Twelve subspecies historically have been recognized, primarily on the basis of ventral coloration, the extent of white in the tail, crown color, and the extent of black on the face:
miniatus (Swainson 1827); described as Setophaga miniata. Type locality woods of Valladolid [= Morelia], Michoacán, Mexico. Occurs in Mexico from southern Sonora, southwestern Chihuahua, and San Luis Potosí south to southern Oaxaca and western Chiapas. Breast and belly dark vermilion red, face black. The outer three rectrices are broadly tipped with white, and the white is more extensive than it is in the other four subspecies from southern Mexico and northern Central America (molochinus, intermedius, hellmayri, and connectens; Figure 2).
molochinus Wetmore 1942; described as Myioborus miniatus molochinus. Type locality Volcán San Martín, Sierra de Tuxtla, Veracruz, Mexico. Endemic to the Sierra de los Tuxtlas of southeastern Veracruz in eastern Mexico. Similar to miniatus, but with much less white in the outer rectrices (Figure 2), brighter red underparts, and a relatively shorter tail (see Measurements, Table 1).
intermedius (Hartlaub 1852); described as Setophaga intermedia. Type locality Guatemala; restricted to Panajachel, western Guatemala by Griscom (1932: 341). Occurs in southern Mexico (eastern Oaxaca and northern and eastern Chiapas) and eastern Guatemala northeast of the Pacific cordillera. Compared to miniatus, breast and belly more reddish orange and with much less white in the tail (similar in extent to hellmayri and connectens; Figure 2).
hellmayri van Rossem 1936; described as Myioborus miniatus hellmayri. Type locality Volcán de Santa Ana, Sonsonate, El Salvador. Distribution historically described as the Pacific cordillera from southern Guatemala through southwestern El Salvador (van Rossem 1936, Curson et al. 1994), but museum specimens from the Pacific cordillera of southern Chiapas, Mexico (e.g., from the mountains northeast of Mapastepec) are generally assigned to hellmayri as well. Underparts are salmon orange and the outer tail feathers, like intermedius and connectens, have very little white (Figure 2).
connectens Dickey and van Rossem 1928; described as Myioborus miniatus connectens. Type locality Los Esesmiles, Chalatenango, El Salvador. Occurs in the mountains of the interior cordillera of El Salvador and Honduras south to northern Nicaragua. Underparts orange compared to the reddish orange of intermedius and the salmon orange of hellmayri. White in the outer rectrices is very limited, similar to intermedius and hellmayri (Figure 2).
comptus Wetmore 1944; described as Myioborus miniatus comptus. Type locality Cerro Santa María, a spur of Volcán Rincón de la Vieja, above Hacienda Santa María, Costa Rica. Restricted to the mountains of western and central Costa Rica. Breast and belly yellowish orange, and the outer tail feathers have significantly more white than molochinus, intermedius, hellmayri, and connectens, and slightly more white than miniatus; the outer three rectrices (rectrices 4-6) are broadly tipped in white, and some birds have a smaller white spot on rectrix 3 (Figure 2). As originally described by Wetmore (1944), very similar to aurantiacus, but darker above and somewhat more orange below.
aurantiacus (Baird 1865); described as Setophaga aurantiaca. Type locality Dota Mountains, San José, and Barranca, Costa Rica; restricted to Santa María de Dota by Deignan (1961: 549). Occurs in eastern Costa Rica and western Panama. Very similar to comptus, but slightly paler above and less orange below. The pattern of white in the outer rectrices is essentially identical to comptus (Figure 2).
ballux Wetmore and Phelps 1944; described as Myioborus miniatus ballux. Type locality near Queniquea, Táchira, Venezuela. Occurs in southeastern Panama (Darién), northern Colombia (excluding the Sierra Nevada de Santa Marta) and western Venezuela south through the Colombian Andes to northern Ecuador. As originally described, similar to verticalis but with less extensive white on the outer rectrices; similar to pallidiventris but yellow underparts tinged with orange, especially on the breast; and similar to aurantiacus but paler yellow below with more extensive white in the rectrices (Wetmore and Phelps 1944; Figure 2).
