods.

 We investigated the responses of grass‐layer beetles to three fire regimes (unburnt – fires excluded; early – annual fires lit early during the dry season; late – annual fires lit late during the dry season) as part of a landscape‐scale fire experiment at Kapalga in Australia’s Northern Territory, where replicated fire regimes were applied to 15–20‐km2landscape units over a 5‐year period. We also sought to identify beetle species that might act as indicators of particular fire regimes, and examined the extent to which analysis at the family level is sufficient to reveal patterns evident from species‐level analysis.

 Beetles were sampled using sweep nets during February (mid‐wet season) and May (end of wet season) each year, from 1989 (18 months prior to the imposition of fire treatments) to 1995 (after 5 years of treatments).

 A total of 3865 beetles from 233 species was recorded, with the dominant families Chrysomelidae (leaf beetles) and Curculionidae (weevils) contributing 91% of all beetles and 57% of total species.

 Total beetle abundance, species richness, family richness and the abundances of one of the 10 most common species were significantly affected by fire treatment according toanova. In all cases, beetle abundance and richness were similar in the two burning treatments, but greater than in the unburnt treatment. These differences were only apparent during the second half of the experiment. The responses were mirrored by changes in composition at species, family and guild levels, according to multivariate analysis.

 According to indicator analysis, five beetle species were significant indicators of late fires, and one of early fires. All these species were infrequently recorded and therefore of limited use for management. However, two common species were indicative of burnt habitats if early and late treatments are considered together.

 Family richness was highly correlated (r2 = 0·615) with species richness, and multivariate analysis of family‐level abundances revealed the compositional changes in relation to fire that were evident in species‐level analysis. Family was therefore a reliable surrogate of species for detecting beetle responses.

 Although we found significant effects of our experimental treatments, in the broader context of overall beetle dynamics the assemblages appeared to be remarkably resilient to fire. This reflects a long history of association with frequent fire, and is consistent with many other components of the northern Australian fauna, where fire appears to be of secondary importance to variation in rainfall and soil type.

 The lack of effect of fire timing on grass‐layer beetles calls into question a management paradigm that focuses largely on fire intensity, and suggests that fire management needs to be more mindful of fire frequency.
The interplay between culling and density‐dependence in the great cormorant: a modelling approach
Authors: Frederiksen M. , Lebreton J.‐D. , Bregnballe T.
Published: March 2003

The population of great cormorantsPhalacrocorax carbo sinensisbreeding in northern Europe has increased from 5000 pairs around 1970 toc. 100 000 pairs in the late 1990s, leading to serious conflicts with fishery and aquaculture interests. Management action, including widespread culling, has been taken in several countries.

 Since 1990, presumed density‐dependent declines in demographic performance have appeared in cormorant populations. We employed an extended Leslie matrix model to study the interaction between culls and density‐dependence in regulating breeding and autumn population sizes, with emphasis on evaluating the effects of culling.

 During 1979–92, the breeding population of great cormorants in northern Europe increased by 18% year−1, in accordance with observed life‐cycle parameters before the appearance of density‐dependent declines.

 We modelled six scenarios with varying assumptions about the strength of density‐dependence in adult survival and the proportions of breeding cormorants. A series of cull estimates was also included. Scenarios with moderate or strong levels of density‐dependence provided predictions that fit the observed numbers of breeding pairs, whereas scenarios without density‐dependence in survival overestimated real population growth.

 The most well‐supported scenarios indicated that the effect of culls at the present level (1998–99: 17 000 cormorants shot) was limited (< 10% reduction at equilibrium). Increasing the annual cull to 30 000 still had a limited effect, whereas shooting 50 000 birds year−1led to population extinction within 20–40 years. Shooting a fixed proportion of the population exceeding a threshold, through density‐dependent culling, could eliminate differences among scenarios and stabilize the population.

