Page 47 - Land Snails of New Mexico

in the Sangre de Cristo Mountains, itoccurred above 8,400 ft
(Dillon and Metcalf, this volume). In both cases, D. whitneyi occurred at lower elevations in the transect. W e have found
separationtospecies(D. whitneyiorD.shimekii)tobe difficult
forsomepopulationsinthe7,500-9,000ftelevationinnorthern
New Mexico. Possiblyhybridizationisinvolved,orperhapsthe
presence of two species together may cause confusion in
identification. Discusshimekiiis,perhaps,aPleistocenerelict inthesouthernmostRockyMountains,inNew Mexicoandin
Arizona, where Bequaert and Miller (1973:151) recorded it from onlythreestations,allathighelevations.
Family Oreohelicidae
Formerly, all members of this family were placed in the genus Oreohelix, which comprised two subgenera, Oreohelix and Radiocentrum. Radiocentrum shells differ from those of
Oreohelixinhaving,onthefirst1% whorls,distinctive,well defined radial riblets parallel with the growth lines. Pilsbry (1939:541)describedtheseas"delicate,retractiveradialrib striae."
Therearealsodifferencesinthegenitaliaofthetwo groups.
M e m b e r s of Oreohelix are live-bearing snails, whereas those of Radiocentrum are egg-layers. Babrakzai, Miller, and Ward (1975:10) deemed the differences between these groups to be
deserving of generic recognition and elevated Radiocentrum to . a full genus.
It has been customary to place the family Oreohelicidae in
the superfamily Helicacea (or Helicoidea), which includes the
large New Mexican snails of the genera Sonorella and
HumboldtianaandtheintroducedHelix.However,Emberton NewMexicoDistribution--WehavefoundO.s.depressa
(1991) has recommended allying the Oreohelicidae with the family Discidae. This phylogenetic arrangement has been followed here. Emberton's interpretation was based on an analysis of anatomical structures, although he pointed out (1991:221) the importance of also applying molecular methods in the construction of land-snail phylogenies. Until such molecularinformationisavailableandisapplied,phylogenies may continue to be somewhat speculative and subject to differences in interpretation. One wonders, then, ifthe
oreohelicidshavefoundtheirtruephylogenetichomewiththis relocationorifothershiftsawaitthem.
Genus Oreohelix
Snails of this genus are called "mountainsnails" (Turgeon, 1988:141-142). The name isappropriate because, from northern NewMexicoandArizonanorthwardintheRockyMountains,
they are the major large, casually observed, land snails. SpeciesofOreohelix,withlargeelevatedshells,occurinthe mountainsofnorthernNew Mexico,intheSierraBlanca-Nogal Peakcomplextothesoutheast,andintheSanMateo Mountains BlackRange-Mogollon Mountains complex to the southwest. In the literature, those from the northern part of the state, south to the Sandia Mountains, have been assigned to O. strigosa depressa (Cockerell); those from Sierra Blanca-Nogal Peak, to O. strigosa nogalensis Pilsbry, and those from the San Mateo
generallydistributedinthetwo major mountain masses ofnorth central New Mexico-–the Sangre de Cristo and the Jemez Mountains, east and west of the Rio Grande Rift Valley, respectively. It has been collected by Smartt in the Sandia Mountains, where it exists seemingly only as a localized population. Smartt also has acquired specimens of O. s. depressa(NMMNH98) fromtheChuskaMountains,SanJuan Co.,probablyfromBeautifulMountainintheboundaryareaof ArizonaandnorthwesternNewMexico.These4specimens(3 freshand1faded)werecollectedinsummer, 1987.Pilsbry (1939:431) assigned specimens of Oreohelix from "5 miles east ofZuñi,McKinleyCo.,"inthewest-centralpartofNew Mexico to O. s. depressa. However, specimens that w e have from the ZuñiareaareO. houghiMarshall.The ratheraridhabitatthere
issurelynotthatnormallychosenbyO.s.depressa.We have not collected O. s. depressa from east of the Sangre de Cristo Mountains, but Pilsbry (1939:431) reported itfrom Folsom, Union Co., this based on a lot of 12 shells collected by E. B. Howard in 1931 (ANSP 156440).
Habitat--For such a wide-ranging snail as O. s. depressa, anygeneralizationabouthabitatisdifficult.Itoccupieshabitats from the Transition to Hudsonian Life Zones. Hoff (1962:53) wrote "Specimens were taken only at elevations where considerablemoistureoccursinsoilandlitteranditissuggested thatinadequatemoisturemay be an importantfactordetermining the lower limitofrange in elevation." Hoff (pp. 52-53) reported
Mountains-Black Range-Mogollon Mountains, to Oreohelix subrudis (Reeve). Brandauer (1988) analyzed populations of O. strigosa and O. subrudis from throughout the range of the genus in Colorado and concluded that the two species could not be separated,taxonomically,inthatstate.She assignedColorado "subrudis"toO. strigosa.
W e are reluctant to follow the procedure of Brandauer regarding New Mexico strigosa and subrudis for several reasons, including: 1) lack of a thorough study of the genus in N e w Mexico; 2) an electrophoretic analysis by Rees (1988) showingdifferencesbetweenstrigosaandsubrudisinColorado, and unpublished electrophoretic data suggesting some differences between them in New Mexico, and 3) in New Mexico, unlike the situation in Colorado where there appear be no clearly discernible geographic ranges attributable to each of the two forms, the species have been considered as occupying
definite, allopatric ranges (as outlined above).
Oreohelix strigosa depressa (T.D.A. Cockerell, 1890, as Patula). The Nautilus, 3:102. T.L.: a canyon near Durango, La Plata Co., Colorado. (Rocky mountainsnail)
General Distribution--Pilsbry(1939:Fig. 296) mapped O.
strigosa strigosa (Gould) as occurring in southern British
Columbia, Washington, northernmost Oregon, northern Idaho,
a n d w e s t e r n M o n t a n a . H e m a p p e d O . s. d e p r e s s a a s o c c u r r i n g
from western Wyoming and southeastern Idaho, southward to
northern Arizona and N e w Mexico. Thus, as considered by
Pilsbry, both of these major subspecies of O. strigosa are widely distributed.
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