Reorganization of bird communities along a rainforest elevation gradient during a strong El Niño event in Papua New Guinea

The El Niño 2015 event, most extreme since 1997, led to severe droughts in tropical wet Papua New Guinea (PNG), reducing May to October dry season rainfall by 75% in the lowlands and 25% in the highlands. Such droughts are likely to have significant effects on terrestrial ecosystems, but they have been poorly explored in Papua New Guinea. Here, we report changes in bird community composition prior to, during, and after the 2015 El Niño event along the elevational gradient ranging from 200 m to 2700 m a.s.l. at the Mt. Wilhelm rainforest in PNG. The abundance of birds in the lowlands dropped by 60% but increased by 40% at elevations above 1700 m during El Niño year. In the following year, the individual bird species reached mean population sizes similar to pre-El Niño years but did not fully recover. Species richness roughly followed the pattern of observed abundance and quickly and fully re-established after the event to the pre- El Niño values. Thus, at least some terrestrial birds seem to react quickly to the extreme droughts in lowlands and shift to less affected mountain habitats. We recorded upper elevational range limits to shifts by more than 500 m a.s.l. in 22 bird species (out of 237 recorded in total) during El Niño year, in contrast to their typical ranges. Our study suggests that a strong El Niño event can have strong but reversible effects on bird communities as long as they have an opportunity to move to more favorable sites through undisturbed habitats.

Vertical stratification and defensive traits of caterpillars against parasitoids in a lowland tropical forest in Cameroon

Insect herbivores and their parasitoids play a crucial role in terrestrial trophic interactions in tropical forests. These interactions occur across the entire vertical gradient of the forest. This study compares how caterpillar communities, and their parasitism rates, vary across vertical strata and between caterpillar defensive strategies in a semi deciduous tropical forest in Nditam, Cameroon. Within a 0.1 ha plot, all trees with a diameter at breast height (DBH) ≥ 5 cm were felled and systematically searched for caterpillars. We divided the entire vertical gradient of the forest into eight, five-metre strata. All caterpillars were assigned to a stratum based on their collection height, reared, identified, and classified into one of three defensive traits: aposematic, cryptic and shelter-building. Caterpillar species richness and diversity showed a midstory peak, whereas density followed the opposite pattern, decreasing in the midstory and then increasing towards the highest strata. This trend was driven by some highly dense shelter-building caterpillars in the upper canopy. Specialisation indices indicated decreasing levels of caterpillar generality with increasing height, a midstory peak in vulnerability, and increasing connectance towards the upper canopy, although the latter was likely driven by decreasing network size. Both aposematic and shelter-building caterpillars had significantly higher parasitism rates than cryptic caterpillars. Our results highlight nuanced changes in caterpillar communities across forest strata and provide evidence that defences strategies are important indicators of parasitism rates in caterpillars and that both aposematic and shelter-building caterpillars could be considered a "safe haven" for parasitoids.

Recent developments and prospects of sustainable remediation treatments for major contaminants in soil: A review

Rapid industrialisation and urbanisation are contributing to the entry of emerging contaminants into the environment, posing a significant threat to soil health and quality. Therefore, several remediation technologies have been investigated and tested at a field scale to address the issue. However, these remediation technologies face challenges related to cost-effectiveness, environmental concerns, secondary pollution due to the generation of by-products, long-term pollution leaching risks, and social acceptance. Overcoming these constraints necessitates the implementation of sustainable remediation methodologies that prioritise approaches with minimal environmental ramifications and the most substantial net social and economic advantages. Hence, this review delves into diverse contaminants that threaten soil health and quality. Moreover, it outlines the research imperatives for advancing innovative remediation techniques and effective management strategies to tackle this concern. The review discusses a remediation treatment train approach that encourages resource recovery, strengthens the circular economy, and employs a Life Cycle Assessment (LCA) framework to assess the environmental impacts of different remediation strategies. Additionally, the study explores mechanisms to integrate sustainability principles into soil remediation practices. It underscores the necessity for a comprehensive and systematic approach that takes into account the economic, social, and environmental consequences of remediation methodologies in the development of sustainable solutions.

Tropical butterflies use thermal buffering and thermal tolerance as alternative strategies to cope with temperature increase

Climate change poses a severe threat to many taxa, with increased mean temperatures and frequency of extreme weather events predicted. Insects can respond to high temperatures using behaviour, such as angling their wings away from the sun or seeking cool local microclimates to thermoregulate or through physiological tolerance. In a butterfly community in Panama, we compared the ability of adult butterflies from 54 species to control their body temperature across a range of air temperatures (thermal buffering ability), as well as assessing the critical thermal maxima for a subset of 24 species. Thermal buffering ability and tolerance were influenced by family, wing length, and wing colour, with Pieridae, and butterflies that are large or darker in colour having the strongest thermal buffering ability, but Hesperiidae, small, and darker butterflies tolerating the highest temperatures. We identified an interaction between thermal buffering ability and physiological tolerance, where species with stronger thermal buffering abilities had lower thermal tolerance, and vice versa. This interaction implies that species with more stable body temperatures in the field may be more vulnerable to increases in ambient temperatures, for example heat waves associated with ongoing climate change. Our study demonstrates that tropical species employ diverse thermoregulatory strategies, which is also reflected in their sensitivity to temperature extremes.

Thermoregulatory ability and mechanism do not differ consistently between neotropical and temperate butterflies

Climate change is a major threat to species worldwide, yet it remains uncertain whether tropical or temperate species are more vulnerable to changing temperatures. To further our understanding of this, we used a standardised field protocol to (1) study the buffering ability (ability to regulate body temperature relative to surrounding air temperature) of neotropical (Panama) and temperate (the United Kingdom, Czech Republic and Austria) butterflies at the assemblage and family level, (2) determine if any differences in buffering ability were driven by morphological characteristics and (3) used ecologically relevant temperature measurements to investigate how butterflies use microclimates and behaviour to thermoregulate. We hypothesised that temperate butterflies would be better at buffering than neotropical butterflies as temperate species naturally experience a wider range of temperatures than their tropical counterparts. Contrary to our hypothesis, at the assemblage level, neotropical species (especially Nymphalidae) were better at buffering than temperate species, driven primarily by neotropical individuals cooling themselves more at higher air temperatures. Morphology was the main driver of differences in buffering ability between neotropical and temperate species as opposed to the thermal environment butterflies experienced. Temperate butterflies used postural thermoregulation to raise their body temperature more than neotropical butterflies, probably as an adaptation to temperate climates, but the selection of microclimates did not differ between regions. Our findings demonstrate that butterfly species have unique thermoregulatory strategies driven by behaviour and morphology, and that neotropical species are not likely to be more inherently vulnerable to warming than temperate species.

