Factors affecting Grey‐headed Flying‐fox (Pteropus poliocephalus: Pteropodidae) foraging in the Melbourne metropolitan area,Australia

Abstract Factors affecting the foraging of mobile native fauna in highly fragmented urban landscapes have seldom been quantified at large spatial scales. We investigated factors affecting foraging by Grey‐headed Flying‐foxes (Pteropus poliocephalus; ‘flying‐foxes’) in the greater Melbourne metropolitan area. Flying‐foxes established a continuously occupied colony site in the Royal Botanic Gardens Melbourne in 1986, and the size of the colony has subsequently increased greatly. We used a stratified‐random sampling design to examine the importance of six variables on the detection of foraging flying‐foxes: (i) distance from the colony site (0–10, 10–20 and 20–30 km); (ii) distance from the Yarra River (0–5 and 5–20 km); (iii) the relative tree density of the municipality; (iv) whether the site was a park or street; (v) whether there was a relatively high or low density of trees at the site; and (vi) whether food was or was not detected at the site. We surveyed 240 sites within a 30‐km radius of the colony site for foraging flying‐foxes in both May and October 2002. The probability of detecting a foraging flying‐fox declined with increasing distance from the colony site, but increased with increasing tree cover, and was higher for parks compared with streets and when food was present. Flying‐foxes were observed foraging in a number of plant genera that have no species that naturally occur in the Melbourne area. Flying‐foxes in Melbourne thus forage on planted resources that are widely distributed within a fragmented landscape, and are an example of a positive response by a native species to the process of urbanization.     

Latitudinal range shifts in Australian flying‐foxes: A re‐evaluation

Recent range shifts towards higher latitudes have been reported for many animals and plants in the northern hemisphere, and are commonly attributed to changes in climate. Relatively little is known about such changes in the southern hemisphere, although it has been suggested that latitudinal distributions of the fruit‐bats Pteropus alecto and Pteropus poliocephalus changed during the 20th century in response to climate change in eastern Australia. However, historical changes in these species distributions have not been examined systematically. In this study we obtained historical locality records from a wide range of sources (including banding and museum records, government wildlife databases and unpublished records), and filtered them for reliability and spatial accuracy. The latitudinal distribution of each species was compared between eight time‐periods (1843–1920, 1921–1950, five 10‐year intervals between 1950 and 2000, and 2001–2007), using analyses of both the filtered point data (P. alecto 870 records, P. poliocephalus 2506) and presence/absence data within 50 × 50 km grid cells. The results do not support the hypothesis that either species range is shifting in a manner driven by climate change. First, neither the northern or southern range limits of P. poliocephalus (Mackay, Queensland and Melbourne, Victoria respectively) changed over time. Second, P. alecto's range limit extended southward by 1168 km (approximately 10.5 degrees latitude) during the twentieth century (from approximately Rockhampton, Queensland to Sydney, New South Wales). Within this zone of southward expansion (25–29°S), the percentage of total records that were P. alecto increased from 8% prior to 1950 to 49% in the early 2000s, and local count data showed that its abundance increased from several hundred to more than 10 000 individuals at specific roost sites, as range expansion progressed. Pteropus alecto expanded southward at about 100 km/decade, compared with the 10–26 km/decade rate of isotherm change, and analyses of historical weather data show that the species consequently moved into recently‐colder regions than it had previously occupied. Neither climate change nor habitat change could provide simple explanations to explain P. alecto's observed rapid range shift. More generally, climate change should not be uncritically inferred as a primary driver of species range shifts without careful quantitative analyses.     

Factors affecting the occupation of a colony site in Sydney,New South Wales by the Grey‐headed Flying‐fox Pteropus poliocephalus (Pteropodidae)

Previous authors have reported that Pteropus poliocephalus colony sites are occupied in response to blossom availability. However, in the present study it is reported that at the Gordon site in suburban Sydney, colony numbers were negatively correlated with the occurrence of pollen in the droppings. In addition, in contrast to reported occupational patterns at other colony sites, where flying‐foxes are not present at the site during winter and early spring, the Gordon site was occupied by substantial numbers of flying‐foxes throughout the entire period of 62 months from 1985 to 1990. As a result of the introduction of plants native to other parts of Australia and exotics from other continents, there is a variety of foods available throughout the year in the Sydney region, in comparison with less urbanized areas. This food supply permits the occupation of the Gordon colony site during winter and spring and reduces the migratory behaviour of flying‐foxes throughout the year. It is concluded that in the absence of a restrictive food supply, the occupational pattern of the Gordon colony of P. poliocephalus is the result of the reproductive requirements of the species modified by the vagaries of blossom production in the native forests outside the foraging range of the colony.     