sanctaemartae Zimmer 1949; described as Myioborus miniatus sanctaemartae. Type locality Las Nubes, Santa Marta, Colombia, Restricted to the Sierra Nevada de Santa Marta, northern Colombia. Similar to pallidiventris, with its pale yellow underparts, but with significantly less white in the outer rectrices (Figure 2).
pallidiventris (Chapman 1899); described as Setophaga verticalis pallidiventris. Type locality Quebrada Seca [inland from Cumaná], northeastern Venezuela. Occurs in northern Venezuela, from Falcón east to Sucre and Monagas. Similar to sanctaemartae and verticalis, but with considerably more white in the tail than sanctaemartae (Figure 2), and paler below than verticalis.
subsimilis Zimmer 1949; described as Myioborus miniatus subsimilis. Type locality Alamor, Peru. Occurs in the western Andes in southwestern Ecuador and northwestern Peru. Zimmer (1949) recognized this subspecies as distinct from verticalis of the neighboring eastern Andes on the basis of its paler ventral coloration (similar to pallidiventris) and relative reduction of black on the forehead and sides of the crown. Zimmer also suggested that subsimilis could be distinguished from verticalis by "the lesser extent of white on the tail" (Zimmer 1949, p. 13), but systematic measurement of museum specimens indicates no such difference (Figure 2).
verticalis (d’Orbigny and Lafresnaye 1837); described as Setophaga verticalis. Type locality Ayupaya, Bolivia. Occurs in the eastern Andes from southern Ecuador (Loja) south to central Bolivia, and in the tepuis of southern Venezuela, western Guyana, and northern Brazil. Similar in ventral coloration to ballux but with significantly more white in the outer rectrices (Figure 2); specimens of verticalis, particularly those from the southern part of the range (central Bolivia), have more extensive tail white than any other subspecies of Slate-throated Redstart (Figure 2), and the extent of white decreases gradually over the range of verticalis from south to north (Zimmer 1949).
The legitimacy of recognizing all 12 subspecies is open to debate. Pérez-Emán et al. (2010) examined genetic variation across most of the geographic range of Slate-throated Redstart, examining variation in two mitochondrial genes from 36 specimens of 10 of the 12 recognized subspecies. Although Mexican and Central American subspecies were well represented in the genetic sampling, representatives of sanctaemartae, pallidiventris, and Pantepui verticalis were not included in the analysis. The study identified four well-supported monophyletic groups: (1) a well-differentiated and genetically distinct basal lineage comprising the nominate subspecies miniatus (northern and central Mexico); (2) a clade comprising the subspecies molochinus and intermedius (Sierra de Los Tuxtlas of eastern Mexico and the interior highlands of southern Mexico and Guatemala); (3) a Central American lineage representing populations belonging to four poorly differentiated subspecies, hellmayri, connectens, comptus, and aurantiacus; the lack of genetic structure in this clade, which is sister to the molochinus/intermedius lineage, is surprising given that hellmayri and connectens are geographically isolated from comptus and aurantiacus by several hundred kilometers of Nicaraguan lowlands, and that these two subspecies groups differ considerably in both ventral coloration and tail white (Figure 2); and (4) a clade of South American subspecies (ballux, subsimilis, and verticalis) that requires more extensive sampling to resolve adequately.
Because the Central American subspecies are not genetically well differentiated, at least in terms of variation in mtDNA, some might argue that they should not be recognized as distinct subspecies (Pérez-Emán et al. 2010). However, they nonetheless appear to be locally adapted evolutionary units; field experiments in Costa Rica have shown that the substantial geographic variation in tail pattern (Figure 2) is adaptive and likely driven by diversifying selection for enhanced flush-pursuit foraging performance (Mumme et al. 2006, Pérez-Emán et al. 2010). On the other hand, some subspecific distinctions in Central America are questionable; for example, comptus (northern and central Costa Rica) and aurantiacus (southern Costa Rica and western Panama) are very difficult to distinguish by ventral coloration, tail pattern (Figure 2), and mtDNA, and retaining both as distinct subspecies is difficult to defend (Pérez-Emán et al. 2010). Similarly, because much of the variation in ventral coloration and tail pattern in South America is continuous and clinal, consolidation of some South American subspecies may be inevitable unless future genetic work reveals unexpected evidence of strong genetic structure within the continent.