Insect herbivory and herbivores of Ficus species along a rain forest elevational gradient in Papua New Guinea

Classic research on elevational gradients in plant–herbivore interactions holds that insect herbivore pressure is stronger under warmer climates of low elevations. However, recent work has questioned this paradigm, arguing that it oversimplifies the ecological complexity in which plant–insect herbivore interactions are embedded. Knowledge of antagonistic networks of plants and herbivores is however crucial for understanding the mechanisms that govern ecosystem functioning. We examined herbivore damage and insect herbivores of eight species of genus Ficus (105 saplings) and plant constitutive defensive traits of two of these species, along a rain forest elevational gradient of Mt. Wilhelm (200–2,700 m a.s.l.), in tropical Papua New Guinea. We report overall herbivore damage 2.4% of leaf area, ranging from 0.03% in Ficus endochaete at 1,700 m a.s.l. to 6.1% in F. hombroniana at 700 m a.s.l. Herbivore damage and herbivore abundances varied significantly with elevation, as well as among the tree species, and between the wet and dry season. Community‐wide herbivore damage followed a hump‐shaped pattern with the peak between 700 and 1,200 m a.s.l. and this pattern corresponded with abundance of herbivores. For two tree species surveyed in detail, we observed decreasing and hump‐shaped patterns in herbivory, in general matching the trends found in the set of plant defenses measured here. Our results imply that vegetation growing at mid‐elevations of the elevational gradient, that is at the climatically most favorable elevations where water is abundant, and temperatures still relatively warm, suffers the maximum amount of herbivorous damage which changes seasonally, reflecting the water availability

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

10.1186/s12862-020-01646-zBMC Evolutionary Biology2018

Climate, host phylogeny and the connectivity of host communities govern regional parasite assembly

Aim Identifying barriers that govern parasite community assembly and parasite invasion risk is critical to understand how shifting host ranges impact disease emergence. We studied regional variation in the phylogenetic compositions of bird species and their blood parasites (Plasmodium and Haemoproteus spp.) to identify barriers that shape parasite community assembly. Location Australasia and Oceania Methods We used a dataset of parasite infections from >10,000 host individuals sampled across 29 bioregions. Hierarchical models and matrix regressions were used to assess the relative influences of interspecies (host community connectivity and local phylogenetic distinctiveness), climate and geographic barriers on parasite local distinctiveness and composition. Results Parasites were more locally distinct (co-occurred with distantly related parasites) when infecting locally distinct hosts, but less distinct (co-occurred with closely related parasites) in areas with increased host diversity and community connectivity (a proxy for parasite dispersal potential). Turnover and the phylogenetic symmetry of parasite communities were jointly driven by host turnover, climate similarity and geographic distance. Main conclusions Interspecies barriers linked to host phylogeny and dispersal shape parasite assembly, perhaps by limiting parasite establishment or local diversification. Infecting hosts that co-occur with few related species decreases a parasite’s likelihood of encountering related competitors, perhaps increasing invasion potential but decreasing diversification opportunity. While climate partially constrains parasite distributions, future host range expansions that spread distinct parasites and diminish barriers to host shifting will likely be key drivers of parasite invasions

Ficus trees with upregulated or downregulated defence did not impact predation on their neighbours in a tropical rainforest

Trees can emit volatile organic compounds (VOCs) when under attack by herbivores, and these signals can also be detected by natural enemies and neighbouring trees. There is still limited knowledge of intra- and inter-specific communication in diverse habitats. We studied the effects of induced VOC emissions by three Ficus species on predation on the focal Ficus trees in a lowland tropical rainforest in Papua New Guinea. Further we assessed predation across a phylogenetically diverse set of neighbouring tree species. Two of the focal tree species, Ficus pachyrrhachis and F. hispidioides, have strong alkaloid-based constitutive defences while the third one, F. wassa, is lower in constitutive chemical defences. We experimentally manipulated the jasmonic acid signalling pathway by spraying the focal individuals with either methyl jasmonate (MeJA) or diethyldithiocarbamic acid (DIECA). These treatments induce increases or decreases in VOC emissions, respectively. We tested the possible effects of VOC emissions on each focal Ficus tree and two of its neighbours by measuring the predation rate of plasticine caterpillars. We found that predation increased after the MeJA application in only one focal tree species, F. wassa, while the DIECA application had no effect on any of the three focal species. Further, we did not detect an effect of our treatments on predation rates across neighbouring trees. Neither the phylogenetic distance of the neighbouring tree from the focal tree nor the physical distance from the focal tree had any effect on predation rates for any of the three focal Ficus species. These results suggest that even congeneric tree species vary in their response to the MeJA and DIECA treatment and subsequent response to VOC emissions by predators. Our results also suggest that MeJA effects did not spill over to neighbouring trees in highly diverse tropical rainforest vegetation

