Austral Ecology (2005) 30, 1–13
Does biogeographical history matter? Diversity and
distribution of lotic midges (Diptera: Chironomidae)
in the Australian Wet Tropics
BRENDAN G. MCKIE,1,2,3* RICHARD G. PEARSON1,2 AND PETER S. CRANSTON2,3
1
School of Tropical Biology, James Cook University, Townsville, Queensland, Australia, 2Rainforest
Cooperative Research Centre, and 3Entomology Department, University of California, Davis,
California, USA
Abstract We examined broad scale patterns of diversity and distribution of lotic Chironomidae (Diptera) within
the Wet Tropics bioregion of northern Queensland, Australia. Field surveys across broad latitudinal and altitudinal
gradients within the Wet Tropics revealed a fauna of 87 species-level taxa in 49 genera comprising three main
elements: a small genuinely tropical fraction, and larger cosmopolitan and Gondwanan components. The latter group
originated when Australia, as part of the ancient Gondwana supercontinent, was situated over Antarctic latitudes
with a cooler, wetter climate than today. In the Wet Tropics, cool Gondwanan taxa occurred predominantly in upland
and shaded lowland sites, but no species appeared narrowly temperature restricted, and there was no faunal zonation
with altitude. Most chironomid species occurred at all latitudes within the Wet Tropics, with no evidence for an
enduring effect of the historical rainforest contractions on current-day distribution patterns. These findings contrast
with those for aquatic faunas elsewhere in the world and for the terrestrial Wet Tropics fauna. We relate this to the
generally broad environmental tolerances of Australian chironomids, and comment on why the latitudinal diversity
gradient does not apply to the Australian chironomid fauna.
Key words: altitude, diversity gradients, faunal zonation, Gondwana, tropical streams.
INTRODUCTION
Knowledge of patterns of diversity and distribution of
lotic organisms is deficient, especially outside the
temperate northern hemisphere and at very large
spatial scales (Vinson & Hawkins 1998). Consequently,
the applicability of a latitudinal diversity gradient to
freshwater ecosystems (Coffman 1989; Flowers 1991)
and the generality of the humped relationship between
altitude and diversity exhibited by some northern
hemisphere systems (Minshall 1985; Casas & VilchezQuero 1993) are both unclear. Previous study of the
broad-scale distributional patterns of lotic eastern
Australian chironomids, assessed by sampling the cast
skins of emerging adults (pupal exuviae) at multiple
locations and times within a latitudinal gradient,
showed no evidence for a larger regional species pool
in the tropics of northern Queensland than in the
temperate south-east (Cranston 2000a). Furthermore,
species believed restricted to cool south-eastern
*Corresponding author. Present address: Department of
Ecology and Environmental Science, Umeå University, SE90187 Umeå, Sweden. E-mail: [email protected],
Fax: + 46 90 7866705.
Accepted for publication February 2004.
streams, with biogeographical affinities (sister-taxon
relationships) with other Gondwanan landmasses
(particularly southern South America and New
Zealand) and assumedly from cool-adapted lineages,
were found to have anomalous presence in Australia’s
tropical north (Cranston 2000a). Here we extend these
observations by focusing on patterns of chironomid
diversity and distribution within northern Queensland’s Wet Tropics bioregion. In particular, we assess
how restricted the cool Gondwanan component is in its
distribution within the Wet Tropics.
The Wet Tropics bioregion, between the cities of
Cooktown and Townsville along the east coast of
northern Queensland, Australia (Fig. 1), has high
but seasonal rainfall, with summer wet season falls
(ca 600 mm/month in the vicinity of Tully Gorge)
substantially greater than those of the winter dry season
(ca 150 mm/month, Pearson 1994). These conditions
favour tropical rainforests, which straddle a spine of
mountains that frequently rise to over 1000 m a.s.l.
(Nix 1991; Goosem et al. 1999). Beyond the bioregion,
the climate is hotter and drier, and rainforest gives way
to xeric vegetation types (Switzer 1991). Despite
covering just 0.01% of the surface of Australia
(1 849 725 ha), the Wet Tropics supports a major
proportion of the continent’s terrestrial plant and
animal species, including 65% of its fern species, 36%
D I V E R S I T Y A N D D I S T R I B U T I O N O F W E T T R O P I C S C H I R O N O M I DA E
of its mammals, 60% of its butterflies and 41% of its
freshwater fishes (Pusey & Kennard 1996; Goosem
et al. 1999). Regional endemism among the terrestrial
fauna is also high, with 25% of the region’s plant and
vertebrate species occurring nowhere else (Williams &
Pearson 1997; Goosem et al. 1999). Similar data are
unavailable for freshwater invertebrates, though
diversity of some freshwater insects (notably
Trichoptera) appears higher than in comparable areas
of south-eastern Australia (Benson & Pearson 1988;
2
Lake et al. 1994), in contrast to Cranston’s (2000a)
observations for chironomids.
The range of rainforests within the Wet Tropics
has oscillated with climatic fluctuations during the
Quaternary, due to their specific temperature and
rainfall requirements (Quilty 1994). Glaciation at
higher latitudes was associated with a global reduction
in rainfall, and during the last glacial maximum in the
Pleistocene (13 000–8000 years ago), most Australian
tropical rainforest was displaced by drier sclerophyll
Fig. 1. Locations of surveyed stream sites. Sites are identified further in Table 1. Boxes represent discrete blocks of tropical
rainforest.
3
B. G. MCKIE ET AL.
forests. Isolated moist refugia did remain, the largest
centred on the Thornton and Atherton uplands
(Fig. 1, Nix 1991). As the climate ameliorated, rainfall
increased and rainforest expanded to its current extent
(Hopkins et al. 1996), but modern diversity and
distribution patterns of several groups of terrestrial
organisms bear the signature of past rainforest contractions. For example, diversity and endemicity of
vertebrates are greatest in the large refugial areas,
which maintained the largest vertebrate populations
during the glacial period (Williams & Pearson 1997;
Williams 1997; Winter 1997). Patterns for flightless
terrestrial bugs and beetles are more complex,
evidently because smaller rainforest refugia maintained significant populations of rainforest arthropods
Table 1.
(Yeates et al. 2002; C. A. M. Reid pers. comm., 2000).
In contrast, current-day diversity patterns of the Wet
Tropics freshwater fish and Trichoptera faunas seem
little affected by the Pleistocene contractions, with most
species homogeneously distributed throughout the
region’s latitudinal range (Pusey & Kennard 1996;
Pearson in press).
