Chatham Islands Research Articles

New Zealand Lithothelium (Pyrenulaceae) — description of a new species Lithothelium kiritea sp. nov., with notes on L. australe

Lithothelium kiritea A.J. Marshall, Aptroot, de Lange & Blanchon sp. nov. (Pyrenulaceae) is described from Aotearoa / New Zealand. The new species has a mainly coastal and mostly westerly distribution in Aotearoa / New Zealand and is thus far known only from the bark of living Cordyline australis (Asparagaceae). The new species is separated from Lithothelium australe (treated here as endemic to the Chatham Islands), by its corticolous, rather than saxicolous habit, white to pale buff (when fresh) thallus and large ascospores (measuring 32−40 × 12−15 μm). Lithothelium kiritea is easily recognised and usually abundant in the locations where it has been found, yet it seems to have not been collected until 1973 when it was sampled once and then not collected again until 2018. Currently, specimens matching L. kiritea have not been reported from Australia, so we recommend it be searched for there. Within Aotearoa / New Zealand, we propose that the species be assessed as ‘Not Threatened’ using the New Zealand Threat Classification System.

Taraxacum pseudohamatum Dahlst. (Asteraceae, Cichorioideae) – a new naturalisation from the Chatham Islands, Aotearoa / New Zealand

Taraxacum pseudohamatum is reported from Rēkohu / Wharekauri / Chatham Island in the Chatham Islands, Aotearoa / New Zealand. This species is an addition to that island group’s naturalised flora and the New Zealand Botanical Region. It is also the second member of Taraxacum Sect. Hamatum to be recorded from the islands. The first species of that section to be recorded from the islands is Taraxacum hamatum, which is still only known from a collection made from Hokorereoro / Rangatira / South East Island. Taraxacum pseudohamatum is locally common on Rēkohu / Wharekauri / Chatham Island. The species is described using material from that island, and notes on its recognition and distinction from T. hamatum presented. The ecology of the species on Rēkohu / Wharekauri / Chatham Island is described.

Stable Isotope Analysis Reveals Feral Cat Diet on the Chatham Islands

Feral cats are significant invasive predators in New Zealand and are widely associated with drastic declines in breeding seabird populations. Suppressing or controlling feral cat populations has been a major conservation focus in large island ecosystems, including Rēkohu (The Chatham Islands). The Chatham Island tāiko (Pterodroma magentae) naturally persists in a single breeding colony after experiencing rapid population declines in the 19th & 20th centuries. A deeper understanding of feral cat ecology and diet is required to ensure control methods maximise conservation benefits. We used stable isotope analysis of feral cat fur, claws, and bone collagen to investigate the ecology and diet of feral cats trapped in the Tuku Nature Reserve on Rēkohu (The Chatham Islands). We predicted that cat diet would be highly specialised among individuals but relatively stable over time. To estimate the relative contribution of available prey to feral cat diets we employed Bayesian mixing models. Standard ellipse areas were used to understand diet stability over time. Our results have implications for the ongoing management of the Chatham Island Taiko.
 Supervised by: Cilla Wehi

Mid-Cretaceous wood of Waihere Bay, Pitt Island, Chatham Islands, New Zealand

Summary The mid-Cretaceous is an important time for the diversification of forests globally, including the rise to dominance of the angiosperms and the beginning of the isolation of Zealandia. In New Zealand, little information is available on the mid-Cretaceous xyloflora. New specimens of fossil wood from the mid-Cretaceous Tupuangi Formation were collected from Waihere Bay, Pitt Island, Chatham Islands, of which 16 well-preserved samples were identified, representing Araucariaceae (Agathoxylon, 5 samples), Cupressaceae (Taxodioxylon and Cupressinoxylon, one sample each), Podocarpaceae (Protophyllocladoxylon, one sample), and the ‘Group B’ and ‘Group C’ Mesozoic conifers (four samples each) defined in Bamford & Philippe (2008). Of these, only Taxodioxylon had been identified previously from the Tupuangi Formation. Two new species are erected, Cupressoxylon dianneae sp. nov. and Protophyllocladoxylon jacobusii sp. nov. These records are important for understanding the mid-Cretaceous flora of New Zealand and the history of the unique modern flora of New Zealand.

