Galaxiasfossils from Miocene lake deposits, Otago, New Zealand: The earliest records of the Southern Hemisphere family Galaxiidae (Teleostei)

New records of immature aquatic Diptera from the Foulden Maar Fossil-Lagerstätte, New Zealand, and their biogeographic implications

Background

The biogeographical and ecological history of true flies (Diptera) in New Zealand is little known due to a scarcity of fossil specimens. Here, we report a fauna of immature aquatic dipterans from freshwater diatomites of the early Miocene Foulden Maar Fossil-Lagerstätte in southern New Zealand.

Methods

We document 30 specimens of immature dipterans, mostly pupae, and compare their external morphology to extant aquatic Diptera. Based on the reconstructed paleoenvironment of Foulden Maar, we discuss taxonomic, ecological and taphonomic implications of this early Miocene fauna.

Results

Among Chironomidae, one pupal morphotype is attributed to Tanypodinae, one pupal morphotype and one larval morphotype are placed into Chironomus (Chironominae) and a further morphotype into Chironominae incertae sedis. Chaoboridae are represented by a pupal morphotype congeneric or very close to the extant Chaoborus, today globally distributed except for New Zealand. Additional immature specimens are likely larvae and puparia of brachyceran flies but cannot be identified to a narrower range. These finds document an aquatic dipteran fauna in New Zealand in the earliest Miocene and highlight Neogene extinction as a factor in shaping the extant Diptera fauna in New Zealand. Immature aquatic dipterans were a common and likely ecologically important component of the early Miocene Foulden Maar lake. Preservation of larvae and pupae may have been promoted by diatomaceous microbial mats and the light colour of the diatomite likely facilitated spotting of these minute fossils in the field.

Ancient DNA from the extinct New Zealand grayling (Prototroctes oxyrhynchus) reveals evidence for Miocene marine dispersal

The evolutionary history of Southern Hemisphere graylings (Retropinnidae) in New Zealand (NZ), including their relationship to the Australian grayling, is poorly understood. The NZ grayling (Prototroctes oxyrhynchus) is the only known fish in NZ to have gone extinct since human arrival there. Despite its historical abundance, only 23 wet and dried, formalin-fixed specimens exist in museums. We used high-throughput DNA sequencing to generate mitogenomes from formalin-fixed P. oxyrhynchus specimens, and analysed these in a temporal phylogenetic framework of retropinnids and osmerids. We recovered a strong sister-relationship between NZ and Australian grayling (P. mareana), with a common ancestor ~13.8 Mya [95% highest posterior density (HPD): 6.1–23.2 Mya], after the height of Oligocene marine inundation in NZ. Our temporal phylogenetic analysis suggests a single marine dispersal between NZ and Australia, although the direction of dispersal is equivocal, followed by divergence into genetically and morphologically distinguishable species through isolation by distance. This study provides further insights into the possible extinction drivers of the NZ grayling, informs discussion regarding reintroduction of Prototroctes to NZ and highlights how advances in palaeogenetics can be used to test evolutionary hypotheses in fish, which, until relatively recently, have been comparatively neglected in ancient-DNA research.

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

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.

Hedycarya macrofossils and associated Planarpollenites pollen from the early Miocene of New Zealand

PREMISE OF THE STUDY

The history of the basal angiosperm family Monimiaceae is based largely on fossil wood and leaf and floral fossils of uncertain affinity. Fossilized leaves with a well-preserved cuticle and Hedycarya-like flowers, including one with in situ pollen tetrads and fruits from an early Miocene lacustrine diatomite deposit in southern New Zealand implies a long record for Hedycarya in New Zealand. The flowers contain pollen grains that are very similar to those of the modern New Zealand species Hedycarya arborea and the Australian H. angustifolia but are considerably smaller.

METHODS

We undertook comparative studies of the leaf, flower and fruit morphology of the newly discovered macrofossils and compared the in situ pollen grains from the flower with dispersed pollen grains from extant species.

KEY RESULTS

The leaves are referred to a new, extinct species, Hedycarya pluvisilva Bannister, Conran, Mildenh. & D.E.Lee, (Monimiaceae), and associated with fossilized Hedycarya-like flowers that include in situ pollen and an infructescence of three drupes from the same site. Phylogenetic analysis placed the fossil into Hedycarya, sister to H. angustifolia in a clade with H. arborea and Levieria acuminata. A new name, Planarpollenites fragilis Mildenh., is proposed for dispersed fossil pollen tetrads at the site and those associated with the flower.

CONCLUSIONS

The fossils are similar to those of modern Australian and New Zealand Hedycarya species, suggesting that the genus and related taxa have been significant components of the rainforests of Australia and the former Zealandian subcontinent for most of the Cenozoic.

A fossil Fuchsia (Onagraceae) flower and an anther mass with in situ pollen from the early Miocene of New Zealand

PREMISE OF THE STUDY

Fuchsia (Onagraceae) anthers, pollen, and an ornithophilous Fuchsia-like flower from an earliest Miocene lacustrine diatomite deposit at Foulden Maar, southern New Zealand confirm a long record for Fuchsia in New Zealand and probably an equally long history for its distinctive honeyeater pollination syndrome. The anthers contain in situ pollen of the fossil palynomorph previously assigned to Diporites aspis Pocknall et Mildenh. (Onagraceae: Fuchsia L.). •

METHODS

We undertook comparative studies of the flower and anther morphology of the newly discovered macrofossils and compared the in situ pollen grains from the anthers with dispersed pollen grains from extant species. •

KEY RESULTS

The anther mass is referred to a new, extinct species, Fuchsia antiqua D.E.Lee, Conran, Bannister, U.Kaulfuss & Mildenh. (Onagraceae), and is associated with a fossilized Fuchsia-like flower from the same small mining pit. Because Diporites van der Hammen is typified by a fungal sporomorph, the replacement name for D. aspis is Koninidites aspis (Pocknall & Mildenh.) Mildenh. gen. & comb. nov. Phylogenetic placement of the fossils agrees with a proximal position to either sect. Skinnera or sect. Procumbentes. These are the oldest macrofossils of Fuchsia globally. •

CONCLUSIONS

The floral structures are remarkably similar to those of modern New Zealand Fuchsia. They suggest that the distinctive honeyeater bird-pollination syndrome/association seen in modern New Zealand was already established by the late Oligocene-earliest Miocene. The implications for the biogeography and paleoecology of Fuchsia in Australasia are discussed.

Earliest orchid macrofossils: Early Miocene Dendrobium and Earina (Orchidaceae: Epidendroideae) from New Zealand

Fossil leaves of two Early Miocene orchids (Dendrobium and Earina) are reported from New Zealand. The distinctive, raised tetra- to cyclocytic stomatal subsidiary cells of Earina and characteristic papilla-like absorbing glands and "ringed" guard cells of Dendrobium support the placement of the fossils into these genera. These therefore represent the first Orchidaceae macrofossils with cuticular preservation, the oldest records for subfamily Epidendroideae, as well as the first New Zealand and southern hemisphere fossil records for Orchidaceae. These taxa belong in basal clades to the Vandeae/Cymbideae or Epidendreae (Earina) and the Australasian clade of Dendrobium sensu lato. This phylogenetic placement demonstrates expansion of epiphytic orchids into Zealandia by the mid-Cenozoic and an important role for southern continents in the diversification of Orchidaceae.