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, 276 (1658), 815-21

Relict or Colonizer? Extinction and Range Expansion of Penguins in Southern New Zealand

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Relict or Colonizer? Extinction and Range Expansion of Penguins in Southern New Zealand

Sanne Boessenkool et al. Proc Biol Sci.

Abstract

Recent human expansion into the Pacific initiated a dramatic avian extinction crisis, and surviving taxa are typically interpreted as declining remnants of previously abundant populations. As a case in point, New Zealand's endangered yellow-eyed penguin (Megadyptes antipodes) is widely considered to have been more abundant and widespread in the past. By contrast, our genetic and morphological analyses of prehistoric, historic and modern penguin samples reveal that this species expanded its range to the New Zealand mainland only in the last few hundred years. This range expansion was apparently facilitated by the extinction of M. antipodes' previously unrecognized sister species following Polynesian settlement in New Zealand. Based on combined genetic and morphological data, we describe this new penguin species, the first known to have suffered human-mediated extinction. The range expansion of M. antipodes so soon after the extinction of its sister species supports a historic paradigmatic shift in New Zealand Polynesian culture. Additionally, such a dynamic biological response to human predation reveals a surprising and less recognized potential for species to have benefited from the extinction of their ecologically similar sister taxa and highlights the complexity of large-scale extinction events.

Figures

Figure 1
Figure 1
Spatio-temporal genetic relationships and distribution of Megadyptes penguins. (a) Prehistoric South Island sequences (M. waitaha sp. nov.) are shown in red, M. antipodes sequences are shown in blue. Numbers on the main branches in the unrooted Bayesian phylogram represent posterior probabilities and ML bootstrap support. (b) Maps show the distribution of (i) Megadyptes before AD 1500, (ii) Megadyptes after AD 1800 on the South Island and subantarctic Campbell and Auckland Islands of New Zealand. Sampling sites are indicated with labels for prehistoric (P1–P11) and modern (M4–M11) samples, and prehistoric sites are further split in northern and southern South Island (NSI and SSI, respectively). The number of samples possessing each haplotype varied between 1 and 94 (see fig. S1 in the electronic supplementary material). It is assumed modern Megadyptes inhabited Campbell Island prior to AD 1500, as they do at present, but there is currently no palaeontological evidence to support this.
Figure 2
Figure 2
(ac) Holotype left femur of M. waitaha (CM AV13269). (a) Ventral view; (b) dorsal view; and (c) lateral view. (d) Ventral view of M. antipodes femur (CM AV32415). (e) Plot showing the size differences of M. waitaha and M. antipodes femora. Length and width in mm of M. waitaha (red triangles) and M. antipodes (blue circles) femora. Asterisks indicate two of the three prehistoric South Island samples (i.e. the two femora from P6 to P9 in figure 1) that cluster genetically with M. antipodes. The data revealed support the consistent genetic and morphological differences between M. antipodes and M. waitaha. Anatomical abbreviations: ct, crista trochanteris; fp, fossa poplitea; io, impressiones obturatoriae; lic, linea intermuscular candalis. The ventral view of M. waitaha femur (a) shows several drill holes resulting from the sampling of the bone.
Figure 3
Figure 3
Average length of M. waitaha (red triangles) and M. antipodes (blue circles) (a) femur, (b) humerus, (c) coracoid and (d) tarsometatarsus. Megadyptes waitaha bones are divided into southern and northern South Island (figure 1). Error bars are standard error intervals; numbers next to symbols represent sample sizes (n). Four separate single factor ANOVAs showed significant differences among the groups: (a) F2,58=91.2, (b) F2,48=52.2, (c) F2,34=48.6, (d) F2,34=18.9; all p≤0.0001. Post hoc analysis (Scheffe) revealed significant differences between M. antipodes and both southern and northern M. waitaha (all p≤0.0015), but not between southern and northern M. waitaha.

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