Page 62 - Land Snails of New Mexico

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Ashmunella harrisi occurs in two unnamed canyons on the east side of Goat Mountain in the southeastern part of the San Andres Mountains (see Metcalf and Smartt, 1977:866, Fig. 6). Along Bear Canyon south of Goat Mountain, A. harrisi hybridizeswithA.pasonispasonisDrake.A clinegradingfrom onespeciestotheotherisshown infourcollectionstakenalong the south-facing wall of Bear Canyon. At the easternmost of these localities (Metcalf and Smartt, 1977: Fig. 6), shells are c l o s e t o t h o s e o f A . h a r r i s i a t o r n e a r its t y p e l o c a l i t y o n t h e e a s t side of Goat Mountain. To the west, shell characters ofA. p. pasonisbecomeprogressivelymore evidentinpopulationsand,
atBear Canyon's upper end, shells are indistinguishable from A.
p. pasonis found elsewhere. Like other Ashmunellas of the
southern San Andres Mountains, A. harrisi has been taken only in accumulations of limestone talus.
Ashmunella pasonis pasonis (R. J. Drake, 1951, as Polygyra). Revista de la Sociedad Malacológica "Carlos de la Torre," 8:44. T.L.: Vinton Canyon, in the northern Franklin Mountains, El Paso Co., Texas. (Franklin Mountain woodlandsnail)
Ashmunella pasonis pasonis is exceptional in several ways: in shell features, in occupying two widely separated mountain ranges, and in seemingly hybridizing with two other species of Ashmunella. Ithas the most elaborate dentitional development ofany oftheknown Ashmunellas. Inthisrespect,Dr.Robert D r a k e , its d i s c o v e r e r a n d a u t h o r , w a s r e m i n d e d o f a P o l y g y r a , he originally placed itin that genus (1951), but transferred itto Ashmunella in a laterpaper (Drake, 1952).
Fossils in the Franklin Mountains of El Paso Co., Texas, provide good evidence that A. p. pasonis evolved from an ancestorlikethesubspecies,A.pasonispolygyroidea Vagvolgyi (Metcalf and Smartt, 1977:862). The polygyroidea subspecies occurs as a fossil throughout the Franklin Mountains, and still livesinthecentralpartoftherange.We assumethatatsome time afterA. pasonis pasonis arose from an A. p. polygyroidea like ancestor, itdispersed northward into the southern part of the SanAndresMountainsofNewMexico,whereitoccursintwo areas. In the more northern area,A. p. pasonis occurs atleast fromHembrillo,LostManandDeadManCanyonssouthto Mayberry Canyon, and it hybridizes with A. kochii sanandresensis in the northern part of San Andres Peak. Ashmunella p, pasonis occurs in upper Little San Nicholas C a n y o n i n t h e s o u t h , b u t it d o e s n o t h y b r i d i z e w i t h A . k. k o c h i i there. In the southern area, it also occurs on Black Mountain, a n d o n its n o r t h s l o p e , w h i c h is t h e s o u t h w a l l o f B e a r C a n y o n , it hybridizes with A. harrisi, as noted above (Metcalf and Smartt, 1977:866-868).
Because A. p. pasonis is able to hybridize with two other speciesofAshmunella ofthe San Andres Mountains, thissurely suggests that most of the group of Ashmunellas of the San Andres-Organ-Franklin Mountains chain, with depressed shell morphology, are closely related. Genetic analysis of the relationships within this complex should prove especially interesting.
Throughout its range in the San Andres Mountains,
Ashmunellap, pasonis has been found only in accumulations of limestone talus.
A s h m u n e l l a a u r i c u l a t a J. V a g v o l g y i , 1 9 7 4 . P r o c e e d i n g s of the Biological Society of Washington, 87:150, Pl. 1, Fig. 5,5a,T.L.:givenasBoulderCanyon inthesouthernOrgan Mountains (but see below).
D i s t r i b u t i o n — T h e c a n y o n c o m m o n l y c a l l e d B o u l d e r C a n y o n is at the extreme southern end of the Organ Mountains, where w e have found only A. organensis (collected on the west wall of the canyon). It appears that there is an error in Vagvolgyi's placing the type locality of A. auriculata in Boulder Canyon. T o our knowledge, A. auriculata occurs in the Organ Mountains from lower Fillmore Canyon northward. Itisthe speciesofthe Organ Needles area and northward to Baylor Peak. In Fillmore C a n y o n , it h a s n o t b e e n t a k e n a b o v e t h e " N a r r o w s . " A s h m u n e l l a organensis replaces itto the south and to the southeast around Organ Peak (including uppermost Fillmore Canyon).
Habitat--In Fillmore Canyon and on Baylor Peak, A. auriculata inhabits rhyolitic talus, where mounds of angular, reddish stones are numerous. In the area of the Organ Needles, it must accommodate to a monzonitic rock-type that does not fracture into angular stones, but instead weathers into rounded rocksthatdo notproduce themounds oftalus,fullofinterstices, typical of rhyolitic talus. Colonies of A. auriculata are less readilylocatedinthemonzoniticOrgan Needlesareathantothe north or south, and may not be as numerous.
Ashmunella todseni A. L. Metcalf and R. A. Smartt, 1977. Proceedings of the Biological Society of Washington,90:854, Pl. 1,Figs, b,e. T.L.: Maple Canyon,
northeastern Organ Mountains, Doña Ana Co., New Mexico. (Maple Canyon woodlandsnail)
Ashmunellatodsenihasthemostrestrictedoccurrenceofthe
three species of Ashmunella inhabiting the Organ Mountains. It has been taken only in the northeastern part of the mountains, in MapleandTexasCanyons,theupperbranchesofwhichare juxtaposed on opposing sides ofa ridge. Itmay possibly occur in the southeastern part of the range. That area w a s inaccessible to us because of military restrictions. Ashmunella todseni inhabits rhyolitic talus in the canyons noted, and itis abundant atthetypelocalityinaprominenttalusaccumulationon theeast sideoftheeasternbranch ofMaple Canyon. Ashmunella todseni has not been found to intergrade or hybridize with the other Ashmunellas ofthe Organ Mountains.
Ashmunella organensis H. A. Pilsbry, 1936. The Nautilus, 49:101. T.L.: western slope of the Organ Mountains, above Dripping Spring from 7,000 to 7,500ft (estimated), Doña Ana Co., New Mexico. (Organ Mountain woodlandsnail)
Distribution—Ashmunella organensis inhabits the southern part of the Organ Mountains, from upper Fillmore Canyon southward to Finley and Boulder Canyons. The type locality is