Structuring Interaction Networks Between Epiphytic Bryophytes and Their Hosts in Yunnan, SW China

Ecological networks are commonly applied to depict general patterns of biotic interactions, which provide tools to understand the mechanism of community assembly. Commensal interactions between epiphytes and their hosts are a major component of species interactions in forest canopies; however, few studies have investigated species assemblage patterns and network structures of epiphyte–host interactions, particularly non-vascular epiphytes in different types of forest. To analyze the characteristics of network structures between epiphytes and their hosts, composition and distribution of epiphytic bryophytes were investigated from 138 host individuals using canopy cranes in a tropical lowland seasonal rain forest (TRF) and a subtropical montane moist evergreen broad-leaved forest (STF), in Southwest China. We structured binary networks between epiphytic bryophytes and their hosts in these two forests, which presented 329 interactions in the TRF and 545 interactions in the STF. Compared to TRF, the bryophyte–host plant networks were more nested but less modular in the STF. However, both forests generally exhibited a significantly nested structure with low levels of specialization and modularity. The relatively high nestedness may stabilize the ecological networks between epiphytic bryophytes and their hosts. Nevertheless, the low modularity in epiphyte–host networks could be attributed to the lack of co-evolutionary processes, and the low degree of specialization suggests that epiphytes are less likely to colonize specific host species. Vertical distribution of the bryophyte species showed structured modules in the tree basal and crown zones, probably attributing to the adaptation to microclimates within a host individual. This study highlights the nested structure of commensal interaction between epiphytic bryophytes and host trees, and provides a scientific basis to identify key host tree species for conservation and management of biodiversity in forest ecosystems.

Persistent Effects of Historical Selective Logging on a Vascular Epiphyte Assemblage in the Forest Canopy of the Western Ghats, India

Forest canopies have been dubbed the last biological frontier and continue to remain underexplored. Vascular epiphytes form a rich assemblage of plants within the forest canopy and apart from sustaining diverse taxa, they also fulfill critical ecological functions. Vascular epiphytes are particularly sensitive to perturbations of microclimate and microhabitat within the canopy, especially from anthropogenic changes such as logging. The forests of the megadiverse Western Ghats in India harbor a rich assemblage of vascular epiphytes, but their ecology has not been examined systematically. We compared the diversity, abundance, and composition of a vascular epiphyte assemblage between an unlogged and a historically selectively logged forest in the southern Western Ghats, India, and identified factors affecting the epiphyte assemblage. Canopies of 100 trees each in selectively logged and unlogged forests were accessed using the single-rope technique. We found 20 species of vascular epiphytes with the assemblage dominated by members of Orchidaceae. The diversity and abundance of epiphytes were significantly greater in the selectively logged forest. One host tree, Cullenia exarillata, supported the greatest number of epiphytes in both forest stands. The niche widths of epiphyte species, computed with host tree species as a resource, were similar between the two stands but a greater number of species pairs overlapped in the selectively logged forest. Overall, epiphyte abundance was negatively associated with unlogged forests. Host tree species, tree height, and presence of moss on branches were positively associated with the abundance of epiphytes. Despite being ecologically important, no study has thus far examined the impact of selective logging on the epiphyte assemblage in the Western Ghats. Our findings contribute to the knowledge of vascular epiphytes from South and Southeast Asia and set the stage for future research and conservation.

Tree Species and Epiphyte Taxa Determine the “Metabolomic niche” of Canopy Suspended Soils in a Species-Rich Lowland Tropical Rainforest

Tropical forests are biodiversity hotspots, but it is not well understood how this diversity is structured and maintained. One hypothesis rests on the generation of a range of metabolic niches, with varied composition, supporting a high species diversity. Characterizing soil metabolomes can reveal fine-scale differences in composition and potentially help explain variation across these habitats. In particular, little is known about canopy soils, which are unique habitats that are likely to be sources of additional biodiversity and biogeochemical cycling in tropical forests. We studied the effects of diverse tree species and epiphytes on soil metabolomic profiles of forest floor and canopy suspended soils in a French Guianese rainforest. We found that the metabolomic profiles of canopy suspended soils were distinct from those of forest floor soils, differing between epiphyte-associated and non-epiphyte suspended soils, and the metabolomic profiles of suspended soils varied with host tree species, regardless of association with epiphyte. Thus, tree species is a key driver of rainforest suspended soil metabolomics. We found greater abundance of metabolites in suspended soils, particularly in groups associated with plants, such as phenolic compounds, and with metabolic pathways related to amino acids, nucleotides, and energy metabolism, due to the greater relative proportion of tree and epiphyte organic material derived from litter and root exudates, indicating a strong legacy of parent biological material. Our study provides evidence for the role of tree and epiphyte species in canopy soil metabolomic composition and in maintaining the high levels of soil metabolome diversity in this tropical rainforest. It is likely that a wide array of canopy microsite-level environmental conditions, which reflect interactions between trees and epiphytes, increase the microscale diversity in suspended soil metabolomes.

