. Bulletin. Science. NEW INFORMATION ON HELMINTHOGLYPTA WALKER/ANA 97. Fig. 1. The overall predicted range of H. walkeriana is outlined. Circles represent locations of intermediate types; triangles represent locations of type walkeriana south of Morro Bay; stars represent locations of type morroensis along the Chorro Valley. Site numbers correlate to site numbers in Table 1. Obispo, along the coast near Cayucos, and at several points along the Chorro Valley. One population of type morroensis is abundant on an artificial peninsula created in the Morro Bay estuary circa 1950. Populations found i
. Bulletin. Science. NEW INFORMATION ON HELMINTHOGLYPTA WALKER/ANA 97. Fig. 1. The overall predicted range of H. walkeriana is outlined. Circles represent locations of intermediate types; triangles represent locations of type walkeriana south of Morro Bay; stars represent locations of type morroensis along the Chorro Valley. Site numbers correlate to site numbers in Table 1. Obispo, along the coast near Cayucos, and at several points along the Chorro Valley. One population of type morroensis is abundant on an artificial peninsula created in the Morro Bay estuary circa 1950. Populations found in the center of the overall revised range, as well as at three outlier locations, present unique types featuring characteristics of both type walkeriana and type morroensis. Examination of shell morphometries revealed varying degrees of papulation, incised spiral grooves, umbilicus occlusion, whorl number, and size at sexual maturity. This variation appears to follow a geographical gradient that reflects microclimate shifts following a mesic gradient primarily south to north (wetter to drier) along the coast, and west (coastal) to east (inland). This gradient progresses from globose nonpapillated walkeriana type with well-defined incised spiral grooves, large size at sexual maturity, a more occluded umbilicus, and higher whorl number, to intermediate populations, and eventually to type morroensis with small size at sexual maturity, coarse profuse papulation, open umbilicus, lower whorl number, and reduced pronouncement of incised spiral grooves (Table 1). Size gradients have also been observed in Helminthoglyptid snails on north versus south facing slopes and on moist versus dry sides of California islands (F. G. Hochberg, pers. comm.). Intermediate populations include one population within the City of Morro Bay that appears similar to type walkeriana, yet reaches sexual maturity at a reduced size (Table 1). Several populations similar to type walkeriana exhibit widespread fine
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