 We conclude that culls probably have had a limited effect on cormorant populations, but if carried out in a density‐dependent way they could stabilize numbers near a desired level. However, a reduction in the number of cormorants may not lead to a similar reduction in conflicts, and actions to control damage rather than cormorant populations are likely to be more cost‐effective. If culling is to be continued, we recommend the adoption of an adaptive and co‐ordinated management strategy across Europe. We also advocate the need to account for density‐dependent mechanisms in general culling strategies.
Inflammatory and motor responses by tachykinins in the guinea‐pig oesophageal sphincter
Authors: Conte B. , Parlani M. , Lopez G. , Cirillo R. , Maggi C. A. , Manzini S.
Published: March 2003

1 The aim of this study was to characterize the tachykinin receptors involved in producing plasma protein extravasation and contractile responses of the guinea‐pig oesophageal sphincter.

2 In anaesthetized guinea‐pigs, the selective tachykinin NK‐1 receptor agonist [Sar9,Met(O2)11]substance P produced plasma protein extravasation (PPE) which was not affected by the treatment with the tachykinin NK‐2 receptor antagonist MEN 10627 (1 μmol kg−−1 i.v.) or the histamine H1‐receptor antagonist, diphenhydramine (34.5 μmol kg−−1 i.v.). However, the [Sar9,Met(O2)11]substance P‐induced PPE was blocked by the previous administration of the peptide tachykinin NK‐1 receptor antagonist FK 888 or by the non‐peptide antagonist SR 140333, yielding ED50 values of 1.1 ± 0.2 and 0.01 ± 0.004 μmol kg−−1 i.v., respectively.

3 The tachykinin NK‐2 or NK‐3 receptor agonists [β‐Ala8]neurokinin A (4–10) or [MePhe7]neurokinin B, respectively, produced a weak PPE at high doses. The effect of [MePhe7]neurokinin B‐induced PPE was inhibited by SR 140333.

4 In the guinea‐pig isolated oesophageal sphincter, [Sar9,Met(O2)11]substance P did not exert any contractile effect up to 10 μm. The selective tachykinin NK‐2 receptor agonist ([β‐Ala8]neurokinin A (4–10), produced concentration‐dependent contractions (pD2 = 7.6 ± 0.03) which were inhibited by the selective tachykinin NK‐2 receptor antagonist, MEN 10627 (pA2 = 8.6 ± 0.1). Also, the tachykinin NK‐3 receptor selective agonist [MePhe7]neurokinin B induced concentration‐dependent contractile responses, but these responses were inhibited by MEN 10627.

5 Altogether, these data indicate that the stimulation of tachykinin NK‐1 receptor produces a vascular inflammatory response, while activation of tachykinin NK‐2 receptors mediate the contraction of the guinea‐pig oesophageal sphincter.
Vascular responses to β‐adrenoceptor subtype‐selective agonists with and without endothelium in rat common carotid arteries
Authors: Chiba S. , Tsukada M.
Published: March 2003

1 Using the cannula inserting method, vasodilator responses to β‐adrenoceptor agonists (isoprenaline, denopamine and procaterol) were investigated in isolated and perfused rat common carotid arteries.

2 Each β‐adrenoceptor agonist induced a vasodilation in preparations preconstricted by phenylephrine in a dose‐related manner. The potencies were in the order of isoprenaline > procaterol >> denopamine.

3 Denopamine‐induced dilations were significantly inhibited by 1 nmol betaxolol (a selective β1‐adrenoceptor antagonist), but it was not influenced by 1 nmol ICI 118,551 (a selective β2‐adrenoceptor antagonist). On the other hand, procaterol‐induced vasodilations were significantly inhibited by 1 nmol ICI 118,551 but not modified by 10 nmol betaxolol.

4 ACh‐induced vasodilations disappeared after intraluminal saponin injection to remove endothelium, but procaterol‐ and denopamine‐induced dilations were not modified by removal of the endothelium.