Run,robber, run: parasitic acacia ants use speed and evasion to steal food from ant‐defended trees

Ants that are obligate plant associates protect their host against herbivores and aggressively defend the resources offered by the plant. Workers of Pseudomyrmex nigropilosus Emery (Hymenoptera: Formicidae), an acacia ant that parasitizes the mutualism by not defending the tree, are seen stealing food from other ant‐defended acacia trees. In the present study, hypotheses of evasion, chemical crypsis, chemical repellence and temporal activity patterns are tested in the field aiming to determine how P. nigropilosus enters other acacia trees, successfully circumventing the defence of the resident ants. When parasitic ants are stealing, resident ants are evaded by stopping walking, changing their walking direction or walking faster. Resident and parasitic workers have similar temporal activity patterns. Parasitic workers can walk 2.6‐fold faster compared with any of the three species of acacia‐ants from which they usually steal food. Behavioural assays suggest that P. nigropilosus do not have chemical repellence but that chemical crypsis may be involved in the evasion strategy. This last hypothesis needs to be explored further by chemical and olfactory analyses. The combination of speed and evasive reactions allows parasitic ants to access well‐defended acacia trees.     

Dynamic species distribution models reveal spatiotemporal habitat shifts in native range‐expanding versus non‐native invasive birds in an urban area

Urbanisation as a major driver of changes leads to the extinction of some species while others increase in abundance, especially non‐native species. Spatiotemporal distribution patterns of these successful species are likely to be shaped by their response and tolerance to urban features. This study assesses the anthropo‐ecological requirements of two co‐occurring bird species, the native range‐shifting jackdaw Corvus monedula and the non‐native invasive ring‐necked parakeet Psittacula krameri. We built yearly models over an eight‐year period using an ensemble modelling approach assessing response differences through time and between species. Predictors describing human‐made structures, socio‐ecological proxies and resources availability were extracted from temporally coincident databases. Dispersal and habitat constraints were implemented in final models to provide more realistic forecasts of species future distributions. Ensemble models evaluated with a random partition of the training dataset showed a higher accuracy than those evaluated with an independent dataset from another time period. Our results highlight temporal variations in the relative importance of predictors for both studied species. Single‐season occurrence data may thus be insufficient to characterize species ecological requirements. The ring‐necked parakeet and the jackdaw showed different responses to urban features. Jackdaws preferred the more urbanized part of the city while the distribution of parakeets was strongly positively associated with the density of exotic ornamental trees. We concluded that ring‐necked parakeet range expansion is likely to be driven by its effective ability to exploit urban resources which native species do not or under exploit, suggesting an open window of foraging opportunities. However, the jackdaw may be misled by a high cavity availability and a large amount of low‐quality anthropogenic food in the urban core. We suggest that dynamic SDMs are a critical tool not only to forecast the future expansion of invasive species but also for a better understanding of processes driving urban biodiversity persistence.     

Post‐fire habitat use of the golden‐backed tree‐rat (Mesembriomys macrurus) in the northwest Kimberley,Western Australia

Fire regimes are changing throughout the world. Changed fire patterns across northern Australian savannas have been proposed as a factor contributing to recent declines of small‐ and medium‐sized mammals. Despite this, few studies have examined the mechanisms that underpin how species use habitat in fire‐affected landscapes. We determined the habitats and resources important to the declining golden‐backed tree‐rat (Mesembriomys macrurus) in landscapes partially burnt by recent intense fire. We aimed to (i) compare the relative use of rainforest and savanna habitats; (ii) examine the effect of fire history on use of savanna habitats; and (iii) identify key foraging and denning resources. Habitat selection was examined by comparing the availability of eight habitat types around real (used) and generated (available) location points. Individuals used a range of habitats, but consistently selected long unburnt rainforest in preference to recently burnt savanna (1–12 months post‐fire); however, recently burnt savanna was used in preference to long unburnt savanna. Tree‐rats foraged in Terminalia hadleyana, Planchonia rupestris, Celtis philippensis and Owenia vernicosa, tree species that are found in a variety of habitat types. Individuals used a range of den sites, including cliffs, trees, logs, scree and stags found throughout the study area. Although multiple factors may have led to the decline of Mes. macrurus across its range, these results are consistent with the idea that changes in the savanna structure as a consequence of contemporary fire patterns could also have a role. The continued persistence of Mes. macrurus in the northwest Kimberley may be supported by land management strategies that conserve fruiting and hollow‐bearing trees, and maintain the availability of fire‐sensitive vegetation types.     

