Great Barrier Island Research Articles

Productivity‐decomposition dynamics of Typha orientalis at Kaitoke Swamp, Great Barrier Island, New Zealand

The productivity and decomposition of Typha orientalis at Kaitoke Swamp on Great Barrier Island, New Zealand, were measured to determine the annual dynamics of its biomass. These interactions, including peat accumulation under nutrient‐rich conditions, are often poorly understood. Annual productivity and maximum “standing” above‐surface and below‐surface biomass were measured using sequential harvest plots. Decomposition was determined using recently dead T. orientalis leaves in mesh litter bags placed on, above, and below the swamp surface. The annual productivity of T. orientalis (c. 3 kg m−2) is within world‐wide estimates for swamp wetland species. The order of decomposition of leaf litter at Kaitoke Swamp is: below surface > surface > above surface. Litter bag mesh size did not affect decomposition processes, indicating that larger decomposer animals probably do not have a significant influence on biomass loss in the site. Peat accumulation was estimated based on observations and measurements of the entrainment process. T. orientalis had low estimated peat accumulation, with 6.5% (0.19 kg m−2 yr1) of the annual production remaining after all components had been underground for 5 years. Consequently a large amount of the annual production of biomass is lost from the site. The ratio of maximum biomass to annual productivity was 2.2, also indicating low biomass accumulation.

Cyperus insularis (Cyperaceae), a new species of sedge from northern New Zealand

Cyperus insularis Heenan et de Lange is described as a new species for plants that have previously been considered to be a northern variant of C. ustulatus. This new species is distinguished from C. ustulatus by a suite of floral and vegetative characters. These include grey‐green leaves and involucral bracts, light pink or light purple‐pink leaf sheaths, a uniformly green culm, the inflorescence rays usually branched, glumes and ray bracts green at flowering and drying yellow brown to light brown at fruiting, and longer spikes, anthers, and filaments. The chromosome number of C. insularis is 2n = 112–114. C. insularis occurs mainly on northern offshore islands, and appears to be the only species of Cyperus present on the Kermadec, Three Kings, Poor Knights, and Mokohinau islands, while it is sympatric with C. ustulatus on the Hen and Chickens Islands, Great Barrier Island, and at several mainland locations. A lectotype for C. ustulatus f. grandispiculosus is selected from the Carse Herbarium.

Sedimentary evidence for tsunami on the northeast coast of New Zealand / Arguments sédimentaires attestant un tsunami sur la côte nord-est de la Nouvelle-Zélande

Abstract Extensive thin gravel sheets mantle coastal dunes at Henderson Bay (Northland) and Whangapoua Bay (Great Barrier Island) on the Northeast coast of North Island, New Zealand. At each site, the surface distribution of the gravel has been mapped and sampled. At each locality the gravels extend above the 2-3 m (above MSL) limit of storm surge to 14-m elevation at Whangapoua and 32 m at Henderson Bay. The area of gravel exposed is 30,000 m2 at Whangapoua and 120,000 m2 at Henderson Bay. The gravel sheets are single-clast thick and comprise poorly sorted, granule to cobble-sized clasts. Particles are sub-rounded to sub-angular, indicating wave abrasion. A fluvial or colluvial origin for these deposits is discounted for both sites due to their isolation from streams and hillslopes. We also discount the possibility that these deposits are the product of aeolian transport on the basis of clast size (up to 67 mm) and elevation. We propose that they were swept there by tsunami. The freshwater wetlands behind the Henderson Bay dunefield provide further evidence for tsunami run-up. Here, a vibra- core records the landward reworking of beach and dune sand and Loisels Pumice into a freshwater wetland where it is preserved as a 5-cm interbed within peat. Bracketing radiocarbon ages on the enclosing peat provide a maximum age of 5590-5310 cal yr. BP and a minimum age of 1180-930 cal yr. BP for the sand-pumice deposit. At Whangapoua, optical ages on dunes sands from below the gravels range from 6700 ± 500 to 3700 ± 500 BP. However, the most reliable age estimate for the tsunami deposits is derived from Loisels Pumice, which is independently dated to 660-510 years BP. Within this time frame, the most probable mechanism for tsunami generation was the collapse of a submarine caldera (Healy caldera) that occurred circa 700 years BP on the Kermadec ridge to the north of New Zealand.

