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The images below were created from the New Zealand Trichoptera Database using a
biogeographic mapping and analysis program written by Ian Henderson called "Amnesia".
An early version of this program can be downloaded from
but it does not run well under Windows XP. I am working on a new version.
Vicariance (non-overlapping distibutions
of closely related species). The genus Cryptobiosella is a good example
with four species, all rather
rare and with distinct ranges in the central part of New Zealand. The map
is shown with a minimal spanning tree joining the locations for each species.
Disjunctions (gaps in the distribution).
Rakiura vernale (a spiral-cased caddis whose adults emerge early in spring)
is found on Stewart Island (Rakiura) and also in the northwest of the South Island,
a gap of over 400 km. Many similar disjunctions, in a wide variety of New
Zealand animals and plants, were documented by Michael Heads (1988, Biological
Journal of the Linnean Society 63,
161-176) who proposed movement along the alpine fault as a cause.
Some caddis that show different disjunctions are Hydrobiosis harpidiosa, Oeconesus
incisus and Zepsyche acinaces (search for them in the database).
Local endemics Many species
are found in only a restricted part of New Zealand. In many cases the restriction
is to a particular island, e.g. Orthopsyche fimbriata (North Island), Hydrobiosis
lindsayi (Chathams) and Traillochorema rakiura (Stewart), but
many others, like the examples below, have limits not related to present-day sea
Species richness and
The map below shows the number of species recorded from 20 x 20 km grid squares.
White squares show where we have no data yet but many other squares have not been adequately explored. The map reflects collecting effort to some extent with the highest diversity (91
species) at Cass (Canterbury University field station near Arthurs Pass).
spots" at 20 km resolution (red or orange squares) are Cragieburn (80), Devils Ck Reefton (75),
Flora Stm - Cobb Dam (73), L Rotoiti - St Arnaud (73), Franz Josef (73), Lower Buller Gorge (72), Borland Burn (70) and Mangatainoka
R (70). The highest number of species collected from a single grid reference (100
m resolution) is Middle Bush Stm, Cass (59).
In general, the highest diversity of Trichoptera
is found in forested, mountainous regions but especially in the north-western quarter
of the South Island - from Arthurs Pass to Nelson, and the southern North Island.