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Abstract

Sugarbirds are a family of two socially-monogamous passerine species endemic to southern Africa, with the Cape sugarbird (Promerops cafer) occurring in the fynbos biome of south-western South Africa and Gurney’s sugarbird (Promerops gurneyi) occurring in the grasslands of eastern South Africa, eSwatini and Zimbabwe. The distribution of P. gurneyi is fragmented in comparison to that of P. cafer, owing to the sparse occurrence of the silver sugarbush (Protea roupelliae), a fire-sensitive species that is Gurney’s sugarbird’s preferred source of food, shelter and nesting sites. According to recent data, P. gurneyi populations are in decline and revision of the species’ IUCN conservation status to a threatened category may be warranted. It is, therefore, necessary to understand genetic diversity and risk of inbreeding in this species. We used six polymorphic microsatellite markers and one mitochondrial gene (ND2) to assess genetic diversity and structure of P. gurneyi in South Africa. We used maximum entropy modelling to predict the historical and future distributions of P. gurneyi and several other declining co-distributed grassland birds – all of which show a similar trend of increasingly limited suitable habitat through time. We describe novel universal avian primers which amplify the entire ND2 coding sequence across a broad range of bird orders. Our results suggest low levels of genetic structure at mitochondrial and microsatellite loci with no detectable inbreeding and large effective population sizes. We conclude that it is unlikely that inbreeding poses an immediate risk to the persistence of P. gurneyi in South Africa, although further work is required to assess the extent of genetic divergence among geographically isolated populations.

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