Here we characterize the biogeographical affinities of
the regional chironomid fauna, and consider relationships between patterns of diversity and distribution and
both historical (the Pleistocene rainforest contractions)
and ecological (especially altitude) factors. We examine
evidence derived from two species-level surveys of
lotic Chironomidae. The first sampled the riffleinhabiting fauna of 32 streams, covering the full
Streams sampled in the riffle and leaf pack surveys
Map Locality
Paluma
Kirrama
Mission Beach
Tully Gorge
Atherton
Mt. Bellenden Kerr – Mt. Bartle Frere
Malbon Thompson Range (Yarrabah)
Kuranda – Lamb Range
Black Mountain
Mount Lewis
Mossman/Mt. Carbine
Mt. Windsor
Daintree (Mount Thornton)
Lorna Doone (Far Northern)
Map
ref.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
Stream
Name
Keelbottom
Little Crystal
Birthday
Camp
Goddard
Bridge
Yuccabine
Limbo
Pixies
Charappa
North Johnson
Nigger
Bartle Frere
Kearney
Malbon Thompson
Simmonds
Oombunghi
Kauri
Breach
Clohesy
Shoteel
Rifle
Allan
Windmill
Mary
Gorge
Carbine
Mt Windsor
Oliver
Emmagen
Baird
Bloomfield
Woobadda
Gap
Wallaby
Scrubby
Altitude
(m a.s.l.)
Stream Order &
Dominant Lithology
Survey sampled
600
400
800
850
500
100
600
20
60
620
500
900
1400
80
100
40
40
900
700
700
450
440
350
900
900
80
1175
960
20
20
200
20
100
150
300
140
3 (Granite)
3 (Granite-P)
3 (Granite-P)
2 (Granite)
3 (Granite)
3 (Granite)
3 (Granite)
3 (Alluvium/Met.)†
3 (Volcanics)
3 (Granite)
3 (Granite)
3 (Granite)
1 (?)
3 (Basalt/Granite)†
2 (Granite)
2 (Granite)
3 (Granite)
1 (Granite)
3 (Granite)
2 (Granite)
2 (Metam.)
3 (Metam.)
3 (Metam.)
2 (Granite)
2 (Granite)
2 (Hodgk./Granite)†
3 (Granite)
3 (Granite)
3 (Hodgk.)
4 (Hodgk.)
4 (Hodgk.)
4 (Hodgk.)
4 (Hodgk.)
2 (Granite)
2 (Alluvium)
3 (Granite)
R94
LP
R93 & LP
R93 & LP
R93
R93
R93
R93
R93 & LP
R93
R93
R94
R95
R94
R93
R93
R94
R93
R93
LP
R93 & LP
R93
R93
R93 & LP
LP
R94
R94
R94
LP
R93 & LP
R93
R93
R93
R93
R93
R94
†
Requires on-site verification. Map locality and ref. refer to Fig. 1. Lithology: Granite P, porphyrytic granite; Hodgk., Hodgkinson granites and metamorphics, including siliceous cherts; Met., metamorphics. Survey sampled: R93, riffle survey 1993
(November – December); R94, riffle survey 1994 (May – July); R95, riffle survey 1995 (November); LP, leaf pack survey
(August – September 1997).
D I V E R S I T Y A N D D I S T R I B U T I O N O F W E T T R O P I C S C H I R O N O M I DA E
latitudinal and altitudinal range of the Wet Tropics; the
second sampled the fauna of pool leaf packs from 10
streams.
METHODS
Riffle survey: sampling and identification
The 36 Wet Tropics streams sampled in the riffle and
leaf pack surveys are listed in Table 1, with their
location plotted in Figure 1. Riffle-inhabiting chironomids were sampled from 32 of these sites over three
years as part of a broader study of the region’s freshwater communities (Pearson in press). All streams flow
through tropical rainforest and are characterized by
very soft waters (hardness 1.8–21 mg/L) of low conductivity (22–111 S/cm) and variable but usually
mildly acidic pH (5.5–6.8) (Butler & Pearson 1998).
On the mountain peaks, annual mean air temperatures
generally fall between 17 and 21C, but occasionally
drop below zero in the winter. The coastal lowlands are
warmer, especially in the north of the bioregion where
the average annual mean temperature is often above
25C (Nix 1991). More southerly lowlands are a few
degrees cooler, and regimes on the inland tablelands
are similar to those of the mountain tops. Most sites
(23) were sampled in the late dry season (November
and December) of 1993 (R93, Table 1). The remaining
sites, expanding altitudinal, latitudinal and seasonal
coverage, were sampled in May and June 1994,
following the end of the wet season, except for Bartle
Frere (the highest mountain in the region at 1622 m
a.s.l.), which was sampled in November 1995 (R94R95, Table 1).
At each stream site, two riffles were sampled by
thoroughly disturbing the substrate within six
randomly placed 25 cm 25 cm quadrats (three per
riffle) upstream of a dip net (63 m mesh), with
collected material preserved in 70% ethanol. Because of
the large number of larval chironomids found (approx.
7400), individuals were identified to species level from
only two of the six samples collected per site, one per
riffle. Abundance was highly clumped, with one or two
samples from each site typically yielding many more
individuals than the remainder, and so in each case
the samples selected were those yielding the greatest
number of individuals. These samples represented
57 9% (mean standard deviation) of individuals
collected per site. Diversity was also well represented in
these samples. For example, average richness per site
was 71% of that found by Cranston (2000a), despite
his samples integrating all habitats, and richness of the
two samples for one stream (Birthday Creek, 17
species) was comparable to that assessed from six
riffles intensively sampled as part of another study in
4
1999 (19 species, BGM unpubl. data). Individuals
were slide mounted in Hoyer’s aqueous solution and
identified using the keys of Cranston (1997a,b,
2000b). Novel morphospecies with distinctive
mouthpart morphologies were given a mnemonic
(e.g. a number preceded by the letters ‘FNQ’ (Far
North Queensland) for an undescribed putative
genus).
During the 1993 sampling trip, physico-chemical
data were recorded from each site, as detailed in
Butler and Pearson (1998). Methodology followed the
Queensland ‘State of the Rivers’ pro-forma (Andersen
1993), and included measures of temperature, pH and
conductivity, replicate measures (10) of width, depth
and water flow over the stream reach sampled, as well
as estimates of substrate composition and percent
canopy cover (shading). By necessity, the exact time at
which temperature measurements were taken varied
among sites, but all were taken in the shade during
daylight hours, and temperatures of Wet Tropics
streams typically vary by less than two degrees over a
24-h period (B. G. McKie, P. Wulf and R. G. Pearson,
unpubl. data, 2002).
Leaf-pack survey for chironomids of the
Wet Tropics
As leaf packs support a different chironomid assemblage from riffles, a survey of this habitat from 10
streams was conducted in the 1997 dry season
(August–September, Table 1), to broaden the understanding of the Wet Tropics fauna. Samples consisted
of fist-sized handfuls (volume approximately 300 cm3)
of leaves, collected from dense accumulations in
slower-flowing pools, which were placed directly into a
plastic bag containing 70% alcohol. Five separate leaf
packs were sampled over a reach of approximately
100 m at each stream site. Chironomid larvae were
identified as described above.
Biogeographical categorization
Where possible, species were allocated to biogeographical groupings comprising Gondwanan taxa,
with recent postulated phylogenetic (sister group)
linkages to other Gondwanan landmasses, and cosmopolitan taxa. Within the Gondwanan group, two
subgroups can be recognized: cool, with current
southern temperate distributions; and warm, with
modern distributions in the warmer parts of the
southern continents, often including tropical Africa.