Indirect maternal effects via nest microbiome composition drive gut colonization in altricial chicks

Gut microbial communities are complex and heterogeneous and play critical roles for animal hosts. Early-life disruptions to microbiome establishment can negatively impact host fitness and development. However, the consequences of such early-life disruptions remain unknown in wild birds. To help fill this gap, we investigated the effect of continuous early-life gut microbiome disruptions on the establishment and development of gut communities in wild Great tit (Parus major) and Blue tit (Cyanistes caeruleus) nestlings by applying antibiotics and probiotics. Treatment neither affected nestling growth nor their gut microbiome composition. Independent of treatment, nestling gut microbiomes of both species grouped by brood, which shared the highest numbers of bacterial taxa with both nest environment and their mother. Although fathers showed different gut communities than their nestlings and nests, they still contributed to structuring chick microbiomes. Lastly, we observed that the distance between nests increased inter-brood microbiome dissimilarity, but only in Great tits, indicating that species-specific foraging behaviour and/or microhabitat influence gut microbiomes. Overall, the strong maternal effect, driven by continuous recolonization from the nest environment and vertical transfer of microbes during feeding, appears to provide resilience towards early-life disruptions in nestling gut microbiomes.

Bird preferences for fruit size, but not color, vary in accordance with fruit traits along a tropical elevational gradient

Birds constitute one of the most important seed dispersal agents globally, especially in the tropics. The feeding preferences of frugivorous birds are, therefore, potentially of great ecological importance. A number of laboratory-based and observational studies have attempted to ascertain the preferences of certain bird species for certain fruit traits. However, little attention has been paid to community-wide preferences of frugivorous birds and the impact this may have on fruit traits on a broader scale. Here, we used artificial fruits of different colors and sizes to investigate community-wide fruit trait preferences of birds at three sites along an elevational gradient in Papua New Guinea. We recorded attack rates on artificial fruits as visible impressions made by a bird's beak during a feeding attempt. We also measured the colors and sizes of real fruits at each site, and the gape widths of frugivorous birds, allowing for comparisons between bird feeding preferences and bird and fruit traits. Regardless of elevation, red and purple fruits were universally preferred to green and attacked at similar rates to one another, despite strong elevational patterns in real fruit color. However, elevation had a significant effect on fruit size preferences. A weak, non-significant preference for large fruits was recorded at 700 m, while medium fruits were strongly preferred at 1700 m and small fruits at 2700 m. These patterns mirror those of both real fruit size and frugivorous bird gape width along the gradient, suggesting the potential for selective pressure of birds on fruit size at different elevations.

Climate variability and aridity modulate the role of leaf shelters for arthropods: A global experiment

Current climate change is disrupting biotic interactions and eroding biodiversity worldwide. However, species sensitive to aridity, high temperatures, and climate variability might find shelter in microclimatic refuges, such as leaf rolls built by arthropods. To explore how the importance of leaf shelters for terrestrial arthropods changes with latitude, elevation, and climate, we conducted a distributed experiment comparing arthropods in leaf rolls versus control leaves across 52 sites along an 11,790 km latitudinal gradient. We then probed the impact of short- versus long-term climatic impacts on roll use, by comparing the relative impact of conditions during the experiment versus average, baseline conditions at the site. Leaf shelters supported larger organisms and higher arthropod biomass and species diversity than non-rolled control leaves. However, the magnitude of the leaf rolls' effect differed between long- and short-term climate conditions, metrics (species richness, biomass, and body size), and trophic groups (predators vs. herbivores). The effect of leaf rolls on predator richness was influenced only by baseline climate, increasing in magnitude in regions experiencing increased long-term aridity, regardless of latitude, elevation, and weather during the experiment. This suggests that shelter use by predators may be innate, and thus, driven by natural selection. In contrast, the effect of leaf rolls on predator biomass and predator body size decreased with increasing temperature, and increased with increasing precipitation, respectively, during the experiment. The magnitude of shelter usage by herbivores increased with the abundance of predators and decreased with increasing temperature during the experiment. Taken together, these results highlight that leaf roll use may have both proximal and ultimate causes. Projected increases in climate variability and aridity are, therefore, likely to increase the importance of biotic refugia in mitigating the effects of climate change on species persistence.

Herbivory on the pedunculate oak along an urbanization gradient in Europe: Effects of impervious surface, local tree cover, and insect feeding guild

Urbanization is an important driver of the diversity and abundance of tree-associated insect herbivores, but its consequences for insect herbivory are poorly understood. A likely source of variability among studies is the insufficient consideration of intra-urban variability in forest cover. With the help of citizen scientists, we investigated the independent and interactive effects of local canopy cover and percentage of impervious surface on insect herbivory in the pedunculate oak (Quercus robur L.) throughout most of its geographic range in Europe. We found that the damage caused by chewing insect herbivores as well as the incidence of leaf-mining and gall-inducing herbivores consistently decreased with increasing impervious surface around focal oaks. Herbivory by chewing herbivores increased with increasing forest cover, regardless of impervious surface. In contrast, an increase in local canopy cover buffered the negative effect of impervious surface on leaf miners and strengthened its effect on gall inducers. These results show that-just like in non-urban areas-plant-herbivore interactions in cities are structured by a complex set of interacting factors. This highlights that local habitat characteristics within cities have the potential to attenuate or modify the effect of impervious surfaces on biotic interactions.

