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 tolerances, 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 tolerances 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 to 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 due to their increased thermal tolerance and desiccation resistance.

No abstract

During the last 150 years, incursions of non-native species have been prevalent throughout the South West Pacific. The allodapine bee, Braunsapis puangensis (Cockerell) (Xylocopinae: Allodapini), was introduced to Fiji between 1965 and 2003, most likely from India. Until very recently, little was known about its dispersal ability and subsequent geographical spread across Fiji. Our study greatly increases the geographical records of B. puangensis across Viti Levu, Fiji's largest island, as well as surrounding islands including Vanua Levu, Taveuni and Mana Island. We found that B. puangensis is present throughout all major regions of Viti Levu, and it appears to be highly vagile. In Fiji, we only found B. puangensis foraging on introduced plant species, but nesting in both native and introduced plant species. Increased pollination of weedy exotic plants by this bee could increase their abundance in Fiji. Populations of B. puangensis in Fiji require close monitoring to detect environmental effects including spread of invasive weed species and knock-on effects to ecosystem interactions.

Recent studies suggest an alarming decline in pollinators across many regions of the world due to multiple factors. One potential factor is climate change, which poses both direct and indirect threats to pollinator populations. To help ameliorate the impact of declining populations on the function of ecological and agricultural systems, there is a need to identify species that may adapt to limit the magnitude of this pollination deficit. The South West Pacific has a highly depauperate endemic bee diversity and numerous non‐indigenous species, including honeybees. One allodapine bee, Braunsapis puangensis, has been accidentally introduced to Fiji where it has rapidly spread across multiple islands and become locally abundant. It is a long‐tongued bee, unaffected by honeybee pathogens, and has the potential to become an important crop pollinator. Here, we model the distribution of this species under different climate scenarios to determine how it is likely to respond to future climate change. We show that its distribution is unlikely to contract, but potentially expand with climate warming. These scenarios therefore indicate that the plasticity in B. puangensis populations may allow it to represent an important crop pollinator in this region should honeybee populations decline.