Butterfly,seedling, sapling and tree diversity and composition in a fire‐affected Bornean rainforest

Abstract: Fire‐affected forests are becoming an increasingly important component of tropical landscapes. The impact of wildfires on rainforest communities is, however, poorly understood. In this study the density, species richness and community composition of seedlings, saplings, trees and butterflies were assessed in unburned and burned forest following the 1997/98 El Niño Southern Oscillation burn event in East Kalimantan, Indonesia. More than half a year after the fires, sapling and tree densities in the burned forest were only 2.5% and 38.8%, respectively, of those in adjacent unburned forest. Rarefied species richness and Shannon's H’ were higher in unburned forest than burned forest for all groups but only significantly so for seedlings. There were no significant differences in evenness between unburned and burned forest. Matrix regression and Akaike's information criterion (AIC) revealed that the best explanatory models of similarity included both burning and the distance between sample plots indicating that both deterministic processes (related to burning) and dispersal driven stochastic processes structure post‐disturbance rainforest assemblages. Burning though explained substantially more variation in seedling assemblage structure whereas distance was a more important explanatory variable for trees and butterflies. The results indicate that butterfly assemblages in burned forest were primarily derived from adjacent unburned rainforest, exceptions being species of grass‐feeders such as Orsotriaena medus that are normally found in open, disturbed areas, whereas burned forest seedling assemblages were dominated by typical pioneer genera, such as various Macaranga species that were absent or rare in unburned forest. Tree assemblages in the burned forest were represented by a subset of fire‐resistant species, such as Eusideroxylon zwageri and remnant dominant species from the unburned forest.     

Primers for the amplification of nuclear introns in Heliconius butterflies

I described the development of degenerate polymerase chain reaction (PCR) primers for intron‐containing regions of nine candidate wing patterning and pigmentation genes in Heliconius butterflies. Primers were developed by comparing sequence data from Drosophila melanogaster, Precis coenia, and a variety of other insects so they are likely to be applicable widely among the butterfly family Nymphalidae and perhaps Lepidoptera in general. The amplified regions are highly variable and should be useful for inferring relationships among closely related species and estimating the phylogeographical and population genetic structure of individual species.     

Migration in butterflies: a global overview

Insect populations including butterflies are declining worldwide, and they are becoming an urgent conservation priority in many regions. Understanding which butterfly species migrate is critical to planning for their conservation, because management actions for migrants need to be coordinated across time and space. Yet, while migration appears to be widespread among butterflies, its prevalence, as well as its taxonomic and geographic distribution are poorly understood. The study of insect migration is hampered by their small size and the difficulty of tracking individuals over long distances. Here we review the literature on migration in butterflies, one of the best-known insect groups. We find that nearly 600 butterfly species show evidence of migratory movements. Indeed, the rate of ‘discovery’ of migratory movements in butterflies suggests that many more species might in fact be migratory. Butterfly migration occurs across all families, in tropical as well as temperate taxa; Nymphalidae has more migratory species than any other family (275 species), and Pieridae has the highest proportion of migrants (13%; 133 species). Some 13 lines of evidence have been used to ascribe migration status in the literature, but only a single line of evidence is available for 92% of the migratory species identified, with four or more lines of evidence available for only 10 species – all from the Pieridae and Nymphalidae. Migratory butterflies occur worldwide, although the geographic distribution of migration in butterflies is poorly resolved, with most data so far coming from Europe, USA, and Australia. Migration is much more widespread in butterflies than previously realised – extending far beyond the well-known examples of the monarch Danaus plexippus and the painted lady Vanessa cardui – and actions to conserve butterflies and insects in general must account for the spatial dependencies introduced by migratory movements.     