In contrast to these patterns, a cosmopolitan component comprises mostly broadly ranging taxa, both
within Australia and elsewhere, with various relationships, some to proximate landmasses to the north,
5
B. G. MCKIE ET AL.
but without close phylogenetic association with
Gondwanan landmasses.
Analysis
Distributional data were ordinated using Non-metric
Multidimensional Scaling (NMS, Clarke 1993).
Similarities in chironomid faunal composition among
sites were assessed additionally using UPGMA
(unweighted pair group arithmetic average) cluster
analysis (Sneath & Sokal 1973). These analyses were
conducted using the PC-ORD for Windows multivariate analysis package (Version 4.0 1999, MjM
Software, Gleneden Beach, Oregon, USA). Additionally, an Analysis of Similarities (ANOSIM) was
carried out using Primer for Windows (Version 5.2.9,
2002, Primer-E Ltd, Plymouth, UK) to assess
differences between sites sampled in 1993 and 1994.
Since the main interest was assessing similarities
between sites, rather than groupings of samples
within sites, data for the two riffle or five leaf pack
samples (in the riffle and leaf pack surveys, respectively) from each site were pooled prior to analysis.
All analyses used Bray-Curtis dissimilarities as the
distance measure.
Following ordination, simultaneous plots of streams
and species in the ordination space were produced
using PC-ORD. Scores for the species were calculated
via weighted averaging, whereby stream unit scores are
used to weight the average position of each species
along the ordination axes. This allows for a visual
assessment of relationships between species and sites,
similar to a traditional principal components biplot, but
one which better accounts for non-linearity in these
relationships (McCune & Mefford 1999).
Riffle survey samples had been collected up to
7 years prior to identification, and some were poorly
preserved. For three genera (the orthoclads Corynoneura and Thienemanniella and the Chironominae
Tanytarsus), antennal characteristics crucial for
species recognition were damaged. Therefore, data
were pooled for two Corynoneura and two or three
Thienemanniella species in the analyses. Two Tanytarsus
species could be recognized from all sites, because
characters important for species recognition were
adequately preserved. Remaining Tanytarsus were
excluded from analyses. These measures were unnecessary for the leaf-pack survey.
Riffle survey data were additionally analysed using
univariate regression, in order to assess relationships
between species diversity and the altitude and latitude
of the study sites. Standard measures of species
diversity were used (evenness, species richness and
the Shannon-Wiener, Simpson and Berger-Parker
diversity indices), calculated using the Species
Diversity & Richness program (Version 1.2, 1997,
Pisces Conservation, Lymington, UK).
In the riffle survey, assemblage composition
appeared to be influenced by altitude (see Results
below), and so univariate regression was used to
explore relationships between altitude and stream
physico-chemical characteristics. Where replicate
measures were taken at each site (e.g. for depth,
width and water flow), the response variable consisted
of the average of the 10 readings. All regressions were
carried out using SPSS for Windows (version 10.0.5,
1989–1999, SPSS Inc., Chicago, USA).
Fig. 2. Riffle Survey: results from NMS ordination (Bray-Curtis dissimilarities) of ln(x + 1) transformed chironomid
abundance data. Ordination in three dimensions, axes 1 & 2 plotted; stress = 0.16. (a) Stream site coordinates, with altitude
categories superimposed: () <200 m a.s.l., ( ) 200–599 m a.s.l., () 600 m a.s.l. (refer to Table 1 for site numbers); (b)
species coordinates, calculated using weighted averaging, with biogeographical categories superimposed: () cosmopolitan or
tropical, () warm Gondwanan, () cool Gondwanan, () other cool-temperate species, (+) uncertain .
D I V E R S I T Y A N D D I S T R I B U T I O N O F W E T T R O P I C S C H I R O N O M I DA E
RESULTS
Composition of the Wet Tropics fauna
Raw data from the riffle and leaf pack Wet Tropics
surveys are available online at http://entomology.
ucdavis.edu/chiropage/Wtsurvey. The 87 chironomid
taxa distinguished from the surveys are mostly distinct
species, but for 4–6 genera, distinguishing larval
species on the basis of morphology is problematical,
so the number of species found may be an underestimate. Fifteen of the 49 genera distinguished were
novel, and within previously recognized genera, some
species were novel. Over half the genera found occur
worldwide, though at least four are probably recent
colonisers from Asia. Approximately 25% of the fauna
(at least 21 species in 14 genera) have Gondwanan
affinities, either with warmer, tropical parts of the
former Gondwanan supercontinent (7 taxa, including
Nilotanypus and Harrisius species), or more usually
cool-temperate regions (at least 14 species, including
Echinocladius martini, Botryocladius grapeth, Australopelopia prionoptera and Riethia species). Five of the cool
Gondwanan species were novel, but their morphological affinity with described Gondwanan species is
easily recognized (McKie 2002). Several other species
also may have been Gondwanan, as otherwise worldwide genera such as Rheotanytarsus, Polypedilum and
6
Cricotopus include species in the Wet Tropics with
present-day distributional patterns centred on
Australia’s temperate south-east, similar to the cool
Gondwanan taxa mentioned above, suggesting
common phyletic origins. Hereafter, these are referred
to as ‘temperate-zone species’.
Riffle survey
Ordination and cluster analyses
Two separate analyses of riffle survey data were carried
out. The first focused only on the sites sampled in 1993
whereas the second included data for all sites (see
Table 1). An ANOSIM testing for differences between
samples collected in 1993 and 1994 was not significant
(Global R = 0.094, P = 0.174), and since both the
1993-only and combined-years analyses yielded similar
results, only the second is presented here.
Combined-years data were ordinated in three
dimensions. In confirmation of the ANOSIM analysis,
sampling season appeared not to affect assemblage
composition, as sites sampled in 1994 were interspersed with those sampled in 1993. Rather, assemblage composition was influenced by altitude, as most
high altitude sites separated from the remainder along
axis 1 (Fig. 2a). Prominent in chironomid assemblages
Fig. 3. Riffle Survey: Classification of all sites by UPGMA cluster analysis, superimposed with latitude (() >19S, () 18–19S,
() 17–17.99S, () 16S) and altitude (() <200 m a.s.l., ( ) 200–599 m a.s.l., () 600 m a.s.l.) categories. The arrowed
cluster contains all Daintree sites, other geographic groupings (Fig. 1) are widely dispersed through the dendrogram.
