Comparative cytogenetics of North Island tree wētā in sympatry

Abstract

In North Island New Zealand three species of tree wētā (Hemideina) have narrow regions of overlap. Using detailed measurements of chromosomes we compared the karyotypes of Hemideina thoracica with those of Hemideina crassidens and Hemideina trewicki. Although H. thoracica and H. trewicki have the same diploid number (2n = 17 [XO], 18 [XX]), distinct from H. crassidens (2n = 15 [XO] 16 [XX]); the karyotypes of H. trewicki and H. crassidens are more similar to each other than either is to H. thoracica. Elements within each karyotype were identified that are species specific and will aid identification of putative hybrids. Quantitative cytogenetics was used to identify the sex chromosome for H. crassidens and H. trewicki, which in contrast to previous inferences, is most likely the fifth-longest metacentric chromosome in H. crassidens, and the third-longest metacentric chromosome in H. trewicki.