5 Pretreatment with L‐NG‐nitroarginine methyl ester (L‐NAME) readily inhibited ACh‐induced vasodilations. However, neither procaterol‐ or denopamine‐induced vasodilation was modified by L‐NAME treatment.

6 From these results, it is concluded that in the rat common carotid arteries (1) there are abundant β2‐ and a few β1‐adrenoceptors, and (2) there is no participation of the endothelium‐dependent mechanism in β‐adrenoceptor mediated vasodilations.
Effects of P5, a novel oxazolo(3,2‐a)pyridine derivative with a long‐acting antihypertensive activity, on different agonist‐mediated pressor responses in pithed rats
Authors: Martín E. , Sevilla M. A. , Morán A. , Martín M. L. , Román L. San
Published: March 2003

1 An oxazolo(3,2‐a)pyridine derivative P5, described chemically as (±)‐ethyl‐7‐(3‐nitrophenyl)‐5,8a‐dimethyl‐6‐methoxycarbonyl‐2,3,8,8a‐tetrahydro‐7H‐oxazolo[3,2‐a]pyridin‐8‐carboxylate, is a novel compound that has been synthesized as a possible antihypertensive prodrug of the 1,4‐dihydropyridine type. Its antihypertensive activity was described in a previous study by the authors (Morán, Martin, Velasco, Martin, San Roman, Caballero, Puebla, Medarde & San Feliciano, 1997).

2 The aim of this work was to establish in vivo, the possible mechanisms participating in this antihypertensive action. Accordingly, we examined the effect of P5 on the pressor responses induced in pithed rats by noradrenaline (an α1‐, α2‐ and β‐adrenoceptor agonist), xylazine (an α2‐adrenoceptor agonist), methoxamine (an α1‐adrenoceptor agonist), angiotensin I, angiotensin II, L‐NAME (a nitric oxide synthase inhibitor) and BayK 8644 (a calcium channel agonist) and compared them with those of nifedipine, used as the reference drug.

3 Intravenous (i.v.) administration of P5 (2.5–10 mg kg–1) inhibited the pressor responses to noradrenaline (1 μg kg–1), xylazine (80 μg kg–1), angiotensin I (0.5 μg kg–1), angiotensin II (0.5 μg kg–1), BayK 8644 (30 μg kg–1) and L‐NAME (10 mg kg–1). Nifedipine (10 μg kg–1, i.v.) reduced the pressor responses to all these agonists and also to methoxamine (2 μg kg–1).

4 However, P5 was more effective than nifedipine in inhibiting these responses and its inhibitory effect lasted longer. Intravenous infusion of calcium gluconate (1 ml kg–1 min–1) reversed the reduction in the pressor responses as a result of nifedipine. The effects of P5 were only reversed at 2–3 h after administration.

5 These results suggest that P5 has a strong capacity to inhibit the pressor responses to several agonists after its i.v. administration and that such effects are related to its potent antihypertensive activity.
Changes of the responses of single sympathetic ganglionic neurones to substance P following desensitization
Authors: Simmons M. A.
Published: March 2003

1 The neuropeptide substance P (SP) exerts an excitatory effect on sympathetic neurones by inhibiting a time‐ and voltage‐dependent potassium current. During prolonged application of SP, the response desensitizes. The changes in kinetics of the SP response in single neurones after desensitization have been studied in an attempt to gain some insight as to the molecular mechanism of desensitization in live, functioning neurones.

2 Desensitization to SP resulted in subsequent SP responses being smaller, but the time course was unchanged in desensitized cells compared with non‐desensitized cells.

3 Experimental manipulations were performed to decrease receptor and G protein function for comparison to desensitization. Intracellular application of GDPβS, to decrease G protein function, led to successive responses to agonist becoming smaller and slower. When functional muscarinic receptors were decreased by extracellular application of propylbenzilylcholine mustard (PrBCM), the response to muscarine became smaller, but the time course was unchanged compared with the change in time course produced by PrBCM vehicle alone.