7
B. G. MCKIE ET AL.
from these sites were several cool (southern) Gondwanan species from the Orthocladiinae (for example,
species j, o, p and q in Fig. 2b: Echinocladius martini,
Botryocladius grapeth, novel species FNQ-2 and Stictocladius sp.) and species from cosmopolitan genera with
modern-day cool temperate, south-east Australian
distributions (temperate-zone species), including
species of Rheotanytarsus (species d and m in Fig. 2b),
Polypedilum (species k) and Cricotopus (species b and
c). Mid and low altitude sites that were positioned with
the high altitude sites in the ordination (towards the
right of axis one), such as Goddard, Bridge, Rifle and
Gap Creeks (streams 5, 6, 22 and 34 in Fig. 2) also
supported several species from these biogeographical
groupings (including the cool Gondwanan aphrotenine
Aphroteniella filicornis, point r). Overall, species
richness of Gondwanan and other temperate-zone
species was significantly related to altitude (regression
analysis: richness = 3.6 + 0.002 altitude, R2 = 0.25,
P = 0.003). The mean and standard deviation of richness values for these groups in low-, mid- and high
altitude bands (as defined in Fig. 2a) were 3.7 1.7,
4.6 1.7 and 5.7 1.6 species, respectively.
The only cool-Gondwanan taxa found in multiple
sites positioned towards the opposite (left) side of the
Fig. 4. Relationship between altitude and stream temperature of the 23 Riffle Survey sites sampled in the first trip
(Table 1), with canopy shade categories (() <25%, () 25–
49%, () 50–74%, () >75%) superimposed and selected
sites labelled with their stream number. Multiple regression
analysis: Altitude t = –7.8, P < 0.001; Shade t = –4.7,
P < 0.001; R2 = 0.832.
Table 2.
ordination space were two Riethia species (the two
species marked i in Fig. 2b) and the tanypod Australopelopia prionoptera (species l). No other temperate-zone
species were common in these streams. More typical of
lowland sites were species from tropical and cosmopolitan genera. For example, a cosmopolitan species of
Rheocricotopus was rare at high altitudes but often very
abundant at lower altitude sites (point f), while the
tropical Thienemannimyia occurred exclusively at
sites of lower altitude (point e). Tropical and cosmopolitan species of Rheotanytarsus, Dicroctendipes and
Polypedilum (the three species plotted around point g
in Fig. 2b) occurred at all altitudes, as did the warm
Gondwanan Nilotanypus and Harrisius (points h
and n).
Some mid-and low altitude streams were positioned
to the right of the ordination space but somewhat apart
from the main cluster of high altitude sites. Most
distant was Simmonds Creek (stream 16), which had
an unusual fauna with species that were rare or
absent elsewhere, including a novel cool-Gondwanan
orthoclad species (point s). Of the two sites occurring
in the upper right-hand corner of the ordination
space, Oombunghi Creek (stream 17) supported some
cool Gondwanan and southern elements, such as
Eukiefferiella (species a) whereas North Johnson
(stream 11) was a very low diversity site that grouped
with Oombunghi because of the mutual occurrence of
a few cosmopolitan and tropical species.
No groupings due to latitude were apparent and
overall, geographical proximity explained little of the
clustering pattern in the UPGMA analysis (Fig. 3). For
example, geographically adjacent Paluma sites,
Birthday and Camp Creeks (numbers 3 and 4),
and Lamb Range sites, Kauri and Breach Creeks
(numbers 18 and 19), occur on widely divergent
terminal branches. Similarly, although all four
Daintree sites (numbers 30–33) occur in a single
large cluster (arrowed in Fig. 3), within that cluster
these sites were mostly well separated. However,
certain altitudinally similar sites clustered despite
being widely separated geographically, including
high elevation sites Birthday Creek and Bartle Frere
(13), and low elevation sites Kearney (14) and Gorge
Creeks (26).
Effect of stream altitude on three physical variables: mean standard deviation (sd) for three altitudinal bands
Altitudinal band
(m a.s.l.)
n
Water Temperature (C)
(mean SD)
Stream Width (m)
(mean SD)
Current Velocity (m s-1)
(mean SD)
< 200
200–599
600
9
7
7
23.77 2.07
21.33 1.32
19.57 2.11
16.02 6.06
11.59 5.50
9.56 2.24
0.21 0.12
0.20 0.13
0.10 0.03
Regression analyses: temperature = 24.2–0.006 altitude, R2 = 0.64, P < 0.001; Width = 16.1–0.009 altitude, R2 = 0.28,
P = 0.009*; Velocity = –0.2–0.0004 altitude, R2 = 0.23, P = 0.019*.
*Response variable was average of 10 readings, log transformed.
D I V E R S I T Y A N D D I S T R I B U T I O N O F W E T T R O P I C S C H I R O N O M I DA E
The distribution of diversity and abundance
There were no relationships between either latitude or
altitude and any measure of species diversity, regardless
of whether regression analyses focused only on sites
sampled in one season or on the combined data
set (e.g. regression analysis of species richness from
the 1993 survey: richness = 12.8 + 0.002 altitude,
R2 = 0.049, P = 0.23; relationships with other indices
of even lower significance).
Altitude and stream physico-chemical characteristics
Three physico-chemical variables measured from the
23 streams sampled during the (1993) survey trip
decreased significantly with increasing altitude: water
temperature, stream width and water current (Table 2).
Multiple regression analysis indicated that both altitude
and shade affect stream temperatures in the Wet
Tropics (altitude, t = –7.8, P < 0.001; shade t = –4.7,
P < 0.001; R2 = 0.832). Heavily shaded low- and midaltitude streams consistently fell below the regression
line plotted in Fig. 4, which predicts temperature for
streams of a given altitude.
Leaf pack survey
Leaf pack survey data were ordinated in two dimensions (Fig. 5), with higher altitude sites separating out
from the remainder along axis 1. As in the riffle survey,
species richness of cool Gondwanan and other temperate zone chironomids was significantly related to
altitude (regression analysis: richness = 2.6 + 0.005 altitude, R2 = 0.47, P = 0.029). Cool-Gondwanan
8
species associated with upland sites included B. grapeth
and E. martini (points b and n in Fig. 5b), novel
orthoclad species FNQ-3, FNQ-2 and FNQ-1 (points
a, j and s), and to a lesser extent, the aphrotenine
A. filicornis (point h). Also associated with higher altitude sites were temperate-zone species from the otherwise cosmopolitan genera Rheotanytarsus, Corynoneura
and Polypedilum (points p, q and r). Other species from
these genera, known only from the tropics, were found
predominately at low altitudes or at all elevations
(points f, g and i), as were representatives of the
cosmopolitan Rheocricotopus and Dicrotendipes (points
k and o). As in the riffle survey, the cool Gondwanan
tanypod A. prionoptera (point d) and the warm
Gondwanan tanypod Nilotanypus and Chironomini
Harrisius (points c and l) were found equally at all
altitudes, but in contrast with the earlier survey, the two
cool Gondwanan Riethia species (points e and m) were
found predominately at high altitudes.
UPGMA analysis of the leaf pack data defined two
distinct clusters, one consisting entirely of sites falling
within the 17–16S latitudinal band, and another with
all the more southern sites plus the more northern
Shoteel and Windmill Creeks (numbers 21 and 24,
Fig. 6). The two Paluma sites (numbers 3 and 4)
clustered together, but other geographically adjacent
sites occurred on widely separated branches (e.g.
numbers 20 and 21, 24 and 25, 29 and 30).