Food availability as a major driver in the evolution of life‐history strategies of sibling species

Life‐history theory predicts trade‐offs between reproductive and survival traits such that different strategies or environmental constraints may yield comparable lifetime reproductive success among conspecifics. Food availability is one of the most important environmental factors shaping developmental processes. It notably affects key life‐history components such as reproduction and survival prospect. We investigated whether food resource availability could also operate as an ultimate driver of life‐history strategy variation between species. During 13 years, we marked and recaptured young and adult sibling mouse‐eared bats (Myotis myotis and Myotis blythii) at sympatric colonial sites. We tested whether distinct, species‐specific trophic niches and food availability patterns may drive interspecific differences in key life‐history components such as age at first reproduction and survival. We took advantage of a quasi‐experimental setting in which prey availability for the two species varies between years (pulse vs. nonpulse resource years), modeling mark‐recapture data for demographic comparisons. Prey availability dictated both adult survival and age at first reproduction. The bat species facing a more abundant and predictable food supply early in the season started its reproductive life earlier and showed a lower adult survival probability than the species subjected to more limited and less predictable food supply, while lifetime reproductive success was comparable in both species. The observed life‐history trade‐off indicates that temporal patterns in food availability can drive evolutionary divergence in life‐history strategies among sympatric sibling species.     

Habitat differentiation among three Nigeria–Cameroon chimpanzee (Pan troglodytes ellioti) populations

Ecological niche models (ENMs) are often used to predict species distribution patterns from datasets that describe abiotic and biotic factors at coarse spatial scales. Ground‐truthing ENMs provide important information about how these factors relate to species‐specific requirements at a scale that is biologically relevant for the species. Chimpanzees are territorial and have a predominantly frugivorous diet. The spatial and temporal variation in fruit availability for different chimpanzee populations is thus crucial, but rarely depicted in ENMs. The genetic and geographic distinction within Nigeria–Cameroon chimpanzee (Pan troglodytes ellioti) populations represents a unique opportunity to understand fine scale species‐relevant ecological variation in relation to ENMs. In Cameroon, P. t. ellioti is composed of two genetically distinct populations that occupy different niches: rainforests in western Cameroon and forest–woodland–savanna mosaic (ecotone) in central Cameroon. We investigated habitat variation at three representative sites using chimpanzee‐relevant environmental variables, including fruit availability, to assess how these variables distinguish these niches from one another. Contrary to the assumption of most ENM studies that intact forest is essential for the survival of chimpanzees, we hypothesized that the ecotone and human‐modified habitats in Cameroon have sufficient resources to sustain large chimpanzee populations. Rainfall, and the diversity, density, and size of trees were higher at the rainforest. The ecotone had a higher density of terrestrial herbs and lianas. Fruit availability was higher at Ganga (ecotone) than at Bekob and Njuma. Seasonal variation in fruit availability was highest at Ganga, and periods of fruit scarcity were longer than at the rainforest sites. Introduced and secondary forest species linked with anthropogenic modification were common at Bekob, which reduced seasonality in fruit availability. Our findings highlight the value of incorporating fine scale species‐relevant ecological data to create more realistic models, which have implications for local conservation planning efforts.     

