Page 32 - Land Snails of New Mexico

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show that the species flourished at lower elevations at times duringthePleistocene.Itisespeciallycommon inPleistocene sediments along the Rio Grande and Pecos River Valleys in the southern part of the state. Ashbaugh and Metcalf (1986) found it a c o m m o n s p e c i e s i n P l e i s t o c e n e , s p r i n g - r e l a t e d d e p o s i t s n e a r Placitas,Doña Ana Co.;atKeen SpringintheTularosaBasin, and in Nash Draw, Eddy Co. All these areas are xeric habitats thatwouldbeinimicaltothespeciestoday.
Pupilla muscorum (C. Linnaeus, 1758, as Turbo). Systema Naturae, seu Reyna tria Naturae systematica proposita, per classes, ordines, genera et species, Edition 10,p.767. T.L.:Europe,withoutpreciselocalitygiven, but holotype from Sweden. (widespread column)
General Distribution-This is a Holarctic species found in Europe and Asia, in North America from Alaska south into the northernconterminousUnitedStates,andsouthtoNew Mexico and Arizona in the Rocky Mountains.
Variation and New Mexico Distribution--Twoformsof
P. muscorum occur inNew Mexico. The larger,more typical form occurs in the higher mountains from the Sierra Blanca Mountains in Lincoln Co. northward to the Sangre de Cristo and San Juan Mountains.
Pilsbry described (1914) a form, xerobia, from Duran Butte,
immediately south of Duran, Torrance Co. As he noted later
(Pilsbry, 1948,935), this "is a small, compact form which I took
atonetimetobeasubspecies....Similarshellsoccurin
numerous Colorado localities, with intermediate sizes
connecting with ordinary muscorum, so that itis apparently to
be regarded as an arid station hunger form rather than a true
race." ThesmallxerobiaformstilloccursonDuranButteand
isfound from that area discontinuously on mountains and mesas northeastwardinNewMexicotoColfaxandUnionCounties.Its
small size issurely not a direct ontogenetic result of unfavorable habitat, as implied in Pilsbry's term "hunger form," but more likely genetically based, because specimens are uniformly small over most of northeastern N e w Mexico, even including the higher forested elevations of Sierra Grande and Johnson Mesa.
OnthebasisoftheNewMexicomaterial,onecouldmakea case for considering xerobia a subspecies of P. muscorum. However, as Pilsbry noted above, ifsimilar small forms are found in other regions and have presumably evolved separately in several such regions, then the use of trinomials might lead to unnecessary confusion. Also, with a species having such a broad, Holarctic distribution, itseems especially prudent to be cautious in partitioning the taxon into subspecies.
The smallxerobiaform occursmainly on isolatedmountains andmesasinnortheasternNew Mexico.Inmostofthisarea,at present, there is no possibility of intergrading with populations in the Sangre de Cristo Mountains to the west, because of the intervening lowlands of the Canadian River Valley. In the extreme northern part of the state, however, there seems to be evidence of intergradation in the higher country associated with RatonMesaandeastward,whereP.muscorumextendsalong the basaltic mesas (Hunter Mesa, Mesa de Maya) eastward to BlackMesainnorthwesternCimarronCo.,Oklahoma.
speciesofmontaneforests,mainlyintheCanadianLifeZone. It
reacheselevationsinexcessof10,000ft.Thesmallerxerobia
form occurs in varied habitats from the relatively arid Upper
Sonoran Zone represented by Duran Butte, with only sparse
pinyon-juniper stands, up to the Transition Zone habitats of Sierra Grande and some of the mesas of the northern
borderlands.
Paleontology--InsouthernNew Mexico,Pupillamuscorum is c o m m o n in Pleistocene deposits at elevations lower (at 4,000 to 5,000 ft) than where it occurs today. At times in the Pleistocene, it must have had a much wider distribution. In contrast to its present montane preferences, in Pleistocene depositsarobustformofP.muscorum isoftenassociatedwith marshy and spring-related habitats, as noted by Ashbaugh and Metcalf (1986:11).
Pupilla hebes (C. F. Ancy, 1881, as Pupa). Le Naturaliste, 3:389. T.L.: White Pine Co., Nevada. (crestless column)
General Distribution--The species has been reported from the mountains of various western states, except California, and it has been reported also from northern Chihuahua, México. B e q u a e r t a n d M i l l e r ( 1 9 7 3 : 1 8 0 - 1 8 1 ) r e c o r d e d it f r o m n u m e r o u s localitiesinArizonawhereitiswidespread.Colorado and New Mexico areon theeasternperipheryofitsrange.
N e w Mexico Distribution--Pilsbry (1948,936) reported the speciesfrom"MagdalenaMt.,SocorroCo." Hoff(1962:57) r e c o r d e d it f r o m P e c o s B a l d y i n M o r a C o . a t 1 1 , 9 0 0 f t , a n d f r o m LakePeak,SantaFeCo.,at12,000ft.Hesuggested:"The occurrence of this species at high elevations may explain the relativelyfewrecordsforNew Mexico." Ourcollectionsfrom the Magdalena Mountains and Lake Peak have not revealed this species.We havetakenspecimensfromtwolocalitiesinthe Zuñi Mountains in Cibola and McKinley Counties and from two localities in the Shuree Lakes area in the Sangre de Cristo Mountains, Colfax Co. In N e w Mexico, itseems to occur only in the north-central and northwestern parts of the state, where further collections probably will reveal additional populations.
Habitat--In the Zuñi Mountains, P. hebes was taken at elevationsof7,475ftbyD.W.Taylorandbyusat8,000ftin forestedmontanehabitats.The latterhabitatconsistedofalush, wet meadow near Ojo Redondo Spring. Ithas been collected from similar habitats in the Sangre de Cristo Mountains.
Pupilla syngenes (H. A. Pilsbry, 1890, as Pupa). The Nautilus, 4:3, 39, Pl. 1, Fig. 7. T.L.: Arizona, with precise locality not given. (top-heavy column)
General Distribution—This species has been recorded from Arizona, Colorado, Montana, N e w Mexico, Utah, and Wyoming. B e q u a e r t a n d M i l l e r ( 1 9 7 3 : 6 1 ) r e g a r d e d it a s a r e p r e s e n t a t i v e o f their Rocky Mountain Molluscan Province.
New Mexico Distribution and Habitat—Pilsbry
(1948:940) recorded P. syngenes from San Rafael, Valencia
(now Cibola) Co. The collection was m a d e in the 1890s by E. H.
Ashmun,We havetakenthespeciesattwolocalitiesintheZuñi Mountains.
Habitat--The larger, more typical form is very much a
Our localitiesareinZuñi and Bluewater Canyons at7,200