DISCUSSION
Consistent trends in lotic chironomid distributions
within the Wet Tropics bioregion related to altitude,
Fig. 5. Leaf Pack Survey: results from NMS ordination (Bray-Curtis dissimilarities) of ln(x + 1) transformed chironomid
abundance data. Ordination in two dimensions, stress = 0.13. (a) Stream site coordinates, with altitude categories superimposed:
() <200 m a.s.l., ( ) 200–599 m a.s.l., () 600 m a.s.l.; (b) species coordinates, calculated using weighted averaging, with
biogeographical categories superimposed (refer to Table 1 for site numbers); (b) species coordinates, calculated using weighted
averaging, with biogeographical categories superimposed: () cosmopolitan or tropical, () warm Gondwanan, () cool
Gondwanan, (+) other cool-temperate species, (+) uncertain.
9
B. G. MCKIE ET AL.
with high elevation assemblages more likely to include
orthoclad taxa with cool (southern) Gondwanan
affinities (e.g. E. martini, B. grapeth), together with
species from cosmopolitan genera with modernday predominately cool temperate, south-eastern
Australian distributions (e.g. Rheotanytarsus flabellatus,
‘Cricotopus conicornis’). Some, if not all, cool-Gondwanan genera appear to have originated in the Cretaceous or early Tertiary (Brundin 1966; Cranston &
Edward 1992; Cranston & Edward 1999) when protoAustralia, as part of the fragmenting Gondwanan
supercontinent, was cooler than now (annual polar air
temperature range estimate: –5 to +8C), with sea-ice
probably forming in the winter (Cranston & Naumann
1991; Quilty 1994). Preponderance of cool Gondwanan and other temperate zone taxa in cooler upland
locations in an otherwise warm region seems related to
temperature, one of the few stream physico-chemical
characteristics to vary systematically with altitude in the
Wet Tropics.
Cool Gondwanan orthoclads do occur in lowerelevation streams, although less frequently. Lower
altitudes in the Wet Tropics also support cooleradapted terrestrial vertebrate faunas, but ‘only in
those areas characterized by high annual mean rainfall
and frequent cloud cover, where mountains and ridges
drop steeply to the sea’ (Nix 1991). This ‘mountain
mass’ (‘massenerhebung’) effect (Nix 1991) might
similarly affect the fauna of streams that drop rapidly
down steep coastal escarpments (e.g. those east of the
range in the Daintree and Malbon-Thompson lowlands; Fig. 1), limiting the scope for warming. Stream
shading further suppresses lowland water temperatures
(Fig. 4), with shaded lowland sites, such as Goddard
(5), Bridge (6) and Gap (34) Creeks supporting cool
Gondwanan Orthocladiinae and other temperate zone
species. In contrast, the less-shaded upland creeks
Yuccabine (7) and Charappa (10) were between two
and three degrees warmer than predicted for their
altitude, and yielded no cool Gondwanan orthoclads.
Thus upland and cooler lowland sites appear to permit
persistence in northern Queensland of cool temperate
southern elements, including several cool Gondwanan
species.
In contrast, a suite of apparently warm-tolerant
species dominated the warmer lowland streams. This
suite comprised representatives of a general Queensland ‘background fauna’, which characterize the warmhot lowland, often ephemeral, streams flowing through
open shrubland, savannah and grassland ecosystems
outside the Wet Tropics (e.g. species of Rheocricotopus
and Dicrotendipes), circum-tropical taxa (e.g. Thienemannimyia and a species of Rheotanytarsus which is
identifiable with the Northern Territory and south-east
Asian Rheotanytarsus oss, Kyerematen et al. 2000) and
warm Gondwanan species of Nilotanypus and
Harrisius. Cool Gondwanan species occurring frequently in warmer lowland systems may either have
evolved away from characteristic ‘cool-Gondwanan’
physiologies (as has occurred for species from coolGondwanan radiations inhabiting warm systems in
central Australia, e.g. Cranston & Edward 1999)
or else may be capable of behaviourally maintaining
preferred body temperatures (possible for the tanypod
A. prionoptera, which being free-roaming may be better
able to exploit microclimate temperature differences
than the more sedentary tubicolous Gondwanan
orthoclads).
However, whether any Australian lotic chironomid
species is strictly ‘stenothermic’, or able to operate with
maximal efficiency over a narrow temperature range, is
debatable (Brundin 1966; McKie et al. in press). No
Wet Tropics chironomid seemed narrowly constrained
by temperature in this study. Even cool Gondwanan
chironomids occur over a relatively broad range of
temperatures, particularly at a continental scale (waters
below 8C in Australia’s south-east, and above 20C in
the tropics), compared with strictly cool stenothermous
species from other regions. For example, Rossaro
(1991a, 1991b) and Casas and Vilchez-Quero (1993)
clearly distinguished alpine and/or winter-active coldstenothermous chironomids in Italy and Spain, respectively. In tropical Africa and the Americas, high altitude
macroinvertebrate faunas (presumed cold-adapted) in
Fig. 6. Leaf pack survey: Classification of all sites by UPGMA cluster analysis, superimposed with (() >19S, () 18–19S,
() 17–17.99S, () 16S) and altitude (() <200 m a.s.l., ( ) 200–599 m a.s.l., () 600 m a.s.l.) categories.
D I V E R S I T Y A N D D I S T R I B U T I O N O F W E T T R O P I C S C H I R O N O M I DA E
mountain ranges over 2000 m a.s.l. can be identified
that are quite distinct from those inhabiting the
surrounding tropical lowlands (Harrison & Hynes
1988; Flowers 1991; collated data in Jacobsen et al.
1997). In the Wet Tropics, where the highest peak is
under 1700 m a.s.l., there is no discrete upland
chironomid fauna, only species that exhibit greater
abundance and frequency in upland locations. Even the
restricted areas of south-eastern Australia subject to
annual snowfall do not support chironomid faunas
distinct from nonalpine montane streams. Limited
sampling of streams in the alpine Kosciosko National
Park (c. 36S, > 2000 m a.s.l.) produced several
Gondwanan species that also occur in the Queensland
Wet Tropics, as well as species occurring at much lower
altitudes in south-eastern Australia (Boothroyd &
Cranston 1995; Cranston 1997a; Cranston & Edward
1999). The widespread distribution across broad
latitudinal and altitudinal bands of Australian running
water chironomids show their relatively unconstrained
ecology (Brundin 1966), as is substantiated by
ecophysiological studies demonstrating broad temperature tolerances, even for cool Gondwanan species
(McKie et al. in press). Such broad tolerances may
reflect the paucity of alpine and strongly seasonal
systems, and the drought-related thermal fluctuations
that Australian lotic systems are regularly but unpredictably subjected to (Finlayson & McMahon 1988;
Lake 1995; Closs & Lake 1996). This reasoning does
not apply to lentic chironomids, which seem more
temperature-restricted than the lotic fauna (Wright &
Cranston 2000; Dimitriadis & Cranston 2001).