Relationships between the age of northern Kantou plain (central Japan) coppice woods used for production of Japanese forest mushroom logs and butterfly assemblage structure

To discern mechanisms maintaining the diversity of grassland and forest butterflies in coppice woods managed for the production of Japanese forest mushroom logs, we investigated the butterfly fauna in cut-over land tracts shortly after felling and 5 year later, and in forest stands 10, 15, and 25 year after felling (here, we use the term “forests” when referring to the chronosequence of these treed stands). Butterfly species richness and diversity (H′) and the densities of individuals were highest in cut-over lands 5 year after clear-cutting, followed by 25-year-old forest stands. In forests, the richness and densities of forest butterfly species were higher than were those of grassland species. Among forest stands of different ages, forest butterfly species’ richness and the densities of individuals were highest in 25-year-old woods nearing felling time. Some forest butterfly species were observed only in forests. The species richness and densities of grassland butterflies were much higher in cut-over lands 0 and 5 year post felling than in forests; grassland species were rarely found in stands ≥10 year old. Thus, cut-over lands seem to function as temporary habitats for grassland species. Furthermore, the number of forest butterfly species was the same in cut-over lands 5 year after felling and in 25-year-old forest stands; the densities of forest butterfly species was higher in these cut-over lands than in the forest stands. Forest butterfly species living on cut-over land 5 year post felling sipped flower nectar, laid eggs on host plants, and practiced territorial behaviour involved in mate finding. Hence, these cut-over lands functioned as important habitats for various developmental stages of forest butterflies. In conclusion, traditional coppicing in woods for production of Japanese forest mushroom logs is very important for the maintenance of diversity in grassland and forest butterfly species.     

Isolation and characterization of microsatellites in two tropical butterflies,Drupadia theda and Arhopala epimuta (Lepidoptera: Lycaenidae)

Little is known about the effect of El Niño Southern Oscillation‐induced fires on the genetic diversity of tropical rainforest species. Here, I report on the isolation and characterization of 10 microsatellite loci, five loci each, for two lycaenid butterfly species in East Kalimantan, Indonesia, namely Drupadia theda and Arhopala epimuta, which will be used to specifically study the impact of disturbance on genetic diversity. Microsatellite enrichment was carried out using streptavidin‐coated magnetic beads. Positive colonies were identified with the three‐primer polymerase chain reaction (PIMA). Cross‐species amplifications conducted both within and between genera were successful in 16 out of 20 tests.     

Effects of fire on understorey birds in Kimboza Forest Reserve in the eastern foothills of the Uluguru Mountains,Tanzania

Fire is one of the main threats facing the long‐term survival of the forests in the Eastern Arc Mountains. Yet, our understanding of how it affects fauna, particularly birds, is still poor. A fire that originated on surrounding farmland burned approximately half of Kimboza Forest Reserve between 13 and 15 October 2010. To better understand how birds respond to fire, a short‐term study of understorey bird diversity and abundance in this forest reserve was conducted by comparing burned and unburned sites twenty months post‐fire. Capture rates were significantly higher at the unburned site compared to the burned site. Bird species diversity was also higher at the unburned site than at the burned site. Despite the brevity of the study, the results suggest that fire has negative effects on forest avifauna and forest fires need to be prevented at Kimboza Forest Reserve as they affect the distribution and diversity of understorey birds.     

Genome size variation in butterflies (Insecta,Lepidotera, Papilionoidea): a thorough phylogenetic comparison

Butterflies have been of great interest to naturalists for centuries, and the study of butterflies has been an integral part of ecology and evolution ever since Darwin proposed his theory of natural selection in 1859. There are > 18 000 butterfly species worldwide, showing great diversity in morphological traits and ecological niches. Compared with butterfly diversity, however, patterns of genome size variation in butterflies remain poorly understood, especially in a phylogenetic context. Here, we sequenced and assembled the mitogenomes of 68 butterflies and measured the genome sizes (C-values) of 67 of them. We also assembled 10 mitogenomes using reads from GenBank. Among the assembled 78 mitogenomes, those from 59 species, 23 genera and one subfamily are reported for the first time. Combining with published data of mitogenomes and genome size, we explored the patterns in genome size variation for 106 butterfly species in a phylogenetic context based on analyses of mitogenomes from 264 species covering six families. Our results show that the genome size of butterflies has a 6.4-fold variation ranging from 0.203 pg (199 Mb) (Nymphalidae: Heliconius xanthocles) to 1.287 pg (1253 Mb) (Papilionidae: Parnassius orleans). Within families, the largest variation was found in Papilionidae (5.9-fold: 0.22–1.29 pg), followed by Nymphalidae (4.8-fold: 0.2–0.95 pg), Pieridae (4.4-fold: 0.22–0.97 pg), Hesperiidae (2.2-fold: 0.3–0.66 pg), Lycaenidae (2.6-fold: 0.39–1.02 pg) and Rioidinidae (1.8-fold: 0.48–0.87 pg). Our data also suggest that butterflies have an ancestral genome size of c. 0.5 pg, and some ancestral genome size increase or decrease events along different subfamilies or tribes produce the diversity of genome size variation in diverse butterflies. Our data provide novel insights into patterns of genome size variation in butterflies and are an important reference for future genome sequencing programmes.     

