bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sapwood capacitance is greater in evergreen sclerophyll species growing in high compared to low‐rainfall environments
Authors: Richards Anna E. , Wright Ian J. , Lenz Tanja I. , Zanne Amy E. 
Published: October 2013

Summary

The capacitative release of water from sapwood allows photosynthesis to continue for longer into dry periods, both diurnally and seasonally. However, costs of high capacitance include increased vulnerability to xylem cavitation. The degree of reliance on stored water is predicted to differ among environments as a result of this trade‐off.

Xylem water potential and sapwood capacitance were measured on 32 evergreen sclerophyll shrub and tree species in eastern Australia, sampled from four sites contrasting in soil nutrients and rainfall.

Capacitance calculated over species' typical shoot water potential operating range was threefold higher for species from high compared to low‐rainfall sites, and 1·5‐fold higher for species from high compared to low‐nutrient sites.

To determine whether these site differences were related to extrinsic (e.g. water availability) or intrinsic (e.g. species anatomical construction) factors, we calculated capacitance at two common operating ranges; that is, the mean range in water potential observed for low‐rainfall species (ΔΨlow rain) and the mean range for high‐rainfall species (ΔΨhigh rain). While no difference was seen between low‐ and high‐rainfall species in release of stored water across ΔΨhigh rain, across ΔΨlow rain, the high‐rainfall species released 38% more stored water than low‐rainfall species. Presumably these differences reflect underlying differences in anatomy, such as wood density, which was lower in high‐rainfall species.

These results accord with predictions that (i) species from wetter sites exhibit less negative stem water potentials and high sapwood capacitance, enabling them to maintain function under variable conditions characterized by many short, dry periods, while (ii) species from low‐rainfall sites have wood anatomies conferring tolerance to very low water potentials, with low sapwood capacitance, enabling them to survive longer through unpredictable and extended periods of low rainfall. The finding that the degree to which species rely on stem‐stored water varies with site rainfall suggests that changes in drought regimes (e.g. incidence, duration and severity) under future climates could differentially affect species according to the capacitance properties of their woody tissues.
Exercise changes behaviour
Authors: Sinclair Elektra L. E. , de Souza Carolina R. Noronha , Ward Ashley J. W. , Seebacher Frank 
Published: October 2013

Summary

Exercise, which may be defined as bodily movement produced by the contraction of skeletal muscle and which increases energy expenditure above basal levels, is essential for fitness‐related activities such as foraging, migration and dispersal. The frequency with which individuals engage in exercise depends on a range of intrinsic and environmental factors. Exercise itself can modify behaviour by inducing endocrine changes and by a training effect that increases physiological capacities.

Here, we test the hypothesis that exercise changes behaviour and that there is positive feedback so that performing exercise increases the likelihood of performing exercise‐related behaviours.

We show that there was a training effect that improved sustained swimming performance of mosquitofish (Gambusia holbrooki) exposed to chronic exercise in flowing water for 4 weeks compared to sedentary controls. Exercised fish also became bolder and were quicker to leave a refuge, showed an increasing tendency to explore unfamiliar environments, and were more aggressive than sedentary fish. These physiological and behavioural changes reverted back to control levels when exercised fish assumed a sedentary lifestyle again.

We used the calcium channel blocker nifedipine to decrease swimming performance of exercised fish to control levels, which allowed us to determine whether increased locomotor capacity per se influences behaviour. We show that reducing the swimming performance of exercised fish also reduced exploration and aggression, but it did not affect the latency to leave a refuge (boldness).

Our data show that behavioural phenotypes are not fixed. Exercise changes behaviour and may thereby alter interactions between individuals and dispersal. Environmental changes that demand increased levels of exercise induce behavioural responses that are likely to increase the success of individuals under these changed conditions.
Fortune favours the bold: a higher predator reduces the impact of a native but not an invasive intermediate predator
Authors: Barrios‐O'Neill Daniel , Dick Jaimie T. A. , Emmerson Mark C. , Ricciardi Anthony , MacIsaac Hugh J. , Alexander Mhairi E. , Bovy Helene C. 
Published: October 2013