Specific gut bacterial responses to natural diets of tropical birds

The composition of gut bacterial communities is strongly influenced by the host diet in many animal taxa. For birds, the effect of diet on the microbiomes has been documented through diet manipulation studies. However, for wild birds, most studies have drawn on literature-based information to decipher the dietary effects, thereby, overlooking individual variation in dietary intake. Here we examine how naturally consumed diets influence the composition of the crop and cloacal microbiomes of twenty-one tropical bird species, using visual and metabarcoding-based identification of consumed diets and bacterial 16S rRNA microbiome sequencing. We show that diet intakes vary markedly between individuals of the same species and that literature-based dietary guilds grossly underestimate intraspecific diet variability. Furthermore, despite an effect of literature-based dietary guild assignment of host taxa, the composition of natural diets does not align with crop and cloacal microbiome similarity. However, host-taxon specific gut bacterial lineages are positively correlated with specific diet items, indicating that certain microbes associate with different diet components in specific avian hosts. Consequently, microbiome composition is not congruent with the overall consumed diet composition of species, but specific components of a consumed diet lead to host-specific effects on gut bacterial taxa.

Exogenous Application of Methyl Jasmonate Increases Emissions of Volatile Organic Compounds in Pyrenean Oak Trees, Quercus pyrenaica

The tri-trophic interactions between plants, insects, and insect predators and parasitoids are often mediated by chemical cues. The attraction to herbivore-induced Plant Volatiles (HIPVs) has been well documented for arthropod predators and parasitoids, and more recently for insectivorous birds. The attraction to plant volatiles induced by the exogenous application of methyl jasmonate (MeJA), a phytohormone typically produced in response to an attack of chewing herbivores, has provided controversial results both in arthropod and avian predators. In this study, we examined whether potential differences in the composition of bouquets of volatiles produced by herbivore-induced and MeJA-treated Pyrenean oak trees (Quercus pyrenaica) were related to differential avian attraction, as results from a previous study suggested. Results showed that the overall emission of volatiles produced by MeJA-treated and herbivore-induced trees did not differ, and were higher than emissions of Control trees, although MeJA treatment showed a more significant reaction and released several specific compounds in contrast to herbivore-induced trees. These slight yet significant differences in the volatile composition may explain why avian predators were not so attracted to MeJA-treated trees, as observed in a previous study in this plant-herbivore system. Unfortunately, the lack of avian visits to the experimental trees in the current study did not allow us to confirm this result and points out the need to perform more robust predator studies.

Bats can reach 3626 m a.s.l. in Papua New Guinea: altitudinal range extensions for six rainforest bat species

Bats represent an important, but poorly known component of mammal diversity in Papua New Guinea (PNG). Our surveys in two altitudinal rainforest gradients recorded 43 bat species of which six (Dobsonia minor, D. praedatrix, Hipposideros calcaratus, H. maggietaylorae, Miniopterus australis, Miniopterus sp.) fell outside of their known altitudinal ranges. This enlargement could reflect the lack of past sampling, or a genuine range extension, potentially in response to climate change. Our study highlights the importance of baseline data on the altitudinal distribution of vertebrates, including bats, in PNG for the monitoring of their response to climate change and anthropogenic disturbance.

Great tits (Parus major) flexibly learn that herbivore-induced plant volatiles indicate prey location: An experimental evidence with two tree species

When searching for food, great tits (Parus major) can use herbivore-induced plant volatiles (HIPVs) as an indicator of arthropod presence. Their ability to detect HIPVs was shown to be learned, and not innate, yet the flexibility and generalization of learning remain unclear.We studied if, and if so how, naïve and trained great tits (Parus major) discriminate between herbivore-induced and noninduced saplings of Scotch elm (Ulmus glabra) and cattley guava (Psidium cattleyanum). We chemically analyzed the used plants and showed that their HIPVs differed significantly and overlapped only in a few compounds.Birds trained to discriminate between herbivore-induced and noninduced saplings preferred the herbivore-induced saplings of the plant species they were trained to. Naïve birds did not show any preferences. Our results indicate that the attraction of great tits to herbivore-induced plants is not innate, rather it is a skill that can be acquired through learning, one tree species at a time.We demonstrate that the ability to learn to associate HIPVs with food reward is flexible, expressed to both tested plant species, even if the plant species has not coevolved with the bird species (i.e., guava). Our results imply that the birds are not capable of generalizing HIPVs among tree species but suggest that they either learn to detect individual compounds or associate whole bouquets with food rewards.

Species-specific but not phylosymbiotic gut microbiomes of New Guinean passerine birds are shaped by diet and flight-associated gut modifications

Animal hosts have evolved intricate associations with microbial symbionts, where both depend on each other for particular functions. In many cases, these associations lead to phylosymbiosis, where phylogenetically related species harbour compositionally more similar microbiomes than distantly related species. However, evidence for phylosymbiosis is either weak or lacking in gut microbiomes of flying vertebrates, particularly in birds. To shed more light on this phenomenon, we compared cloacal microbiomes of 37 tropical passerine bird species from New Guinea using 16S rRNA bacterial gene sequencing. We show a lack of phylosymbiosis and document highly variable microbiomes. Furthermore, we find that gut bacterial community compositions are species-specific and tend to be shaped by host diet but not sampling locality, potentially driven by the similarities in habitats used by individual species. We further show that flight-associated gut modifications, coupled with individual dietary differences, shape gut microbiome structure and variation, contributing to the lack of phylosymbiosis. These patterns indicate that the stability of symbiosis may depend on microbial functional diversity rather than taxonomic composition. Furthermore, the more variable and fluid host-microbe associations suggest probable disparities in the potential for coevolution between bird host species and microbial symbionts.

Flexibility and resilience of great tit (Parus major) gut microbiomes to changing diets

Background

Gut microbial communities play important roles in nutrient management and can change in response to host diets. The extent of this flexibility and the concomitant resilience is largely unknown in wild animals. To untangle the dynamics of avian-gut microbiome symbiosis associated with diet changes, we exposed Parus major (Great tits) fed with a standard diet (seeds and mealworms) to either a mixed (seeds, mealworms and fruits), a seed, or a mealworm diet for 4 weeks, and examined the flexibility of gut microbiomes to these compositionally different diets. To assess microbiome resilience (recovery potential), all individuals were subsequently reversed to a standard diet for another 4 weeks. Cloacal microbiomes were collected weekly and characterised through sequencing the v4 region of the 16S rRNA gene using Illumina MiSeq.