Starch grains and xylem cells of sweet potato ( Ipomoea batatas) and bracken ( Pteridium esculentum) in archaeological deposits from northern New Zealand

Starch grains and xylem cells found in prehistoric coprolites and a stone mound provide direct evidence for agriculture. Fossil starch and xylem (vessel elements) of introduced sweet potato ( Ipomoea batatas) root in a mound at Pouerua suggests these structures were used to cultivate this species. Sweet potato starch and xylem in coprolites from Great Barrier Island provide evidence for cultivation and diet. Fossil starch grains and xylem (tracheids) of bracken rhizome in coprolites from Kohika provide the earliest direct evidence for the use of this native plant in New Zealand as a carbohydrate food source. Analysis of xylem in starch storage organs is a valuable addition to the study of starch preserved in archaeological deposits.

Cockle-opening by a Dabbling Duck, the Brown Teal

Many birds feed on bivalve molluscs, but only oystercatchers (Haematopus spp.) are known to prise open the shells. Brown Teal (Anas chlorotis), a dabbling duck endemic to New Zealand, were observed opening Common Cockles (Austrovenus stutchburyi) on Great Barrier Island. The teal jackhammered into the open shells of feeding cockles and quickly scooped out the flesh. Despite having the bill morphology of a typical dabbling duck, they were adept at this feeding method.

The ecology and conservation of Kunzea sinclairii (Myrtaceae), a naturally rare plant of rhyolitic rock outcrops

Kunzea sinclairii is a local endemic on Great Barrier Island, northeastern New Zealand. While variously ranked as vulnerable and endangered in the past, we show that this species is naturally uncommon and under no threat of extinction. Previous assessments of its conservation status have been based on inadequate knowledge of its ecology. K. sinclairii is a rupestral species whose optimum habitat is low shrubland on rhyolitic rock outcrops and cliffs. Because of past logging and burning of forest adjacent to the habitat to which it is adapted, K. sinclairii expanded its range. However, in regeneration back to forest, K. sinclairii is being excluded as it is overtopped by other species. This has led to the impression that it is declining. Similarly, a suggestion that K. sinclairii could be threatened by hybridisation with the more abundant closely related K.ericoides is not supported as the hybrids are confined to the disturbed sites created by logging and fire. This case study highlights the importance of having a good understanding of the ecology of uncommon plant species before making decisions on their conservation. Natural rarity does not itself necessarily equate with increased extinction risk and these taxa should not be classified as threatened.

Geographic variation in morphology and flavonoid chemistry in Hebe pubescens and H. bollonsii (Scrophulariaceae), including a new infraspecific classification for H. pubescens

Geographic variation in morphology, leaf anatomy, and flavonoid chemistry is appraised in Hebe pubescens, H. bollonsii, and allied plants from islands of outer Hauraki Gulf, North Island, New Zealand. The circumscription of H. pubescens is modified to include plants from Great Barrier, Little Barrier, and the Mokohinau Islands, as well as the Coromandel Peninsula and immediately surrounding islands. A new infraspecific classification is proposed for H. pubescens, wherein three subspecies are recognised. Subspecies pubescens occurs on the Coromandel Peninsula and immediately surrounding islands, and also at Papanui Point on the western coast of the Firth of Thames. Subspecies rehuarum occurs on Great Barrier Island. Subspecies sejuncta occurs primarily on the Mokohinau Islands and Little Barrier Island, with a single plant also known on Great Barrier Island. Populations of H. pubescens probably form a cline of variation, and some forms of subsp. sejuncta share morphological features with H. bollonsii, which is here considered restricted to the Poor Knights Islands, the Hen and Chickens Islands, and nearby areas of the Northland coast. Possible relationships of H. pubescens and H. bollonsii are discussed. A key to the taxa of Hebe pubescens is provided.

