Damage to tropical forests caused by cyclones is driven by wind speed but mediated by topographical exposure and tree characteristics.

Each year, an average of 45 tropical cyclones affect coastal areas and potentially impact forests. The proportion of the most intense cyclones has increased over the past four decades and is predicted to continue to do so. Yet, it remains uncertain how topographical exposure and tree characteristics can mediate the damage caused by increasing wind speed. Here, we compiled empirical data on the damage caused by 11 cyclones occurring over the past 40 years, from 74 forest plots representing tropical regions worldwide, encompassing field data for 22,176 trees and 815 species. We reconstructed the wind structure of those tropical cyclones to estimate the maximum sustained wind speed (MSW) and wind direction at the studied plots. Then, we used a causal inference framework combined with Bayesian generalised linear mixed models to understand and quantify the causal effects of MSW, topographical exposure to wind (EXP), tree size (DBH) and species wood density (ρ) on the proportion of damaged trees at the community level, and on the probability of snapping or uprooting at the tree level. The probability of snapping or uprooting at the tree level and, hence, the proportion of damaged trees at the community level, increased with increasing MSW, and with increasing EXP accentuating the damaging effects of cyclones, in particular at higher wind speeds. Higher ρ decreased the probability of snapping and to a lesser extent of uprooting. Larger trees tended to have lower probabilities of snapping but increased probabilities of uprooting. Importantly, the effect of ρ decreasing the probabilities of snapping was more marked for smaller than larger trees and was further accentuated at higher MSW. Our work emphasises how local topography, tree size and species wood density together mediate cyclone damage to tropical forests, facilitating better predictions of the impacts of such disturbances in an increasingly windier world.

Climate change and invasive species: a physiological performance comparison of invasive and endemic bees in Fiji.

Anthropogenic climate change and invasive species are two of the greatest threats to biodiversity, affecting the survival, fitness and distribution of many species around the globe. Invasive species are often expected to have broad thermal tolerance, be highly plastic, or have high adaptive potential when faced with novel environments. Tropical island ectotherms are expected to be vulnerable to climate change as they often have narrow thermal tolerance and limited plasticity. In Fiji, only one species of endemic bee, Homalictus fijiensis, is commonly found in the lowland regions, but two invasive bee species, Braunsapis puangensis and Ceratina dentipes, have recently been introduced into Fiji. These introduced species pollinate invasive plants and might compete with H. fijiensis and other native pollinators for resources. To test whether certain performance traits promote invasiveness of some species, and to determine which species are the most vulnerable to climate change, we compared the thermal tolerance, desiccation resistance, metabolic rate and seasonal performance adjustments of endemic and invasive bees in Fiji. The two invasive species tended to be more resistant to thermal and desiccation stress than H. fijiensis, while H. fijiensis had greater capacity to adjust their CTmax with season, and H. fijiensis females tended to have higher metabolic rates than B. puangensis females. These findings provide mixed support for current hypotheses for the functional basis of the success of invasive species; however, we expect the invasive bees in Fiji to be more resilient to climate change because of their increased thermal tolerance and desiccation resistance.

Scale-Dependent Influences of Distance and Vegetation on the Composition of Aboveground and Belowground Tropical Fungal Communities.

Fungi provide essential ecosystem services and engage in a variety of symbiotic relationships with trees. In this study, we investigate the spatial relationship of trees and fungi at a community level. We characterized the spatial dynamics for above- and belowground fungi using a series of forest monitoring plots, at nested spatial scales, located in the tropical South Pacific, in Vanuatu. Fungal communities from different habitats were sampled using metagenomic analysis of the nuclear ribosomal ITS1 region. Fungal communities exhibited strong distance-decay of similarity across our entire sampling range (3-110,000 m) and also at small spatial scales (< 50 m). Unexpectedly, this pattern was inverted at an intermediate scale (3.7-26 km). At large scales (80-110 km), belowground and aboveground fungal communities responded inversely to increasing geographic distance. Aboveground fungal community turnover (beta diversity) was best explained, at all scales, by geographic distance. In contrast, belowground fungal community turnover was best explained by geographic distance at small scales and tree community composition at large scales. Fungal communities from various habitats respond differently to the influences of habitat and geographic distance. At large geographic distances (80-110 km), community turnover for aboveground fungi is better explained by spatial distance, whereas community turnover for belowground fungi is better explained by plant community turnover. Future syntheses of spatial dynamics among fungal communities must explicitly consider geographic scale to appropriately contextualize community turnover.

Response of primary and secondary rainforest flowers and fruits to a cyclone, and implications for plant-servicing bats.