Genomics reveals repeated landlocking of diadromous fish on an isolated island.

Landlocking of diadromous fish in freshwater systems can have significant genomic consequences. For instance, the loss of the migratory life stage can dramatically reduce gene flow across populations, leading to increased genetic structuring and stronger effects of local adaptation. These genomic consequences have been well-studied in some mainland systems, but the evolutionary impacts of landlocking in island ecosystems are largely unknown. In this study, we used a genotyping-by-sequencing (GBS) approach to examine the evolutionary history of landlocking in common smelt (Retropinna retropinna) on Chatham Island, a small isolated oceanic island 800 kilometres east of mainland New Zealand. We examined the relationship between Chatham Island and mainland smelt and used coalescent analyses to test the number and timing of landlocking events on Chatham Island. Our genomic analysis, based on 21,135 SNPs across 169 individuals, revealed that the Chatham Island smelt was genomically distinct from the mainland New Zealand fish, consistent with a single ancestral colonisation event of Chatham Island in the Pleistocene. Significant genetic structure was also evident within the Chatham Island smelt, with a diadromous Chatham Island smelt group, along with three geographically structured landlocked groups. Coalescent demographic analysis supported three independent landlocking events, with this loss of diadromy significantly pre-dating human colonisation. Our results illustrate how landlocking of diadromous fish can occur repeatedly across a narrow spatial scale, and highlight a unique system to study the genomic basis of repeated adaptation.

Histopathological investigation of four populations of abalone (Haliotis iris) exhibiting divergent growth performance

The black-foot abalone (pāua), Haliotis iris, is a unique and valuable species to New Zealand with cultural importance for Māori. Abalone are marine gastropods that can display a high level of phenotypic variation, including slow-growing or ‘stunted’ variants. This investigation focused on identifying factors that are associated with growth performance, with particular interest in the slow-growing variants. Tissue alterations in H. iris were examined using histopathological techniques, in relation to growth performance, contrasting populations classified by commercial harvesters as ‘stunted’ (i.e., slow-growing) and ‘non-stunted’ (i.e., fast-growing) from four sites around the Chatham Islands (New Zealand). Ten adults and 10 sub-adults were collected from each of the four sites and prepared for histological assessment of condition, tissue alterations, presence of food and presence of parasites. The gut epithelium connective tissue, digestive gland, gill lamellae and right kidney tissues all displayed signs of structural differences between the slow-growing and fast-growing populations. Overall, several factors appear to be correlated to growth performance. The individuals from slow-growing populations were observed to have more degraded macroalgal fragments in the midgut, increased numbers of ceroid granules in multiple tissues, as well as increased prevalence of birefringent mineral crystals and haplosporidian-like parasites in the right kidney. The histopathological approaches presented here complement anecdotal field observations of reduced seaweed availability and increased sand incursion at slow-growing sites, while providing an insight into the health of individual abalone and sub-populations. The approaches described here will ultimately help elucidate the drivers behind variable growth performance which, in turn, supports fisheries management decisions and future surveillance programs.

Hidden diversity in high-latitude Southern Hemisphere environments: Reinstatement of the genus Rama and description of Vandenhoekia gen. nov. (Cladophoraceae, Ulvophyceae, Chlorophyta), two highly variable genera.

The continental coasts and remote islands in the high-latitude Southern Hemisphere, including the subantarctic region, are characterized by many endemic species, high abundance of taxa, and intermediate levels of biodiversity. The macroalgal flora of these locations has received relatively little attention. Filamentous green algae are prolific in the intertidal of southern islands, but the taxonomy, distribution, and evolutionary history of these taxa are yet to be fully explored, mostly due to the difficulty of access to some of these locations. In this study, we examined specimens of the order Cladophorales from various locations in the high-latitude Southern Hemisphere including the subantarctic (the Auckland Islands, Bounty Islands, Campbell Island, Macquarie Island, and Kerguelen Islands), as well as mainland New Zealand, the Chatham Islands, Chile, and Tasmania. The analyses of the rDNA sequences of the samples revealed the existence of two new clades in a phylogeny of the Cladophoraceae. One of these clades is described as the novel genus Vandenhoekia gen. nov., which contains three species that are branched or unbranched. The amended genus Rama is reinstated to accommodate the other clade, and contains four species, including the Northern Hemisphere "Cladophora rupestris." In Rama both branched and unbranched morphologies are found. It is remarkable that gross morphology is not a predictor for generic affiliations in these algae. This study illustrates that much can still be learned about diversity in the Cladophorales and highlights the importance of new collections, especially in novel locations.