Host Plants Association with Longhorn Beetles of Food Value: Traditional Knowledge of the Guaraní as Cultural Identity Keepers

The study of plant-insect interactions and how cultural groups perceive and manage them constitutes one of the interests of ethnoentomology. This work describes the association between host plants and longhorn beetles (Order: Coleoptera; Family: Cerambycidae), an important food among the Guaraní peoples of the province of Misiones, Argentina. Different management methods of host tree species are analyzed in order to promote the rearing of larvae for edible use. We also discuss a story about the mythical origin of cerambicids relayed by the Ava Chiripa Guaraní community. We reflect on the importance of the local worldview in the maintenance of ancestral practices, such as the cultural tasks involved in slash-and-burn agriculture and the intimate knowledge of biological relationships between the cerambycids and their woody host plants.

Electroantennographic Responses of Cerambyx welensii Küster to Host-Related Volatiles

Wood-boring insects, such as Cerambyx welensii Küster, are involved in oak decline in Mediterranean areas. To advance our understanding of the olfactory perception of C. welensii, we recorded electroantennographic (EAG) responses from male and female antennae to 32 tree volatile organic compounds typical of emissions from its main Quercus L. hosts, and also analysed the dose-dependent response. Cerambyx welensii antennae responded to 24 chemicals. Eight odorants elicited the highest EAG responses (normalized values of over 98%): 1,8-cineole, limonene-type blend, β-pinene, pinene-type blend, sabinene, α-pinene, turpentine and (E)-2-hexenal. Cerambyx welensii exhibits a broad sensitivity to common tree volatiles. The high EAG responses to both limonene- and pinene-type blends suggest the detection of specific blends of the main foliar monoterpenes emitted by Q. suber L. and Q. ilex L. (limonene, α- and β-pinene, sabinene and myrcene), which could influence the intraspecific host choice by C. welensii, and in particular, females may be able to detect oak trees with a limonene-type chemotype. In addition, C. welensii showed high antennal activity to some odorants that characterize emissions from non-host tree species (1,8-cineole, β-pinene, α-pinene, turpentine, δ3-carene and camphene). The results obtained may be applicable to optimize monitoring and mass-trapping programmes in an integrated pest management context.

Habitat Ecology of Epiphytic & Terrestrial Orchids in Langchenphu, Jomotsangkha Wildlife Sanctuary, Bhutan

Orchids are the largest and diverse families of flowering plants. Orchids are found growing mostly in tropical climates affecting various communities socio-economically. Among many protected areas in Bhutan, Jomotshangkha Wildlife Sanctuary (JWS) is the least explored in terms of flora and fauna. The study was carried out to assess diversity, host tree preferences and to determine the growth zone of epiphytic orchids along the altitudinal gradient in Langchenphu gewog in JWS. Transect technique was used in which three trails transect were laid out with 10 sampling plots in each transect. Plots size of 20 m × 20 m along the altitudinal gradients were established maintaining an altitudinal interval of 100 meters between each sample plot. A total of 42 species of epiphytic orchids from 20 genera was recorded of23 host tree species under 15 families were recorded. A significant correlation between diversity of orchid and altitude was observed (r = .927, p < .05). Myrtaceae and Theaceae were the most preferred host tree families (14%) followed by Bignoniaceae (13%) and others respectively. The Study concludes that 57% of total species encountered prefers higher canopy & on a tree with rough bark, Pearson chi-square test (X2(1) = 4.7, p< .05) showed a significant difference between trunk, branches, and canopy. Many epiphytic orchids prefer dense canopy (n = 73, 47%) and living trees (99%). Future studies should be focused more on the flowering season for obtaining better information on orchid diversity in the study area.