4 The results have also been compared with simulations from a mathematical model of drug‐receptor–G protein interactions. Under a constrained set of conditions, the model predicts that decreasing the size of the G protein pool will decrease both the magnitude and the time course of the response to agonist. Decreasing receptor levels results in a more efficient decrease in the magnitude of the response but no change in the time course of the response.

5 These data provide evidence that desensitization of the response to SP in single neurones results from a decrease in functional receptors.
Divergence in a transoceanic circumtropical dragonfly on a remote island
Authors: Samways M. , Osborn R.
Published: March 2003

One terrestrial invertebrate that naturally spans the globe and travels vast distances is the dragonfly Pantala flavescens (Fabricius) (Odonata: Libellulidae). Recently, there has been a strong call to compare island with continental biota so as to meaningfully characterize island forms. This is done here. The variation and differences in morphology and behaviour of an African continental (Pietermaritzburg, South Africa) and a remote island population (Easter Island) of P. flavescens was investigated to determine whether the island population was panmictic with the migrant population, or whether it was a founder population. Several morphological characters were measured in both populations, and analysed using PCA, t‐tests, coefficients of variation and Chi‐square analyses. The continental and island populations were significantly different in body colour, head width and femur length. The island population had reduced hindwings, which were also more asymmetrical than the continental population, suggesting that the island individuals were possibly more genetically and environmentally stressed and had less genetic variation than the continental population. The island population was also more robust and flew lower to the ground than the continental population. There was no significant difference in body weight between the two populations because the migrant population had not begun to build up fat reserves for migration. Females were heavier than males in the continental population because they were carrying eggs. This was not the case in the island population because the individuals were not as mature. Colour was significantly different between the two populations, with island individuals having darker wings and abdomens, yet a lighter synthorax colouring than the continental population. Sexual dimorphism was marked in the abdomen and wing colour of the continental population, yet the island individuals showed more difference between the sexes in morphological characters than in colour. The fact that P. flavescens is the only species of dragonfly on Easter Island, and the great distance of the island from any mainland, suggests infrequent arrival of migrants arriving on the island, with resultant reduced genetic variation. The morphological and behavioural differences between the two populations suggests divergence is occurring.
Comparative study of Spanish and Italian terrestrial small mammal coenoses from different biotopes in Mediterranean peninsular tip regions
Authors: Cagnin M. , Moreno S. , Aloise G. , Garofalo G. , Villafuerte R. , Gaona P. , Cristaldi M.
Published: March 2003

A comparison of terrestrial small mammal coenoses belonging to nine different biotopes in the tips of the Iberian and Italian peninsulas was carried out using the pitfall trapping method. The influence of both habitat type and peninsular effect on composition of small mammal coenoses was analysed. In Southern Italy, 203 specimens belonging to seven species were trapped: Suncus etruscus (Savi, 1822), Crocidura suaveolens (Pallas, 1811),
C. leucodon (Hermann, 1780), Microtus savii (de Sélys‐Longchamps, 1838),
Apodemus sylvaticus (L., 1758), A. flavicollis (Melchior, 1834) and
Mus musculus domesticus Schwarz & Schwarz, 1943. In Southern Spain 428 specimens belonging to five species were trapped:
Suncus etruscus, Crocidura russula (Hermann, 1780), Microtus duodecimcostatus (de Sélys‐Longchamps, 1839),
Apodemus sylvaticus and Mus spretus Lataste, 1883. The relative density of small mammals occurring in the nine Spanish sampling stations was twice that recorded in the Italian stations; however the number of species recorded in the different biotopes show similar mean values, ranging from three to five in Andalusia and from three to six in Calabria.
Apodemus sylvaticus was the dominant species in the Calabrian stations, whereas
Crocidura russula prevailed in Andalusia. The biotic diversity values are very similar in the Calabrian and Andalusian biotopes. By contrast, the Insectivora/Rodentia ratio was always higher in Andalusia. The more xerophytic biotopes showed greater similarities between the communities in Southern Spain and Southern Italy, while the cooler biotopes differed between these two peninsulas.
Biogeography of limno‐terrestrial Tardigrada, with particular reference to the Antarctic fauna
Authors: McInnes S. J , Pugh P. J. A
Published: March 2003