Observations of avifauna on Rēkohu / Wharekauri / Chatham Island, Chatham Islands group, in February 2023

Rēkohu / Wharekauri / Chatham Island (hereafter Rēkohu) is the largest island in the Chatham Islands group, 800 km east of the Te Wai Pounamu / South Island, Aotearoa / New Zealand. This island has an avifauna of 170 taxa. Here, we present a list of bird species encountered during an eight-day undergraduate field trip in February 2023. Based on visual encounters or via calls heard, we encountered 38 species of bird (two seabirds, eight coastal birds, six freshwater birds and 22 terrestrial birds) across 13 locations over six days. The most common species sighted were common starlings (Sturnus vulgaris vulgaris), followed by white-fronted terns (Sterna striata) and black swans (Cygnus atratus). We encountered a Chatham Island tūī (Prosthemadera novaeseelandiae chathamensis) in Nikau Bush Reserve, c.35 km north of the translocated population in Awatotara Valley. We also present the first list of bird species for Motuhinahina and a nearby limestone rock stack in Te Whanga Lagoon. Birds encountered there included Chatham Island shag (Leucocarbo onslowi), Pitt Island shag (Phalacrocorax featherstoni), Buff weka (Gallirallus australis hectori) and New Zealand little penguin (Eudyptula minor minor). We formally report the presence of feral emu (Dromaius novaehollandiae), including chicks, at Te Matarae, where there is self-sustaining population following their release to the wild years ago. In previous observations, feral chicken (Gallus gallus gallus) and turkey (Meleagris gallopavo) were ‘semi-wild’ on the basis that observations made of these species were well outside sites of human habitation. In the case of turkey, they are in the process of self-establishing. We suggest a full census is required to determine the status of these populations, particularly emu. As the emu population is self-sustaining, they should be considered as a new addition not only to the avifauna of the Chatham Islands group but to Aotearoa / New Zealand.

Megalaria crispisulcans, a new isidiate species of Megalaria (Ramalinaceae) from Aotearoa / New Zealand

Megalaria crispisulcans .J. Marshall, Blanchon & de Lange (Ramalinaceae) is described as a new species from populations in Te Ika a Maui / North Island of Aotearoa / New Zealand, and on Rēkohu (Chatham Island), Aotearoa / New Zealand. The new species is morphologically closely allied to Megalaria orokonuiana from which it is distinguished by its nrDNA ITS sequence and morphologically by the usual presence of a white prothallus, bright green (when fresh) isidiate thallus and dark black apothecia whose rims are usually crinkled / undulose at maturity. A phylogeny based on nrDNA ITS sequences is presented which recovers Megalaria crispisulcans as sister to M. orokonuiana. The ecology, habitats and conservation status of M. crispisulcans is provided and an update on the conservation status of M. orokonuiana provided. A revised key to the Aotearoa / New Zealand species of Megalaria is provided.

Azolla rubra R.Br. (Salviniaceae) on Rēkohu / Wharekauri / Chatham Island

Azolla rubra (Salviniaceae) is reported from the Chatham Islands for the first time based on chance finds made in February and April 2023 from two lakes in the north-eastern portion of Rēkohu / Wharekauri / Chatham Island (hereafter Rēkohu). The biostatus of Azolla on the islands is reviewed and it is believed that plants are more likely to have arrived naturally via fragments bought to the islands by waterfowl from Aotearoa / New Zealand than by other means, so should be treated as indigenous. We advise that the impact of Azolla on the most sheltered, shallow, freshwater bodies of the islands should be monitored, as hitherto the islands waterbodies have been mostly devoid of free-floating aquatic plants.