Wood-inhabiting fungal responses to forest naturalness vary among morpho-groups

The general negative impact of forestry on wood-inhabiting fungal diversity is well recognized, yet the effect of forest naturalness is poorly disentangled among different fungal groups inhabiting dead wood of different tree species. We studied the relationship between forest naturalness, log characteristics and diversity of different fungal morpho-groups inhabiting large decaying logs of similar quality in spruce dominated boreal forests. We sampled all non-lichenized fruitbodies from birch, spruce, pine and aspen in 12 semi-natural forest sites of varying level of naturalness. The overall fungal community composition was mostly determined by host tree species. However, when assessing the relevance of the environmental variables separately for each tree species, the most important variable varied, naturalness being the most important explanatory variable for fungi inhabiting pine and aspen. More strikingly, the overall species richness increased as the forest naturalness increased, both at the site and log levels. At the site scale, the pattern was mostly driven by the discoid and pyrenoid morpho-groups inhabiting pine, whereas at the log scale, it was driven by pileate and resupinate morpho-groups inhabiting spruce. Although our study demonstrates that formerly managed protected forests serve as effective conservation areas for most wood-inhabiting fungal groups, it also shows that conservation planning and management should account for group- or host tree -specific responses.

Patterns of Fungal Diversity in Needles, Rootlets and Soil of Endemic Pinus Peuce

Pinus peuce Griseb is five-needle pine native in high-altitude montane habitats of the Balkans. The aim was to assess the diversity and composition of fungal communities associated with the soil, rootlets and living needles of P. peuce at three high-altitude forest sites with different edaphic conditions and stand characteristics in southeastern Montenegro. In total, 90 needle, 90 rootlet and 90 soil samples were sampled. DNA amplification using ITS2 rDNA as a marker and high-throughput sequencing resulted in 17,620 high-quality reads, representing 825 fungal taxa. There were 52.5% Basidiomycota, 43.9% Ascomycota and 3.6% Mucoromycotina. There were 118 unique fungal taxa in the rootlets, 230 in the soil and 113 in the needles, with 8 taxa were shared. The most common fungi in rootlets were Rhizopogon mohelensis (11.0%), Suillus sibiricus (8.4%), R. fallax (6.9%), in the soil – Phlebiopsis gigantea (5.1%), Tylospora asterophora (2.9%), Sollicocossima terricola (2.7%), and in the needles – Dothideomycetes sp. 3360_7 (17.6%), Dothideomycetes sp. 3360_10 (10.7%), Leotiomycetes sp. 3360_16 (6.5%). The results showed that the functional tissues and the rhizosphere soil of P. peuce were inhabited by a high diversity of fungi, which were largely specific to each particular substrate, while. the site conditions had only limited effect on associated fungal communities. Associated fungal communities were largely determined by the host tree species, substrate properties and functional capabilities of associated fungi.

Gut Bacteria Associated With Monochamus saltuarius (Coleoptera: Cerambycidae) and Their Possible Roles in Host Plant Adaptations

Monochamus saltuarius (Coleoptera: Cerambycidae) is an important native pest in the pine forests of northeast China and a dispersing vector of an invasive species Bursaphelenchus xylophilus. To investigate the bacterial gut diversity of M. saltuarius larvae in different host species, and infer the role of symbiotic bacteria in host adaptation, we used 16S rRNA gene Illumina sequencing and liquid chromatography-mass spectrometry metabolomics processing to obtain and compare the composition of the bacterial community and metabolites in the midguts of larvae feeding on three host tree species: Pinus koraiensis, Pinus sylvestris var. mongolica, and Pinus tabuliformis. Metabolomics in xylem samples from the three aforementioned hosts were also performed. Proteobacteria and Firmicutes were the predominant bacterial phyla in the larval gut. At the genus level, Klebsiella, unclassified_f__Enterobacteriaceae, Lactococcus, and Burkholderia–Caballeronia–Paraburkholderia were most dominant in P. koraiensis and P. sylvestris var. mongolica feeders, while Burkholderia–Caballeronia–Paraburkholderia, Dyella, Pseudoxanthomonas, and Mycobacterium were most dominant in P. tabuliformis feeders. Bacterial communities were similar in diversity in P. koraiensis and P. sylvestris var. mongolica feeders, while communities were highly diverse in P. tabuliformis feeders. Compared with the other two tree species, P. tabuliformis xylems had more diverse and abundant secondary metabolites, while larvae feeding on these trees had a stronger metabolic capacity for secondary metabolites than the other two host feeders. Correlation analysis of the association of microorganisms with metabolic features showed that dominant bacterial genera in P. tabuliformis feeders were more negatively correlated with plant secondary metabolites than those of other host tree feeders.