The Mystery
In 1973, while exploring the southern coast of Western Australia as part of his PhD, E. Charles Nelson stumbled across a strange looking plant that he eventually named Adenanthos eyrei. Nelson noted how different the leaves of the new species were compared to the A. forrestii plants growing nearby. Since the new species was only known from a single location, it was listed as a conservation priority. However, botanists returning to the same area over the next forty years were unable to relocate A. eyrei, raising the question of whether it was a distinct species, a weird morphological variant of A. forrestii, or possibly even a short-lived hybrid. Without additional collections of A. eyrei, the mystery seemed unlikely to be solved.
THE SLEUTHING
Normally, this kind of mystery could be solved by collecting leaves from living plants for DNA sequencing and then comparing the sequences to related species. The problem was there were no plants of A. eyrei left in the wild to sequence! A second option was to use herbarium specimens, but only one collection of A. eyrei had ever been made, the type specimen, and it is usually very difficult to get permission to destructively sample type specimens, as they are the authoritative link between plants and their names. Thankfully, the type specimen had many leaves (imaged here), and the curator at the Australian National Herbarium (CANB), Brendan Lepschi, also wanted to solve the mystery of A. eyrei, so he gave permission to destructively sample the type. This let us sequence and compare DNA from A. eyrei and related species, including a 1970s specimen of a possible hybrid from the Western Australian Herbarium (PERTH).
THE OUTCOME
With DNA to compare, we discovered that A. eyrei was a hybrid between A. forrestii and A. cuneatus, a species not collected in the area since the 1980s, potentially explaining why there were no recent collections of A. eyrei. Not only did the A. eyrei type specimen show DNA evidence of contributions from both parental species, it also partly matched another historical specimen of a possible hybrid collected less than 200 km away! With the mystery solved, A. eyrei will now be recognised as A. × eyrei to show it is a hybrid, and it should soon be de-prioritised for conservation efforts. This outcome would not have been possible without a chance to sequence DNA from herbarium specimens, and we are grateful to the curators at CANB and PERTH for permission to do so.
To read more about the investigation, check out our recently published paper here. If you want a copy or have questions, feel free to email me.
Benjamin M. Anderson, Western Australian Herbarium (PERTH), Biodiversity and Conservation Science, DBCA