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

10.1093/gbe/evz168Genome Biology and Evolution1182332-234

Ecological factors driving the feather mite associations in tropical avian hosts

Birds host a diversity of ectosymbionts including feather-dwelling arthropods such as feather mites and lice that they have co-evolved and speciated with. Among these ectosymbionts, feather mites have evolved more mutualistic to commensal associations with birds than other groups. However, our understanding of the biological and ecological drivers that shape the associations between avian hosts and feather mites in tropical communities is poor. Thus, to help fill this knowledge gap we investigated the factors that govern feather mite abundances at host community, host species and individual levels in bird communities from different elevations on the tropical island of New Guinea. We examined the effects of abiotic factors, such as temperature and precipitation, the influence of host species, feeding guilds, bill morphology, body region, body conditions and infections with haemosporidian blood parasites on feather mite abundance. We found that feather mites were very prevalent among New Guinean birds and that mite abundance was not significantly different between elevations. Bird species with curved bills experienced significantly lower number of mites compared to species with straight bills. Feather mite abundance was significantly higher on flight feathers than on the rest of the body and mite abundance was not strongly associated with the body condition of individuals in most host species, except for a significant negative relationships in three species. Moreover, we did not find an association between feather mite abundance and blood parasite infections, potentially indicating a non-synergistic association of these two symbionts. Overall, our study demonstrates that tropical avian-feather mite associations are driven by different biotic and abiotic factors at host community, species and individual levels, highlighting the importance of examining these associations at both broad and fine scales to thoroughly understand the evolution of these symbioses

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 towards the Equator, using a global experiment with model caterpillars to measure predation risk. Across an 11,660 km latitudinal gradient spanning six continents, we found increasing predation towards the Equator – with a parallel pattern of increasing predation towards 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 coherent drivers of biotic interaction strength, a finding which needs to be integrated into general theories of herbivory, community organization, and life history evolution

Insects of Mount Wilhelm, Papua New Guinea

Until now the altitudinal factor has not been taken into account to estimate tropical arthropod diversity. The ultimate aim of the terrestrial biodiversity survey "Our Planet Reviewed – Papua New Guinea" was to estimate biological diversity generated by altitudinal turnover of arthropod species. It took place on Mount Wilhelm, Papua New Guinea highest peak (4509 m a.s.l.), and one of the few equatorial mountains outside the Andes left with a continuous undisturbed forest from the sea level all the way to the timber line limit. An unprecedented sampling effort was concentrated over 16 days in 2012 with a semi-simultaneous sampling at eight different elevations (every 500 m from 200 m to 3700 m a.s.l.). Arthropods were collected with various methods: flight interception traps (targeting Coleoptera), Malaise traps (targeting Hymenoptera, Diptera and Hemiptera), Steiner traps (targeting tephritid flies), beating of the understorey vegetation, and insecticide spraying on tree barks (various groups targeted). A botany survey was conducted at each elevation to characterize vegetation. An additional site, Wanang, was sampled according to the same protocol, as replicated lowland site. Our team combined international experts with local postgraduate students, para-ecologists and villagers. Arthropod samples collected during the biotic survey were pre-sorted in Papua New Guinea and forwarded to taxonomists worldwide. The current book presents the first taxonomic results of the biotic survey. Project outputs included not only species discovery, but also direct financial benefits to landowner communities, raised profile of conservation areas, training of paraecologists and postgraduate students, education programmes and, finally, crucial biodiversity information needed for ecological analyses and conservation management

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 towards the Equator, using a global experiment with model caterpillars to measure predation risk. Across an 11,660 km latitudinal gradient spanning six continents, we found increasing predation towards the Equator – with a parallel pattern of increasing predation towards 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 coherent drivers of biotic interaction strength, a finding which needs to be integrated into general theories of herbivory, community organization, and life history evolution