Temporal Variation in the Relative Abundance of Fruit Bats (Megachiroptera: Pteropodidae) in Relation to the Availability of Food in a Lowland Malaysian Rain Forest

The aims of this study were to investigate the diet and relative abundance of fruit bats in a lowland Malaysian rain forest and to test the hypothesis that the local assemblage structure of fruit bats varies significantly over time in relation to the availability of food. In total, 352 fruit bats of eight species were captured during 72,306 m² mist‐net hours of sampling between February 1996 and September 1999. Three species of fruit bats (Balionycteris maculita, Chironax melanocephalus, and Cynopterus brachyotis) that fed on a wide range of “steady state” and “big bang” food resources were captured continuously throughout the study period, with no significant variation in capture rates over time. In contrast, five species that fed exclusively or almost exclusively on “big bang” food resources were sampled intermittently, with significant temporal variation in the capture rates of two species (Cynopterus horsfieldi and Megaerops ecaudatus). Significant variation in the capture rates of the remaining three species (Dyacopterus spadiceus, Eonycteris spelaea, and Rousettus amplexicaudatus) could not be detected due to small sample sizes. Since ephemeral “big bang” food resources were only sporadically available within the study area and were associated with large canopy trees and strangler figs, these results suggest that food abundance, or the availability of specific food items, may be important factors limiting local fruit bat species diversity in old‐growth Paleotropical rain forest. Thus, only three fruit bat species were locally resident within the forest throughout the study period. Therefore, further studies on the ranging behavior and habitat requirements of Malaysian fruit bats are required to assess the adequacy of existing reserves and protected areas.     

Landscape‐scale redistribution of a highly mobile threatened species,Pteropus conspicillatus (Chiroptera,Pteropodidae), in response to Tropical Cyclone Larry

Abstract Severe category 4 Tropical Cyclone Larry, which crossed north‐east Queensland on 20 March 2006, provided a unique opportunity to examine the short‐term impacts of a major disturbance event on the population of a highly mobile threatened species, Pteropus conspicillatus. As we had recorded, the species’ population distribution in colonial roosts (camps) across the region each month for almost 2 years prior to Cyclone Larry, we continued monthly surveying of P. conspicillatus camp‐sites for a year post‐cyclone. Here we report on how P. conspicillatus responded and redistributed immediately after the cyclone, and over the subsequent year. Post‐cyclone, P. conspicillatus typically roosted in smaller camps than pre‐cyclone, suggesting that these animals had largely dispersed to locate available blossoms and fruit. For 6 months after Cyclone Larry, up to 90% of the pre‐cyclone P. conspicillatus population (ca. 250 000) was unaccounted for across the region. Information provided by the general public assisted us in locating six small camps of P. conspicillatus at ‘new’ locations, but contributed little to increase our overall population estimate for the species at this time. After November 2006, the number of P. conspicillatus built up at located camp‐sites until a post‐cyclone peak of 209 000 at the end of the study in March 2007, comparable with the population estimates in March 2005 and 2006. There is no evidence that the cyclone caused significant direct mortality among P. conspicillatus, although there may yet be longer‐term and indirect effects on population size. We suggest that redistribution by P. conspicillatus makes sense ecologically in the face of major habitat disturbance and short‐ to long‐term food resource limitation, and is not unlike the response of other Australian mainland Pteropus species to seasonal changes in food availability.     

Seasonal and inter‐island variation in the foraging strategy of the critically endangered Red‐headed Wood Pigeon Columba janthina nitens in disturbed island habitats derived from high‐throughput sequencing

We studied the feeding ecology of the critically endangered Red‐headed Wood Pigeon Columba janthina nitens, a subspecies endemic to a very remote and highly disturbed oceanic island chain, the Ogasawara Islands. An analysis based on high‐throughput sequencing (HTS) was undertaken on 627 faecal samples collected over 2 years from two island habitats, and food availability and the nutrient composition of the major fruits were also estimated. The HTS diet analysis detected 122 food plant taxa and showed clear seasonal and inter‐island variation in the diet of the Pigeons. The results indicated a preference for lipid‐rich fruits, but the diet changed according to the availability of food resources, perhaps reflecting the foraging strategy of the Pigeons in isolated island habitats with poor food resources. Pigeons also frequently consumed introduced plants at certain times of year, perhaps compensating for the lack of preferred native food resources. However, the degree of dependence on introduced plants appeared to differ between the two island habitats, so the different impacts of introduced plant eradication on the foraging conditions for the Pigeons on each island should be considered. HTS diet analysis combined with field data may be useful for monitoring the foraging conditions of endangered species and may also inform an appropriate conservation strategy in oceanic island ecosystems with complicated food webs that include both native and introduced species.     