The Tardigrada is a cosmopolitan phylum of pre‐Pangaean origin, yet tardigrade families and genera show distinct biogeographic components isolated by two major geological events. Separate Laurasian and Gondwanan familial clusters correlate with the Triassic disintegration of Pangaea, while discrete Antarctic, Australian and New Zealand familial/generic clusters relate to the subsequent Jurassic/Cretaceous disintegration of Gondwana.
Biogeography of the wax scales (Insecta: Hemiptera: Coccidae: Ceroplastinae)
Authors: Gullan Ting‐Kui , Beattie Andrew
Published: March 2003

The modern and native distributions of wax scales are documented and an area cladogram including seventy species is presented. Wax scales are distributed worldwide, but most species are native to either South America or Africa. Their native distribution pattern is discussed in relation to their host‐plant specificity and to the dispersal and vicariance theories of biogeography. The vicariance theory is preferred, because the pattern can be explained satisfactorily by plate tectonics but not by dispersal from a centre of origin. The wax scale group probably originated in the combined South American–African continent at least 97 million yr ago.
Persistence, extinction and different species pools within the flora of lake islands in western Ireland
Authors: Roden C.
Published: March 2003

The vascular flora on twenty‐nine lake islands in Lough Corrib, western Ireland was surveyed in 1992–93. Thirteen of these islands had been surveyed by the author in 1974 (Roden, 1979). Data on species–area curves and species turnover between 1974 and 1992 are presented. Species numbers on each island did not change greatly in the 18‐year interval and extinctions were most common on smaller islands. It is known that six of the islands surveyed are less than 150 years old and their flora must have immigrated over open water during that period. It is shown that this group of species has a different log species/log area regression than the remaining flora, with a much shallower slope (low Z value). The proportion of less widespread species was greatest on islands nearest to the mainland. The implication of different slopes in different species groups and the restriction of turnover to rare species is discussed with reference to the island Theory of Biogeography.
Extinction and replacement in the Indo‐West Pacific Ocean
Authors: Briggs John C.
Published: March 2003

Aim To provide evidence suggesting the existence of a dynamic system of extinction and replacement.

Location The Indo‐West Pacific Ocean.

Methods Utilization of species distribution patterns produced by detailed systematic works.

Results The distribution patterns appear to suggest a sequence of events that is consistent with the centre of origin hypothesis. The East Indies centre is considered to operate according to the centrifugal speciation model.

Main conclusions Disjunct patterns appear to have originated in the East Indies and spread out from there. In cases where the vacated area is occupied by a sibling species, competitive (sympatric) speciation may have occurred. Over time the extinction pattern will gradually extend outward until it is played out among small populations far from their centre of origin
The Holdridge life zones of the conterminous United States in relation to ecosystem mapping
Authors: Lugo A. E. , Brown S. L. , Dodson R. , Smith T. S. , Shugart H. H.
Published: March 2003

Aim Our main goals were to develop a map of the life zones for the conterminous United States, based on the Holdridge Life Zone system, as a tool for ecosystem mapping, and to compare the map of Holdridge life zones with other global vegetation classification and mapping efforts.

Location The area of interest is the forty‐eight contiguous states of the United States.