Results

Initial microbiomes changed significantly with the diet manipulation, but the communities did not differ significantly between the three diet groups (mixed, seed and mealworm), despite multiple diet-specific changes in certain bacterial genera. Reverting birds to the standard diet led only to a partial recovery in gut community compositions. The majority of the bacterial taxa that increased significantly during diet manipulation decreased in relative abundance after reversion to the standard diet; however, bacterial taxa that decreased during the manipulation rarely increased after diet reversal

Conclusions

The gut microbial response and partial resilience to dietary changes support that gut bacterial communities of P. major play a role in accommodating dietary changes experienced by wild avian hosts. This may be a contributing factor to the relaxed association between microbiome composition and the bird phylogeny. Our findings further imply that interpretations of wild bird gut microbiome analyses from single-time point sampling, especially for omnivorous species or species with seasonally changing diets, should be done with caution. The partial community recovery implies that ecologically relevant diet changes (e.g., seasonality and migration) open up gut niches that may be filled by previously abundant microbes or replaced by different symbiont lineages, which has important implications for the integrity and specificity of long-term avian-symbiont associations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42523-021-00076-6.

Endemicity and land-use type influence the abundance-range-size relationship of birds on a tropical island

A single adverse environment event can threaten the survival of small-ranged species while random fluctuations in population size increase the extinction risk of less-abundant species. The abundance-range-size relationship (ARR) is usually positive, which means that smaller-ranged species are often of low abundance and might face both problems simultaneously. The ARR has been reported to be negative on tropical islands, perhaps allowing endemic species in such environments to remain extant. But there is a need to understand how endemism and land-use interact to shape ARR. Using 41 highly replicated transects along the full elevational gradient of Sri Lanka, we determined the following: (a) the direction of ARR, (b) if endemism affects ARR and (c) if land-use (rainforest, buffer and agriculture) changes ARR differently for endemics and non-endemics. Additionally, (d) we identified endemics that had both lower abundances and smaller range sizes, and ranked them from most threatened (specific to rainforests) to least threatened using a weighted-interaction nestedness estimator. (a) We found a positive relationship between species abundances and range size. This positive ARR was maintained among endemic and non-endemic species, across land-use types and at local and regional scales. (b) The ARR interacted with endemicity and land-use. Endemics with smaller range sizes had higher abundances than non-endemics, and particularly higher in rainforests compared to agriculture. In contrast, species with larger range sizes had similar abundances across endemicity and land-use categories. Many endemics with smaller range sizes are globally threatened; therefore, higher abundances may buffer them from extinction risks. (c) Nine (29%) endemics had both below average abundance and elevational range size. The nestedness estimator ranked the endemics Sri Lanka Whistling Thrush Myophonus blighi, Red-faced Malkoha Phaenicophaeus pyrrhocephalus, Sri Lanka Thrush Zoothera imbricata and White-faced Starling Sturnornis albofrontus as the four most vulnerable species to local extinction risk, which corresponds to their global extinction risk. We demonstrate that ARR can be positive on tropical islands, but it is influenced by endemism and land-use. Examining shifts in ARR is not only important to understand community dynamics but can also act as a tool to inform managers about species that require monitoring programmes.

Biomass, abundances, and abundance and geographical range size relationship of birds along a rainforest elevational gradient in Papua New Guinea

The usually positive inter-specific relationship between geographical range size and the abundance of local bird populations comes with exceptions. On continents, the majority of these exceptions have been described from tropical montane areas in Africa, where geographically-restricted bird species are unusually abundant. We asked how the local abundances of passerine and non-passerine bird species along an elevational gradient on Mt. Wilhelm, Papua New Guinea relate to their geographical range size. We collected data on bird assemblages at eight elevations (200–3,700 m, at 500 m elevational increments). We used a standardized point-counts at 16 points at each elevational study site. We partitioned the birds into feeding guilds, and we obtained data on geographical range sizes from the Bird-Life International data zone. We observed a positive relationship between abundance and geographical range size in the lowlands. This trend changed to a negative one towards higher elevations. The total abundances of the assemblage showed a hump-shaped pattern along the elevational gradient, with passerine birds, namely passerine insectivores, driving the observed pattern. In contrast to abundances, the mean biomass of the bird assemblages decreased with increasing elevation. Our results show that montane bird species maintain dense populations which compensate for the decreased available area near the top of the mountain.

Great Tit (Parus major) Uropygial Gland Microbiomes and Their Potential Defensive Roles

The uropygial gland (preen gland) of birds plays an important role in maintaining feather integrity and hygiene. Although a few studies have demonstrated potential defensive roles of bacteria residing within these glands, the diversity and functions of the uropygial gland microbiota are largely unknown. Therefore, we investigated the microbiota of great tit (Parus major) uropygial glands through both isolation of bacteria (culture-dependent) and 16S rRNA amplicon sequencing (culture-independent). Co-culture experiments of selected bacterial isolates with four known feather-degrading bacteria (Bacillus licheniformis, Kocuria rhizophila, Pseudomonas monteilii, and Dermacoccus nishinomiyaensis), two non-feather degrading feather bacteria, one common soil bacterial pathogen and two common fungal pathogens enabled us to evaluate the potential antimicrobial properties of these isolates. Our results show major differences between bacterial communities characterized using culture-dependent and -independent approaches. In the former, we were only able to isolate 12 bacterial genera (dominated by members of the Firmicutes and Actinobacteria), while amplicon sequencing identified 110 bacterial genera (dominated by Firmicutes, Bacteroidetes, and Proteobacteria). Uropygial gland bacterial isolates belonging to the genera Bacillus and Kocuria were able to suppress the growth of four of the nine tested antagonists, attesting to potential defensive roles. However, these bacterial genera were infrequent in our MiSeq results suggesting that the isolated bacteria may not be obligate gland symbionts. Furthermore, bacterial functional predictions using 16S rRNA sequences also revealed the ability of uropygial gland bacteria to produce secondary metabolites with antimicrobial properties, such as terpenes. Our findings support that uropygial gland bacteria may play a role in feather health and that bacterial symbionts might act as defensive microbes. Future investigations of these bacterial communities, with targeted approaches (e.g., bacterial isolation and chemical analyses), are thus warranted to improve our understanding of the evolution and function of these host-microbe interactions.

