Proposal (160) to South American Classification Committee
Split Galapagos Shearwater (Puffinus subalaris) from Audubon's Shearwater (P. lherminieri)
Effect on South American CL: this proposal would split the Audubon's Shearwater (Puffinus lherminieri) into two species, P. lherminieri and P. subalaris.
Background: The taxonomy of the black and white shearwaters has been in flux and contentious since the beginning. Most controversial has been how to deal with the lherminieri/assimilis (Audubon's/Little) complex. Traditional treatment has been based on extent of dark on undertail coverts, extent of dark on face, morphometrics, and tail length in particular and colour of legs. The Peters Checklist (Jouanin and Mougin 1979) recognized the two species as did Warham (1990), but other treatises have ranged from recognizing one species (Bourne 1986), to eight (Shirihai et al. 1995). Sibley and Monroe (1990) recognized five, lherminieri, assimilis, heinrothi, bannermani, and persicus. There is also the intermediate treatment of Carboneras (1992) in HBW, which recognized three species in this complex. Three new taxa have been described since Peters, but these do not need to concern us as they are from the Indian Ocean, but I mention them just to affirm the point that taxonomy of this group has been both controversial and fluid.
The status quo has been to recognize lherminieri (Audubon's) breeding in the Caribbean, Brazilian islands and the Galapagos, tropical Pacific, and tropical Indian ocean; and assimilis (Little) with a dozen subspecies in the South Pacific, South Atlantic, Northeast Atlantic, and south Indian Oceans.
New information: Austin et al. (2004) provided a new molecular phylogeny of the group based on 917 base pairs of the mtDNA cytochrome-b gene. They sampled members of nearly all named subspecies in the complex, often from separate breeding islands, as well as several other small-sized Puffinus for comparison. The complex is polyphyletic, and member taxa sort out into five main lineages that they suggest should be considered species:
(1) lherminieri (Audubon's) includes baroli and boydi both previously considered part of the Little Shearwater; this species is restricted to the Caribbean and subtropical Atlantic Ocean and includes populations breeding in our region of interest (Tobago, Fernando de Noronha etc.);
(2) assimilis (Little) breeding in the temperate Pacific (New Zealand/Australia waters) as well as the Temperate Atlantic (Tristan da Cunha, Gough); this cold-water species is what occurs as a non-breeding visitor to the coast of Chile;
(3) bailloni (Tropical Shearwater) in the tropical Pacific and Indian oceans; not recorded from our area of interest;
(4) newelli (Newell's), which appears to include the taxon myrtae, previously considered part of the Little Shearwater; not known from our region; and (5) finally, subalaris (Galapagos Shearwater) in the Galapagos Islands. Bootstrap support for these nodes is high. I will note that biogeographically the new results make a great deal of sense. Taxa are divided by ocean basins, or by water temperatures.
The most surprising finding is that subalaris is not only in a lineage different from that of the Audubon's Shearwater, where it is traditionally placed, but it is also outside the Little/Audubon's complex and well-differentiated from the entire black-and-white shearwater assemblage (this includes puffinus, opisthomelas, yelkouan etc.). In fact, it is placed sister to the small all dark Pacific taxon nativitatis (Christmas Shearwater). Murphy (1927) first noted that unlike all of the other lherminieri/assimilis taxa, subalaris was odd in having nasal tubes that were firm and corneous, showing no sign of shrinkage in dry specimens. Bretagnolle (in Austin et al. 2004) noted that voice of subalaris is also distinct from that of lherminieri, but gave no additional details.
Recommendation: I recommend a YES vote, to split the highly differentiated subalaris as the Galapagos Shearwater. If accepted placement of subalaris should be between Puffinus puffinus and the larger shearwaters.
Austin, J.J., V. Bretagnolle, and E. Pasquet. 2004. A global molecular phylogeny of the small Puffinus shearwaters and implications for systematics of the Little-Audubon's Shearwater complex. Auk 121: 847-864.
Bourne, W.R.P. 1986. Recent work on the origin and suppression of bird species in the Cape Verde Island, especially the shearwaters, the herons, the kites and the sparrows. Bull. B.O.C. 106: 163-170.
Carboneras, C. 1992. Family Procellariidae (petrels and shearwaters). Pages 216-271 in Handbook of the Birds of the World, vol. 1: Ostrich to Ducks. (J. del Hoyo, A. Elliot, and J. Sargatal, eds.). Lynx Edicions, Barcelona.
Jouanin, C. and J. -L. Mougin. 1979. Order Procellariiformes. Pages 48-121 in Check-list of Birds of the World (E. Mayr and G.W. Cottrell, eds.). Museum of Comparative Zoology, Cambridge, Mass.
Murphy, R.C. 1927. On certain forms of Puffinus assimilis and its allies. American Museum Novitates, no. 276.
Shirihai, H., I. Sinclair, and P.R. Colston. 1995. A new species of Puffinus shearwater from the western Indian Ocean. Bull. B.O.C. 115: 75-87.
Sibley, C.G. and B. L. Monroe, Jr. 1990. Distribution and Taxonomy of Birds of the World. Yale University Press, New Haven, Conn.
Warham, J. 1990. The Petrels: Their Ecology and Breeding Systems. Academic Press, New York.
Alvaro Jaramillo, December 2004
Comments from Remsen: "YES. Burden-of-proof at this point clearly falls on maintaining the traditional classification."
Comments from Stiles: "YES. This group is a classic case where the biological species concept is difficult to apply, especially given that differentiation in color and morphology is limited, such that genetic evidence can be especially useful. In this case, the separation of subalaris makes good sense biogeographically and ecologically as well."
Comments from Pacheco: "YES. Os resultados apresentados por Austin et al. (2004) são convincentes e 'iluminaram' a situação taxonômica do grupo."
Comments from Silva: "YES. Molecular evidence supports the split into two species."
Comments from Robbins: "YES as genetic data in concert with morphological and vocal data indicate that P. subalaris deserves specific rank."
Comments from Nores: "SI, los análisis moleculares y las voces parecen no dejar dudas de que se trata de dos especies."