Surveys of lotic chironomid pupal exuviae conducted during 1998 (Cranston unpubl. data) also
revealed a substantial cool-Gondwanan component
that was distributed across altitudinal bands in the Wet
Tropics. The exuvial surveys, which sampled midges
emerging from all in-stream habitats, including the
most cryptic, also found several species unrecognized
in the larval survey, notably additional species of
Aphroteniinae, Podonominae and Riethia, which add
to the pool of Gondwanan taxa occurring in the Wet
Tropics. Most of these Wet Tropics Gondwanan
chironomids are not endemic to the bioregion, since
they are known from Australia’s south-east (and
exceptionally the south-west). This contrasts with the
terrestrial Wet Tropics biota, in which many of the
Gondwanan plant and vertebrate species are unique
endemics (Winter 1997; Goosem et al. 1999). Thus,
whereas the terrestrial rainforest community represents
the remaining fragments of a formerly widespread
ecosystem that has now disappeared from most of
Australia, the Wet Tropics populations of most Gondwanan chironomids appear to represent ‘northern
outliers’ of distributions that remain variably extensive
in cooler regions of the continent. This reflects the
vagility of chironomids, and also the broad physio-
10
logical tolerances that characterize the Australian fauna
(McKie et al. in press). Nevertheless, some putative
Gondwanan taxa found in the Wet Tropics have not
been recorded previously in Australia, either representing formerly widespread Gondwanan taxa that have
become extinct elsewhere in Australia, or species that
were always more restricted in the former super
continent (possibly evolving during Australia’s
northwards drift) and remain so today.
There is no evidence for an enduring effect of
historical rainforest contractions on current-day
distribution patterns of Wet Tropics Chironomidae.
Our surveys showed no ‘hotspots’ of species richness
associated with rainforest persistence during dry glacial
periods, as observed for terrestrial fauna (Williams
1997). Such regions might be recognized also by the
occurrence of distinct assemblages of sensitive species
missing from localities affected more profoundly by
rainforest contractions, but even the relatively
temperature-sensitive Gondwanan taxa occur in all
major rainforest blocks, including the northern- and
southernmost. These findings are understandable if
Pleistocene aridity and cooling allowed maintenance of
stream shade and flow even as drier sclerophyllous
vegetation replaced wet tropical rainforest. In the
current landscape, chironomid assemblages associated
with suitably cool streams flowing through open
sclerophyll forest, such as Davies Creek (520 m a.s.l. in
the Kuranda Range), harbour Gondwanan taxa and
are undifferentiated from assemblages in closed rainforest streams (P. S. Cranston unpubl. data, 1998).
Furthermore, where Pleistocene aridity did induce
xeric vegetation, streams often may have maintained
riparian strips of closed rainforest vegetation, as seen
today at the periphery of the southern Wet Tropics,
where rainforest extends into blocks of sclerophyllous
vegetation alongside wet stream channels (Pearson in
press). Where streams dried out completely, the vagility
of adult chironomids would allow recolonization as
climate ameliorated and flow returned, obscuring any
effects of these events on distributional patterns.
Apart from the tendency for richness of cool Gondwanan chironomids to increase with altitude, the
general distribution of diversity within the Wet Tropics
was homogeneous, with no linear or non-linear
relationships detected between species richness (or
any other index) and either altitude or latitude (though
the latitudinal range covered in the surveys was
limited). Previous surveys elsewhere (Coffman 1989)
have suggested higher chironomid diversity at middle
to lower altitudes, supporting predictions (e.g. of the
River Continuum Concept) relating to thermal habitat
heterogeneity: high elevation streams tend to fluctuate
less in temperature (being more buffered by groundwater and/or snow), restricting the range of thermal
optima for species to exploit (Vannote & Sweeney
1980; Ward & Stanford 1982; Minshall 1985). It is
11
B. G. MCKIE ET AL.
unknown if the extent of diel and seasonal thermal
fluctuation varies with altitude for Wet Tropics streams,
but the broad thermal tolerances that seem characteristic of Australian lotic chironomids may preclude finescale niche differentiation according to temperature,
reducing tracking of environmental differences along
gradients (McKie et al. in press). This may not apply
for other Australian freshwater groups, as diversity of
Trichoptera relates to altitude in the Wet Tropics, with
higher elevation sites supporting more species (Pearson
in press), possibly indicating greater stenothermy than
in the Chironomidae, or alternatively greater exploitation of specialized food sources or habitats rarer at
lower altitudes (Wiggins & Mackay 1978).
Lotic ecosystems have been argued to provide a
general exception to the trend for species diversity to
be greater in tropical regions (Coffman 1989; Flowers
1991; Allan & Flecker 1993). Greater plant diversity of
tropical rainforests, a postulated associate with speciation in terrestrial insect assemblages (Erwin 1988), is
less likely to drive speciation among lotic insects
because aquatic leaf-shredders consume decayed and
softened material leached of defensive chemicals, and
thus are more generalist than terrestrial phytophages
(Flowers 1991). The relative uniformity of habitat
architecture characteristic of forested streams worldwide (with little variation in the basic substrates: rocks,
sand, wood, leaves) also militates against divergence in
species richness according to latitude – as suggested by
Coffman and De La Rosa (1998), ‘the action of
flowing water on geological materials is not latitude
dependent’. Nonetheless, some evidence suggests
macroinvertebrate species richness may be greater in
tropical streams (Fittkau 1971; Stout & Vandermeer
1975; Minshall 1985; Pearson et al. 1986; Outridge
1987; Lake et al. 1994; Yule 1995), although most of
these comparisons suffer from inconsistent sampling
methods and/or taxonomy (as discussed by Lake et al.
1994; Jackson & Sweeney 1995a). The Cranston
(2000a) systematic survey does not suffer from these
problems and revealed no latitudinal diversity gradient
for eastern Australian lotic chironomids, even accounting for seasonal fluctuations in species composition and
richness. Maintenance of high diversity is favoured
where species responses to environmental variation are
well-differentiated (Chesson 2000), but temperature
tolerances of Australian chironomids seem generally
broad (McKie et al. in press), and Wet Tropics lotic
macroinvertebrates in general, and chironomids in
particular, tolerate remarkably wide oxygen, nutrient
and sedimentation ranges (Connolly & Pearson 1998;
Pearson & Connolly 2000; Connolly et al. 2004), all
factors which can vary in concert with flow in the
Australian environment (Lake 1995; Boulton & Brock
1999). Such broad ecological tolerances make it less
likely that environmental differences between tropical
and temperate systems would be associated with
divergence in species richness. However, Lake et al.
(1994) also sampled eastern Australian streams in a
comparable manner, and concluded that overall diversity of macroinvertebrates was higher in the tropics.
This discrepancy may reflect differences between
richness at the sample scale, assessed by Lake et al.