Last Glacial Maximum led to community-wide population expansion in a montane songbird radiation in highland Papua New Guinea

BACKGROUND

Quaternary climate fluctuations are an engine of biotic diversification. Global cooling cycles, such as the Last Glacial Maximum (LGM), are known to have fragmented the ranges of higher-latitude fauna and flora into smaller refugia, dramatically reducing species ranges. However, relatively less is known about the effects of cooling cycles on tropical biota.

RESULTS

We analyzed thousands of genome-wide DNA markers across an assemblage of three closely related understorey-inhabiting scrubwrens (Sericornis and Aethomyias; Aves) from montane forest along an elevational gradient on Mt. Wilhelm, the highest mountain of Papua New Guinea. Despite species-specific differences in elevational preference, we found limited differentiation within each scrubwren species, but detected a strong genomic signature of simultaneous population expansions at 27-29 ka, coinciding with the onset of the LGM.

CONCLUSION

The remarkable synchronous timing of population expansions of all three species demonstrates the importance of global cooling cycles in expanding highland habitat. Global cooling cycles have likely had strongly different impacts on tropical montane areas versus boreal and temperate latitudes, leading to population expansions in the former and serious fragmentation in the latter.

Spatiotemporal patterns of avian host-parasite interactions in the face of biogeographical range expansions

Exploration of interactions between hosts and parasitic symbionts is important for our understanding of the temporal and spatial distribution of organisms. For example, host colonization of new geographical regions may alter levels of infections and parasite specificity, and even allow hosts to escape from co-evolved parasites, consequently shaping spatial distributions and community structure of both host and parasite. Here we investigate the effect of host colonization of new regions and the elevational distribution of host-parasite associations between birds and their vector-transmitted haemosporidian blood parasites in two geological and geographical settings: mountains of New Guinea and the Canary Islands. Our results demonstrate that bird communities in younger regions have significantly lower levels of parasitism compared to those of older regions. Furthermore, host-parasite network analyses demonstrate that blood parasites may respond differently after arriving to a new region, through adaptations that allow for either expanding (Canary Islands) or retaining (New Guinea) their host niches. The spatial prevalence patterns along elevational gradients differed in the two regions, suggesting that region-specific biotic (e.g., host community) and abiotic factors (e.g., temperature) govern prevalence patterns. Our findings suggest that the spatiotemporal range dynamics in host-parasite systems are driven by multiple factors, but that host and parasite community compositions and colonization histories are of particular importance.

Cloacal swabs and alcohol bird specimens are good proxies for compositional analyses of gut microbial communities of Great tits (Parus major)

BACKGROUND

Comprehensive studies of wild bird microbiomes are often limited by difficulties of sample acquisition. However, widely used non-invasive cloacal swab methods and under-explored museum specimens preserved in alcohol provide promising avenues to increase our understanding of wild bird microbiomes, provided that they accurately portray natural microbial community compositions. To investigate this assertion, we used 16S rRNA amplicon sequencing of Great tit (Parus major) gut microbiomes to compare 1) microbial communities obtained from dissected digestive tract regions and cloacal swabs, and 2) microbial communities obtained from freshly dissected gut regions and from samples preserved in alcohol for 2 weeks or 2 months, respectively.

RESULTS

We found no significant differences in alpha diversities in communities of different gut regions and cloacal swabs (except in OTU richness between the dissected cloacal region and the cloacal swabs), or between fresh and alcohol preserved samples. However, we did find significant differences in beta diversity and community composition of cloacal swab samples compared to different gut regions. Despite these community-level differences, swab samples qualitatively captured the majority of the bacterial diversity throughout the gut better than any single compartment. Bacterial community compositions of alcohol-preserved specimens did not differ significantly from freshly dissected samples, although some low-abundant taxa were lost in the alcohol preserved specimens.

CONCLUSIONS

Our findings suggest that cloacal swabs, similar to non-invasive fecal sampling, qualitatively depict the gut microbiota composition without having to collect birds to extract the full digestive tract. The satisfactory depiction of gut microbial communities in alcohol preserved samples opens up for the possibility of using an enormous resource readily available through museum collections to characterize bird gut microbiomes. The use of extensive museum specimen collections of birds for microbial gut analyses would allow for investigations of temporal patterns of wild bird gut microbiomes, including the potential effects of climate change and anthropogenic impacts. Overall, the utilization of cloacal swabs and museum alcohol specimens can positively impact bird gut microbiome research to help increase our understanding of the role and evolution of wild bird hosts and gut microbial communities.

Gene Flow in the Müllerian Mimicry Ring of a Poisonous Papuan Songbird Clade (Pitohui; Aves)

Müllerian mimicry rings are remarkable symbiotic species assemblages in which multiple members share a similar phenotype. However, their evolutionary origin remains poorly understood. Although gene flow among species has been shown to generate mimetic patterns in some Heliconius butterflies, mimicry is believed to be due to true convergence without gene flow in many other cases. We investigated the evolutionary history of multiple members of a passerine mimicry ring in the poisonous Papuan pitohuis. Previous phylogenetic evidence indicates that the aposematic coloration shared by many, but not all, members of this genus is ancestral and has only been retained by members of the mimicry ring. Using a newly assembled genome and thousands of genomic DNA markers, we demonstrate gene flow from the hooded pitohui (Pitohui dichrous) into the southern variable pitohui (Pitohui uropygialis), consistent with shared patterns of aposematic coloration. The vicinity of putatively introgressed loci is significantly enriched for genes that are important in melanin pigment expression and toxin resistance, suggesting that gene flow may have been instrumental in the sharing of plumage patterns and toxicity. These results indicate that interspecies gene flow may be a more general mechanism in generating mimicry rings than hitherto appreciated.

