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

Abstract

Prehistoric human impacts on megafaunal populations have dramatically reshaped ecosystems worldwide. However, the effects of human exploitation on smaller species, such as anatids (ducks, geese, and swans) are less clear. In this study we apply ancient DNA and osteological approaches to reassess the history of Australasia's iconic black swans () including the palaeo-behaviour of prehistoric populations. Our study shows that at the time of human colonization, New Zealand housed a genetically, morphologically, and potentially ecologically distinct swan lineage (, Poūwa), divergent from modern (Australian) Morphological analyses indicate exhibited classic signs of the 'island rule' effect, being larger, and likely flight-reduced compared to Our research reveals sudden extinction and replacement events within this anatid species complex, coinciding with recent human colonization of New Zealand. This research highlights the role of anthropogenic processes in rapidly reshaping island ecosystems and raises new questions for avian conservation, ecosystem re-wilding, and de-extinction.

Native or not? Ancient DNA rejects persistence of New Zealand's endemic black swan: A reply to Montano et al.

“…The conclusions of Montano et al. () are also at odds with newly published genetic and morphometric comparisons of modern versus ancient New Zealand black swans (Rawlence et al., ), which show that, at the time of first human contact, New Zealand was home to a unique swan taxon ( C. sumnerensis , Pouwa), which was subsequently extirpated and replaced by modern (Australian) C. atratus .…”

“…The anthropogenic origins of extant New Zealand C. atratus are supported by the strong mtDNA similarity between modern New Zealand birds and the south‐eastern Australian population (the source region for translocated individuals) (Rawlence et al., ). Along similar lines, the microsatellite “structure” analysis presented by Montano et al.…”

“…Indeed, Cygnus bones present in New Zealand natural fossil deposits during latter settlement phases (ca. 1450–1800 CE) are genetically and morphologically attributable to C. atratus (Rawlence et al., ). Overall, based on the rapid extinction histories of numerous endemic megafaunal lineages, it seems all but certain that C. sumnerensis was rapidly hunted to extinction long before European arrival.…”

The importance of recognising and conserving biological diversity: a reply to Dussex et al. (2018)

“…It is possible that Dussex et al (2018) are primarily taking issue with the depth of mtDNA differentiation detected between the extant Australian C. atratus and extinct New Zealand C. sumnerensis, whereby Rawlence et al (2017) "proceed to declare a new species of swan based on 1.4% divergence". Apparently, in their view, 1.4% mtDNA divergence (regardless of any other biological differentiation) is simply too small to merit species-level recognition.…”

“…1). Dussex et al's (2018) statements that "This example…demonstrates a preference for one type of data when it tells a more exciting story" and "at least three papers [Rawlence et al (2017) included]…exemplify the issues inherent in ignoring inconvenient lines of evidence for species classification" seem to question the scientific integrity of Rawlence et al (2017). In particular, the allegation that Rawlence et al (2017) misrepresented evidence by showing bias towards a particular dataset is bewildering, especially given that Cygnus molecules and morphology yielded patterns that were completely congruent (Fig.…”