The response of primary (PF) and secondary (SF) rainforests to cyclones has broad implications for servicing fauna and the resilience of forest functions. We collected fine-scale data on the reproductive phenology of plant communities in Fijian PF and SF in 12 monthly surveys before and after Cyclone Tomas (2010). We generated a resource index from the reproductive loads of 2218 trees and 1150 non-trees (>190 species) and trunk and stem diameter to assess patterns in resource abundance for nectarivores and frugivores (hereafter NF resources). We aimed to determine (i) whether species richness of NF resources differed between forests; (ii) the patterns of resilience of NF resources at community level in both forests after a cyclone; and (iii) the effect of response on NF resources for plant-servicing bats (Pteropodidae). In 12 months preceding the cyclone, NF resources were greater in PF trees; non-tree resources fluctuated and were greater in SF. Lower species richness of NF resources in SF indicated that fewer opportunities exist there for exploitation by a diverse fauna. More resources were available for bats in PF. In 12 months following the cyclone, PF flowers and fruits, and SF fruits specifically used by pteropodid bats decreased for trees. Non-tree resources were especially susceptible to the cyclone. No universal pattern of decline was associated with the cyclone; instead, some NF resources declined and others were resilient or responded rapidly to a post-cyclone environment. Both PF and SF demonstrated resilience at the community level via increased flower survival (PF) and rapid flower production (SF). Reduced species richness of NF resources in SF will compromise future resilience and response to disturbance, including for threatened pteropodid bat species. These findings are critical for long-term management of forests, given predicted increases in cyclone frequency and intensity associated with anthropogenic climate change.

High resilience of Pacific Island forests to a category- 5 cyclone.

Assessing how forests respond to, and recuperate from, cyclones is critical to understanding forest dynamics and planning for the impacts of climate change. Projected increases in the intensity and frequency of severe cyclones can threaten both forests and forest-dependent communities. The Pacific Islands are subject to frequent low-intensity cyclones, but there is little information on the effects of high intensity cyclones, or on how forest stewardship practices may affect outcomes. We assess the resistance and resilience of forests in three community-stewarded sites on the island of Tanna, Vanuatu, to the wind-related effects of 2015 Category-5 Cyclone Pam, one of the most intense cyclones to make landfall globally. Drawing on transect data established pre-and post-cyclone, we (1) test whether windspeed and tree structural traits predict survival and damage intensity, and whether this varies across sites; (2) assess post-cyclone regeneration of canopy, ground cover, seedlings, and saplings, and how community composition shifts over time and across sites. In sites that sustained a direct hit, 88 % of trees were defoliated, 34 % sustained severe damage, and immediate mortality was 13 %. Initial mortality, but not severe damage, was lower in areas that received an indirect hit and had lower windspeed. Larger trees and those with lighter wood had a higher probability of uprooting and snapping, respectively. Canopy and ground cover regenerated within three years and seedling and sapling regeneration was widespread across life histories, from pioneer to mature forest species. Three species of non-native vines recruited post-cyclone but within 5 years had largely declined or disappeared with canopy closure. Tanna's historical cyclone frequency, combined with customary stewardship practices that actively maintain a diversity of species and multiplicity of regeneration pathways, are likely responsible for the island's resistance and resilience to an intense tropical cyclone.

Nesobasis rito sp. nov. (Zygoptera: Coenagrionidae), a new species of forest damselfly from Vanua Levu, Fiji.

Nesobasis rito sp. nov. (Holotype , Fiji, Vanua Levu, Drawa, 31 v 2018, A. Rivas-Torres leg.) from the comosa group is here described, illustrated, diagnosed, and compared with morphologically close species of the genus. Nesobasis rito can be distinguished from its related congeners by the shape of the caudal appendages and the ligula. The most similar species are N. comosa and N. heteroneura, which, like N. rito, have the caudal appendages covered by dense setae (especially the first species), but the shape differs clearly in lateral view, with N. rito having longer and more slender appendages, and a basal tooth clearly seen in dorsal view, absent in other members of the comosa group. The specific status of the collected specimens is also supported by the results of genetic analyses, where N. rito appears as a well-supported monophyletic clade. Nesobasis rito also has a distinct distribution from its most similar congeners: it is found on Vanua Levu, while N. comosa is found on Viti Levu and the closely related N. heteroneura is found on Viti Levu and Ovalau. All species of this group are found in streams with native forest riparian vegetation on their respective islands.

Recent introduction of an allodapine bee into Fiji: A new model system for understanding biological invasions by pollinators.

Morphology-based studies have suggested a very depauperate bee fauna for islands in the South West Pacific, and recent genetic studies since have indicated an even smaller endemic fauna with many bee species in this region resulting from human-aided dispersal. These introduced species have the potential to both disrupt native pollinator suites as well as augment crop pollination, but for most species the timings of introduction are unknown. We examined the distribution and nesting biology of the long-tongued bee Braunsapis puangensis that was first recorded from Fiji in 2007. This bee has now become widespread in Fiji and both its local abundance and geographical range are likely to increase dramatically. The impacts of this invasion are potentially enormous for agriculture and native ecosystems, but they also provide opportunities for understanding how social insect species adapt to new environments. We outline the major issues associated with this recent invasion and argue that a long-term monitoring study is needed.