Page 49 - Land Snails of New Mexico

Distribution and Habitat--The species has been reported only from the T.L., above. According to Raymond Schmidt of Chloride, there was a mining settlement called "Rounderville" on thefloorofMineralCreekCanyon (afew appletreesstillpersist there).AMr. OliverlivedinRoundervilleatonetimeandmined in the near vicinity; hence, sometimes the term "Oliver's mine" was used. There were several mines around Rounderville, including the Dreadnaught Mine, still easily located and indicated on the Winston 7-1/2 U S G S Topographic Quadrangle. As oftenisthecaseinaminingzonehereabouts,thereare limestone strata within the predominantly igneous-bedrock sequence,theselimestonestrataassociatedwithamineralization ZOile.
About 0.35 mile south of the Dreadnaught Mine, at ca. 6,750-ft elevation, the thin limestone strata are cut through by erosive action of Mineral Creek. In 1987, w e found O. pilsbryi o c c u r r i n g a b u n d a n t l y t h e r e , b u t t h e a r e a o f its o c c u r r e n c e w a s quite small, no more than 100 ft along the northeast-facing outcrop where Mineral Creek makes a right-angle bend. In 1988 Smartt discovered a second population about 1/4 mi, up-slope fromthefirstlocality,notedabove.Thiswasalsoanareaof limestone outcrop that w a s north-facing, and supported a stand ofGambel Oaks.Ifthesetwolocalitiescomprisetheentirerange ofthespecies,itisverylimited,indeed.A searchoftheentire l e n g t h o f M i n e r a l C r e e k ( w e h a v e n o t s e e n all o f it) a n d o f D r y Creek Canyon, immediately to the north, should be undertaken. W e did not find O. pilsbryi along Chloride Canyon, the next canyon to the south, nor in the steep hilly country south of the Dreadnaught Mine, which we traversed in reaching Mineral Creek from Chloride Canyon.
Oreohelix metcalfei Cockerell Complex oftheBlackRange
This is a complex of related oreohelicids with relatively depressed shells, often carinate and variously ornamented. S p e c i e s i n t h e c o m p l e x o c c u r i n t h e B l a c k R a n g e a n d s o m e o f its associated foothills. Possibly, O. pilsbryi, discussed above, also belongstothiscomplex. Itislikelythatsome raceorspeciesof the complex occurs in most parts of the higher Black Range where there is limestone. These species are strict calciphiles, in contrasttoO. subrudis of the same range, which tolerates areas of igneous bedrock. In the Black Range areas of limestone bedrock occur discontinuously, and itappears that a situation comparable to an island archipelago exists. In the southern part of the Black Range, these "limestone islands" are m u c h larger,
and outcrops of limestone strata may continue for several uninterrupted miles as in the higher parts of the southwestern slopes of the range. T o the north, areas of limestone outcrop becomesmallerandmoreisolated,asinthecaseofthetype locality of O. pilsbryi, discussed above. Limestone strata are fairlycontinuousalongtheeasternfoothillsoftheBlackRange. However,muchofthiscountryisseeminglytooaridtosupport populations of snails of the O. metcalfei complex at present. There is, however, ample fossil evidence of their former occurrence in this calcareous foothill zone, which likely served as a north-south corridor for dispersal of m e m b e r s of the
calciphile O. metcalfei complex, during times equivalent to
Pleistocene glaciations. One might visualize an increasing isolationandfragmentationofpopulationsduringinterglacials, including the Holocene, which promoted speciation of a number of weakly differentiated races within various of the "limestone islands" in the range. Evolution in the group may involve multiple episodes offragmentation and rejoining of populations, especiallyduringthePleistocene.
Racial variability, such as that indicated in the preceding paragraph, is reflected in the various subspecific taxa of O. metcalfei erected by Pilsbry and Ferriss (1917), after their malacologicalsurveyoftheBlackRangein1915.Usingsimilar criteria, additional subspecies could be described from other "limestone island" areas in the range. It seems prudent, while conserving the taxa of Pilsbry and Ferriss for convenience of discussion, not to burden the literature with additional subspecific epithets at this time. Instead, what is needed is a t h o r o u g h s u r v e y , u s i n g s u c h m o d e r n t o o l s a s m a y b e a p p r o p r i a t e to try to bring some synthesizing order into the existing taxonomic situation. Given the insular nature of populations of
O. metcalfei in the Black Range, itseems that this also would involve an interesting application of theoretical island biogeography, as applied to an inland area.
B e l o w , w e list t h e s u b s p e c i e s o f O . m e t c a l f e i n a m e d f r o m t h e BlackRange,togetherwithbriefcomments.We listthemfrom south to north, suggesting that the larger limestone areas of the southern end of the range might be hypothesized as a source area within the archipelago of limestone islands proposed above.
O r e o h e l i x m e t c a l f e i a c u t i d i s c u s H . A . P i l s b r y a n d J. H . Ferriss, 1917. Proceedings of the Academy of Natural Sciences of Philadelphia, 69.98, Pl. 8, Figs. 4, 4a. T.L.: givenby the authors (Pilsbry and Ferriss, 1917:106) as "A limestoneledge,20 minutes'walk down themountain east from the camp on the saddle of Sawyer Peak." Sawyer Peak is a prominent peak, the highest in the southern part oftherange,SierraCo.,New Mexico.
Smartt collected specimens of this subspecies in 1989 about 0.5mi eastofSawyerPeak inTrujilloCanyon.
O r e o h e l i x m e t c a l f e i c o n c e n t r i c a H . A . P i l s b r y a n d J. H . Ferriss, 1917. Proceedings of the Academy of Natural Sciences of Philadelphia, 69.97, Pl. 8, Figs. 1-1d; Pl. 9, Fig. 10. T.L.: Above the "Box" on Silver Creek Canyon, on the north side of the canyon, Black Range, Grant Co., N e w
Mexico.
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Distribution and Habitat--This subspecies inhabits the extensive limestone-bedrock area around the head of the Silver
CreekCanyoncomplexonthewestsideofSawyerPeak,and continues southward. Pilsbry and Ferriss (1917:97) reported it from the south end of the range near Grand Central Mine (=RoyalJohnMine,we suppose),fromthenexttwogulches north of the mine, and on the west side of Sawyer Peak. They notedminorvariationsincolorandsculptureofshellsatthese various localities. Occurring over such an extensive area, it appears that O. m. concentrica is the most widespread of the named subspecies of O. metcalfei in the Black Range.
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