FragSAD: A database of diversity and species abundance distributions from habitat fragments

Habitat destruction is the single greatest anthropogenic threat to biodiversity. Decades of research on this issue have led to the accumulation of hundreds of data sets comparing species assemblages in larger, intact, habitats to smaller, more fragmented, habitats. Despite this, little synthesis or consensus has been achieved, primarily because of non-standardized sampling methodology and analyses of notoriously scale-dependent response variables (i.e., species richness). To be able to compare and contrast the results of habitat fragmentation on species' assemblages, it is necessary to have the underlying data on species abundances and sampling intensity, so that standardization can be achieved. To accomplish this, we systematically searched the literature for studies where abundances of species in assemblages (of any taxa) were sampled from many habitat patches that varied in size. From these, we extracted data from several studies, and contacted authors of studies where appropriate data were collected but not published, giving us 117 studies that compared species assemblages among habitat fragments that varied in area. Less than one-half (41) of studies came from tropical forests of Central and South America, but there were many studies from temperate forests and grasslands from all continents except Antarctica. Fifty-four of the studies were on invertebrates (mostly insects), but there were several studies on plants (15), birds (16), mammals (19), and reptiles and amphibians (13). We also collected qualitative information on the length of time since fragmentation. With data on total and relative abundances (and identities) of species, sampling effort, and affiliated meta-data about the study sites, these data can be used to more definitively test hypotheses about the role of habitat fragmentation in altering patterns of biodiversity. There are no copyright restrictions. Please cite this data paper and the associated Dryad data set if the data are used in publications.

What do we know about birds' use of plant volatile cues in tritrophic interactions?

The first study showing that birds can smell herbivore-induced plant volatiles was published ten years ago. Since then, only 12 studies have been published, showing contradictory results. This review evaluates the role of birds in relation to the crying for help hypothesis and their use of olfactory cues. In accordance with the methodologies used in previous studies, we herein provide a summary of experimental approaches and describe the advantages and disadvantages of experiments conducted in nature versus aviaries. Moreover, we recommend experimental methodologies which lead to a deeper knowledge of the topic, including reflection on the induction of plant defenses and adaptations of birds. Finally, we propose some interesting questions for future research to direct further studies towards a thorough and accurate description of birds' roles in tritrophic interactions.

Improved White Matter Cerebrovascular Reactivity after Revascularization in Patients with Steno-Occlusive Disease

BACKGROUND AND PURPOSE

One feature that patients with steno-occlusive cerebrovascular disease have in common is the presence of white matter (WM) lesions on MRI. The purpose of this study was to evaluate the effect of direct surgical revascularization on impaired WM cerebrovascular reactivity in patients with steno-occlusive disease.

MATERIALS AND METHODS

We recruited 35 patients with steno-occlusive disease, Moyamoya disease (n = 24), Moyamoya syndrome (n = 3), atherosclerosis (n = 6), vasculitis (n = 1), and idiopathic stenosis (n = 1), who underwent unilateral brain revascularization using a direct superficial temporal artery-to-MCA bypass (19 women; mean age, 45.8 ± 16.5 years). WM cerebrovascular reactivity was measured preoperatively and postoperatively using blood oxygen level-dependent (BOLD) MR imaging during iso-oxic hypercapnic changes in end-tidal carbon dioxide and was expressed as %Δ BOLD MR signal intensity per millimeter end-tidal partial pressure of CO₂.

RESULTS

WM cerebrovascular reactivity significantly improved after direct unilateral superficial temporal artery-to-middle cerebral artery (STA-MCA) bypass in the revascularized hemisphere in the MCA territory (mean ± SD, -0.0005 ± 0.053 to 0.053 ± 0.046 %BOLD/mm Hg; P < .0001) and in the anterior cerebral artery territory (mean, 0.0015 ± 0.059 to 0.021 ± 0.052 %BOLD/mm Hg; P = .005). There was no difference in WM cerebrovascular reactivity in the ipsilateral posterior cerebral artery territory nor in the vascular territories of the nonrevascularized hemisphere (P < .05).

CONCLUSIONS

Cerebral revascularization surgery is an effective treatment for reversing preoperative cerebrovascular reactivity deficits in WM. In addition, direct-STA-MCA bypass may prevent recurrence of preoperative symptoms.

Contaminated land and wetland remediation in Nigeria: Opportunities for sustainable livelihood creation

The Niger Delta region of Nigeria is one of the most crude oil impacted deltas globally. The region has experienced over five decades of oil related contamination of the total environment (air, soil, water and biota). In 2011, UNEP released a seminal report on oil impact on Ogoniland environments, which up scaled demands for urgent clean up and restoration of degraded bio-resource rich environments of the Niger Delta, starting from Ogoniland. The Nigerian Government demonstrated renewed political will to remediate contaminated sites in Ogoniland with a launch of the clean-up exercise in June 2016. Stakeholders' expectations from the clean-up include not only environmental remediation but also restoration and creation of sustainable livelihood opportunities to reduce poverty in the region. Most studies have focused on the environmental restoration aspect and identified bioremediation as the likely appropriate remediation approach for Ogoniland, given its low environmental footprints, and low-cost burden on the weak and overstretched economy of Nigeria. This study mapped opportunities for sustainable livelihood creation during the Ogoniland remediation and restoration exercise. Given the value chain of bioremediation and its ancillary activities, the study analysed opportunities and mechanisms for skilled and unskilled job creation and prospects for sustainable livelihoods and knock-on effects. It is anticipated that the clean-up process would lead to economic prosperity and mitigate resource-driven conflicts in the Niger Delta. The study provides an exemplar for waste-to-wealth transformation in regions where natural resource mining has impacted communities, and has dislocated local economies and age-old livelihood structures.

Comparative Analyses of the Digestive Tract Microbiota of New Guinean Passerine Birds

The digestive tract microbiota (DTM) plays a plethora of functions that enable hosts to exploit novel niches. However, our understanding of the DTM of birds, particularly passerines, and the turnover of microbial communities along the digestive tract are limited. To better understand how passerine DTMs are assembled, and how the composition changes along the digestive tract, we investigated the DTM of seven different compartments along the digestive tract of nine New Guinean passerine bird species using Illumina MiSeq sequencing of the V4 region of the 16S rRNA. Overall, passerine DTMs were dominated by the phyla Firmicutes and Proteobacteria. We found bird species-specific DTM assemblages and the DTM of different compartments from the same species tended to cluster together. We also found a notable relationship between gut community similarity and feeding guilds (insectivores vs. omnivores). The dominant bacterial genera tended to differ between insectivores and omnivores, with insectivores mainly having lactic acid bacteria that may contribute to the breakdown of carbohydrates. Omnivorous DTMs were more diverse than insectivores and dominated by the bacterial phyla Proteobacteria and Tenericutes. These bacteria may contribute to nitrogen metabolism, and the diverse omnivorous DTMs may allow for more flexibility with varying food availability as these species have wider feeding niches. In well-sampled omnivorous species, the dominant bacterial genera changed along the digestive tracts, which was less prominent for insectivores. In conclusion, the DTMs of New Guinean passerines seem to be species specific and, at least in part, be shaped by bird diet. The sampling of DTM along the digestive tract improved capturing of a more complete set of members, with implications for our understanding of the interactions between symbiont and gut compartment functions.

