Scott V. C. Groom

Bees in the Southwest Pacific: Origins, diversity and conservation

Bee diversity of the Southwest Pacific has been reported as depauperate despite the otherwise rich biodiversity and complex geological history for this region. However, due to a lack of bee-specific sampling, there is potential for higher bee diversity than previous studies suggest. Here, we review the current literature to summarise the extant diversity for each of the main island groups, the likely passages of species dispersal, and outline the main threats to Southwest Pacific populations. As key pollinators for both cultivated and native angiosperms, ensuring the persistence of native bee populations is critical for both food security and biodiversity conservation. With impending threats from land use change, invasive species and climate change, among others, understanding the true species diversity is important for assigning conservation priorities. We argue that future research in the region must encourage local expertise and build this into global research directions in an effort to address a lack of fundamental knowledge of bee diversity in island ecosystems.

Parallel responses of bees to Pleistocene climate change in three isolated archipelagos of the southwestern Pacific

The impacts of glacial cycles on the geographical distribution and size of populations have been explored for numerous terrestrial and marine taxa. However, most studies have focused on high latitudes, with only a few focused on the response of biota to the last glacial maximum (LGM) in equatorial regions. Here, we examine how population sizes of key bee fauna in the southwest Pacific archipelagos of Fiji, Vanuatu and Samoa have fluctuated over the Quaternary. We show that all three island faunas suffered massive population declines, roughly corresponding in time to the LGM, followed by rapid expansion post-LGM. Our data therefore suggest that Pleistocene climate change has had major impacts across a very broad tropical region. While other studies indicate widespread Holarctic effects of the LGM, our data suggest a much wider range of latitudes, extending to the tropics, where these climate change repercussions were important. As key pollinators, the inferred changes in these bee faunas may have been critical in the development of the diverse Pacific island flora. The magnitude of these responses indicates future climate change scenarios may have alarming consequences for Pacific island systems involving pollinator-dependent plant communities and agricultural crops.

Multiple recent introductions of apid bees into Pacific archipelagos signify potentially large consequences for both agriculture and indigenous ecosystems

The islands of the south west Pacific (SWP) are highly biodiverse, yet records of their bee fauna suggest a region depauperate of a key pollinator suite. Studies of the bees of Fiji based on molecular data have revealed a recent origin with the majority of species having arrived since the last glacial maximum or introduced since human colonization. Here we use DNA barcodes to provide the first detailed account of Apidae bees from Vanuatu, Fiji, and Samoa. We show that most if not all species in these archipelagos have been recently introduced from Australia and south east Asia, with a further species introduced from the New World. Some of these species have become regionally abundant and we discuss the potential impact of introduced pollinators on endemic plant–pollinator associations. Given the wide-reaching role of native pollinators in island systems, yet lack of understanding of SWP pollinator suites, our study highlights the urgent need for more detailed pollinator research in the region.

Diversity and Origins of Fijian Leaf-Cutter Bees (Megachilidae)

Abstract: Bees are key pollinators in almost all terrestrial ecosystems and can have major roles in agricultural production. Records of bees in the Southwest Pacific indicate a very low diversity, with the Fijian bee fauna one of the least diverse, despite an otherwise rich biota. Megachilid bees represent a large proportion of the bee fauna for almost all island groups in the Southwest Pacific and, because they are wood- and stem-nesting, their wide distribution is likely to have been influenced by rafting and anthropogenic maritime trade. Our study is the first to apply molecular techniques to the study of megachilid bees in this region and indicates between four and five recent introductions to Fiji, likely from Southeast Asia. The study also provides the first record of Heriades (Michenerella) in the Southwest Pacific and the first record of the subgenus Megachile (Callomegachile) in Fiji. These results indicate that a large proportion of the Fijian bee fauna is likely to have been introduced only very recently and, therefore, has had only a very recent role in Fijian ecosystems, despite their current abundance. This has very wide implications for understanding Fijian plant-pollinator relationships. We argue that there is a strong need to understand ancient plant-pollinator relationships that may have evolved in Fiji before the mid-late Pleistocene and Holocene and whether these could be disrupted by recent bee introductions.

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.

Origins and implications of apid bees (Hymentopera: Apidae) in French Polynesia: Introduced apid bees in French Polynesia

Island plant–pollinator networks are typically simpler than their continental counterparts and this can make them less resilient to disturbance from exotic species. French Polynesia has a very low diversity of bees, but their status as either native or introduced species has been largely speculative. We combine previous studies with new DNA sequence data to show that 11 bee species have now been recorded for French Polynesia. Haplotype variation at the ‘barcode’ region of the mitochondrial gene cytochrome c oxidase subunit I (COI) for four of these species, Ceratina dentipes Freise, Xylocopa sonorina Smith, Braunsapis puangensis (Cockerell) and Amegilla pulchra (Smith), indicates that they all represent very recent introductions. Apis mellifera Linnaeus was a purposefully introduced species, and four megachilid species probably arrived due to human‐aided dispersal through maritime activities in the Pacific. The two remaining bee species, an unidentified partial specimen of a halictid bee and the colletid bee Hylaeus (P.) tuamotuensis Michener, are collectively known from only four specimens collected in the 1930s and their provenance is uncertain. French Polynesia therefore comprises a region where recently introduced bee species greatly overwhelm any possible native bee fauna. These introductions are likely to have major ecosystem impacts, including disruptions of existing plant–pollinator networks and facilitating the spread of weedy plant species, as well as positive impacts for agriculture. Future biosecurity initiatives need to consider these potential impacts and the likely routes of dispersal to effectively control any further unintended introductions.

Current status of the introduced allodapine bee Braunsapis puangensis (Hymenoptera: Apidae) in Fiji

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, Fijis 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.

Recipe for disruption: multiple recent arrivals of megachilid bees in Pacific archipelagos

When examining how the ecosystems of remote islands have developed, it is important to know the timing of when various elements arrived and whether they then diversified. Our understanding of the histories behind the biodiverse south west Pacific (SWP) archipelagos is limited, and further impeded by the complex geological histories of this region. Previous studies of the SWP short-tongued halictine bee fauna suggest their presence is much younger than the geological ages of these archipelagos, which is surprising given their critical role as pollinators in other terrestrial ecosystems. The long-tongued megachilid bees represent a considerable proportion of the known bee species for the region, yet little is known of their origin. Here we use genetic diversity within mitochondrial DNA to infer the likely ages and origins of megachilid species from Vanuatu, Fiji, and Samoa. Our results indicate a very recent origin for megachilids in the SWP, with many species exhibiting small intraspecific genetic distances. Three species share almost identical haplotypes with specimens from Southeast Asia, suggesting multiple human-aided introductions. Combined with data from recent studies on other bee groups present in the region, our results have broad implications for how the Pacific island biota developed and how we should approach its management.

Potential pollination maintenance by an exotic allodapine bee under climate change scenarios in the Indo-Pacific region

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.