SummaryEmergent multiple predator effects (MPEs) might radically alter predictions of predatory impact that are based solely on the impact of individuals. In the context of biological invasions, determining if and how the individual‐level impacts of invasive predators relates to their impacts in multiple‐individual situations will inform understanding of how such impacts might propagate through recipient communities.Here, we use functional responses (the relationship between prey consumption rate and prey density) to compare the impacts of the invasive freshwater mysid crustaceanHemimysis anomalawith a native counterpartMysis salemaaiwhen feeding on basal cladoceran prey (i) as individuals, (ii) in conspecific groups and (iii) in conspecific groups in the presence of a higher fish predator,Gasterosteus aculeatus.In the absence of the higher predator, the invader consumed significantly more basal prey than the native, and consumption was additive for both mysid species – that is, group consumption was predictable from individual‐level consumption.Invaders and natives were themselves equally susceptible to predation when feeding with the higher fish predator, but anMPEoccurred only between the natives and higher predator, where consumption of basal prey was significantly reduced. In contrast, consumption by the invaders and higher predator remained additive.The presence of a higher predator serves to exacerbate the existing difference in individual‐level consumption between invasive and native mysids. We attribute the mechanism responsible for theMPEassociated with the native to a trait‐mediated indirect interaction, and further suggest that the relative indifference to predator threat on the part of the invader contributes to its success and impacts within invaded communities.
Changes in breeding phenology and population size of birds
Authors: Dunn Peter O. , Møller Anders P. 
Published: October 2013

Summary

Although the phenology of numerous organisms has advanced significantly in response to recent climate change, the life‐history and population consequences of earlier reproduction remain poorly understood.

We analysed extensive data on temporal change in laying date and clutch size of birds from Europe and North America to test whether these changes were related to recent trends in population size.

Across studies, laying date advanced significantly, while clutch size did not change. However, within populations, changes in laying date and clutch size were positively correlated, implying that species which advanced their laying date the most were also those that increased their clutch size the most.

Greater advances in laying date were associated with species that had multiple broods per season, lived in nonagricultural habitats and were herbivorous or predatory. The duration of the breeding season increased for multibrooded species and decreased for single‐brooded species. Changes in laying date and clutch size were not related to changes in population size (for resident or migratory species).

This suggests that, across a wide variety of species, mismatches in the timing of egg laying or numbers of offspring have had relatively little influence on population size compared with other aspects of phenology and life history.
Two‐sex matrix models in assessing population viability: when do male dynamics matter?
Authors: Gerber Leah R. , White Easton R. 
Published: October 2013

SummaryWhile most demographic population models used in conservation rely on female vital rates, recent empirical evidence suggests that male dynamics should be included in population models used for assessing extinction risk.UsingCalifornia sea lionsZalophus californianusas an applied example, we demonstrate that there are situations in which two‐sex models are more appropriate than the commonly used female‐based model.Two‐sex models are relevant in cases where vital rates for sexes differ and for polygamous species such as sea lions. Vital rates targeted for management may therefore respond differently for males and females and for different assumptions about sex ratio.Synthesis and applications. Conservation biologists should carefully consider the social structure and sex ratio of focal species in order to determine whether a two‐sex matrix model will yield more accurate estimates of extinction risk than standard one‐sex models.
Learning the ropes: mussel spat ropes improve fish and shrimp passage through culverts
Authors: David Bruno O. , Tonkin Jonathan D. , Taipeti Kristopher W. T. , Hokianga Hayden T. 
Published: October 2013

Summary

Culvert pipes are regularly used around the world for conveying stream flows underground, through embankments or under road crossings. Installation of these features can have significant negative effects on the passage of freshwater biota and potentially exclude many species from large areas of river networks.

We investigated the installation of mussel spat ropes as a potentially rapid and cost‐effective tool for improving passage of freshwater biota through culvert pipes where internal barrel conditions impede passage. We assessed passage success for two fish species, juvenile rainbow trout Oncorhynchus mykiss (Walbaum 1972) and adult inanga Galaxias maculatus (Jenyns 1842), and one migratory shrimp, Paratya curvirostris (Heller 1862), through culverts of differing length (3 and 6 m), slope (1·5 and 3°) and flow (0·24 and 0·75 L s−1). We hypothesized that ropes would enhance the passage success of these three species, but success rates would differ between species and trial combinations.

Ropes resulted in a reduced water velocity within culvert barrels and significantly improved passage success for all three species. Shrimp benefited most by the presence of ropes, being unable to negotiate any of the pipe combinations in their absence, but exhibiting varying rates of success across all combinations with their presence. Both G. maculatus and O. mykiss were able to negotiate some of the non‐roped pipe combinations, but as the level of difficulty increased, successful passage was only achieved with the ropes present.

Synthesis and applications. We conclude that this relatively inexpensive and easy‐to‐install tool has the potential to substantially improve passage for a range of aquatic biota through various culvert scenarios. We consider that ropes would be particularly useful in situations where internal culvert access is difficult and where various culvert parameters (slope, flow, length) result in internal barrel hydraulics that would normally limit or exclude passage of aquatic biota.
EDITOR'S CHOICE: Stepping stones are crucial for species' long‐distance dispersal and range expansion through habitat networks
Authors: Saura Santiago , Bodin Örjan , Fortin Marie‐Josée 
Published: October 2013

Summary

Climate and land‐use changes will require species to move large distances following shifts in their suitable habitats, which will frequently involve traversing intensively human‐modified landscapes. Practitioners will therefore need to evaluate and act to enhance the degree to which habitat patches scattered throughout the landscape may function as stepping stones facilitating dispersal among otherwise isolated habitat areas.

