A first mtDNA D-loop haplotype comparison between heath hen specimens and prairie-chickens brought the unexpected result that all heath hens tested formed a group very distinct from mainland birds, being most similar genetically to greater prairie chickens from Wisconsin.
A more recent study of the same parameter by Johnson and Dunn verified these results, but disagreed in the placement of the heath hen respective to its relatives, suggesting a closer relationship with the lesser prairie chicken instead.

However, Johnson and Dunn caution against reading too much into these results: while the lesser prairie chicken is considered a distinct species and the genetically apparently equally distinct heath hen would thus likewise deserve species status, mtDNA haplotypes in small populations that have undergone bottlenecks are likely to show higher divergence than they would judging from taxonomic status alone (see also genetic drift).
Thus, given the fact that all heath hen specimens from known localities studied by Johnson and Dunn are Martha's Vineyard birds – where the population may never have exceeded several thousand due to the limited space and limited genetic exchange with the mainland – it is possible that the low genetic diversity and apparent distinctness of the heath hen are an artifact of the small number of useful specimens, all from the same close-knit population.

Prairie chickens were indiscriminately introduced to the Eastern Seaboard after the heath hen was gone from the mainland, but failed to thrive.
There exist a considerable number of supposed heath hen specimens in public collections today, but many – all mainland specimens and those with insufficient locality information – cannot be unequivocally assumed to be heath hens.
For example, a mere seven unequivocal heath hen eggs – equivalent to a very small clutch – are known to be held in public collections today.
That the genus Tympanuchus apparently evolved rapidly and therefore has high morphological but low genetic distinctness between taxa further complicates research.

 
It is also important to note that while introductions of the greater prairie chicken (Tympanuchus cupido pinnatus) were occurring, true heath hens (Tympanuchus cupido cupido) are distinct enough in morphological features to be separated from the greater prairie chicken.
Taking a generous starting date of ~1810 when introductions could have started, and taking into account that Lewis and Clark did not even return from their expedition until 1806,  gives roughly a 60-year period of possible introductions.
From an evolutionary biology aspect, in a 60, or even 100-year timeframe, a species like the greater prairie chicken would not have been able to evolve to the point where it would so closely resemble the native heath hen that it could not be distinguished.

A prime example of this would be in opposing the lesser prairie chicken (Tympanuchus pallidicinctus) which differs from the greater prairie chicken in being smaller, lighter, and having less distinct barring, to the heath hen, which was smaller, darker, and had more distinct barring, meaning that the lesser prairie chicken can be readily distinguished from the greater prairie chicken both morphologically and genetically (much like the heath hen) even if it were found in an area that the greater prairie chicken inhabited.

The apparent distinctness of the species and the failure of the early introductions raises the question of whether the heath hen was uniquely (by comparison with its relatives) adapted to the more oceanic climate of its former area of occurrence, and in consequence, whether a future attempt to establish a population of the western birds on Martha's Vineyard could be bound to fail, possibly even by competing for funding and other resources jeopardizing the extant but much declined populations of the prairie chickens.
Clearly, more research is necessary, for example by analyzing mainland specimens to determine whether they can be assigned to a taxon from molecular and morphological characters.
A first mtDNA D-loop haplotype comparison between heath hen specimens and prairie-chickens brought the unexpected result that all heath hens tested formed a group very distinct from mainland birds, being most similar genetically to greater prairie chickens from Wisconsin. A more recent study of the same parameter by Johnson and Dunn verified these results, but disagreed in the placement of the heath hen respective to its relatives, suggesting a closer relationship with the lesser prairie chicken instead.
However, Johnson and Dunn caution against reading too much into these results: while the lesser prairie chicken is considered a distinct species and the genetically apparently equally distinct heath hen would thus likewise deserve species status, mtDNA haplotypes in small populations that have undergone bottlenecks are likely to show higher divergence than they would judging from taxonomic status alone (see also genetic drift). Thus, given the fact that all heath hen specimens from known localities studied by Johnson and Dunn are Martha's Vineyard birds – where the population may never have exceeded several thousand due to the limited space and limited genetic exchange with the mainland – it is possible that the low genetic diversity and apparent distinctness of the heath hen are an artifact of the small number of useful specimens, all from the same close-knit population.
Prairie chickens were indiscriminately introduced to the Eastern Seaboard after the heath hen was gone from the mainland, but failed to thrive. There exist a considerable number of supposed heath hen specimens in public collections today, but many – all mainland specimens and those with insufficient locality information – cannot be unequivocally assumed to be heath hens. For example, a mere seven unequivocal heath hen eggs – equivalent to a very small clutch – are known to be held in public collections today. That the genus Tympanuchus apparently evolved rapidly and therefore has high morphological but low genetic distinctness between taxa further complicates research.
 
It is also important to note that while introductions of the greater prairie chicken (Tympanuchus cupido pinnatus) were occurring, true heath hens (Tympanuchus cupido cupido) are distinct enough in morphological features to be separated from the greater prairie chicken. Taking a generous starting date of ~1810 when introductions could have started, and taking into account that Lewis and Clark did not even return from their expedition until 1806,  gives roughly a 60-year period of possible introductions. From an evolutionary biology aspect, in a 60, or even 100-year timeframe, a species like the greater prairie chicken would not have been able to evolve to the point where it would so closely resemble the native heath hen that it could not be distinguished.
A prime example of this would be in opposing the lesser prairie chicken (Tympanuchus pallidicinctus) which differs from the greater prairie chicken in being smaller, lighter, and having less distinct barring, to the heath hen, which was smaller, darker, and had more distinct barring, meaning that the lesser prairie chicken can be readily distinguished from the greater prairie chicken both morphologically and genetically (much like the heath hen) even if it were found in an area that the greater prairie chicken inhabited.
The apparent distinctness of the species and the failure of the early introductions raises the question of whether the heath hen was uniquely (by comparison with its relatives) adapted to the more oceanic climate of its former area of occurrence, and in consequence, whether a future attempt to establish a population of the western birds on Martha's Vineyard could be bound to fail, possibly even by competing for funding and other resources jeopardizing the extant but much declined populations of the prairie chickens. Clearly, more research is necessary, for example by analyzing mainland specimens to determine whether they can be assigned to a taxon from molecular and morphological characters.
Heath hen