Methods We wrote a PERL program for determining life zones from climatic data and linked it to the image processing workbench (IPW). The inputs were annual precipitation (Pann), biotemperature (Tbio), sea‐level biotemperature (T0bio), and the frost line. The spatial resolution chosen for this study (2.5 arc‐minute for classification, 4‐km for mapping) was driven by the availability of current state‐of‐the‐art, accurate and reliable precipitation data. We used the Precipitation‐elevation Regressions on Independent Slopes Model, or PRISM, output for the contiguous United States downloaded from the Internet. The accepted standard data for air temperature surfaces were obtained from the Vegetation/Ecosystem Modelling and Analysis Project (VEMAP). This data set along with station data obtained from the National Climatic Data Center for the US, were used to develop all temperature surfaces at the same resolution as the Pann.

Results The US contains thirty‐eight life zones (34% of the world's life zones and 85% of the temperate ones) including one boreal, twelve cool temperate, twenty warm temperate, four subtropical, and one tropical. Seventy‐four percent of the US falls in the ‘basal belt’, 18% is montane, 8% is subalpine, 1% is alpine, and < 0.1% is nival. The US ranges from superarid to superhumid, and the humid province is the largest (45% of the US). The most extensive life zone is the warm temperate moist forest, which covers 23% of the country. We compared the Holdridge life zone map with output from the BIOME model, Bailey's ecoregions, Küchler potential vegetation, and land cover, all aggregated to four cover classes. Despite differences in the goals and methods for all these classification systems, there was a very good to excellent agreement among them for forests but poor for grasslands, shrublands, and nonvegetated lands.

Main conclusions We consider the life zone approach to have many strengths for ecosystem mapping because it is based on climatic driving factors of ecosystem processes and recognizes ecophysiological responses of plants; it is hierarchical and allows for the use of other mapping criteria at the association and successional levels of analysis; it can be expanded or contracted without losing functional continuity among levels of ecological complexity; it is a relatively simple system based on few empirical data; and it uses objective mapping criteria.
Simulating effects of climate change on boreal ecosystem carbon pools in central Canada
Authors: Price D. T. , Peng C. H. , Apps M. J. , Halliwell D. H.
Published: March 2003

AimPossible effects of current and future climates on boreal vegetation dynamics and carbon (C) cycling were investigated using the CENTURY 4.0 soil process model and a modified version of the FORSKA2 forest patch model.

LocationEleven climate station locations distributed along a transect across the boreal zone of central Canada.

MethodsBoth models were driven by detrended long‐term monthly climate data. Using a climate change signal derived from the GISS general circulation model (GCM) 2×CO2equilibrium climate scenario, the output from the two models was then used to compare simulated current and possible future total ecosystem C storage at the climate station locations.

ResultsAfter allowing for their different underlying structures, comparison of output from both models showed good agreement with local field data under current climate conditions. CENTURY 4.0 was able to reproduce spatial variation in soil and litter C densities satisfactorily but tended to overestimate biomass productivity. FORSKA2 reproduced aboveground biomass productivity and spatially averaged biomass densities relatively well. Under the GISS 2×CO2scenario, both models generally predicted small increases in aboveground biomass C density for forest and tundra locations, but CENTURY 4.0 predicted greater decreases in soil and litter pools, for overall decreases in ecosystem C storage in the range 16–19%.

Main conclusionsWith some caveats, results imply that effects of increased precipitation (as simulated by the GISS GCM) would more than compensate for any negative effects of increased temperature on forest growth. Increased temperature would also increase decomposition rates of soil and litter organic matter, however, for a net overall decrease in total ecosystem C storage.
Forest area and distribution in the Mississippi alluvial valley: implications for breeding bird conservation
Authors: Twedt Daniel J. , Loesch Charles R.
Published: March 2003