Dynamic landscapes shape post‐wildfire recolonisation and genetic structure of the endangered Hermes copper (Lycaena hermes) butterfly

1. The coastal sage scrub vegetation community experiences frequent fires, so the long‐term survival of species depends on the rate of recolonisations exceeding the rate of local extinctions. Recolonisation of these post‐wildfire habitats probably requires long‐distance dispersal events. These movements can also counter detrimental impacts associated with inbreeding. 2. The Hermes copper (Lycaena hermes) is an extremely rare butterfly inhabiting coastal sage scrub adjacent to San Diego, California, USA. Habitat loss due to urbanisation and impacts of recent wildfires has greatly restricted its range, prompting the United States Fish and Wildlife Service to list the Hermes copper as a Candidate Species in 2011. 3. Surveys for Hermes copper butterflies in 2010–2013 documented only two recolonisation events following wildfires in 2003 and 2007. Larger populations were readily detected each year, but detection of smaller populations was inconsistent. 4. Amplified fragment length polymorphism was used to identify potential genetic discontinuities within this species across the landscape. Results indicated that movements across much of the landscape were possible historically. However, individuals from three peripheral populations exhibited a higher degree of differentiation, suggesting more restricted dispersal in these regions. 5. From the results, it can be concluded that historically Hermes copper butterflies were able to move among habitat patches prior to recent changes in the landscape. However, low post‐fire recolonisation rates suggest limited contemporary dispersal, probably due to recent habitat fragmentation. This fragmentation is a relatively new event, as the human population in San Diego County experienced substantial growth in the late 20th Century.     

European checkerspots (Melitaeini: Lepidoptera,Nymphalidae) are not aposematic – the point of view of great tits (Parus major)

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High‐prevalence male‐killing Wolbachia in the butterfly Acraea encedana

Inherited bacteria which kill males during early development are widely distributed throughout the insects, but have been little studied outside of a single family of beetles, the Coccinellidae. We have investigated a male‐killing bacterium discovered in the butterfly Acraea encedana. This bacterium belongs to the genus Wolbachia and is identical in wsp gene sequence to a male‐killer in the closely related butterfly A. encedon, suggesting that it has either recently moved between host species or was inherited from a common ancestor of the butterflies. The prevalence of Wolbachia is remarkably high, 95% of females are infected and only 6% of wild caught butterflies are male. Measurements of the vertical transmission efficiency were used to calculate that this high prevalence is the result of infected females producing at least 1.79 times the number of surviving daughters as uninfected females (lower confidence limit is 1.25).     

Species diversity of Ichneurnonidae and Serphidae (Hymenoptera) in an English suburban garden

In the two-year period, 1972–73, 6445 Ichneumonidae of 455 species were caught in a Malaise trap operated in a suburban garden in Leicester, England. An additional 74 species were trapped in 1974. The collection includes a number of species new to the British list. The flight season of ichneumonids extended from March to November or December, with peak abundance and diversity in August. Size of trap samples fluctuated erratically, depending on air temperature. No species was particularly common and many were rare, 141 being taken once only in the two-year period. The commoner species were present throughout the season, supporting the suggestion that ichneumonids are niche-specific rather than host-specific. Parasites of aphidophagous Neuroptera and Syrphidae, of spiders, of micro-Lepidoptera, and of Diptera found in decaying plant material were especially abundant, as is characteristic of the British fauna as a whole. Adult ichneumonids are mobile, and it is assumed that the Malaise trap was sampling an area far larger than the garden in which it was sited, although suburban gardens are a particularly favourable habitat for ichneumonids. Twenty-two species of Serphidae were captured in the Malaise trap during 1972–74, five of them new to Britain.     