Abstract P4-02-13: Can background parenchymal enhancement (BPE) predict the chance of multicentric/ bilateral breast cancer on staging breast MRI?

Purpose: Can background parenchymal enhancement (BPE) predict the chance of multicentric/ bilateral breast cancer on staging Breast MRI?

Materials and Methods: Retrospective review of women diagnosed with breast cancer who underwent a breast MRI for staging of disease was performed at a single institution from October 2012 to September 2015.

Results: Breast MRI for staging was done for 435 patients diagnosed with breast cancer. Ages ranging from 24 to 86 years old (median, 52 years); sizes ranging from 0.5 to 13.5 cm (mean, 3.5 cm). 29 patients (7 %) had biopsy-proven second tumors in the same breast but different quadrant as the primary tumor or in the contralateral breast. From the 435 patients, 304 had minimal/ mild BPE and 103 had moderate/marked BPE (28 missing). Of the patients with an invasive primary cancer and a second tumor in the same breast but different quadrant as the primary tumor or in the contralateral breast, 12 of 29 patients had discordance in subtypes between the primary and secondary tumors (41%) and 17 of 29 had concordance in the subtypes between the primary and secondary tumors (59%). 6.3% (19 out 304) of patients with minimal/ mild BPE had multicentric /bilateral disease and 9.7% (10 out 103) of patients with moderate/ marked BPE had multicentric/ bilateral breast cancer.

Conclusion: 435 patients with recent diagnosis of breast cancer who underwent staging breast MRI for diagnosis of additional sites of disease, 7% was diagnosed with an additional site of cancer. From these group of patients, approximately 6% had other site of disease among patients who had minimal/ mild BPE in the breast MRI versus 10% of patients with moderate/marked BPE. BPE may play a role in the setting of multicentric/ bilateral breast cancer.

Citation Format: Benveniste APA, Ebuoma LO, Jonna A, Sam K, Severs Jr. FJ, Roark A, Sepulveda KA, Tamara O-P, Sedgwick EE. Can background parenchymal enhancement (BPE) predict the chance of multicentric/ bilateral breast cancer on staging breast MRI? [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-02-13.

Higher predation risk for insect prey at low latitudes and elevations

Biotic interactions underlie ecosystem structure and function, but predicting interaction outcomes is difficult. We tested the hypothesis that biotic interaction strength increases toward the equator, using a global experiment with model caterpillars to measure predation risk. Across an 11,660-kilometer latitudinal gradient spanning six continents, we found increasing predation toward the equator, with a parallel pattern of increasing predation toward lower elevations. Patterns across both latitude and elevation were driven by arthropod predators, with no systematic trend in attack rates by birds or mammals. These matching gradients at global and regional scales suggest consistent drivers of biotic interaction strength, a finding that needs to be integrated into general theories of herbivory, community organization, and life-history evolution.

Diet of land birds along an elevational gradient in Papua New Guinea

Food preferences and exploitation are crucial to many aspects of avian ecology and are of increasing importance as we progress in our understanding of community ecology. We studied birds and their feeding specialization in the Central Range of Papua New Guinea, at eight study sites along a complete (200 to 3700 m a.s.l.) rainforest elevational gradient. The relative species richness and abundance increased with increasing elevation for insect and nectar eating birds, and decreased with elevation for fruit feeding birds. Using emetic tartar, we coerced 999 individuals from 99 bird species to regurgitate their stomach contents and studied these food samples. The proportion of arthropods in food samples increased with increasing elevation at the expense of plant material. Body size of arthropods eaten by birds decreased with increasing elevation. This reflected the parallel elevational trend in the body size of arthropods available in the forest understory. Body size of insectivorous birds was significantly positively correlated with the body size of arthropods they ate. Coleoptera were the most exploited arthropods, followed by Araneae, Hymenoptera, and Lepidoptera. Selectivity indexes showed that most of the arthropod taxa were taken opportunistically, reflecting the spatial patterns in arthropod abundances to which the birds were exposed.

Low host specificity and abundance of frugivorous lepidoptera in the lowland rain forests of Papua New Guinea

We studied a community of frugivorous Lepidoptera in the lowland rainforest of Papua New Guinea. Rearing revealed 122 species represented by 1,720 individuals from 326 woody plant species. Only fruits from 52% (171) of the plant species sampled were attacked. On average, Lepidoptera were reared from 1 in 89 fruits and a kilogram of fruit was attacked by 1.01 individuals. Host specificity of Lepidoptera was notably low: 69% (33) of species attacked plants from >1 family, 8% (4) fed on single family, 6% (3) on single genus and 17% (8) were monophagous. The average kilogram of fruits was infested by 0.81 individual from generalist species (defined here as feeding on >1 plant genus) and 0.07 individual from specialist species (feeding on a single host or congeneric hosts). Lepidoptera preferred smaller fruits with both smaller mesocarp and seeds. Large-seeded fruits with thin mesocarp tended to host specialist species whereas those with thick, fleshy mesocarp were often infested with both specialist and generalist species. The very low incidence of seed damage suggests that pre-dispersal seed predation by Lepidoptera does not play a major role in regulating plant populations via density-dependent mortality processes outlined by the Janzen-Connell hypothesis.

The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project

The PREDICTS project-Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)-has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.

