I'm posting this separately, because this should go into reference, in a week or so, once folks have read it.
A couple of further points about this ant and its relatives - F. querquetulana, difficilis, densiventris, microgyna, knighti, dakotensis, etc.: They are members of the informal "Formica microgyna group. This may be a polyphyletic assemblage of Formica species. In other words, although they do share certain characteristics that lead us to group them, and though they are all derived from the F. rufa group, not all are each other's closest relatives, i.e., derived from a single ancestor. Another way to state this is that the characteristics of having small queens and flattened pilosity seem, based on genetic evidence, to have developed several times independently in the F. rufa group. Indeed, a number of F. rufa group species have smallish queens and/or flattened or otherwise unusual pilosity, and seem to be evolving roughly in the direction of microgyna.
The characters that unite them are queens smaller than the largest workers and pilosity hairs that are "spatulate" or narrowly wedge-shaped, i.e., narrow at the base, flattened, and broader toward the tip. All are among the smaller Formica species in the worker caste, as well, with workers usually in about the same size range as fusca or neogagates, and never reaching the more robust size of other rufa-group members. The great majority of them have major workers with narrow heads, as clearly shown in the picture at http://antfarm.yuku.com/topic/9026.
But several years ago, a Finnish researcher interested in the origins and evolution of "slave-making" in the sanguinea group, extracted DNA sequences for a wide variety of Formica species, resulting in a phylogenetic tree (diagram of the evolutionary history) which showed the microgyna group species coming out on various terminal branches scattered among the rest of the North American rufa group species. While not published, and not conclusive until repeated and expanded upon, this study seems to indicate that these "little rufas" are not a coherent family of species, but a random assortment of distant cousins that "kinda" look alike.
A couple of further points about this ant and its relatives - F. querquetulana, difficilis, densiventris, microgyna, knighti, dakotensis, etc.: They are members of the informal "Formica microgyna group. This may be a polyphyletic assemblage of Formica species. In other words, although they do share certain characteristics that lead us to group them, and though they are all derived from the F. rufa group, not all are each other's closest relatives, i.e., derived from a single ancestor. Another way to state this is that the characteristics of having small queens and flattened pilosity seem, based on genetic evidence, to have developed several times independently in the F. rufa group. Indeed, a number of F. rufa group species have smallish queens and/or flattened or otherwise unusual pilosity, and seem to be evolving roughly in the direction of microgyna.
The characters that unite them are queens smaller than the largest workers and pilosity hairs that are "spatulate" or narrowly wedge-shaped, i.e., narrow at the base, flattened, and broader toward the tip. All are among the smaller Formica species in the worker caste, as well, with workers usually in about the same size range as fusca or neogagates, and never reaching the more robust size of other rufa-group members. The great majority of them have major workers with narrow heads, as clearly shown in the picture at http://antfarm.yuku.com/topic/9026.
But several years ago, a Finnish researcher interested in the origins and evolution of "slave-making" in the sanguinea group, extracted DNA sequences for a wide variety of Formica species, resulting in a phylogenetic tree (diagram of the evolutionary history) which showed the microgyna group species coming out on various terminal branches scattered among the rest of the North American rufa group species. While not published, and not conclusive until repeated and expanded upon, this study seems to indicate that these "little rufas" are not a coherent family of species, but a random assortment of distant cousins that "kinda" look alike.