Impacts of forest gaps on butterfly diversity in a Bornean peat-swamp forest

Forest degradation is leading to widespread negative impacts on biodiversity in South-east Asia. Tropical peat-swamp forests are one South-east Asian habitat in which insect communities, and the impacts of forest degradation on them, are poorly understood. To address this information deficit, we investigated the impacts of forest gaps on fruit-feeding butterflies in the Sabangau peat-swamp forest, Central Kalimantan, Indonesia. Fruit-baited traps were used to monitor butterflies for 3 months during the 2009 dry season. A network of 34 traps (n_gap = 17, n_shade = 17) was assembled in a grid covering a 35 ha area. A total of 445 capture events were recorded, comprising 384 individuals from 8 species and 2 additional species complexes classified to genera. On an inter-site scale, canopy traps captured higher species richness than understory traps; however, understory traps captured higher diversity within each site. Species richness was positively correlated with percent canopy cover and comparisons of diversity indices support these findings. Coupled with results demonstrating morphological differences in thorax volume and forewing length between species caught in closed-canopy traps vs. those in gaps, this indicates that forest degradation has a profound effect on butterfly communities in this habitat, with more generalist species being favored in disturbed conditions. Further studies are necessary to better understand the influences of macro-habitat quality and seasonal variations on butterfly diversity and community composition in South-east Asian peat-swamp forests.     

Spatiotemporal distribution and resource use of scoliid wasps (Hymenoptera) in coastal sand dunes

The spatial and temporal distributions of scoliid wasps in the coastal sand dunes at Hakoishi, Kyoto Prefecture, Japan, were investigated using three different sampling methods in 2002 and 2003. Of eight scoliid species collected in the present study, five species, Scolia historionica, Campsomeriella annulata, Scolia decorata, Scolia oculata, and Megacampsomeris schulthessi, were dominant. The flying insects caught by Malaise traps and flower‐visiting insects caught by insect nets were mostly males, and this biased pattern was due to the active mate‐searching behavior of male wasps and their frequent visits to flowers to supplement energy consumed by such behavior. Given that the ground traps caught females exclusively, female wasps seemed to actively engage in host‐searching behavior on and below the ground. Of the wasps caught by Malaise traps and flower‐visit sampling, five dominant species showed spatially different habitat use: S. historionica and C. annulata mainly occupied the grassland zone on the plain (Gp), S. decorata occupied the grassland zone on the terrace (Gt) and the forest zone (Fp), S. oculata occupied the small scrub zone on the plain (Sp), and M. schulthessi occupied the small scrub zone on the terrace (St). Ground trap samples also indicated that S. historionica and C. annulata shared habitats. On the basis of the observed seasonal changes in wasp abundance and the degree of wing wear as an index of wasp age, S. historionica and C. annulata are thought to be bivoltine species, whereas S. decorata, S. oculata, and M. schulthessi are thought to be univoltine species. These scoliid wasp species may play an important role in pollinating coastal plants in the grassland zone.     