Analysis of plant microfossils in prehistoric coprolites from Harataonga Bay, Great Barrier Island, New Zealand

We show results of palynological and phytolith analysis of coprolites from Harataonga Bay, Great Barrier Island. Because human and dog diets may overlap considerably, the microfossil evidence does not with certainty indicate which of these two species deposited them. The coprolites give insights into prehistoric Maori agriculture, gathering of wild plants, diet, and time of year of site occupation. Gourd (Lagenaria siceraria) pollen found in the coprolites shows that this exotic cultigen was being cultivated in the area at the time. The presence of this taxon together with putative truffle spores in the coprolites suggests subsistence components involving both plant domestication and the gathering of wild plants.

Evaporative Water Loss as a Restriction on Habitat Use in Endangered New Zealand Endemic Skinks

Conservation efforts for two endangered lizard species, the chevron skink (Oligosoma homalonotum) and the striped skink (Oligosoma striatum), have been hindered by a lack of knowledge on their habitat preferences. Reports of some individuals being found in moist microenvironments has led to speculation that both species may be physiologically restricted to such habitats. Estimates of water loss in these two species were compared with water loss in two relatively common species, the speckled skink (Oligosoma infrapunctatum) and Falla's skink (Oligosoma fallai), that are inhabitants of semiarid habitats. When the effect of body size was accounted for using analysis of covariance, results indicated that chevron and striped skinks lost 34% more water through evaporation than the semiarid inhabiting species did. When compared to water loss rates in lizards elsewhere, all New Zealand species had relatively high rates of loss for their size. It is predicted that high rates of water loss in chevron and striped skinks would lead to these species preferentially inhabiting moist sites. Recommendations include that future survey effort for both species should be focused on areas with high moisture content. The results also raise implications for land management on Great Barrier Island and provide insight into the current distribution of chevron and striped skinks.

Evaporative Water Loss as a Restriction on Habitat Use in Endangered New Zealand Endemic Skinks

Conservation efforts for two endangered lizard species, the chevron skink (Oligosoma homalonotum) and the striped skink (Oligosoma striatum), have been hindered by a lack of knowledge on their habitat preferences. Reports of some individuals being found in moist microenvironments has led to speculation that both species may be physiologically restricted to such habitats. Estimates of water loss in these two species were compared with water loss in two relatively common species, the speckled skink (Oligosoma infrapunctatum) and Falla's skink (Oligosoma fallai), that are inhabitants of semiarid habitats. When the effect of body size was accounted for using analysis of covariance, results indicated that chevron and striped skinks lost 34% more water through evaporation than the semiarid inhabiting species did. When compared to water loss rates in lizards elsewhere, all New Zealand species had relatively high rates of loss for their size. It is predicted that high rates of water loss in chevron and striped skinks would lead to these species preferentially inhabiting moist sites. Recommendations include that future survey effort for both species should be focused on areas with high moisture content. The results also raise implications for land management on Great Barrier Island and provide insight into the current distribution of chevron and striped skinks.

Sheet-gravel evidence for a late Holocene tsunami run-up on beach dunes, Great Barrier Island, New Zealand

A semi-continuous sheet of granule to cobble-size clasts forms a distinctive deposit on sand dunes located on a coastal barrier in Whangapoua Bay, Great Barrier Island, New Zealand. The gravel sheet extends from the toe of the foredune to 14.3 m above mean sea level and 200 m landward from the beach. Clasts are rounded to sub-rounded and comprise lithologies consistent with local bedrock. Terrestrial sources for the gravel are considered highly unlikely due to the isolation of the dunes from hillslopes and streams. The only source for the clasts is the nearshore to inner shelf of Whangapoua Bay, where gravel sediments have been previously documented. The mechanism for transport of the gravel is unlikely to be storm surge due to the elevation of the deposit; maximum-recorded storm surge on this coast is 0.8 m above mean high water spring tide. Aeolian processes are also discounted due to the size of clasts and the elevation at which they occur. Tsunami is therefore considered the most probable mechanism for gravel transport. Minimum run-up height of the tsunami was 14.3 m, based on maximum elevation of gravel deposits. Optical ages on dune sands beneath and covering the gravel allow age bracketing to 0–4.7 ka. Within this time frame, numerous documented regional seismic and volcanic events could have generated the tsunami, notably submarine volcanism along the southern Kermadec arc to the east-southeast of Great Barrier Island where large magnitude events are documented for the late Holocene. Radiocarbon ages on shell from Maori middens that appear to have been reworked by tsunami run-up constrain the age of this event to post ca. 1400 AD. Regardless of the precise age of this event, the well-preserved nature of the Whangapoua gravel deposit provides for an improved understanding of the high degree of spatial variability in tsunami run-up.