We formulate a new generalized network model of habitat connectivity that accounts for the number of dispersing individuals and for long‐distance dispersal processes across generations. By doing so, we bridge the gap between complex dynamic population models, which are generally too data demanding and hence difficult to apply in practical wide‐scale decision‐making, and simpler static connectivity models that only consider the amount of habitat that can be reached by a single average disperser during its life span.

We find that the loss of intermediate and sufficiently large stepping‐stone habitat patches can cause a sharp decline in the distance that can be traversed by species (critical spatial thresholds) that cannot be effectively compensated by other factors previously regarded as crucial for long‐distance dispersal (fat‐tailed dispersal kernels, source population size).

We corroborate our findings by showing that our model largely outperforms previous connectivity models in explaining the large‐scale range expansion of a forest bird species, the Black Woodpecker Dryocopus martius, over a 20‐year period.

The capacity of species to exploit the opportunities created by networks of stepping‐stone patches largely depends on species‐specific life‐history traits, suggesting that species assemblages traversing fragmented landscapes may be exposed to a spatial filtering process driving long‐term changes in community composition.

Synthesis and applications. Previous static connectivity models seriously underestimate the importance of stepping‐stone patches in sustaining rare but crucial dispersal events. We provide a conceptually broader model that shows that stepping stones (i) must be of sufficient size to be of conservation value, (ii) are particularly crucial for the spread of species (either native or invasive) or genotypes over long distances and (iii) can effectively reduce the isolation of the largest habitat blocks in reserves, therefore largely contributing to species persistence across wide spatial and temporal scales.
Complementary impacts of small rodents and semi‐domesticated ungulates limit tall shrub expansion in the tundra
Authors: Ravolainen Virve T. , Bråthen Kari Anne , Yoccoz Nigel G. , Nguyen Julie K. , Ims Rolf A. 
Published: October 2013

Summary

While shrubs appear to be expanding in Arctic tundra due to climatic warming, patches of tall shrubs in riparian habitats are most likely to colonize new areas. Shrub recruits outside established patches represent the forefront of area expansion, but their dynamics may be sensitive to the action of several herbivore species. The empirical evidence for how different‐sized herbivores affect recruits of tall shrubs is lacking. Moreover, although management and natural population dynamics of herbivores happens at landscape and regional scales, field research on herbivore impacts on shrubs seldom covers these scales.

Reindeer management and different rodent population dynamics result in regional variation in herbivore abundances in arctic Norway. We conducted an herbivore exclusion experiment, covering three low‐arctic river catchments with contrasting herbivore abundances. We assessed the impacts of small rodents and reindeer on growth, and survival of willow Salix spp. recruits after 3 years of herbivore exclusion.

As expected, the Salix recruits increased in sizes and had lower mortality when released from herbivores. Both types of herbivores had strong impacts on size and survival of Salix recruits.

Spatially contrasting results were consistent with regional differences in the abundance of reindeer and rodents; herbivore impacts on shrubs were found when at least one type of herbivore was abundant. However, the impact was not independent of herbivore species. While both browsing from reindeer and rodents pruned the recruits and prevented them from escaping the field layer, the rodents also inflicted substantial mortality and thus thinned the stand of recruits.

Synthesis and applications. Sympatric populations of rodents and reindeer have strongly complementary impacts on shrub recruits and may limit the expansion potential of tall shrubs even in the most productive habitats of arctic tundra. The spatial correspondence between shrub recruits performance and herbivore abundances, found after a short time period, suggests that the extent of tall shrub expansion in tundra is contingent on current variation and future trends in herbivore populations. In areas where humans control large herbivore populations, management may opt to counteract climate‐driven shrub expansion also in habitats that are most prone to such expansion.
Phenotypic plasticity promotes persistence following severe events: physiological and morphological responses of seagrass to flooding
Authors: Maxwell Paul S. , Pitt Kylie A. , Burfeind Dana D. , Olds Andrew D. , Babcock Russell C. , Connolly Rod M. 
Published: October 2013

Summary

Severe events such as floods or cyclones can have large ecological effects on the structure and functioning of ecosystems. The capacity of an ecosystem to adapt to, or absorb, the effects of a severe event depends on the severity and longevity of the event and the tolerance of the species present.

Seagrasses exhibit phenotypic plasticity at the plant to meadow scale through a variety of physiological and morphological acclimations to light stress to enhance photosynthetic capacity. These acclimations provide early warning of the possible risk of larger scale seagrass loss and can therefore be used in predicting how ecosystems might respond to severe events.

