Morphological variation in the shells of <i>Placostylus</i> species (Gastropoda: Bulimulidae) in New Zealand and implications for their conservation

Abstract

Abstract Shell morphologies of five extant populations of Placostylus bollonsi, 12 of P. ambagiosus, and one of P. hongii from three locations in the far north of New Zealand (Three Kings Islands, Te Paki, and Whangaruru North Head Scenic Reserve), were compared. Overall, little difference between populations could be detected within the species P. bollonsi and P. ambagiosus using a Principal Components Analysis on 10 or 14 shell characters. Only the West Island population of P. bollonsi seemed morphologically distinct from the remaining populations also endemic to the Three Kings Islands group. Although there were many differences between individual populations and subspecies of P. ambagiosus and P. hongii, taken collectively, there were only three coarse groups: (1) P. a. whareana; (2) P. a. michiei, P. a. pandora, P. a. paraspiritus; and (3) P. a. watti, P. a. annectens, P. a. keenorum, P. a. leslyae, P. a. consobrinus, P. a. ambagiosus, P. a. “nouvelle”, P. hongii. The results agreed only in part with a study on the allozymes of many of the same populations, and differed in many respects from other studies on Placostylus she.ll morphology. It was concluded that investment into the conservation of the genus should take a conservative approach and reflect the greater array of geographically and genetically distinct forms rather than the fewer discrete morphological forms based on shell characters identified in this study.