New Zealand’s Marine Fish Hotspots of Richness and Endemism Lie in Different Places

The waters surrounding Aotearoa New Zealand have long been celebrated as a marine biodiversity treasure trove, home to roughly 19 percent endemic fish species shaped by 83 million years of isolation from the closest major landmass. But a new study reveals something startling: the places where marine fishes are most numerous and the places where evolution has generated its rarest treasures are not the same places at all. For scientists trying to understand how biodiversity is created and maintained in the ocean, this geographic mismatch is more than a curiosity—it is a window into the distinct processes that build life in the sea.

Published in Frontiers of Biogeography, the research by André P. Samayoa, J. David Aguirre, Ana N. H. Samayoa, and Libby Liggins of Massey University maps the biogeography of New Zealand’s marine ray-finned fishes using phylogenetic measures of richness and endemism. Rather than simply counting species, the team incorporated the evolutionary relationships among 313 taxa occurring in waters between 0 and 500 meters deep, using a comprehensive molecular phylogeny of New Zealand’s marine fishes. The result is a phylogenetic landscape that reveals where young lineages are being born, where old lineages persist as living fossils, and where distantly related taxa converge in a mixing zone of evolutionary histories.

The study area spans a bounding box of 30 degrees latitude by 20 degrees longitude in the Southwest Pacific, encompassing New Zealand’s main and offshore islands within jurisdictional waters. The team compiled distributional maps for each taxon using AquaMaps, a web-based tool that generates occurrence probability maps based on environmental variables such as sea surface temperature, salinity, primary productivity, and ice coverage, combined with occurrence data from open-access repositories and expert knowledge. This approach allowed the researchers to infer ranges in areas of the ocean that are difficult to sample directly, particularly open-water locations far from coastal survey efforts.

To identify centres of endemism, the team employed the categorical analysis of neo- and paleoendemism, or CANAPE, a statistical method that distinguishes locations with an over-representation of spatially rare short phylogenetic branches from locations with an over-representation of spatially rare long phylogenetic branches. Short branches represent recently diverged lineages—neoendemism—while long branches represent ancient lineages that have persisted over vast timescales—paleoendemism. The method integrates randomization results of phylogenetic endemism and relative phylogenetic endemism, running 999 randomizations across the metrics to create null distributions for each grid cell of the study area.

The findings are striking. Species richness and phylogenetic diversity generally declined with increasing latitude, with an initial poleward increase peaking at 35 degrees South along the North Island, after which values progressively decreased toward the subantarctic. But endemism told a different story entirely. Endemism reached maximum values in the northernmost oceanic islands, where neoendemism dominated. Significant paleoendemism clustered around two coastal areas of mainland New Zealand: the Hauraki Gulf in the North Island and the surrounding areas of the Banks Peninsula in the South Island.

CANAPE identified 318 cells with significantly high phylogenetic endemism, of which 289 displayed neoendemism, 22 paleoendemism, 6 mixed endemism, and 1 super endemism. Centres of neoendemism were concentrated in the upper quarter of the study area, including the subtropical oceanic islands of Norfolk Island and Rangitāhua, as well as the Colville Ridge. Of the 22 paleoendemism cells identified, 18 were found in the coastal clusters. Paleoendemism dominated in the Hauraki Gulf, where 8 of 12 cells displayed the signature, and in Pegasus Bay, where 3 of 5 cells did. In the Canterbury Bight, 12 of 23 cells displayed neoendemism, 7 paleoendemism, and 4 mixed endemism.

The richness maximum appears to be the result of a range overlap between distantly related tropical taxa shifting towards high latitudes and a lower number of older temperate taxa. The East Auckland Current connects the northeast coast of the North Island with warmer waters in the northwest, facilitating the occurrence of tropical and subtropical fishes in northern areas. As oceanic warming intensifies richness peaks of marine fauna at subtropical latitudes, the researchers expect a future tropicalization of New Zealand’s marine fish fauna in northern areas, strengthening the species richness and phylogenetic diversity peaks around 35 degrees South.

Neoendemism is likely driven by the isolation of young volcanic islands. The subtropical islands of Rangitāhua and Norfolk Island are of recent geological emergence, radically contrasting with the older New Zealand landmass. Molecular evidence shows that marine fishes endemic to remote oceanic volcanic islands of the Southwest Pacific tend to be lineages that diverged after the emergence of the oldest island, suggesting that these subtropical offshore islands generate new marine fish lineages. The isolation factors that prevail in these islands, such as geographical distance and oceanography, along with lower wave energy than in mainland New Zealand, appear to shape the generation of young endemic lineages.

Coastal paleoendemism might be the legacy of locally stable environmental conditions that served as a refuge for relict lineages over time. The Hauraki Gulf covers 14,000 square kilometers of marine area on the northeastern coast of the North Island, with annual sea temperature variations of 12.5 to 22.0 degrees Celsius at the surface. The semi-enclosed gulf has represented a museum for lineage relicts, with old marine fish lineages likely persisting over time due to stable environmental conditions. The continental shelf along the Canterbury Bight and Pegasus Bay is wide, up to 120 kilometers, and the eastern coast of the South Island is characterized as a significant nursery area for marine fishes. The low number of old individual lineages locally present appear to pre-date the estimated age of Gondwanan splitting.

Interestingly, this marine biogeographic pattern is the opposite of what has been found in New Zealand’s terrestrial environments, where neoendemism was high in the South Island due to younger alpine habitats, and paleoendemism was found in the North Island due to its role as a refugium during past interglacial periods. These opposing patterns exemplify how different processes shape distinct island biogeographic patterns between marine and terrestrial environments within the same region. The study highlights the evolutionary relevance of Norfolk Island and Rangitāhua in marine fish biogeography, backing local conservation efforts within already defined marine areas of legal protection, the Norfolk Marine Park and the Kermadec Islands Marine Reserve. The coincidental identification of endemism centres within the Banks Peninsula Marine Mammal Sanctuary is a significant incentive for future biogeographic research in the area, and the researchers believe the potential conservation value of marine fishes along the mid-eastern coast of the South Island serves as an additional stimulus for marine protection strategies in the region.

Subject of Research: Centres of species richness, neoendemism, and paleoendemism for marine fishes occur in different regions of Aotearoa New Zealand

Article Title: Centres of species richness, neoendemism, and paleoendemism for marine fishes occur in different regions of Aotearoa New Zealand

Article References: Samayoa, A. P., Aguirre, J. D., Smith, A. N. H., & Liggins, L. (2025). Centres of species richness, neoendemism, and paleoendemism for marine fishes occur in different regions of Aotearoa New Zealand. Frontiers of Biogeography, 18, Article e134560. https://doi.org/10.21425/fob.18.134560

Image Credits: AI Generated

DOI: 10.21425/fob.18.134560

Keywords: Centres, species, richness, neoendemism, paleoendemism, marine, fishes, occur, different, regions, Aotearoa, Zealand