Picoides - Systematics

Systematics

The genus is in need of revision. Two species which have a somewhat different color pattern, especially on the head and neck - the Striped and the Checkered Woodpecker - have turned out to belong in Veniliornis, a genus most closely related to Picoides. On the other hand, the Smoky-brown Woodpecker (Picoides fumigatus) seems to be an early offshoot of Picoides. Its unique coloration (similar to the unrelated Okinawa Woodpecker) would be an adaptation to dense forest habitat, although due to its distinctiveness it is not inconceivable that it belongs into a genus of its own and merely is a case of molecular convergence. The American Three-toed Woodpecker was until recently considered conspecific with the Eurasian one (Sibley & Monroe 1990), and the Lesser Spotted Woodpecker is often placed in the genus Dendrocopos. Indeed, that genus is sometimes merged into Picoides, but this is neither generally accepted nor well supported.

Analysis of mtDNA COI and Cyt b sequences suggests that Picoides is really three genera (Moore et al., 2006). One is a group of small four-toed species and the Eurasian P. minor, whereas the other group unites the larger species and would include the Smoky-brown Woodpecker. The three-toed species consititute a different lineage closer to some species of Dendrocopos.

All three groups are notable for the high degree of convergent evolution in plumage patterns existing between them (Weibel & Moore, 2005; Moore et al., 2006). There are several pairs of species from different groups which are almost alike; the most notable example is the Downy and Hairy Woodpeckers, which are not closely related but independently evolved a plumage pattern that is identical down to minor details.

• Small group
  • Downy Woodpecker, Picoides pubescens
  • Nuttall's Woodpecker, Picoides nuttallii
  • Ladder-backed Woodpecker, Picoides scalaris
• Large group
  • Red-cockaded Woodpecker, Picoides borealis
  • Smoky-brown Woodpecker, Picoides fumigatus - formerly in Veniliornis
  • Hairy Woodpecker, Picoides villosus
  • White-headed Woodpecker, Picoides albolarvatus
  • Strickland's Woodpecker, Picoides stricklandi
  • Arizona Woodpecker, Picoides arizonae
• Three-toed group (Picoides sensu stricto)
  • Eurasian Three-toed Woodpecker, Picoides tridactylus
  • American Three-toed Woodpecker, Picoides dorsalis
  • Black-backed Woodpecker, Picoides arcticus