A 6000‐year palaeoenvironmental record from Harataonga, Great Barrier Island, New Zealand

A pollen, sediment, and tephra record from a drained swamp at Harataonga contains a history of the local coastal environment from the Mid Holocene. This commences c. 6000 cal yr BP in a freshwater environment with swamp forest composed mainly of Laurelia, Leptospermum, Ascarina, and Cyathea spp. Dodonaea and Cyperaceae grew on margins of this forest. Forest on the hills surrounding the wetland comprised mainly Metrosideros, with emergent Dacrydium and Libocedrus. Ascarina, Rhopalostylis, and Cyathea dealbata type were a significant part of the understorey of the hillside forest. Around the time of deposition of the 5550 cal yr BP Whakatane tephra, a freshwater lake developed at the site. Extensive Cyperaceae swamp developed on the fringes of the lake. Shortly after c. 2900 cal yr BP, Dacrycarpus briefly invaded swamp forest, possibly as a result of storm disturbance, and the site made the final transition to swamp. Myrsine and then Hebe shrubs invaded fringes of the swamp as the water table fell, possibly as a result of a change to drier conditions in the Late Holocene. Polynesian deforestation, as indicated by the presence of abundant charcoal and Pteridium spores, is recorded in this core as occurring shortly after deposition of the c. 600 cal yr BP Kaharoa tephra.

Parioglossus (Teleostei: Gobioidei: Microdesmidae) in New Zealand

The genus Parioglossus is known widely across the Indo‐West Pacific from tropical western Pacific islands (Fiji, Vanuatu, New Caledonia), through eastern subtropical to tropical Australia, in south‐east Asia and north to Japan, and west across the Indian Ocean to Madagascar. It is hitherto not recorded from New Zealand, but is here reported from a stream near North Cape in far northern New Zealand, and another draining a wetland on Great Barrier Island in the north‐east of the country. New Zealand specimens do not conform completely to any published descriptions of Parioglossus, but this seems likely to reflect inadequacies in the published descriptions. The fish appear closest to the eastern Australian P. marginalis. Typical habitat is unclear, though simple testing of euryhalinity suggests an ability to inhabit marine, brackish, and possibly fresh waters. Whether the species has been long present in New Zealand waters, undiscovered, has dispersed to New Zealand across the Tasman Sea in ocean currents, or was brought to New Zealand in ballast water discharged from ships, is not known. Parioglossus is one of several species newly discovered in New Zealand waters, for which various explanations are possible.

High Spatial Resolution of Pollen and Charcoal in Relation to the c. 600 year BP Kaharoa Tephra: Implications for Polynesian Settlement of Great Barrier Island, Northern New Zealand

Analysis of high spatial resolution of nine pollen profiles (150m–6·5km apart) from Great Barrier Island shows that between 7500 and 600 calibrated year bp, the island had a low frequency of natural fires compared with elsewhere in the northern North Island. Except for one site which has locally sourced pre-Kaharoa charcoal, source of this charcoal in the Awana–Kaitoke area is uncertain. If local pre-Kaharoa burning did occur at other sites in this area, it was patchy, occurring at different times in different places, and was small-scale. Charcoal was first recorded c.1700 year bp, then again after c.1200 year bp. Pre-Kaharoa charcoal on Great Barrier may be interpreted as either an increased frequency of natural fires in the region due to climatic change to drier conditions, or small-scale, localized initial human impact, or some combination of these factors. Major post-Kaharoa burning in the Awana–Kaitoke area was also patchy, commencing at different times in different places. The presence of the Kaharoa Tephra on Great Barrier Island allows the commencement of major, sustained Polynesian deforestation at Awana–Kaitoke to be reliably dated to c.600 year bp at some sites, and possibly up to 50 years later at other sites.

