Page 63 - Land Snails of New Mexico

in Ice Canyon, to the south of Fillmore Canyon. T h e species also e x t e n d s n o r t h e a s t w a r d i n t o R o c k S p r i n g s C a n y o n , w h e r e it o c c u r s b e t w e e n t h e r a n g e s o f A . a u r i c u l a t a t o t h e n o r t h w e s t a n d A. todseni to the east. It is broadly distributed, altitudinally, o c c u r r i n g a s h i g h a s 8 , 2 0 0 ft o r h i g h e r o n O r g a n P e a k a n d a s l o w a s 5 , 3 7 0 ft i n t h e s o u t h e r n e n d o f t h e O r g a n M o u n t a i n s .
H a b i t a t - - T h r o u g h o u t its r a n g e i n t h e O r g a n M o u n t a i n s , A . organensis is an inhabitant of igneous-rock talus--in m o s t cases ofrhyoliticrock.Thisistrueeven inthehigher,forestedpartsof the range, which approximate the Transition Life Zone. In the lower elevations of the southern end of the range, it is rather surprising to find this s a m e A s h m u n e l l a living in isolated talus accumulations exposed to the sun, and in a habitat of markedly xeric character.
AmongpopulationsofA.organensis,thereismarked variation in size, shape, coloration, and thickness of shell (Metcalf, 1984b:38). These characteristics are intergradational among populations and are related to elevation. The largest shellstakenwereat7,900ftandthesmallestshells,at6,300ft. Meansandextremesinshelldiameter,forasampleof10shells from these and an intermediate population, are as follows (in mm):7,900ft,15.2mm (14.9-16.2mm),7,350ft,14.3mm
(13.6-15.2mm);6,300ft,11.5mm (11.0-12.1mm).
SpeciesofSouthernNew Mexico, West oftheRio Grande
Ashmunella tetrodon tetrodon H. A. Pilsbry and J. H. Ferriss, 1915. The Nautilus, 29:15,29, Pl. 1, Figs. 1-3a. T.L.: Dry Creek Canyon, southwestern Mogollon Mountains, in and above the "Box" from 6,000 to 7,000 ft, Catron Co., N e w Mexico. (Dry Creek woodlandsnail)
Ashmunella tetrodon mutator H. A. Pilsbry and J. H. Ferriss, 1915. The Nautilus, 29:31, Pl. 1,Figs 3-6. T.L.: Dry Creek Canyon, southwestern Mogollon Mountains, Catron Co., N e w Mexico.
Ashmunella tetrodon inermis H. A. Pilsbry and J. H. Ferriss, 1915. The Nautilus, 29:33, Pl. 1,Fig. 7. T.L.: Dry Creek Canyon, southwestern Mogollon Mountains, Catron Co.,New Mexico.
AshmunellatetrodonanimorumH.A.PilsbryandJ.H. Ferriss, 1917. Proceedings of the Academy of Natural Sciences of Philadelphia, 69.89, Pl. 7, Figs. 2, 2b. T.L.: at Holden'sSpring,BlackRange,SierraCo.,New Mexico.
AshmunellatetrodonfragilisH.A.PilsbryandJ.H. Ferriss, 1917. Proceedings of the Academy of Natural Sciences of Philadelphia, 69.89, Pl. 7, Figs. 1, 1b. T.L.: Cave Creek Canyon in the eastern foothills of the Black Range, along a wagon road north from Hillsboro to Hermosa, from a talus accumulation (slide) on a hillside,
Sierra Co., N e w Mexico.
Distribution--We have listed the above subspecies of A. tetrodon to reflect the present situation according to the published literature. This would recognize races of A. tetrodon in three widely separated areas: 1) in the southwestern Mogollon
Mountains; 2) in the Black Range, mainly at higher elevations in t h e n o r t h e r n p a r t o f t h e r a n g e , b u t w i t h o n e s e e m i n g l y i s o l a t e d p o p u l a t i o n ( A . t. f r a g i l i s ) i n t h e e a s t e r n f o o t h i l l s , a n d 3 ) i n t h e southern part of the San Mateo Mountains, Socorro, and Sierra Counties.When heworkedwiththiscomplex,Pilsbry(whowith James Ferrissnamed allitssubspecies)visualizedthatfurther collecting would reveal populations that would connect the subspecies geographically. Thus, he noted (1940:939) thatA. tetrodon "may be expected to occur widely in the central and easternMogollons,stillunexplored." As itturnedout,however, only A. mogollonensis appears to occur in the central and eastern Mogollons, leaving the three groups of putative A. tetrodon widely separated.
An analysisofthesystematicsoftheA. tetrodoncomplex is muchneeded.Theoutcomeofsuchastudycannotbepredicted firmly, of course, but it appears likely that the number of subspecies might be reduced and the number of species, increased. It is probable that the three representatives of s o called"A.tetrodon"fromtheMogollonandSanMateo MountainsandtheBlackRangemayprovetobeseparate species that have evolved convergently in regard to shell morphology. Itispossible, however, that these taxa may, instead, be separated derivatives of a common ancestral tetrodon, formerlywidespreadinwest-centralNew Mexico.Itisalmost
surely the case that three subspecies cannot be substantiated as occurringinashortsegmentofDryCreekCanyoninthe southwestern Mogollon Mountains, as listed above. One possibilitythatcouldexplainthesituationisthatthissegment of thecanyonisazoneofhybridizationbetweenA. tetrodonandA. m o g o l l o n e n s i s . A l t h o u g h w e s e e s o m e e v i d e n c e t o s u g g e s t it, sufficient collecting has not been done to support or reject this hypothesis.
Habitat--In the Mogollon Mountains, A. tetrodon appears to be limited to deep canyons. Along creek bottoms of these n a r r o w c a n y o n s , d e c i d u o u s t r e e s p r o d u c e a n a b u n d a n t l e a f litter where snails occur under and around stones and logs. Presumably they could not exist, at present, on the relatively arid, steep ridges that separate canyons such as Dry Creek Canyon from Sheridan and Little Dry Creek Canyons to the west and east. In the San Mateo Mountains and northern Black
Range,ontheotherhand,so-called"tetrodon"isasnailofthe higher forests of the ranges, where it most commonly is associated with accumulations of talus of igneous rocks.
The isolatedpopulationnamedAshmunella tetrodonfragilis by Pilsbry and Ferris (1917) also occurs in igneous rock-talus on a north-facing canyon wall at the lowermost end of Cave Creek Canyon, north of Hillsboro, Sierra Co. Apparently specimens of A. t.fragilis had not been observed or collected at the T.L. between 1915,whenFerrissfounditthere,and 1995,eighty yearslater,when we wereabletovisitthelocality,andfoundthe snailstillinhabitingthetalusslide.
A s h m u n e l l a c o c k e r e l l i c o c k e r e l l i H . A . P i l s b r y a n d J. H . Ferriss, 1917, Proceedings of the Academy of Natural SciencesofPhiladelphia,69:90,Pl.7,Figs 3,3a,3b,4,9, Pl. 10, Fig. 2. T.L.: ravine u p the trail to S a w y e r P e a k f r o m Grand Central Mine, southwestern Black Range, Grant Co.,New Mexico.(BlackRangewoodlandsnail)
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