Characteristics of hollows and hollow‐bearing trees in semi‐arid river red gum woodland and potential limitations for hollow‐dependent wildlife

Up to 37 species of the birds and microbats inhabiting inland Australia are dependent on tree cavities for breeding or roosting. The river red gum (Eucalyptus camaldulensis), a well‐known hollow‐bearing tree species, occurs in linear semi‐arid woodland along thousands of kilometres of ephemeral river channels and is the only tree species that provides widespread, aggregated hollow resources across a landscape otherwise dominated by shrublands. Here we assess the type and quantity of hollows available along ephemeral rivers of the MacDonnell Ranges bioregion in central Australia and determine which characteristics of river red gums best predict the abundance and characteristics of different tree hollows, as first steps towards assessing the current availability of hollows in the region. Approximately a third of all river red gums sampled were hollow‐bearing, but individual trees with abundant hollows were rare. Further, 36% of hollows had an entrance ≤ 5 cm, and 37% had entrances which were 6–10 cm in diameter, whereas only 13% of hollows had an entrance diameter > 20 cm suitable for larger hollow‐using species. Large and high hollows only occurred on trees that did not display post‐disturbance resprouting. Trees with multiple and diverse hollows were rare and tended to be in advanced stages of senescence and had larger stems (82.3 ± 3.33 cm) and were taller (14.4 ± 0.53 m) compared to non‐hollow‐bearing trees (23.44 ± 1.68 cm, 8.0 ± 0.34 m). Further research is required to establish whether the current abundance of hollows and diversity of hollow types are limiting to cavity‐dependent wildlife, and to identify any threats to availability of hollows.     

Predicting the Competitive Regime of Female <Emphasis Type="Italic">Colobus vellerosus</Emphasis> from the Distribution of Food Resources

We examined the spatial and temporal distribution of the foods of ursine colobus (Colobus vellerosus) at Boabeng-Fiema, Ghana as a means to predict the monopolizablity and usurpability of their food resources. Recent evidence suggests that food may not be limiting for folivorous primates, and that male sexual coercion may be a more important influence on folivore social organization. To address the question, we collected focal data on the feeding behavior of adult females and males over 11 mo (September 2000-August 2001) on 2 groups: WW (n = 31–33 individuals) and B (n = 8–16 individuals). We also conducted phenological monitoring and a tree survey of the two-group home ranges to establish food availability and distribution. We used 2 behavioral or organism-defined indicators of feeding behavior to assess potential resource contestability: food site residence time and distance moved between food sites. The colobus fed on a high diversity of species, most of their food trees were not clumped in distribution, within-tree interfood distances were short, and food trees were large. The only condition associated with the potential for monopolization was low food tree density. However, low food tree density may be offset by the colobus’ use of large trees. Taken together, the ecological and behavioral indicators suggest the food resources of Colobus vellerosus had a low potential for monopolization. Our results also indicate mature leaves had the longest food site residence time, which may suggest they should be the most usurpable plant part, though their presumed low quality and high abundance probably counteracted the effect. The pattern implied the potential for direct feeding competition among Colobus vellerosus at Boabeng-Fiema was low and agonistic interactions over food are not expected. Instead, a group size effect on feeding efficiency should be a more predominant influence on feeding efficiency, if food is limiting for the species.     

Context‐dependent conservation of the cavity‐nesting European Roller

To maximize the effectiveness of conservation interventions, it is crucial to have an understanding of how intraspecific variation determines the relative importance of potential limiting factors. For bird populations, limiting factors include nest‐site availability and foraging resources, with the former often addressed through the provision of artificial nestboxes. However, the effectiveness of artificial nestboxes depends on the relative importance of nest‐site vs. foraging resource limitations. Here, we investigate factors driving variation in breeding density, nestbox occupation and productivity in two contrasting study populations of the European Roller Coracias garrulus, an obligate cavity‐nesting insectivorous bird. Breeding density was more than four times higher at the French study site than at the Latvian site, and there was a positive correlation between breeding density (at the 1‐km² scale) and nest‐site availability in France, whereas there was a positive correlation between breeding density and foraging resource availability in Latvia. Similarly, the probability of a nestbox being occupied increased with predicted foraging resource availability in Latvia but not in France. We detected no positive effect of foraging resource availability on productivity at either site, with most variation in breeding success driven by temporal effects: a seasonal decline in France and strong interannual fluctuations in Latvia. Our results indicate that the factors limiting local breeding density can vary across a species' range, resulting in different conservation priorities. Nestbox provisioning is a sufficient short‐term conservation solution at our French study site, where foraging resources are typically abundant, but in Latvia the restoration of foraging habitat may be more important.     