Vascular Dysfunction in Leukoaraiosis

BACKGROUND AND PURPOSE

The pathogenesis of leukoaraiosis has long been debated. This work addresses a less well-studied mechanism, cerebrovascular reactivity, which could play a leading role in the pathogenesis of this disease. Our aim was to evaluate blood flow dysregulation and its relation to leukoaraiosis.

MATERIALS AND METHODS

Cerebrovascular reactivity, the change in the blood oxygen level-dependent 3T MR imaging signal in response to a consistently applied step change in the arterial partial pressure of carbon dioxide, was measured in white matter hyperintensities and their contralateral spatially homologous normal-appearing white matter in 75 older subjects (age range, 50-91 years; 40 men) with leukoaraiosis. Additional quantitative evaluation of regions of leukoaraiosis was performed by using diffusion (n = 75), quantitative T2 (n = 54), and DSC perfusion MRI metrics (n = 25).

RESULTS

When we compared white matter hyperintensities with contralateral normal-appearing white matter, cerebrovascular reactivity was lower by a mean of 61.2% ± 22.6%, fractional anisotropy was lower by 44.9 % ± 6.9%, and CBF was lower by 10.9% ± 11.9%. T2 was higher by 61.7% ± 13.5%, mean diffusivity was higher by 59.0% ± 11.7%, time-to-maximum was higher by 44.4% ± 30.4%, and TTP was higher by 6.8% ± 5.8% (all P < .01). Cerebral blood volume was lower in white matter hyperintensities compared with contralateral normal-appearing white matter by 10.2% ± 15.0% (P = .03).

CONCLUSIONS

Not only were resting blood flow metrics abnormal in leukoaraiosis but there is also evidence of reduced cerebrovascular reactivity in these areas. Studies have shown that reduced cerebrovascular reactivity is more sensitive than resting blood flow parameters for assessing vascular insufficiency. Future work is needed to examine the sensitivity of resting-versus-dynamic blood flow measures for investigating the pathogenesis of leukoaraiosis.

Midpoint attractors and species richness: Modelling the interaction between environmental drivers and geometric constraints

We introduce a novel framework for conceptualising, quantifying and unifying discordant patterns of species richness along geographical gradients. While not itself explicitly mechanistic, this approach offers a path towards understanding mechanisms. In this study, we focused on the diverse patterns of species richness on mountainsides. We conjectured that elevational range midpoints of species may be drawn towards a single midpoint attractor - a unimodal gradient of environmental favourability. The midpoint attractor interacts with geometric constraints imposed by sea level and the mountaintop to produce taxon-specific patterns of species richness. We developed a Bayesian simulation model to estimate the location and strength of the midpoint attractor from species occurrence data sampled along mountainsides. We also constructed midpoint predictor models to test whether environmental variables could directly account for the observed patterns of species range midpoints. We challenged these models with 16 elevational data sets, comprising 4500 species of insects, vertebrates and plants. The midpoint predictor models generally failed to predict the pattern of species midpoints. In contrast, the midpoint attractor model closely reproduced empirical spatial patterns of species richness and range midpoints. Gradients of environmental favourability, subject to geometric constraints, may parsimoniously account for elevational and other patterns of species richness.

Evaluating Functional Diversity: Missing Trait Data and the Importance of Species Abundance Structure and Data Transformation

Functional diversity (FD) is an important component of biodiversity that quantifies the difference in functional traits between organisms. However, FD studies are often limited by the availability of trait data and FD indices are sensitive to data gaps. The distribution of species abundance and trait data, and its transformation, may further affect the accuracy of indices when data is incomplete. Using an existing approach, we simulated the effects of missing trait data by gradually removing data from a plant, an ant and a bird community dataset (12, 59, and 8 plots containing 62, 297 and 238 species respectively). We ranked plots by FD values calculated from full datasets and then from our increasingly incomplete datasets and compared the ranking between the original and virtually reduced datasets to assess the accuracy of FD indices when used on datasets with increasingly missing data. Finally, we tested the accuracy of FD indices with and without data transformation, and the effect of missing trait data per plot or per the whole pool of species. FD indices became less accurate as the amount of missing data increased, with the loss of accuracy depending on the index. But, where transformation improved the normality of the trait data, FD values from incomplete datasets were more accurate than before transformation. The distribution of data and its transformation are therefore as important as data completeness and can even mitigate the effect of missing data. Since the effect of missing trait values pool-wise or plot-wise depends on the data distribution, the method should be decided case by case. Data distribution and data transformation should be given more careful consideration when designing, analysing and interpreting FD studies, especially where trait data are missing. To this end, we provide the R package “traitor” to facilitate assessments of missing trait data.

Identifying Significant Changes in Cerebrovascular Reactivity to Carbon Dioxide

BACKGROUND AND PURPOSE

Changes in cerebrovascular reactivity can be used to assess disease progression and response to therapy but require discrimination of pathology from normal test-to-test variability. Such variability is due to variations in methodology, technology, and physiology with time. With uniform test conditions, our aim was to determine the test-to-test variability of cerebrovascular reactivity in healthy subjects and in patients with known cerebrovascular disease.

MATERIALS AND METHODS

Cerebrovascular reactivity was the ratio of the blood oxygen level-dependent MR imaging response divided by the change in carbon dioxide stimulus. Two standardized cerebrovascular reactivity tests were conducted at 3T in 15 healthy men (36.7 ± 16.1 years of age) within a 4-month period and were coregistered into standard space to yield voxelwise mean cerebrovascular reactivity interval difference measures, composing a reference interval difference atlas. Cerebrovascular reactivity interval difference maps were prepared for 11 male patients. For each patient, the test-retest difference of each voxel was scored statistically as z-values of the corresponding voxel mean difference in the reference atlas and then color-coded and superimposed on the anatomic images to create cerebrovascular reactivity interval difference z-maps.

RESULTS

There were no significant test-to-test differences in cerebrovascular reactivity in either gray or white matter (mean gray matter, P = .431; mean white matter, P = .857; paired t test) in the healthy cohort. The patient cerebrovascular reactivity interval difference z-maps indicated regions where cerebrovascular reactivity increased or decreased and the probability that the changes were significant.

CONCLUSIONS

Accounting for normal test-to-test differences in cerebrovascular reactivity enables the assessment of significant changes in disease status (stability, progression, or regression) in patients with time.