High and dry: post‐fire tree seedling establishment in subalpine forests decreases with post‐fire drought and large stand‐replacing burn patches

Aim Climate warming and increased wildfire activity are hypothesized to catalyse biogeographical shifts, reducing the resilience of fire‐prone forests world‐wide. Two key mechanisms underpinning hypotheses are: (1) reduced seed availability in large stand‐replacing burn patches, and (2) reduced seedling establishment/survival after post‐fire drought. We tested for regional evidence consistent with these mechanisms in an extensive fire‐prone forest biome by assessing post‐fire tree seedling establishment, a key indicator of forest resilience. Location Subalpine forests, US Rocky Mountains. Methods We analysed post‐fire tree seedling establishment from 184 field plots where stand‐replacing forest fires were followed by varying post‐fire climate conditions. Generalized linear mixed models tested how establishment rates varied with post‐fire drought severity and distance to seed source (among other relevant factors) for tree species with contrasting post‐fire regeneration adaptations. Results Total post‐fire tree seedling establishment (all species combined) declined sharply with greater post‐fire drought severity and with greater distance to seed sources (i.e. the interior of burn patches). Effects varied among key species groups. For conifers that dominate present‐day subalpine forests (Picea engelmannii, Abies lasiocarpa), post‐fire seedling establishment declined sharply with both factors. One exception was serotinous Pinus contorta, which did not vary with either factor. For montane species expected to move upslope under future climate change (Larix occidentalis, Pseudotsuga menziesii, Populus tremuloides) and upper treeline species (Pinus albicaulis), establishment was unrelated to either factor. Greater post‐fire tree seedling establishment on cooler/wetter aspects suggested local topographic refugia during post‐fire droughts. Main conclusions If future drought and wildfire patterns manifest as expected, post‐fire tree seedling establishment of species that currently characterize subalpine forests could be substantially reduced. Compensatory increases from lower montane and upper treeline species may partially offset these reductions, but our data suggest important near‐ to mid‐term shifts in the composition and structure of high‐elevation forests under continued climate warming and increased wildfire activity.     

The effect of fire interval on post‐fire understorey communities in Yellowstone National Park

Questions: How does the time interval between subsequent stand‐replacing fire events affect post‐fire understorey cover and composition following the recent event? How important is fire interval relative to broad‐ or local‐scale environmental variability in structuring post‐fire understorey communities? Location: Subalpine plateaus of Yellowstone National Park (USA) that burned in 1988. Methods: In 2000, we sampled understorey cover and Pinus contorta density in pairs of 12–yr old stands at 25 locations. In each pair, the previous fire interval was either short (7–100 yr) or long (100–395 yr). We analysed variation in understorey species richness, total cover, and cover of functional groups both between site pairs (using paired t‐tests) and across sites that experienced the short fire intervals (using regression and ordination). We regressed three principal components to assess the relative importance of disturbance and broad or local environmental variability on post‐fire understorey cover and richness. Results: Between paired plots, annuals were less abundant and fire‐intolerant species (mostly slow‐growing shrubs) were more abundant following long intervals between prior fires. However, mean total cover and richness did not vary between paired interval classes. Across a gradient of fire intervals ranging from 7–100 yr, total cover, species richness, and the cover of annuals and nitrogen‐fixing species all declined while the abundance of shrubs and fire‐intolerant species increased. The few exotics showed no response to fire interval. Across all sites, broad‐scale variability related to elevation influenced total cover and richness more than fire interval. Conclusions: Significant variation in fire intervals had only minor effects on post‐fire understorey communities following the 1988 fires in Yellowstone National Park.     

Threatened mammals become more predatory after small‐scale prescribed fires in a high‐rainfall rocky savanna

Understanding mechanisms underlying fire regime effects on savanna fauna is difficult because of a wide range of possible trophic interactions and feedbacks. Yet, understanding mechanisms underlying fauna dynamics is crucial for conservation management of threatened species. Small savanna mammals in northern Australia are currently undergoing widespread declines and regional extinctions partly attributable to fire regimes. This study investigates mammal trophic and ecosystem responses to fire in order to identify possible mechanisms underlying these declines. Mammal trophic responses to fire were investigated by surveying mammal abundance, mammal diet, vegetation structure and non‐mammal fauna dynamics in savannas six times at eight sites over a period of 3 years. Known site‐specific fire history was used to test for trophic responses to post‐fire interval and fire frequency. Mammal and non‐mammal fauna showed only minor responses of post‐fire interval and no effect of fire frequency. Lack of fauna responses differed from large post‐fire vegetation responses. Dietary analysis showed that two mammal species, Dasyurus hallucatus and Isoodon auratus, increased their intake of large prey groups in recently burnt, compared to longer unburnt vegetation. This suggests a fire‐related change in trophic interactions among predators and their prey, after removal of ground‐layer vegetation. No evidence was found for other changes in food resource uptake by mammals after fire. These data provide support for a fire‐related top‐down ecosystem response among savanna mammals, rather than a bottom‐up resource limitation response. Future studies need to investigate fire responses among other predators, including introduced cats and dingoes, to determine their roles in fire‐related mammal declines in savannas of northern Australia.     