Does a long‐term shift in Wood Stork diet foreshadow adaptability to human‐induced rapid environmental change?

To preserve biodiversity, identifying at‐risk populations and developing conservation plans to mitigate the effects of human‐induced rapid environmental change (HIREC) are essential. Changes in diet, especially for food‐limited species, can aid in detecting populations being impacted by HIREC, and characterizing the quality, abundance, and temporal and spatial consistency of newly consumed food items may provide insight concerning the likelihood of a species persisting in a changing environment. We used Wood Storks (Mycteria americana) nesting in the Florida Everglades as a model system to study the possible effects of HIREC on a food‐limited population. We compared the diets of Wood Storks in 2013 and 2014 with those reported during the 1970s before major anthropogenic activities affected the Everglades system and prey availability. Wood Storks in our study consumed more large‐bodied sunfish species (Lepomis spp.), fewer native marsh fishes, and more non‐native fish species than during the 1970s. Large sunfish and non‐native fish are relatively rare in the drying pools of Everglades marshes where storks traditionally forage, suggesting that Wood Storks may be using novel foraging habitats such as created wetlands (i.e., canals and stormwater ponds). Although created wetlands have long hydroperiods conducive to maintaining large‐bodied fishes and could provide alternative foraging habitat when prey availability is reduced in natural marshes, additional studies are needed to determine the extent to which these wetlands are used by Wood Storks and, importantly, the quality of prey items potentially available to foraging Wood Storks in created wetlands.     

Molecular phylogeny of Osmanthus (Oleaceae) based on non‐coding chloroplast and nuclear ribosomal internal transcribed spacer regions

Abstract The phylogenetic relationships of Osmanthus Lour. were investigated using the nuclear ribosomal internal transcribed spacer (ITS) regions and non‐coding chloroplast regions (psbA‐trnH, trnL‐F). The two datasets support the conclusion that Osmanthus is polyphyletic, with some species of the subtribe Oleinae nested within Osmanthus. Osmanthus didymopetalus P. S. Green is nested within the clade formed by species of section Osmanthus in two trees. Osmanthus attenuatus P. S. Green, O. yunnanensis P. S. Green, and O. gracilinervis R. L. Lu of traditional section Osmanthus are clearly divergent from other accessions, and do not form a monophyletic group with other Osmanthus accessions. Osmanthus marginatus Hemsl. is embedded in the clade formed by species of section Osmanthus in the ITS tree. In cpDNA trees all species of section Osmanthus are placed in the large clade and all species of section Leiolea formed a group. The taxonomic incongruence among trees for ITS and cpDNA indicate hybridization, as introgression may have occurred among some species of sections Osmanthus and Leiolea. Phylogeny of Osmanthus is discussed in light of molecular and morphological data, and a revised infrageneric classification with three sections (Leiolea, Siphosmanthu, and Osmanthus) is presented. The section Linocieroides is abandoned and united with section Osmanthus.     

The importance of food supply in high‐productivity ecosystems: Short‐term experimental tests with small rodents

Food availability is considered to be a primary factor affecting animal populations, yet few experimental tests have been performed to evaluate its actual importance in species‐rich ecosystems such as rainforests. It has been suggested that in such systems certain plant species may act as “keystone” resources for animals, but the importance of presumed keystone resources for populations has not been quantified experimentally. Using complementary seed removal and seed‐addition experiments, we determined how the supply of a presumed keystone resource, seeds of Araucaria angustifolia, affects short‐term demography of their main consumer group (small rodents) in a biodiversity hotspot, the Brazilian Atlantic Forest. We hypothesized that (i) the harvest of A. angustifolia seeds by human populations has negative impacts on rodents, and (ii) these seeds are a limiting resource for rodent populations. To test these hypotheses, we monitored populations of two species of numerically dominant rodents (Delomys dorsalis and Akodon montensis) within replicated control‐experimental plots. Manipulations of seed supply over 2 years had little effect on population size, body condition, survival, or reproduction of the two rodents, suggesting that, in the short‐term (within one generation), their populations are not food limited in Araucaria forests. Despite apparently having all the characteristics of a keystone resource, as currently defined in the literature, the seeds of A. angustifolia had limited influence on the short‐term demography of their main consumer group. In situations where purported keystone resources are seasonally abundant, their actual importance may be lower than generally assumed, and these resources then may have only localized and temporary effects on consumer populations.     

