Tringa Linnaeus, 1758
Systema Naturae ed.10 p.148
Tringa is a genus of waders, containing the shanks and tattlers. They are mainly freshwater birds, often with brightly coloured legs as reflected in the English names of six species, as well as the specific names of two of these and the Green Sandpiper. They are typically associated with northern hemisphere temperate regions for breeding. Some of this group - notably the Green Sandpiper - nest in trees, using the old nests of other birds, usually thrushes.
The Willet and the tattlers have recently been found to belong in Tringa; these genus changes were formally adopted by the American Ornithologists' Union in 2006.
The present genus in the old, more limited sense was even further subdivided into Tringa proper and Totanus, either as subgenera or as full genera. The available DNA sequence data suggests however that neither of these is monophyletic and that the latter simply lumps together a number of more of less closely related apomorphic species. Therefore is seems unwarranted to recognize Totanus even as a subgenus for the time being.
These are listed in systematic sequence:
* Green Sandpiper, Tringa ochropus
Tringa legs are either red (Spotted Redshank, T. erythropus), ...
... yellow (Lesser Yellowlegs, T. flavipes), ...
... pale green (Common Greenshank, T. nebularia), ...
... or ochre (Green Sandpiper, T. ochropus)
The shanks' and tattlers' closest relatives are sandpipers of the genera Actitis and Xenus. Together with these, they are related to the phalaropes, as well as the turnstones and calidrids. The large genus Tringa and the two very small genera which are most closely related form a phylogeny similar to the situation found in many other shorebird lineages such as calidrids, snipes and woodcocks, or gulls.
The same study has indicated that some morphological characters such as details of the furcula and pelvis have evolved convergently and are no indicators of close relationship. Similarly, the leg/foot color wildly varies between close relatives, with the Spotted Redshank, the Greater Yellowlegs, and the Common Greenshank for example being more closely related among each other than to any other species in the group; the ancestral coloration of the legs and feet was fairly certainly drab buffish as in e.g. the Green Sandpiper. On the other hand, the molecular phylogeny reveals that the general habitus and size as well as the overall plumage pattern are good indicators of an evolutionary relationship in this group.
The Spotted Greenshank, a rare and endangered species, was not available for molecular analyses. It is fairly aberrant and was formerly placed in the monotypic genus Pseudototanus. It appears closest overall to the semipalmata-flavipes and the stagnatilis-totanus-glareola groups, though it also has some similarities to the Greater Yellowlegs and Common Greenshank.
Fossil shanks are known since the Miocene, possibly even since the Eo-/Oligocene some 33-30 million years ago (mya) which would be far earlier than most extant genera of birds. However, it is uncertain whether Tringa edwardsi indeed belongs into the present-day genus or is a distinct, ancestral form. The time of the Tringa-Actitis-Xenus-Phalaropus divergence has been tentatively dated at 22 mya, the beginning of the Miocene; even if the dating is largely conjectural, it suggests that T. edwardsi does indeed not belong into the modern genus. Molecular dating - which is not too reliable however - indicates that the diversification into the known lineages occurred between 20 and 5 mya. The fossil record contains species formerly separated in Totanus from the Early Miocene onwards. Although these are usually known from very scant remains, the fact that apparently apomorphic Tringa as well as a putative phalarope are known from about 23-22 mya indicates that the shank-phalarope group had already diverged into the modern genera by the start of the Miocene. The biogeography of living and fossil species - notably the rarity of the latter in well-researched North American sites - seems to suggest that Tringa originated in Eurasia. Time and place neatly coincide with the disappearance of the last vestiges of the Turgai Sea, and this process may well have been a major factor in the separation of the genera in the shank-phalarope clade. Still, scolopacids are very similar osteologically, and many of the early fossils of presumed shanks require revaluation.
* ?Tringa edwardsi (Quercy Late Eocene/Early Oligocene of Mouillac, France)
"Tringa" hoffmanni is now in Ludiortyx. While its relationships are disputed, it was not a charadriiform.
1. ^ Pereira & Baker (2005), Banks et al. (2006)
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