Host specificity shapes fish viromes across lakes on an isolated remote island

Fish viromes often provide insights into the origin and evolution of viruses affecting tetrapods, including those associated with imporant human diseases. However, despite fish being the most diverse vertebrate group, their viruses are still understudied. We investigated the viromes of fish on Chatham Island (Rēkohu), a geographically isolated island housing 9% of New Zealand's threatened endemic fish species. Using metatranscriptomics, we analyzed samples from seven host species across 16 waterbodies. We identified 19 fish viruses, including 16 potentially novel species, expanding families such as the Coronaviridae, Hantaviridae, Poxviridae, and the recently proposed Tosoviridae. Surprisingly, virome composition was not influenced by the ecological factors measured and smelt (Retropinna retropinna) viromes were consistent across lakes despite differences in host life history, seawater influence, and community richness. Overall, fish viromes across Rēkohu were highly diverse and revealed a long history of co-divergence between host and virus despite their unique and geographically isolated ecosystem.

Numerical Modeling and GNSS Observations of Ionospheric Depletions Due To a Small‐Lift Launch Vehicle

AbstractSpace launches produce ionospheric disturbances which can be observed through measurements such as Global Navigation Satellite System signal delays. Here we report observations and numerical simulations of the ionospheric depletion due to a Small‐Lift Launch Vehicle. The case examined was the launch of a Rocket Lab Electron at 22:30 UTC on 22 March 2021. Despite the very small launch vehicle, ground stations in the Chatham Islands measured decreases in slant total electron content for navigation satellite signals following the launch. Global Ionosphere Thermosphere Model results indicated ionospheric depletions which were comparable with these measurements. Measurements indicated a maximum decrease of 2.7 TECU in vertical total electron content, compared with a simulated decrease of 2.6 TECU. Advection of the exhaust plume due to its initial velocity and subsequent effects of neutral winds are identified as some remaining challenges for this form of modeling.

Review of the genus Nesomalium Steel, 1964 (Coleoptera, Staphylinidae, Omaliinae), with description of two new species from Ewing and Chatham islands.

The New Zealand genus Nesomalium Steel, 1964 (Omaliini) with six species is reviewed and redescribed, and briefly compared with related genera. All species are redescribed and illustrated, including two new species: N. marrisi sp. n. from Chatham Island and N. lescheni sp. n. from Ewing Island (Auckland islands). Lectotypes are designated for Omalium insulare Kiesenwetter, 1877 and O. pacificum Kiesenwetter, 1877. The key to species is provided. Nesomalium insulare (Kiesenwetter, 1877) is recorded from Adams and Ewing islands for the first time.

Diet variation of common smelt across a salinity gradient in coastal lakes on Rēkohu (Chatham Island)

ABSTRACT Sea level rise threatens ecosystem function in coastal lakes by increasing salinity and altering community composition. As mobile generalists, fish have considerable influence on the stability of a system by impacting trophic network structure. Understanding their diet across abiotic gradients, including salinity, can show key characteristics of their ecological role, and predator diet shifts may serve as warning signs of food web restructuring. Stomach contents analysis was used to look at the diet of Retropinna retropinna (common smelt) across shallow coastal lakes on Rēkohu (Chatham Island). Smelt diets from 10 lakes (seven freshwater; three salt-influenced) were analysed. Comparisons of salt-influenced and freshwater lakes showed shifts in composition. Smelt in freshwater lakes predominantly consumed herbivorous, omnivorous, or predatory insect larvae while diet in salt-influenced lakes was dominanted by crustacean shredders. Population diet varied somewhat less among salt-influenced lakes than among freshwater lakes, suggesting homogenisation of smelt diet with salinity. Differences in composition and heterogeneity did not translate to consistent differences in total niche width or individual specialisation between freshwater and salt-influenced lakes. Further development of knowledge on biological structure across salinity gradients is essential to understand ecosystem function under future climate scenarios.