Nutrition‐ and sex‐dependent utilization of body resources in relation to reproduction in a scorpionfly

Reproduction often comes at a cost of a reduction in body functions. In order to enhance their reproductive output, some insect species degenerate their thoracic muscles, typically resulting in reduced flight ability. From a life‐history trade‐off perspective, we expect the importance of body resource utilization to be amplified both with increased reproductive expenditure and with increased resource limitation. In this study, we measured age‐related changes in thorax weight, as a measure of flight muscle size, during a major part of the adult lifespan in males and females of the scorpionfly Panorpa vulgaris. The aim of the study was twofold: first to investigate whether scorpionflies have the potential to degenerate their flight muscles; second, and more importantly, to determine whether the magnitude of flight muscle degeneration is a plastic response in relation to resource availability, and if it differs between the sexes. The results clearly demonstrate that food availability does influence investment in flight muscle development. The build‐up of the thoracic muscles was strongly influenced by nutrient availability. Furthermore, the age‐related decrease in thorax weight was significantly different for males and females. Only females showed a strong age‐dependent decrease in thorax weight, indicative of muscle degeneration, yet no difference between food treatments was detected. For males, there was no significant directional change in thorax weight. Nevertheless, with increasing age, the difference in thorax weight between food treatments increased significantly. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 199–207.     

Plasticity in gas‐exchange physiology of mature Scots pine and European larch drive short‐ and long‐term adjustments to changes in water availability

Adjustment mechanisms of trees to changes in soil‐water availability over long periods are poorly understood, but crucial to improve estimates of forest development in a changing climate. We compared mature trees of Scots pine (Pinus sylvestris) and European larch (Larix decidua) growing along water‐permeable channels (irrigated) and under natural conditions (control) at three sites in inner‐Alpine dry valleys. At two sites, the irrigation had been stopped in the 1980s. We combined measurements of basal area increment (BAI), tree height and gas‐exchange physiology (Δ¹³C) for the period 1970–2009. At one site, the Δ¹³C of irrigated pine trees was higher than that of the control in all years, while at the other sites, it differed in pine and larch only in years with dry climatic conditions. During the first decade after the sudden change in water availability, the BAI and Δ¹³C of originally irrigated pine and larch trees decreased instantly, but subsequently reached higher levels than those of the control by 2009 (15 years afterwards). We found a high plasticity in the gas‐exchange physiology of pine and larch and site‐specific responses to changes in water availability. Our study highlights the ability of trees to adjust to new conditions, thus showing high resilience.     

How a measure of tree structural complexity relates to architectural benefit‐to‐cost ratio,light availability,and growth of trees

Aboveground tree architecture is neither fully deterministic nor random. It is likely the result of mechanisms that balance static requirements and light‐capturing efficiency. Here, we used terrestrial laser scanning data to investigate the relationship between tree architecture, here addressed using the box‐dimension (D_b), and the architectural benefit‐to‐cost ratio, the light availability, and the growth of trees. We detected a clear relationship between D_b and the benefit‐to‐cost ratio for the tested three temperate forest tree species (Fagus sylvatica L., Fraxinus excelsior L., and Acer pseudoplatanus L.). In addition, we could also show that D_b is positively related to the growth performance of several tropical tree species. Finally, we observed a negative relationship between the strength of competition enforced on red oak (Quercus rubra L.) trees and their D_b. We therefore argue that D_b is a meaningful and integrative measure that describes the structural complexity of the aboveground compartments of a plant as well as its relation to structural efficiency (benefit‐to‐cost ratio), productivity, and growing conditions (competition or availability of light).