Systematic Studies of New Zealand Trichoptera and Critical Analysis of Systematic Methods

Abstract

Aspects of the systematics of New Zealand Trichoptera (caddisflies) are studied and systematic philosophies and methods analysed. Eleven new species are described and figured: In the Philopotamidae; 4 species of Cryptobiosella n.gen., a monotypic genus Xenobiosella n.gen., and one species of Hydrobiosella. In the Philorheithridae two new species and a new combination in Philorheithrus are proposed and in the Helicophidae 3 new species in Alloecentrella are described. The status of the two species of Zelolessica, which differ in the adult stage only in size, is examined. Available material is analysed for commingled distributions of size characters. The techniques used are derived from genetic complex segregation analysis, and are examined critically, particularly in size, is examined. Available material is analysed for commingled distributions of size characters. The techniques used are derived from genetic complex segregation analysis, and are examined critically, particularly in relation to parsimony. A serious methodological error in using General Linear Model techniques to 'standardize' the data before searching for commingled distributions is identified and an approach to minimize this error is proposed. Evidence of two size morphs is presented. The bimodal pattern is shown to be partly due to non-random sampling with respect to sex and time of season, which are both correlated with adult size. The phylogenetic (cladistic) techniques of Wagner tree, and transformation series analysis, are applied and critically examined. Homoplasy (cladistic incongruence of characters) is found to be a general feature of systematic pattern in both form (taxonomic) and spatial (biogeographical) analysis. Reticulate patterns of evolution are exemplified by the analyses of 2 Trichopteran families. The rationale of cladistic methodology and vicariance biogeography is discussed in relation to homoplasy, parsimony and recombination of characters; a concept derived from the panbiogeographic synthesis. The claim that the use of parsimony in cladistics does not imply that evolution is parsimonious, is disputed. Cladistic analysis is shown to strive for the elimination or suppression of information contrary to the dominant cladistic pattern. The Wagner tree method is discussed in detail, including its justification as a cladistic method, and inadequacies of published algorithms. A computer programme is provided to perform a modification of the Wagner method and find multiple minimal length trees. The biogeography of New Zealand Trichoptera is analysed including distributions within New Zealand, and transoceanic relationships. A distinction between 'Gondwanan' and 'Pacific' distribution patterns is considered, utilizing cladistic and panbiogeographic analysis. The majority of New Zealand Trichoptera have external relationships based on the southern Pacific Ocean. A minor component have relationships based on the Indian Ocean. Within New Zealand, major patterns of distribution are identified. These patterns are not strongly related to present day land distribution, proposed Pleistocene refugia; nor are they interrelated in hierarchical (cladistic) patterns. The panbiogeographic concept of 'Horstian Dispersal' is suggested as an alternative to explanations involving refugia, migrations and vicariance processes for the complex linear patterns of distribution within New Zealand. A synthesis of transoceanic and local biogeography with geology and palaeogeography is considered. The two major patterns of transoceanic relationships are found to be related to local distributions. Some aspects of these patterns are compatible with current accretionary and fragmentary geological models of the south-west Pacific and with Cenozoic tectonics within New Zealand. However, it is concluded that approaches to biogeography that search for a simplification of distribution patterns by reference to past geographies, may be unrealistic.