Mercury in Ten Storm-Petrel Populations from the Antarctic to the Subtropics

The oceans become increasingly contaminated as a result of global industrial production and consumer behaviour, and this affects wildlife in areas far removed from sources of pollution. Migratory seabirds such as storm-petrels may forage in areas with different contaminant levels throughout the annual cycle and may show a carry-over of mercury from the winter quarters to the breeding sites. In this study, we compared mercury levels among seven species of storm-petrels breeding on the Antarctic South Shetlands and subantarctic Kerguelen Islands, in temperate waters of the Chatham Islands, New Zealand, and in temperate waters of the Pacific off Mexico. We tested for differences in the level of contamination associated with breeding and inter-breeding distribution and trophic position. We collected inert body feathers and metabolically active blood samples in ten colonies, reflecting long-term (feathers) and short-term (blood) exposures during different periods ranging from early non-breeding (moult) to late breeding. Feathers represent mercury accumulated over the annual cycle between two successive moults. Mercury concentrations in feathers ranged over more than an order of magnitude among species, being lowest in subantarctic Grey-backed Storm-petrels (0.5 μg g−1 dw) and highest in subtropical Leach’s Storm-petrels (7.6 μg g−1 dw, i.e. posing a moderate toxicological risk). Among Antarctic Storm-petrels, Black-bellied Storm-petrels had threefold higher values than Wilson’s Storm-petrels, and in both species, birds from the South Shetlands (Antarctica) had threefold higher values than birds from Kerguelen (subantarctic Indian Ocean). Blood represents mercury taken up over several weeks, and showed similar trends, being lowest in Grey-backed Storm-petrels from Kerguelen (0.5 μg g−1 dw) and highest in Leach’s Storm-petrels (3.6 μg g−1 dw). Among Antarctic storm-petrels, species differences in the blood samples were similar to those in feathers, but site differences were less consistent. Over the breeding season, mercury decreased in blood samples of Antarctic Wilson’s Storm-petrels, but did not change in Wilson’s Storm-petrels from Kerguelen or in Antarctic Black-bellied Storm-petrels. In summary, we found that mercury concentrations in storm-petrels varied due to the distribution of species and differences in prey choice. Depending on prey choices, Antarctic storm-petrels can have similar mercury concentrations as temperate species. The lowest contamination was observed in subantarctic species and populations. The study shows how seabirds, which accumulate dietary pollutants in their tissues in the breeding and non-breeding seasons, can be used to survey marine pollution. Storm-petrels with their wide distributions and relatively low trophic levels may be especially useful, but more detailed knowledge on their prey choice and distributions is needed.

Preverbal Determiners and the Passive in Moriori

This paper examines the curious occurrence of preverbal determiners in Moriori (Chatham Islands), which are best analyzed as passive markers. In some Moriori sentences, a determiner is found following the clause-initial tense/aspect particle and preceding the verb. Examining the morphological markings of the arguments in these sentences shows that the verb is in the passive form, though without the usual -Cia passive suffix. This paper demonstrates that preverbal determiners mark a passive verb, and are in complementary distribution with the standard passive suffix. Previous analyses for preverbal determiners, including being part of continuous aspect particle or introducing a nominalized verb, are ruled out. Preverbal determiners which identify a verb as passive are not found in any other Polynesian language, making this construction unique.

Metabolomics approach reveals size-specific variations of blackfoot abalone (Haliotis iris) in Chatham Islands, New Zealand

Metabolomics approach reveals size-specific variations of blackfoot abalone (Haliotis iris) in Chatham Islands, New Zealand

Local variation in the timing of reproduction and recruitment in a widely distributed diadromous fish

