Revision, phylogeny, and biogeography of the New Zealand endemic genus Agnosthaetus (Coleoptera: Staphylinidae)

The staphylinid genus Agnosthaetus Bernhauer, 1939 was created for two new species, and four others described by Thomas Broun between 1910 and 1921. Seventy years later the genus is here revised to include 34 species, 28 of which are new. Agnosthaetus is endemic to New Zealand and exhibits remarkable interspecific diversity in genital and secondary sexual structures, an unusual degree of short-range endemism, and very low levels of geographic sympatry. It is known only from the mainland, and all species have restricted ranges within an island. Endemism is predictably high in southern and northern South Island, but the southern part of North Island is unusual in being a centre of endemism. Phylogenetic analysis of morphological characters reveals that Agnosthaetus 1) is strongly supported as monophyletic by a uniquely derived epipharyngeal structure; 2) is divided into major eastern and western lineages; and 3) is phylogenetically overdispersed within North and South Islands, and within traditional areas of endemism. Factors underlying the distribution patterns are discussed in light of the phylogeny, and it is shown that several subclades exhibit classic disjunctions associated with the Alpine fault and Manawatu strait.