The identification of an unusual flying-fox found in Sydney raised more questions than answers
Identifying Australian flying-foxes is usually straightforward, as each of our five species looks very distinctive. However, when a flying-fox with unusual facial markings turned up in Sydney, the experts were stumped, and turned to DNA and the Australian Centre for Wildlife Genomics to unravel the mystery. Our detective work also highlighted the complexity of relationships amongst flying-fox species and the importance of museum collections in identifying species and unravelling their relationships.
After large, widespread storms in April 2015, a flying-fox (Pteropus sp.) with unusual facial markings was found dead in Sydney and brought to the Australian Museum for identification. The unusual pale straw-coloured ring around its face was unlike any known flying-fox found in Australia. One thought was that it had been blown into Australia from nearby Pacific Islands after the storm, but its morphology did not match any of the known Island flying-foxes either. So where did this animal come from? There were three remaining possibilities: 1) it was a hybrid between two Australian species 2) it was an Australian species with unique markings or 3) it was an entirely new species.
Close comparison of the animal against specimens in the AM’s Mammal Collection showed that apart from the unique facial markings it was very similar to the Black flying-fox (Pteropus alecto), but the fur on the body was more like that of a Grey-headed flying-fox (Pteropus poliocephalus). This combination of features suggested that the unknown flying-fox may have been a hybrid between Black and Grey-headed flying-foxes.
To investigate this further, we used DNA analysis to look at five genes that are useful for telling the different flying-fox species apart. Three of these genes are only passed from mother to offspring, showing the maternal lineage, while for the other two genes, one copy comes from each parent. We found that the maternal lineage of the unusual flying-fox matched Black flying-foxes from the Museum’s collection. However, when we looked at the other two genes we did not find any evidence of Grey headed flying-fox DNA. It seems then that the unusual flying-fox may be a peculiar-looking Black flying-fox, or the result of historic hybridization between Black flying-foxes and another species (possibly Grey-headed or even Spectacled flying-foxes), which would need further genetic testing to decipher.
One of the most interesting outcomes of our research was that when trying to determine the species, we compared genetic data from the unusual flying-fox to both reference data we generated from the multiple samples from the AM’s Mammal Collection, as well as to existing data generated from previous studies. Surprisingly this produced two different results! Had we only used existing data, we might have assumed the unusual flying-fox was a new species altogether, most similar to species from the Pacific Islands. However, generating our own data from our museum specimens revealed a new maternal lineage of Black flying-fox that had not been documented before. Only a handful of Black flying-fox samples had been genetically analyzed prior to this study, and these could not be distinguished from Spectacled flying-foxes. This previous work had hypothesized that Black and Spectacled flying-foxes either had only recently diverged or were hybridizing. However, our data show that in addition to Black/Spectacled flying-fox lineage, there is a second distinct lineage which is unique to Black flying-foxes and to which the unusual flying-fox belongs.
Our study showed that the unusual flying-fox was most likely an unusual Black flying-fox, although it may be the result of historic (possibly ongoing) hybridization between Black flying-foxes and another species. However, we also found that relationships amongst different flying-foxes are more complex than previously thought, and confirmed that some species do hybridize. This study highlighted the importance of museum collections in cataloging the range of biodiversity within a species, which assisted greatly in unravelling the mystery of this individual flying-fox. The availability of this expertly identified data in museum collections around the world is incredibly important to scientists who are trying to better understand the relationships between species.
Dr Linda Neaves, Postdoctoral researcher ACWG, AMRI & Royal Botanic Gardens Edinburgh
Dr Greta Frankham, AMRI Postdoctoral Fellow, ACWG.
Dr Mark D. B. Eldridge, Principal Research Scientist, Terrestrial Vertebrates, AMRI
Dr Anja Divljan, Technical Officer, Terrestrial Vertebrates, AMRI