(1994), and the overall in-stream species pool, or
differences in the ecological characteristics of the focal
taxa (chironomids compared with the entire macroinvertebrate assemblage). Clearly more research is
required before generalizations can be made about the
global patterning of lotic diversity and the processes
underlying those patterns.
ACKNOWLEDGEMENTS
Jacqui Nolan, Gordie Kovacs, Niall Connolly, Linda
Davis and other staff of the Australian Centre for
Tropical Freshwater Research assisted with sample
collection and sorting. Funding for the riffle survey (as
part of the ‘Stream Classification Project’) was provided by the Land and Water Resources Research and
Development Corporation (LWRRDC), and the Rainforest Cooperative Research Centre funded the leaf
pack survey. The senior author was supported by an
Australian Postgraduate Award. We are grateful to
Leon Barmuta, Andrew Boulton and Athol Mclachlan,
who read the doctoral thesis on which this manuscript
is based and made several suggestions that greatly
improved its quality, as did the comments of two
anonymous referees.
REFERENCES
Allan J. D. & Flecker A. S. (1993) Biodiversity conservation in
running waters: identifying the major factors that threaten
destruction of riverine species and ecosystems. Bioscience 43,
32–43.
Andersen J. R. (1993) State of the Rivers Project Report 2:
Implementation Manual. Department of Primary Industries,
Queensland, Brisbane.
Benson L. J. & Pearson R. G. (1988) Diversity and seasonality of
adult Trichoptera captured in a light-trap at Yuccabine
Creek, a tropical Australian rainforest stream. Aust. J. Ecol.
13, 337–44.
Boothroyd I. K. G. & Cranston P. S. (1995) Two Orthocladiinae
(Chironomidae) genera common to New Zealand and
Australia: Pirara N. Gen. and Eukiefferiella Thienemann. In:
Chironomids, From Genes to Ecosystems (ed. P. S. Cranston)
pp. 389–408. CSIRO, Melbourne.
Boulton A. J. & Brock M. A. (1999) Australian Freshwater
Ecology: Processes and Management. Gleneagles Publishing,
Glen Osmond, South Australia.
Brundin L. (1966) Transantarctic Relationships and Their Significance as Evidenced by Chironomid Midges. Almqvist & Wiksell,
Stockholm.
Butler B. & Pearson R. G. (1998) Overview of Physical, Chemical
and Biological Features of Wet Tropics Streams. ACTFR Report
D I V E R S I T Y A N D D I S T R I B U T I O N O F W E T T R O P I C S C H I R O N O M I DA E
no. 98/26. Australian Centre for Tropical Freshwater
Research, James Cook University, Townsville.
Casas J. J. & Vilchez-Quero A. (1993) Altitudinal distribution of
lotic chironomid (Diptera) communities in the Sierra
Nevada mountains (Southern Spain). Annls Limnol. 29,
175–87.
Chesson P. (2000) Mechanisms of maintenance of species
diversity. Annu. Rev. Ecol. Syst. 31, 343–66.
Clarke K. R. (1993) Non-parametric multivariate analyses of
changes in community structure. Aust. J. Ecol. 18, 117–43.
Closs G. P. & Lake P. S. (1996) Drought, differential mortality
and the coexistence of native and an introduced fish species
in a south east Australian intermittent stream. Env. Biol.
Fishes 47, 17–26.
Coffman W. P. (1989) Factors that determine the species richness of lotic communities of Chironomidae. Acta Biol. Debr.
Oecol. Hung. 3, 95–100.
Coffman W. P. & De La Rosa C. (1998) Taxonomic Composition and Temporal Organization of Tropical and Temperate
Assemblages of Lotic Chironomidae. J. Kansas Entomol. Soc.
71, 388–406.
Connolly N. M. & Pearson R. G. (1998) Macroinvertebrates as
Monitors of River Health in the Tropics: Appendix D – the Effect
of Sedimentation on Benthic Invertebrates in Tropical Streams.
LWRRDC report no. JCU 11 & ACTFR no. 98/20.
Australian Centre for Tropical Freshwater Research, James
Cook University, Townsville.
Connolly N. M., Crossland M. R. & Pearson R. G. (2004) Effect
of low dissolved oxygen on survival, emergence, and drift of
tropical stream macroinvertebrates. J. N. Am. Benthol. Soc.
23, 251–70.
Cranston P. S. (1997a) Identification Guide to the Chironomidae of
New South Wales. Australian Water Technologies Pty Ltd,
West Ryde.
Cranston P. S. (1997b) The Australian Rheotanytarsus
Thienemann and Bause (Diptera: Chironomidae) revised,
with emphasis on the immature stages. Invert. Taxon. 11,
705–34.
Cranston P. S. (2000a) August Thienemann’s influence on
modern chironomidology – an Australian perspective. Verh.
Internat. Verein. Limnol. 27, 278–83.
Cranston P. S. (2000b) Three new species of Chironomidae
(Diptera) from the Australian Wet Tropics. Mem. Queensland
Mus. 46, 107–27.
Cranston P. S. & Edward D. H. D. (1992) A sytematic
reappraisal of the Australian Aphroteniinae (Diptera:
Chironomidae) with dating from vicariance biogeography.
Syst. Entomol. 17, 41–54.
Cranston P. S. & Edward D. H. D. (1999) Botryocladius Gen.n.:
a new transantarctic genus of orthocladiine midge (Diptera:
Chironomidae). Syst. Entomol. 24, 305–33.
Cranston P. S. & Naumann I. D. (1991) Biogeography. In: The
Insects of Australia, 2nd edn (ed I. D. Neumann) pp. 180–97.
Melbourne University Press, Melbourne.
Dimitriadis S. & Cranston P. S. (2001) An Australian Holocene
climate reconstruction using Chironomidae from a tropical
volcanic maar lake. Palaeogeog. Palaeoclimatol. Palaeoecol.
176, 109–31.
Erwin T. L. (1988) The tropical forest canopy: the heart of biotic
diversity. In: Biodiversity (eds E. O. Wilson & F. M. Peter)
pp. 123–9. National Academy Press, Washington DC.
Finlayson B. L. & McMahon T. A. (1988) Australia vs. the
world: A comprehensive analysis of streamflow characteristics. In: Fluvial Geomorphology in Australia (ed. R. F.
Warner) pp. 17–40. Academic Press, Sydney.
12
Fittkau E. J. (1971) Distribution and ecology of Amazonian
chironomids (Diptera). Can. Entomol. 103, 407–13.
Flowers R. W. (1991) Diversity of stream-living insects in
north western Panama. J. North Am. Benthol. Soc. 10,
322–34.
Goosem S., Morgan G. & Kemp J. E. (1999) Chapter 7. Wet
Tropics. In: The Conservation Status of Queenslands Bioregional Ecosystems (eds P. Sattler & R. Williams) pp. 1–55.
Environmental Protection Agency, Brisbane.
Harrison A. D. & Hynes H. B. N. (1988) Benthic fauna of
Ethiopian mountain streams and rivers. Arch. Hydrobiol.
Supplement 81, 1–36.
