[Ornithology • 2016] Leucocarbo chalconotus & L. stewarti • Genetic and Morphological Evidence for Two Species of Leucocarbo Shag (Pelecaniformes, Phalacrocoracidae) from southern South Island of New Zealand

An Otago shag Leucocarbo chalconotus breeding colony, showing (from left) juvenile, pied and dark bronze variations. 

watercolor painting by Derek ONLEY  DOI: 10.1111/zoj.12376

  Leucocarbo stewarti Foveaux shag (top), Leucocarbo chalconotus Otago shag (middle) and Leucocarbo onslowi Chatham Island shag

watercolor painting by Derek ONLEY   

Leucocarbo shags are a species-rich seabird clade exhibiting a southern circumpolar distribution. New Zealand's endemic Stewart Island shag, Leucocarbo chalconotus (G. R. Gray, 1845), comprises two regional groups (Otago and Foveaux Strait) that show consistent differences in relative frequencies between pied (black and white) and bronze (wholly dark) plumages, the extent and colour of facial carunculation, body size (based on postcranial morphometrics), and breeding season. Moreover, previous genetic research on modern and historical specimens utilizing mitochondrial DNA control-region sequences has also shown that the Otago and Foveaux lineages may not be sister taxa; instead, in several analyses the Otago lineage is sister to the endemic Chatham Island shag, Leucocarbo onslowi (Forbes, 1893). We present new ancient DNA analyses of the type specimens for the Otago and Foveaux Strait lineages of L. chalconotus, including a phylogenetic reanalysis of the available ancient, historical, and modern control-region sequence data for these lineages (including L. onslowi), and additional statistical analyses incorporating new morphometric characters. These analyses indicate that under the diagnosable species concept the two lineages of Stewart Island shag represent two separate species, which we now recognize as the Otago shag, Leucocarbo chalconotus (G. R. Gray, 1845), and the Foveaux shag, Leucocarbo stewarti (Ogilvie-Grant, 1898).

Keywords: ancient DNA; Chatham Island shag; Foveaux shag; Leucocarbo chalconotus; Leucocarbo onslowi; Leucocarbo stewarti; morphometrics; osteology; Otago shag; Stewart Island shag

Figure 1. Distributional and morphological data for Otago, Foveaux, and Chatham Island shags.
A, map of New Zealand showing the location of the Chatham Islands and Otago/Foveaux Strait study sites. Blue circles represent the prehistoric distribution of Otago shag outside the study area. B, distribution of Chatham Island shag breeding colonies and roosting sites (green circles). The Chatham Island shag exhibits pied plumage only (white pie chart) with pronounced bright orange caruncles in breeding plumage (orange pie chart). C, distribution of Otago (blue circles) and Foveaux (red circles) shag breeding colonies and roosting sites. Otago shag populations have 20–30% pied morphs (pie charts; black: dark-bronze; white: pied) and 50:50% small bright orange caruncles : dark orange scattered papillae in prenuptial breeding plumage (pie charts; yellow: small bright orange caruncles; grey: dark orange scattered papillae) compared with 50–60% pied morph and dark orange scattered papillae in prenuptial breeding plumage in the Foveaux shag.

In (C), multiple breeding colonies and roosting sites are represented at the following locations (from north to south): Otago Peninsula including Long Beach, Aramoana, Otago Harbour, Taiaroa Head, Boulder Beach, Papanui Beach, Allans Beach, Wharekakahu Island, and Gull Rocks; Seal Rocks and Ruapuke Island; Easy Harbour and Shag Rock. In (C), the Leucocarbo shag species illustrating plumage characters are: pied morph (Otago shag), bronze morph (Foveaux shag), small caruncles (Otago shag), and scattered papillae (Foveaux shag). Figure adapted from Rawlence et al. (2014).DOI: 10.1111/zoj.12376 

Pelecaniformes
Phalacrocoracidae Reichenbach, 1760

Leucocarbo Bonaparte, 1857

[type species (by subsequent designation, Ogilvie-Grant, 1898)
Carbo bougainvillii Lesson, 1837]

Leucocarbo chalconotus otago shag || Gracalus chalconotus G. R. Gray, 1845
Diagnosis. A species of Leucocarbo most closely related to L. stewarti and L. onslowi but distinguished from these species by the plumage characters and allometries outlined in Table 1.

Distribution. Formerly the eastern South Island, NZ. Leucocarbo chalconotus bones have been recorded from Late Quaternary and archaeological deposits along the entire eastern coastline of South Island (e.g., Worthy, 1998a; Smith, 2011). Now restricted to Otago from Lake Ki-Wainono to The Sisters (based on historical museum skins and modern specimens), with modern vagrants north to Banks Peninsula (see Fig. 1). Rare modern beach wrecks on Stewart Island (Rawlence et al., 2015).

  Leucocarbo stewarti Foveaux shag (top), Leucocarbo chalconotus Otago shag (middle) and Leucocarbo onslowi Chatham Island shag

watercolor painting by Derek ONLEY   

Leucocarbo stewarti foveaux shag || Phalacrocorax stewarti Ogilvie-Grant, 1898
Diagnosis. A species of Leucocarbo most closely related to L. chalconotus and L. onslowi but distinguished from these species by the plumage characters and allometries outlined in Table 1.

Distribution. Restricted to Foveaux Strait and Stewart Island (based on historical museum skins and modern specimens). Leucocarbo stewarti bones have been recorded from Late Quaternary and archaeological deposits from this region (e.g., Worthy, 1998b). Rare archaeological and modern beach wrecks in Otago (Rawlence et al., 2014, 2015).

Type Localities: The type locality of Gracalus chalconotus G. R. Gray, 1845 is currently considered to be Otago Province. However, the Otago Province included Southland and Foveaux Strait until 1861. We consider that the likely type locality is in fact Karitane, where the type specimen was likely collected by Percy Earl in 1843 (Scofield et al., 2012). Although Earl spent the majority of his time at Karitane, Earl only travelled as far south as the Clutha River, which is still within the range of the Otago lineage, but may have had Māori collect for him elsewhere (Scofield et al., 2012).
The type locality of Phalacrocorax stewarti Ogilvie-Grant, 1898 is Bluff (a town in Southland), where specimens were collected by Baron A. von Hugel on 13 February 1875 (Ogilvie-Grant, 1898 contra Stewart Island, Gill et al., 2010). Ogilvie-Grant (1898) designated three syntypes (NHMUK 1880.5.3.1, 1880.5.3.2, and 1880.5.3.6), all pied morphs. Warren (1966) only segregated and listed the syntype 1880.5.3.6 for inclusion in the NHMUK type collection, but this action does not affect the status of the remaining unselected syntypes. NHMUK 1880.5.3.1 and 1880.5.3.2 are currently labelled as Phalacrocorax campbelli huttoni (reflecting a previous taxonomic treatment) and we did not attempt to obtain DNA from them. As all three syntypes were collected from the same locality at the same time, and 1880.5.3.6 clusters with individuals from Foveaux Strait (Figs. 4, 6, Appendix 1), we refer 1880.5.3.1 and 1880.5.3.2 to L. stewarti.

Nicolas J. Rawlence, R. Paul Scofield, Hamish G. Spencer, Chris Lalas, Luke J. Easton, Alan J. D. Tennyson, Mark Adams, Eric Pasquet, Cody Fraser, Jonathan M. Waters and Martyn Kennedy. 2016. Genetic and Morphological Evidence for Two Species of Leucocarbo Shag (Aves, Pelecaniformes, Phalacrocoracidae) from southern South Island of New Zealand. Zool. J. Linn. Soc. DOI: 10.1111/zoj.12376 

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