Fire history of Araucaria–Nothofagus forests in Villarrica National Park, Chile

Aim In this study we examine fire history (i.e. c. 500 yr bp to present) of Araucaria–Nothofagus forests in the Andes cordillera of Chile. This is the first fire history developed from tree rings for an Araucaria–Nothofagus forest landscape. Location The fire history was determined for the Quillelhue watershed on the north side of Lanin volcano in Villarrica National Park, Chile. The long‐lived Araucaria araucana was commonly associated with Nothofagus pumilio and N. antarctica in more mesic and drier sites respectively. Methods Based on a combination of fire‐scar proxy records and forest stand ages, we reconstructed fire frequency, severity, and the spatial extent of burned areas for an c. 4000 ha study area. We used a composite fire chronology for the purpose of determining centennial‐scale changes in fire regimes and comparing the pre‐settlement (pre‐1883) and post‐settlement fire regimes. In addition, we contrasted Araucaria and Nothofagus species as fire‐scar recorders. Results In the study area, we dated a total of 144 fire‐scarred trees, representing 46 fire years from ad 1446 to the present. For the period from ad 1696 to 2000, using fire dates from Araucaria and Nothofagus species, the composite mean fire interval varied from 7 years for all fires to 62 years for widespread events (i.e. years in which ≥ 25% of recorder trees were scarred). Sensitivity to fire was different for Araucaria and Nothofagus species. More than 98% of the fires recorded by Nothofagus species occurred during the 1900s. The lack of evidence for older fire dates (pre‐1900) in Nothofagus species was due to their shorter longevity and greater susceptibility to being killed by more severe fires. Whereas the thin‐barked N. pumilio and N. antarctica are often destroyed in catastrophic fire events, large and thick‐barked Araucaria trees typically survive. The spatial extent of fires ranged from small patchy events to those that burned more than 40% of the entire landscape (c. > 1500 ha). Main conclusions Fire is the most important disturbance shaping the Araucaria–Nothofagus landscape in the Araucarian region. The forest landscape has been shaped by a mixed‐severity fire regime that includes surface and crown fires. High‐severity widespread events were relatively infrequent (e.g. 1827, 1909 and 1944) and primarily affected tall Araucaria–N. pumilio forests and woodlands dominated by Araucaria–N. antarctica. Although there is abundant evidence of the impact of Euro‐Chilean settlers on the area, the relative influence of this settlement on the temporal pattern of fire could only be tentatively established due to the relatively small number of pre‐1900 fire dates. An apparent increase in fire occurrence is evident in the fire record during Euro‐Chilean settlement (post‐1880s) compared with the Native American era, but it may also be the result of the destruction of evidence of older fires by more recent stand‐devastating fires (e.g. 1909 and 1944). Overall, the severe and widespread fires that burned in Araucaria–Nothofagus forests of this region in 2002, previously interpreted as an ecological novelty, are within the range of the historic fire regimes that have shaped this forested landscape.     