Hopkins M., Head J., Ash J., Hewett R. & Graham A. (1996)
Evidence of a Holocene and continuing recent expansion of
lowland rain forest in humid, tropical North Queensland.
J. Biogeog. 23, 737–45.
Jackson J. K. & Sweeney B. W. (1995a) Present status and future
directions of tropical stream research. J. North Am. Benthol.
Soc. 14, 5–11.
Jacobsen D., Schultz R. & Encalada A. (1997) Structure and
diversity of stream invertebrate assemblages: the influence of
temperature with altitude and latitude. Freshwater Biol. 38,
247–61.
Kyerematen R., Andersen T. & Saether O. (2000) A review of
Oriental Rheotanytarsus Thienemann & Bause, with descriptions of some new species (Insecta, Diptera, Chironomidae).
Spixiana 23, 225–58.
Lake P. S. (1995) Of floods and droughts: river and stream
ecosystems of Australia. In: Ecosystems of the World, Vol. 22:
River and Stream Ecosystems (eds C. E. Cushing, K. W.
Cummins & G. W. Minshall) pp. 659–94. Elsevier,
Amsterdam.
Lake P. S., Schreiber E. S. G., Milne B. J. & Pearson R. G. (1994)
Species richness in streams: Patterns over time, with stream
size and with latitude. Verh. Internat. Verein. Limnol. 25,
1822–6.
McCune B. & Mefford M. J. (1999) Multivariate Analysis of
Ecological Data Vesion 4.0 (PC-Ord Help System). MjM
Software, Gleneden Beach, Oregon.
McKie B. G. L. (2002) Multiscale abiotic, biotic and biogeographic influences on the ecology and distribution of lotic
Chironomidae (Diptera) in the Australian Wet Tropics. PhD
Thesis, School of Tropical Biology, James Cook University,
Townsville.
McKie B. G., Cranston P. S. & Pearson R. G. (in press)
Gondwanan mesotherms and cosmopolitan eurytherms:
effects of temperature on the development and survival of
Australian Chironomidae (Diptera) from tropical and
temperate populations. Mar. Freshwater Res.
Minshall G. W. (1985) Species richness in streams of different
size from the same drainage basin. Am. Nat. 125, 16–38.
Nix H. A. (1991) Biogeography: pattern and process. In:
Rainforest Animals: Atlas of Vertebrates Endemic to Australia’s
Wet Tropics (Kowari 1) (eds H. A. Nix & M. A. Switzer)
pp. 10–39. Australian National Parks and Wildlife Service,
Canberra.
Outridge P. M. (1987) Possible causes of high species diversity
in tropical Australian freshwater macrobenthic communities.
Hydrobiologia 150, 95–107.
Pearson R. G. (1994) Limnology in the northeastern tropics of
Australia, the wettest part of the driest continent. Mitt.
Internat. Verein. Limnol. 24, 155–63.
Pearson R. G. (in press) Biodiversity of the freshwater invertebrates of the Wet Tropics region of north-eastern Australia:
patterns and possible determinants. In: Tropical Rainforests:
13
B. G. MCKIE ET AL.
Past, Present and Future (eds B. Birmingham, C. Dick &
C. Moritz). University of Chicago Press, Chicago.
Pearson R. G., Benson L. G. & Smith R. E. W. (1986) Diversity
and abundance of the fauna in Yuccabine Creek, a tropical
rainforest stream. In: Limnology in Australia (eds P. De
Decker & W. D. Williams) pp. 329–42. CSIRO, Melbourne.
Pearson R. G. & Connolly N. M. (2000) Nutrient enhancement,
food quality and community dynamics in a tropical rainforest stream. Freshwater Biol. 43, 31–42.
Pusey B. J. & Kennard M. J. (1996) Species richness and
geographical variation in assemblage structure of the freshwater fish fauna of the wet tropics region of northern
Queensland. Mar. Freshwater Res. 47, 563–73.
Quilty P. G. (1994) The background: 144 million years of
Australian palaeoclimate and palaeogeography. In: History of
the Australian Vegetation: Cretaceous to Recent (ed. R. S. Hill)
pp. 14–43. Cambridge University Press, Cambridge.
Rossaro B. (1991a) Chironomids and water temperature. Aquat.
Ins. 13, 87–98.
Rossaro B. (1991b) Factors that determine Chironomidae
species distribution in fresh waters. Boll. Zool. 58, 281–6.
Sneath P. H. A. & Sokal R. R. (1973) Numerical Taxonomy. W.H.
Freeman, San Francisco.
Stout J. & Vandermeer J. (1975) Comparison of species richness
for stream-inhabiting insects in tropical and mid-latitude
streams. Am. Nat. 109, 263–80.
Switzer M. A. (1991) Introduction. In: Rainforest Animals: Atlas
of Vertebrates Endemic to Australia’s Wet Tropics (Kowari 1) (eds
H. A. Nix & M. A. Switzer) pp. 1–9. Australian National
Parks and Wildlife Service, Canberra.
Vannote R. L. & Sweeney B. W. (1980) Geographical analysis of
thermal equilibria: a conceptual model for evaluating the
effect of natural and modified thermal regimes on aquatic
insect communities. Am. Nat. 115, 667–95.
Vinson M. R. & Hawkins C. P. (1998) Biodiversity of stream
insects: variation at local, basin and regional scales. Annu.
Rev. Entomol. 43, 271–93.
Ward J. V. & Stanford J. A. (1982) Thermal responses in the
evolutionary ecology of aquatic insects. Annu. Rev. Entomol.
27, 97–117.
Wiggins G. B. & Mackay R. J. (1978) Some relationships
between systematics and trophic ecology in Nearctic aquatic
insects, with special reference to Trichoptera. Ecology 59,
1211–29.
Williams S. E. (1997) Patterns of mammalian species richness in
the Australian tropical rainforests: are extinctions during
historical contractions of the rainforest the primary determinants of current regional patterns in biodiversity. Wildl.
Res. 24, 513–30.
Williams S. E. & Pearson R. G. (1997) Historical rainforest
contractions, localized extinctions and patterns of vertebrate
endemism in the rainforests of Australia’s wet tropics. Proc.
R. Soc. Lond. B264, 709–16.
Winter J. W. (1997) Responses of non-volant mammals to the
late Quaternary climatic changes in the Wet Tropics region
of north-eastern Australia. Wildl. Res. 24, 493–511.
Wright I. & Cranston P. S. (2000) Are Australian lakes different?
– Chironomid and chaoborid exuviae from Lake McKenzie,
a coastal temperate dune lake. Verh. Internat. Verein. Limnol.
27, 303–8.
Yeates D. K., Bouchard P. & Monteith G. B. (2002) Patterns
and levels of endemism in the Australian Wet Tropics
rainforest: evidence from flightless insects. Invert. Syst. 16,
605–19.
Yule C. M. (1995) Benthic invertebrate fauna of an aseasonal
tropical mountain stream on Bougainville Island, Papua New
Guinea. Mar. Freshwater Res. 46, 507–18.