Apodemia mormo (Mormon metalmark) is a principally Nearctic butterfly in the family Riodinidae. It is a particularly fascinating species for ecological and evolutionary research, as evidenced by its shifting taxonomic classifications. Conflicting observations of host plants utilized, distinctive morphologies, and a wide range of occupied habitats have prompted investigation into several potential subspecies. To date, two genetic studies have been done on A. mormo, with analysis revealing that disjunct populations are genetically and phenotypically distinct. These studies support a potential need for refined taxonomies, although a larger body of data is required to make clear decisions.
Populations of A. mormo are widely distributed throughout western North America, with peripheral colonies located in Canada and Mexico. The Canadian populations have historically lacked scientific study, prompting a series of investigations in the past decade. A. mormo is the only representative of the family Riodinidae, a primarily Neotropic family consisting of roughly 1500 species, that lives in Canada. Conservation efforts are complicated by a dependency on human activity for habitat success. Soil disturbances, caused by human and railway traffic, are critical for the survival of host plants and subsequent A. mormo populations; however, overbearing human presence can lead to habitat destruction. Conservation statuses have been repeatedly defended by research, and recovery strategies developed in response. Rather than a continuous distribution, A. mormo colonies occur in semi-isolated patches. Population studies have found that small amounts of geographic distance between colonies (15–20 km) are significant to hinder gene flow, and render populations phenotypically distinct. Temperature differentials between Southern California and Canada may help to explain these observed differences. Since exposure to sunlight supports increased survival in cold habitats, laying eggs on exposed rocky surfaces could be an adaptive advantage in the Canadian populations. Regardless, these populations still require ovipositing nearby suitably mature host plants, since the larvae will require adequate protection and nutrients once hatched. In contrast, Wick observed “amber coloured” eggs the size of a “pinhead” in the Saskatchewan population. Egg development is potentially dependent on habitat choice, temperature, and exposure to solar radiation; further studies are needed in regards to A. mormo.
Genetics
Population genetics
The proper taxonomic classifications for Apodemia mormo are still under debate. Because the species tends to occur in small, isolated populations, the relatedness between populations is frequently questioned. A population genetics study conducted by Proshek revealed that the British Columbia and Saskatchewan populations of A. mormo in Canada are genetically distinct; furthermore, they uncovered higher genetic diversity in eastern vs. western populations, emphasizing low diversity in the British Columbia population.
- A. m. langei <small>Comstock, 1938</small> In general, the butterfly has a wingspan of 25–35 mm, with males being slightly smaller than females. Females are further differentiated from males by their number of functional legs; females possess three pairs, while males do not utilize their shortened forelegs and thus only have two. The Canadian populations have been described as having white checked dark brown wings, a gray body, green eyes, and black and white banded antennae. There is a reddish tint towards the base of the forewings, and the ventral side of the wings are gray. Furthermore, habitat loss might result from invasive, competitive plant species. A. mormo populations would severely suffer if these intruders successfully outcompete local Eriogonum species, given their dependency on the host plant. Finally, Eriogonum plants go into senescence after 10–15 years. This poses a significant problem for habitat maintenance, and suggests a need for regular dispersal of new Eriogonum plants as part of conservation efforts.