A reconstruction of the history of a Holocene sand dune on Great Barrier Island, northern New Zealand, using pollen and phytolith analyses

AbstractAim To reconstruct the history of a Holocene sand dune using pollen and phytolith analyses, and to identify the strengths, weaknesses and compatibility of these two methods in the interpretation of Quaternary coastal environments.Location Great Barrier Island, northern New Zealand.Methods Pollen and phytolith analyses were carried out on a sequence through a Holocene sand dune containing a palaeosol.Results Phytoliths were present throughout the sequence. Grass phytoliths increased at the expense of tree phytoliths following fire disturbance. Pollen (and spores) was preserved only in the palaeosol part of the profile. Pteridium fern spores increased at the expense of tall tree pollen following the fire disturbance.Main conclusions Lack of phytolith production by many species and problems of taxonomic specificity in many others restricts the usefulness of phytolith analysis to defining only broad vegetation types. In New Zealand, gymnosperms are invisible in the phytolith record and ferns are extremely under‐represented. In contrast, pollen analysis usually provides a great deal of information regarding the composition of a particular vegetation type. The loss of microscopic charcoal fragments during the phytolith extraction process is a disadvantage in the reconstruction of environments where fires have occurred. The greater durability of phytoliths compared with pollen means that phytoliths may be found in sediments where pollen has not been preserved. The phytolith record may also provide evidence of wetter environments that are not apparent in the pollen record. Unlike grass pollen, which is widely dispersed and therefore blurs the spatial record, the presence of grass phytoliths in sediments indicates a local source. The simultaneous application of both methods potentially provides a powerful tool in ecological interpretation and the reconstruction of Quaternary coastal environments.

Palynology, sedimentology and environmental significance of Holocene swamps at northern Kaitoke, Great Barrier Island, New Zealand.

Pollen and sediment analyses of two cores from coastal freshwater swamps at northern Kaitoke (Kaitoke Swamp and Police Station Swamp), Great Barrier Island, show that c. 7300 calibrated yr B.P. Kaitoke Swamp was an estuary with tidal flats. Avicennia, now absent from the swamp area, was present in the estuary. By c. 4500 yr B.P. fresh water conditions had developed at the Kaitoke Swamp site as marine influences decreased. Around the same time, fresh water swamp conditions commenced at the Police Station Swamp site on the surface of a low lying area of a Late Pleistocene dune. A sandy layer at Kaitoke may represent rapid infilling followed by a dry soil surface until c. 1000 yr B.P. Conifer‐hardwood forest on the hills surrounding the sites c. 7300‐c. 1800 yr B.P. was dominated by Dacrydium and Metrosideros. During this period, environmental conditions were relatively stable, with little change in forest composition. Between 1800 yr and 800 yr B.P. Kaitoke Swamp was reflooded, and the Police Station Swamp extended as a shallow lake over the nearby dune flat. These new shallow swamps were invaded by swamp forest (mainly Dacrycarpus with some Laureha). The presence of charcoal and Ptendmm spores above the Kaharoa Tephra suggests that major Polynesian deforestation at northern Kaitoke began c. 600 calibrated yr B.P.

A Late Quaternary palynological and sedimentological record from two coastal swamps at southern Kaitoke, Great Barrier Island, New Zealand.

Pollen and sediment analyses of two cores from southern Kaitoke (Forsythes’ Paddock and Blackwells Bush), Great Barrier Island, show that at c 7500 cal yr B P, the area was an estuary with tidal flats and Avicennia By c 3000 cal yr B P, a Restionaceae (Leptocarpus) salt marsh had developed in the estuary as marine influences lessened By c cal 2550 yr B P, tresh water swamp (Cypencede‐Gleichenia‐Leptospermum) had replaced the salt marsh Conifer‐hardwood forest surrounding the southern Kaitoke sites from c 7500‐c 2800 cal yrBP was dominated by Dacrydium Mettosideros and Libocedius After c 2800 cal yr B P, Metrosideros was replaced by Agathis, Pin llocladm and Prumnopitvs taxifolta, suggesting climatic change to more variable conditions The presence ot the Kaharoa Tephra suggests that major Polynesian deforestation at southern Kaitoke began c 600 cal yr B P Minor pre‐Kaharoa fire disturbance is evident c 1750 cal yr B P and c 1290–970 cal yr B P

