An Akania (Akaniaceae) inflorescence with associated pollen from the early Miocene of New Zealand

Abstract

PREMISE OF THE STUDY:An Akania-like inflorescence, including flowers with in situ pollen was recovered from the remarkable Konservat-Lagerstätte lacustrine diatomite deposit at Foulden Maar, Otago indicating the presence of Akaniaceae in southern New Zealand during the early Miocene. The flowers, although slightly smaller than the sole modern Australian species, A. bidwillii, contain pollen grains that are very like that taxon. The pollen also resembles that of the monospecific sister genus Bretschneidera from Southeast Asia and India, although that taxon has flowers with very different morphology from this genus. METHODS:The floral morphology of the fossil and in situ pollen grains were compared with flowers and pollen grains from extant species of Akaniaceae and related taxa. KEY RESULTS:The fossil inflorescence and associated pollen are referred to a new, extinct species of Akania: Akania gibsonorum. The floral structures and pollen resemble those of the modern Australian Akania species. CONCLUSIONS:The discovery of fossil flowers of Akania in an early Miocene lake deposit in New Zealand, coupled with earlier recognition of Akaniaceae leaves from the Paleocene epoch and wood from the Miocene epoch in South America suggests that the genus was once widespread in former Gondwana landmasses. The extinction of Akaniaceae in New Zealand and South America, and its present relictual distribution in eastern Australia, is most likely related to post-Miocene climatic cooling.