ABSTRACT Īnanga (Galaxias maculatus) is a widespread freshwater fish, found around coastal New Zealand, Chatham Islands, southern Australia and southern South America, exhibiting both diadromous and land-locked life history patterns. We assessed population size structure, size at maturity, timing of reproduction, and post-reproductive survival in the Waikouaiti and Kakanui rivers, two regionally important G. maculatus populations in southern New Zealand. Size at maturity varied between rivers and sexes, with males generally maturing at smaller sizes than females. The timing of reproduction and recruitment was observed to vary across a relatively small spatial scale. Population length-frequencies indicated that both populations exhibited annual population dynamics, with most individuals spawning in their first year, then apparently dying soon afterwards (as indicated by a marked drop in post-spawning abundance). However, a few individuals with recently spent or resting gonads were present over the winter months, indicating some post-spawning survival. There was a lower frequency of exceptionally large (putatively 1+) individuals than reported for other populations around New Zealand and elsewhere, suggesting over-winter survival following spawning varies. Based on the variation in life history characters over small spatial scales, we suggest that management of regionally important G. maculatus populations should be based on catchment level information.

Largest-known fossil penguin provides insight into the early evolution of sphenisciform body size and flipper anatomy

AbstractRecent fossil discoveries from New Zealand have revealed a remarkably diverse assemblage of Paleocene stem group penguins. Here, we add to this growing record by describing nine new penguin specimens from the late Paleocene (upper Teurian local stage; 55.5–59.5 Ma) Moeraki Formation of the South Island, New Zealand. The largest specimen is assigned to a new species, Kumimanu fordycei n. sp., which may have been the largest penguin ever to have lived. Allometric regressions based on humerus length and humerus proximal width of extant penguins yield mean estimates of a live body mass in the range of 148.0 kg (95% CI: 132.5 kg–165.3 kg) and 159.7 kg (95% CI: 142.6 kg–178.8 kg), respectively, for Kumimanu fordycei. A second new species, Petradyptes stonehousei n. gen. n. sp., is represented by five specimens and was slightly larger than the extant emperor penguin Aptenodytes forsteri. Two small humeri represent an additional smaller unnamed penguin species. Parsimony and Bayesian phylogenetic analyses recover Kumimanu and Petradyptes crownward of the early Paleocene mainland NZ taxa Waimanu and Muriwaimanu, but stemward of the Chatham Island taxon Kupoupou. These analyses differ, however, in the placement of these two taxa relative to Sequiwaimanu, Crossvallia, and Kaiika. The massive size and placement of Kumimanu fordycei close to the root of the penguin tree provide additional support for a scenario in which penguins reached the upper limit of sphenisciform body size very early in their evolutionary history, while still retaining numerous plesiomorphic features of the flipper.UUID: https://zoobank.org/15b1d5b2-a5a0-4aa5-ba0a-8ef3b8461730

Non-breeding behaviour in the Brown Skua (Stercorarius antarcticus lonnbergi): insights from modelling moulting patterns and stable isotope analyses

ABSTRACT Long-term changes in the life history and behaviour of seabirds during the non-breeding season can reflect shifts in environmental conditions. However, long-term marine studies are scarce, particularly on southern hemisphere seabirds. Here, we used moult scores from 86 Brown Skuas (Stercorarius antarcticus lonnbergi), a large predatory seabird breeding on the Chatham Islands, Aotearoa/New Zealand to model both the timing and duration of primary feather moult. In addition, we analysed stable isotope values (δ13C and δ15N) from 62 modern (2014–16) and ten museum tail feathers. These data provide insights into the non-breeding behaviour of Brown Skua. Interestingly, our results show that the primary feather moult occurred prior to birds departing the colony, starting on average on 2 January ± 5 days (SE). The average start of primary feather moult occurred five days prior to the end of breeding (7 January ± 10 days (SD)) and 42 days before the birds departed the colony (13 February ± 11 days (SD)). The average duration of primary feather moult was 189 ± 14 days (SE). Importantly, low δ13C values in four females suggested that tail feather moult might also occur while skuas are at the colony. There was no difference in tail feather δ13C and δ15N values between any pairwise comparison of modern and museum years. However, values of δ15N from tail feathers sampled in 2014 were different from those sampled in 2015 and 2016. This large annual variation in δ15N values from tail feathers over such a short period makes long-term comparisons difficult to interpret, particularly between years with low sample sizes. While the stable isotope analyses of tail feathers are informative, we recommend future studies of skuas sample the primary coverts rather than tail feathers.