The palynology and sedimentology of a coastal swamp at Awana, Great Barrier Island, New Zealand, from c. 7000 yr B.P. to present

Pollen and sediment analysis of two Holocene cores from Awana, Great Barrier Island, shows that at 7000 calibrated yr B P the local swamp was an estuanne salt marsh dominated by Restionaceae By c 6000 yr B P the water table was lower, and a fresh water swamp (Gleichenta‐Leptospermum) had replaced the salt marsh Regional conifer‐hardwood forest c 7000 yr B P was initially co‐dominated by Libocedrus and Dacrydmm cupressinum Libocedrus declined from c 6000 yr B P During the period c 6000‐c 2500 yr B P, relatively stable environmental conditions ensued with little change in local or regional vegetation Around 2500 yr B P, the swamp surface became drier and was invaded by Dacrycarpus and Laureha swamp forest This forest was subsequently repeatedly disturbed (not by fire), indicating climatic change to drier and windier conditions Ascanna lucida was periodically a major component of swamp forest Disturbance is also recorded in the clastic (mineral) sediments, where beds of sand within finer‐grained sediment and peat are interpreted as wind blown material derived from partly devegetated dunes to seaward The presence of the Kaharoa Tephra allows the timing of major Polynesian deforestation at Awana to be reliably dated to c 600 calibrated yr B P In contrast, we see no evidence in the clastic sediment record of disturbance at Awana since Kaharoa time We attribute this to the maintenance of stable dunes by a herb/scrub cover despite nearby fires, or to the presence of scrub or forest buffering the swamp from ablating dunes

B-chromosome origin in the endemic New Zealand frogLeiopelmahochstetterithrough sex chromosome devolution

The endemic New Zealand frog Leiopelma hochstetteri has variable numbers of mitotically stable B chromosomes. To assess whether the B chromosomes were derived from the autosome complement, they were isolated by micromanipulation and their DNA amplified by degenerate oligonucleotide primed PCR. Southern hybridizations of B chromosome DNA probes to genomic DNA from males and females characterized by differing numbers of B chromosomes demonstrated that the B chromosomes were derived from the univalent W sex chromosome characteristic of North Island populations. The presence of homologous B chromosome specific sequences from geographically distinct populations indicates a single origin of the B chromosomes. Furthermore, a primitive homology shared by B chromosomes and the W sex chromosome from an ancestral WZ/ZZ karyotype, which is still present in frogs from Great Barrier Island, shows that the B chromosomes originated soon after the univalent W sex chromosome had originated. Sequence analysis revealed that B chromosome DNA is composed of repeat sequences and has the potential to form stable hairpin structures. The molecular dynamics of these structures may reflect an inherent propensity to undergo rapid change in nucleotide sequence and chromosome structure.

B-chromosome origin in the endemic New Zealand frog Leiopelma hochstetteri through sex chromosome devolution.

The endemic New Zealand frog Leiopelma hochstetteri has variable numbers of mitotically stable B chromosomes. To assess whether the B chromosomes were derived from the autosome complement, they were isolated by micromanipulation and their DNA amplified by degenerate oligonucleotide primed PCR. Southern hybridizations of B chromosome DNA probes to genomic DNA from males and females characterized by differing numbers of B chromosomes demonstrated that the B chromosomes were derived from the univalent W sex chromosome characteristic of North Island populations. The presence of homologous B chromosome specific sequences from geographically distinct populations indicates a single origin of the B chromosomes. Furthermore, a primitive homology shared by B chromosomes and the W sex chromosome from an ancestral WZ/ZZ karyotype, which is still present in frogs from Great Barrier Island, shows that the B chromosomes originated soon after the univalent W sex chromosome had originated. Sequence analysis revealed that B chromosome DNA is composed of repeat sequences and has the potential to form stable hairpin structures. The molecular dynamics of these structures may reflect an inherent propensity to undergo rapid change in nucleotide sequence and chromosome structure.