Marín et al 2010
Marín-Espinoza, Ouellet & Navarro-Rodríguez 2010. Is a
Sporophila lineola/bouvronides/restricta (Aves: Emberizidae) complex a species ring case?: a theorical approach.
The Biologist (Lima): 8(2): 212-234.
sisbib.unmsm.edu.pe/BVRevistas/biologist/v08_n2/pdf/a08v08n2.pdf
ABSTRACT: Despite that no ring species have yet been convincingly demonstrated in the western hemisphere,
Sporophila lineola/bouvronides/restricta complex may provide a plausible theoretical model in South America. There are at present three distinct forms, with varying proportions of sedentary and partially migratory “races”:
S. lineola (
L),
S. bouvronides (
B) and
S. restricta (
R). Two characters are most obviously subject to variation: the extent (or absence) of white on the crown, and the amount (or absence) of dark mottling or barring on the white underparts.
L and
B populations occur sympatrically and seasonally, with one of them breeding (
B) and the other non-breeding (
L) and possessing subtly different song patterns. Interestingly,
R is a stable “race” confined to the northwestern corner of South America (i.e., NE Colombia). In addition, there is a highly variable population exhibiting a combination of characters (hybrids?) reported between breeding areas
B (e.g., Venezuela) and breeding areas
L (e.g., SE Brazil). Moreover, the total extent of the breeding range of the
L population is nearly unknown; similarly, where
B populations spend the non-breeding season is not yet known. Likewise, we don't know if
R populations migrate. If so, it may represent an incipient ring species pattern. Indeed, our hypothesis is consistent with southern american biogeographical history, involving isolation mechanisms. In the first phase, an ancestral species was split into two populations (due to andean uplift), one to the north (
R) and the other to the east; secondarily, Pliocene times would have subdivided
L (subequatorial breeding) and
B (supraequatorial breeding). With the advent of pleistocenic and holocenic regressions and climatic fluctuations, the successive secondary contacts permitted
L and
B interconnections, involving both ethological (e.g., the cromo-vocalic gradual differentiation) and seasonal isolating mechanisms (e.g., “turnover” of circannual rhythms), which are still in progress, giving way to subpopulations showing complicated and subtle intergradation (clines?) between the three basic forms. It should be emphasized that while we may make reasonable deductions to elucidate some problems, we admit the need for agreed-upon criteria by ornithologists about centers of origin, dispersal and vicariance-panbiogeographic events. Comparison need to be made with molecular systematics in order to reconstruct, for example, a calculation of the time that has elapsed since the
L, B, R lineages diverged and in turn the real distributional and speciational patterns of the complex.
Richard (with thanks to Manuel Plenge for posting on NEOORN)