Geographically contrasting biodiversity reductions in a widespread New Zealand seabird

Abstract

Unravelling prehistoric anthropogenic impacts on biodiversity represents a key challenge for biologists and archaeologists. New Zealand's endemic Stewart Island Shag (Leucocarbo chalconotus) comprises two distinct phylogeographic lineages, currently restricted to the country's south and southeast. However, fossil and archaeological remains suggest a far more widespread distribution at the time of Polynesian settlement ca. 1280 AD, encompassing much of coastal South Island. We used modern and ancient DNA, radiocarbon dating, and Bayesian modelling, to assess the impacts of human arrival on this taxon. Our analyses show that the southeast South Island (Otago) lineage was formerly widespread across coastal South Island, but experienced dramatic population extinctions, range retraction and lineage loss soon after human arrival. By comparison, the southernmost (Foveaux Strait) lineage has experienced a relatively stable demographic and biogeographic history since human arrival, retaining much of its mitochondrial diversity. Archaeological data suggest that these contrasting demographic histories (retraction vs. stability) reflect differential human impacts in mainland South Island vs. Foveaux Strait, highlighting the importance of testing for temporal and spatial variation in human-driven faunal declines.

Did interaction between human pressure and Little Ice Age drive biological turnover in New Zealand?

“…The LIA (Figs & ) post‐dates the human‐driven extirpation of New Zealand's mainland terrestrial and marine megafauna (Figs & ), but closely corresponds with a drastic drop in human population size in the cold‐temperate southern region of New Zealand at around 1500 AD (Rawlence et al ., ). Moreover, the LIA onset also corresponds with the northward expansions of subantarctic Megadyptes and Phocarctos lineages to mainland New Zealand (Fig.…”

“…For penguins and sea lions, mainland extinction of one lineage apparently paved the way for colonization by subantarctic island lineages, facilitated by the cooler temperatures of the Little Ice Age (LIA) that improved mainland habitability while reducing human pressure. (a) Polynesian human population size estimates for the south-east (Otago) and south (Foveaux Strait) of the South Island of New Zealand, based on syntheses of archaeological data (Rawlence et al, 2015b). (b) Extinction timings of the largest and smallest species of moa (Aves: Dinornithiformes) across New Zealand.…”

Ancient DNA and morphometric analysis reveal extinction and replacement of New Zealand's unique black swans

“…New Zealand's rich archaeological record [24] presents intriguing opportunities to unravel the often complex dynamics between human populations and indigenous wildlife [25][26][27][28][29][30][31]. Recent analyses of ancient DNA (aDNA) have led to paradigmatic shifts in our understanding of the evolution of NZ's biota [32].…”

Invader or resident? Ancient-DNA reveals rapid species turnover in New Zealand little penguins

“…Indeed, radiocarbon dating and genetic data together imply that E. minor occupied this region of southern New Zealand since at least the Late Pleistocene (34 kya) until human arrival [20]. This study thus adds to a growing appreciation of human-driven impacts (distinct from climate-driven change), ultimately leading to species turnover [16,19,21,22].…”