Mottled Duck - Systematics

Systematics

The Floridan population, which occurs approximately south of Tampa, is separated as the nominate subspecies Anas fulvigula fulvigula and is occasionally called the Florida Duck or Florida Mallard.) by being somewhat lighter in color and less heavily marked; while both subspecies are intermediate between female Mallards and American Black Ducks, the Florida Mottled Duck is closer to the former and the Mottled Duck closer to the latter in appearance; this is mainly recognizable in the lighter head being quite clearly separated from the darker breast in Mottled, but much less so in Florida Mottled Ducks. As the subspecies' ranges do not overlap, these birds can only be confused with female Mallards and American Black Ducks however; particularly female American Black Ducks are often only reliably separable by their dark purple speculum from Mottled Ducks in the field.

mtDNA control region sequence data indicates that these birds are derived from ancestral American Black Ducks, being far more distantly related to the Mallard, and that the subspecies, as a consequence of their rather limited range and sedentary habits, are genetically well distinct already (McCracken et al. 2001).

As in all members of the "mallardine" clade of ducks, they are able to produce fertile hybrids with their close relatives, the American Black Duck and the Mallard. This has always been so to a limited extent; individuals of the migratory American Black ducks which winter in the Mottled Duck's range may occasionally stay there and mate with the resident species, and for the Mallard, which colonized North America later, the same holds true (McCracken et al. 2001).

While the resultant gene flow is presently no cause for concern, habitat destruction and excessive hunting could eventually reduce this species to the point where the hybridization with mallards would threaten to make it disappear as a distinct taxon (Rhymer & Simberloff 1996). This especially applies to the Florida Duck (Mazourek & Gray 1994), in the fairly small range of which rampant habitat destruction due to urbanization and draining of wetlands has taken place in the last decades; this in combination with climate change affecting the Everglades could be sufficient to cause the Florida Duck to decline to a point where hunting would have to be restricted or prohibited (McCracken et al. 2001). At present, these birds too appear to be holding their own with a population of 50.000-70.000 individuals (BirdLife International 2004).