Knowing the current forest distribution and patch size characteristics is integral to the development of geographically defined, habitat‐based conservation objectives for breeding birds. Towards this end, we classified 2.6 million ha of forest cover within the Mississippi Alluvial Valley using 1992 thematic mapper satellite imagery. Although historically this area, from southern Illinois to southern Louisiana, was dominated by forested wetlands, forest cover remains on less than 25% of the floodplain. Remaining forest cover is comprised of > 38,000 discrete forest patches > 2 ha. Mean patch area (64.1±5.2 ha; x̄±SE) was highly skewed towards small fragment size. Larger patches had a higher proportion of more hydric forest cover classes than did smaller patches which had a higher proportion of less hydric forest cover classes. Public lands accounted for 16% of remaining forested wetlands. Fewer than 100 forest patches exceeded our hypothesized habitat objective (4000 ha minimum contiguous forest area) intended to support self‐sustaining populations of forest breeding birds. To increase the number of forest patches exceeding 4000 ha contiguous area, and thereby increase the likelihood of successful forest bird conservation, we recommend afforestation adjoining existing forest fragments ≥1012 ha and focused within designated Forest Bird Conservation Regions.
Biogeography of the Limacoidea sensu lato (Gastropoda: Stylommatophora): vicariance events and long‐distance dispersal
Authors: Hausdorf B.
Published: March 2003

Aim Reconstruction of the historical biogeography of the Limacoidea sensu lato (including the Staffordiidae, Dyakiidae, Gastrodontoidea, Parmacelloidea, Zonitidae, Helicarionoidea and Limacoidea). Evaluation of the relative importance of dispersal and its consequences.

Location World‐wide.

Methods Weighted ancestral area analysis.

Results The ancestral areas of the individual clades have been delimited using weighted ancestral area analysis and a sequence of possible vicariance and dispersal events has been suggested. The results of the ancestral area analysis have tentatively been correlated with Cretaceous and Tertiary palaeogeography. The widely overlapping distribution patterns of several families of the Limacoidea testify to extensive dispersal events. Dispersal capacity of land snails is correlated with body size. The significant negative correlation between body size and distribution area size corroborates the importance of passive dispersal for the evolution of the distribution patterns.

Main conclusions The existence of extensive dispersal events of poor active dispersers like land snails diminishes the importance of recent distribution patterns for the reconstruction of palaeogeography. On the other hand, dispersal ensures that biogeographical data reflect the geographical configurations at a given time and renders the use of palaeobiogeographic data for the reconstruction of palaeogeographic configurations of the respective age possible.
Upsides and downsides: contrasting topographic gradients in species richness and associated scenarios for climate change
Authors: Fleishman Erica , Fay John P. , Murphy Dennis D.
Published: March 2003

Aim

We tested whether montane butterflies exhibit similar responses to elevation in two adjacent mountain ranges in the Great Basin; whether surface water availability, canyon depth and canyon width vary predictably with elevation; and whether those factors act in conjunction with elevation to generate the observed gradients in species richness. These variables might reasonably be expected to affect species richness of butterflies and can be derived readily for most landscapes. We also explored how climate change may affect species distributions in both mountain ranges.

Location

Field research was conducted in the Toiyabe and Toquima ranges, Lander and Nye counties, Nevada, USA.

Methods

We obtained data for 102 locations in the Toiyabe Range and 49 locations in the Toquima Range. These locations covered an elevational gradient ofc.1350 m in the Toiyabe Range and 900 m in the Toquima Range. Species richness data were based upon comprehensive field inventories. Elevation was measured by differentially corrected global positioning systems. Values for the remaining predictive variables were derived using geographic information systems. Availability of surface water was quantified as the distance from the centre of the inventory route to the nearest permanent source of running or standing water.

Results

In the Toiyabe Range, species richness decreases as elevation increases. Water availability and canyon depth and width vary predictably with elevation, but do not interact with elevation to affect species richness patterns. In the Toquima range, in contrast, species richness increases as elevation increases, and no other predictive variable covaries with elevation.

Main conclusions

We suggest that range‐specific gradients in climatic severity contribute to the distinct elevational gradients in species richness. In the face of climate change, species richness patterns in the Toquima range will likely remain similar. The elevational gradient in species richness in the Toiyabe range may flatten, or the patterns in the two ranges may converge.