Diversity and composition of fruit-feeding butterflies in tropical <Emphasis Type="Italic">Eucalyptus</Emphasis> plantations

Production landscapes are rarely considered as priority areas for biodiversity conservation in the tropics. Tree plantations have the potential to provide a conservation service in much of the humid tropics since they are rapidly increasing in extent and present less of a structural contrast with native vegetation than many more intensive agricultural land-uses. We used hierarchical partitioning to examine the factors that influence the value of large-scale Eucalyptus plantations for tropical fruit-feeding butterflies (Lepidoptera: Nymphalidae) in the Brazilian Amazon. We focused on evaluating the importance of landscape versus stand-level factors in determining the diversity and composition of butterfly assemblages, and how butterfly-environment relationships vary within and between subfamilies of Nymphalidae. Native understorey vegetation richness had the strongest independent effect on the richness, abundance and composition of all fruit-feeding butterflies, as well as a subset of species that had been recorded in nearby primary forests. However, overall patterns were strongly influenced by the most abundant subfamily (Satyrinae), and vegetation richness was not related to the abundance of any other subfamily, or non-Satyrinae species, highlighting the importance of disaggregating the fruit-feeding Nymphalidae when examining butterfly-environment relationships. Our results suggest that plantations can help conserve a limited number of forest species, and serve to highlight the research that is necessary to understand better the relationship between fruit-feeding butterflies and environmental variables that are amenable to management.     

Determinants of foraging profitability in two nectarivorous butterflies

ABSTRACT.

• 1 I studied flower selection and foraging energetics of Agraulis vanillae L. (Nymphalidae) and Phoebis sennae (Pieridae), two butterfly species common to north central Florida. I identified the major nectar resources exploited by several populations of these butterflies and, for each plant species, measured available nectar volumes and concentrations, corolla lengths, and density. I quantified foraging behaviour of each butterfly species at each nectar source (flower visitation rate and percentage of foraging time in flight), and used these data to estimate the net rate of energy intake of each butterfly species at each nectar source.
• 2 Estimated mean energy contents of individual flowers of the eleven exploited plant species spanned three orders of magnitude, ranging between 0.015 and 9.27 joules. Mean energy content of individual flowers was strongly correlated with mean foraging profit of both butterfly species.
• 3 Mean nectar volume strongly influenced energy content and varied widely within and among species, ranging from 0.0076 to 1.853 μ1. Nectar concentration varied between 17.1% and 40.4% sucrose-equivalents. Nectar volume was the best single predictor of foraging profitability (correlation coefficients of 0.994 and 0.984 for Phoebis and Agraulis respectively). Corolla length also strongly affected foraging profitability for both butterfly species; flower species with longer corollas were generally more profitable.
• 4 Flower density and nectar concentration showed weak or nonsignificant associations with foraging profitability.
• 5 The usefulness and limitations of these floral characteristics as bases for foraging selectivity, and the selective pressures foraging butterflies might place on the visited plants are discussed.

     

Influence of fire severity on stand development of Araucaria araucana–Nothofagus pumilio stands in the Andean cordillera of south‐central Chile

Fire is the prevalent disturbance in the Araucaria–Nothofagus forested landscape in south‐central Chile. Although both surface and stand‐replacing fires are known to characterize these ecosystems, the variability of fire severity in shaping forest structure has not previously been investigated in Araucaria–Nothofagus forests. Age structures of 16 stands, in which the ages of approximately 650 trees were determined, indicate that variability in fire severity and frequency is key to explaining the mosaic of forest patches across the Araucaria–Nothofagus landscape. High levels of tree mortality in moderate‐ to high‐severity fires followed by new establishment of Nothofagus pumilio typically result in stands characterized by one or two cohorts of this species. Large Araucaria trees are highly resistant to fire, and this species typically survives moderate‐ to high‐severity fires either as dispersed individuals or as small groups of multi‐aged trees. Small post‐fire cohorts of Araucaria may establish, depending on seed availability and the effects of subsequent fires. Araucaria's great longevity (often >700 years) and resistance to fire allow some individuals to survive fires that kill and then trigger new Nothofagus cohorts. Even in relatively mesic habitats, where fires are less frequent, the oldest Araucaria–Nothofagus pumilio stands originated after high‐severity fires. Overall, stand development patterns of subalpine Araucaria–N. pumilio forests are largely controlled by moderate‐ to high‐severity fires, and therefore tree regeneration dynamics is strongly dominated by a catastrophic regeneration mode.