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Supplementary methods and results

Mean values of branch transformation parameters λ, κ and δ for median (black triangles) and minimum (blue triangles) elevations. Solid black and blue bars indicate 95% highest posterior densities (HPD) for median and minimum elevations, respectively. Parameter values are indicated along the bar showing the minimum and maximum possible values for each factor and whether it supports the taxon cycle (blue), niche conservatism (red) or both (purple).

The Fijian islands that were sampled. Parentheses indicate the period in which they were sampled followed by the number of sequences from each island.

Maximum credibility tree from Bayesian phylogenetic analysis of Fijian Homalictus based on analysis of the COI gene showing posterior probabilities at nodes. Branch color represents geographic extent.

Discriminant analysis of principal components for the SNP data showing the clustering of each species. Inset graph showing the Bayesian information criterion (BIC) values for each inferred clustering level, with the lowest inferred BIC being the preferred number of clusters.

Super-generalism is a pollinator trait where species obtain floral resources from a very wide range of plant species. Theoretical and empirical studies suggest that on islands with low pollinator diversity, such pollinators should evolve to exploit a very wide range of floral morphologies. Super-generalism has implications not only for securing pollination network stability, but also for the invasibility of potential weeds that require specialist pollinators in their original ranges. Here we expand earlier studies on bees in Fiji to include a wider range of bee-plant interactions for bees that have been recently introduced into Fiji as well as the endemic Fijian halictine bee, Homalictus fijiensis. Our data show that the endemic Fijian bee has a much wider range of floral hosts than introduced bees, and this extends to pollen larceny of solanoid plant species that are usually buzz pollinated. Importantly, solanoid plants were not visited by introduced bee species, including the honeybee Apis mellifera, which is usually regarded as a super-generalist. Our findings are important because they add critical support to the hypothesis that super-generalism evolves in insular ecosystems with low pollinator diversity and that this may make such ecosystems vulnerable to invasion by exotic weeds. However, insular super-generalists may also have potential to stabilize plant-pollinator networks and may also be effective pollinators for exotic crop species, and this needs to be further explored in agricultural settings. Refereed/Peer-reviewed

Island biogeography explores how biodiversity in island ecosystems arises and is maintained. The topographical complexity of islands can drive speciation by providing a diversity of niches that promote adaptive radiation and speciation. However, recent studies have argued that phylogenetic niche conservatism, combined with topographical complexity and climate change, could also promote speciation if populations are episodically fragmented into climate refugia that enable allopatric speciation. Adaptive radiation and phylogenetic niche conservatism therefore both predict that topographical complexity should encourage speciation, but they differ strongly in their inferred mechanisms. Using genetic (mitochondrial DNA (mtDNA) and single-nucleotide polymorphism (SNP)) and morphological data, we show high species diversity (22 species) in an endemic clade of Fijian Homalictus bees, with most species restricted to highlands and frequently exhibiting narrow geographical ranges. Our results indicate that elevational niches have been conserved across most speciation events, contradicting expectations from an adaptive radiation model but concordant with phylogenetic niche conservatism. Climate cycles, topographical complexity, and niche conservatism could interact to shape island biodiversity. We argue that phylogenetic niche conservatism is an important driver of tropical island bee biodiversity but that this phylogenetic inertia also leads to major extinction risks for tropical ectotherms under future warming climates.

A new mutillid wasp, Ephutomorpha tyla Hearn,Williams & Parslow sp. nov., is described from adult female and male specimens from the Dandenong Ranges in Victoria, Australia. Adult mutillids were repeatedly found in nests of the hylaeine bee Amphylaeus morosus (Smith, 1879) (Hylaeinae) and reared from host nest cells. This represents the first recorded host–parasite association between Mutillidae and hylaeine bee species. Refereed/Peer-reviewed

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. Refereed/Peer-reviewed