The physiological and morphological responses of 12 seagrass (Zostera muelleri) meadows to a severe flood were examined to test two main hypotheses: (i) that the physiological and morphological characteristics of seagrass would differ between meadows along the established chronic water quality gradient, in a pattern consistent with prior acclimations which have been shown to enhance photosynthetic capacity and (ii) that physiological and morphological responses to the flood would differ between meadows in a manner consistent with their position along the water quality gradient.

Meadows had different physiological and morphological characteristics across the water quality gradient, with meadows subject to chronically poorer water quality exhibiting characteristics consistent with those that maximize photosynthetic capacity. Despite a large discrepancy in impact among meadows, all meadows sampled responded consistently to the flood, exhibiting only physiological changes with no significant reduction in biomass. This suggests that photoacclimation to chronically poor conditions can enable seagrasses to withstand the effects of severe events, such as floods.

Synthesis. Phenotypic plasticity in habitat‐forming species can result in a large variation in their responses to severe events, such as floods or cyclones. Acclimation to prior poor environmental conditions can promote persistence in habitat‐forming species, such as seagrasses, following severe events. The measurement of phenotypic characteristics along an impact gradient can therefore provide an indication of the response of habitat‐forming species to severe events.
Different combinations of multiple defence traits in an extrafloral nectary‐bearing plant growing under various habitat conditions
Authors: Yamawo Akira , Tagawa Jun , Hada Yoshio , Suzuki Nobuhiko 
Published: October 2013

Summary

The effects of multiple defence traits on herbivory under different abiotic conditions have not been reported in the literature. To clarify the relations between plant defence traits and abiotic factors in the field, we investigated the plasticity of multiple defence traits in young Mallotus japonicus growing in three habitat conditions: open sites, forest edges and treefall gaps.

The plants used multiple defence traits differently in three habitats. At open sites, trichomes, pellucid dots and extrafloral nectaries (EFNs) were expressed better than at the treefall gaps, but food bodies (lipid‐rich particles) were fewer. Fewer ants were observed on the plants at open sites than on plants in other habitats.

Leaves collected from the open sites were consumed less by the generalist herbivore, Spodoptera litura, than leaves collected from the other habitats. The effect of ants on herbivore exclusion was not readily apparent at open sites. Light intensity at the open sites was high. Soil water contents were low.

Tolerance was greater in the forest edge condition, where light intensity and soil water contents were intermediate.

Synthesis. The defence tactics of EFN‐bearing plants in the field must be determined considering the complex effects of different abiotic factors. Each plant can change its combination of defence traits in response to abiotic habitat conditions.
Beyond nectar sweetness: the hidden ecological role of non‐protein amino acids in nectar
Authors: Nepi Massimo 
Published: October 2013

SummaryStudies from the last decade clearly demonstrate that nectar is much more than just a simple alimentary reward for pollinators. Considerable progress has been made in recent years with regard to the chemical ecology of nectar, demonstrating unequivocally that its chemistry is strongly involved in the interactions between plants and a larger variety of organisms – from bacteria to fungi and animals – than previously thought. As far as plant–pollinator relationships are concerned, attention has recently been directed towards secondary compounds, mainly alkaloids that are able to induce a wide range of behavioural and physiological responses in floral visitors. Nonetheless the study of some other secondary compounds, such as non‐protein amino acids (NPAAs), has been neglected. The roles of these substances in nectar are still unknown although several ecological and physiological functions have been attributed to a number of NAAs in both animals and plants in several ecological and physiological contexts.The existence of NPAAs in floral nectar was first reported in early surveys of nectar composition dating from the 1970s. Since that time, only a very few papers have mentioned the presence of these compounds in nectar, but without any hypothesis relating to their ecological role and their putative effect on flower visitors. This appears surprising considering that interaction with other organisms is a recognized function of NPAAs in plants.Here, after exploring the multiple roles of NPAAs at the community level and focusing on the more recent advances in nectar chemistry and ecology, I review the small body of literature relating to the presence of NPAAs in nectar before outlining some ecological roles in the light of complex, nectar‐mediated, plant–animal interactions that have been recognized recently for other nectar secondary compounds based also on data and information obtained for other biological systems (from arthropods to humans).Synthesis. By integrating data obtained from both literature and field observations, I have arrived at the proposal that non‐protein amino acids in nectar may contribute to the plant–insect network of interactions in a number of ways: by affecting the physiology of the nervous system of the insect, regulating nectar intake through phagostimulation and promoting muscle function during flight. Confirmation of these hypotheses is needed in order to reinforce the concept that plants are able to affect the foraging behaviour of insects through nectar chemistry, thereby eventually optimizing their pollination effectiveness.