Fulva-rudis-texana complex

This group includes the taxonomically problematic species Aphaenogaster rudis and Aphaenogaster picea. Gary Umphrey studied this complex and published his findings in his dissertation and a Canadian Journal of Zoology publication.

Umphrey determined this complex contained 10 forms. Each was identified by a unique code that includes the karyotype number. This work has yet to be followed up with a taxonomic treatment of the complex. It remains unclear if these forms should all be considered species. His dissertation section that includes a key to the forms begins with this sentence: "The following key is probably one of the most difficult to use that was ever constructed, at least for such a small group of species, as it utilizes canonical variates, karyotypes, and electorphoretic information."

The following are notes that are synthesized from Umphrey (1992). Each code includes a number, which represents the basic karotype for that form.

fulva

This is one of the few species in the complex that is distinguishable from others in the complex by an easy to assess morphological feature. Queens of Aphaenogaster fulva possess a mespleurae that is entirely rugose, in contrast to the largely smooth and shiny mesopleurea of Queens from the other forms.

This species is widespread in eastern North America and prefers to nest in rotten logs and stumps in mesic forest. In comparison to other ants in this complex colonies are generally larger and nesting density is typically low. When bothered by curious myrmecologists this is the most aggressive species in this group.

N16

Favors well-drained, drier open-habitats and is unusual for the complex in its preference for unshaded nesting sites. Its soil nests have an exposed entrance, rather than being found under a covering object.

N17

Similar to N18 but occurs further west from this form. Found in mesic forests nesting under covering objects and in the soil.

N18

Believed to be Aphaenogaster picea. This is the most cold tolerant ant in the complex. It occurs in northeastern North America, into southeastern Canada and down into Georgia at higher elevations in the Appalachians. This latter portion of its range is likely dependent on average temperature. It is among the last of the forest species to drop out of the ant community at higher forested sites and at the lower end of its elevational range it begins dropping out where the warmer average temperatures allow N22 to become common.

N19

A Missouri variant found by James Trager nesting under stones and in rotten wood. Nests in open woods, under stones and in rotten wood, and on rocky slopes under stones.

N20

Aphaenogaster carolinensis. A coastal plain and piedmont species. Known from the Florida panhandle, Georgia, the Carolinas and New Jersey. It nests in many different forest types. At a local scale it more commonly occurd as mostly small colonies with relatively small workers. In some situations small nests co-occur with larger nests that also have larger average workers. Within piedmont habitats this form favors less mesic forest types, which are favored by N22a.

N21a

Aphaenogaster miamiana. A species that generally has long propodeal spines. Throughout Florida, west to Louisiana and possibly as far north as the North Carolina coastal plain.

N21b

Aphaenogaster texana. A southwestern form known from Texas and Arizona. Its range needs to be informed by better sampling in the midwest and Mexico. Presumed to be absent from the southeast.

N22a

Aphaenogaster rudis. Found in mesic forests of the Piedmont and lower elevations in the Appalachians, westward through the forests of Tennessee, Kentucky, southern Ohio, Indiana and west to at least Missouri.

N22b

Differentiated from N22b by a difference in a single isozyme, this form prefers dryer and more open forests habitats than N22a. Thought to be widespread across the northeastern and midwestern US but only occasionally encountered.

References

Umphrey, G. J. 1992. Differentiation of sibling species in the ant genus Aphaenogaster: karyotypic, electrophoretic, and morphometric investigations of the fulva-rudis-texana complex. Ph.D. dissert., Carleton University, Canada, 282 p.

Umphrey, G. J. 1996. Morphometric discrimination among sibling species in the fulva-rudis-texana complex of the ant genus Aphaenogaster (Hymenoptera: Formicidae). Canadian Journal of Zoology 74:528-559.