Journal of the Royal Society of Western Australia, 90(3), September 2007 
the outcrops presented from Finder et al. (2000) are also 
not directly comparable to our figures as these authors 
included Protozoa, Rotifera and Oligochaetes in their list 
and most Diptera (generally the most speciose group) 
were identified to species, whereas we omitted these 
groups and incompletely identified dipterans. However 
the dominant taxonomic groups in both studies were 
comparable, but often slightly richer in our study — 
Coleoptera (15 taxa versus 12 taxa), Cladocera (13 versus 
11) and Ostracoda (12 versus 12). The higher riclmess in 
our study most probably is a direct result from the 
sampling intensity: Finder et al. (2000) sampled around 
10 pools whereas we sampled 57 pools on Wave Rock. 
The only species we added to the list of Finder et al. 
(2000) were the beetle Hyphydrus, the small crustaceans 
Ephemeroporus hybridus and Candonocypris incosta, 
the listing of what was previously identified as Cyziciis 
as Caenestheriella mariae and the further identification 
of Limnadia as L. badia (see Timms, 2006). As Finder et 
al. (2000) found, many species occurred in only a few 
pools, a phenomenon with implications for sampling 
intensity and conservation policies (see later).. The list 
will grow by increasing the search area and by more 
detailed identifications, particularly of the Turbellaria, 
Oligochaeta (e.g.. Finder, 2003) Tardigrade, Nematoda 
and Mesostigmatid and Trombidoid mites. One 
particular difficulty in this is the large morphological 
variation between populations of passive dispersers on 
different outcrops. A studied example is the fairy shrimp 
Branchinella longirostris with large morphological 
variations between populations on a series of outcrops 
from the south to the north of WA (M. Zofkova & B. 
Timms, unpublished data). 
Six species (f0%) on our list are endemic to granitic 
gnammas (Table 1). For the Whcatbelt as a whole the 
figure is about 30 species (13%) (Finder et al. 2000, 2004; 
A. Finder pers.com.). The difference might be due to the 
much larger area covered by Finder et al. (2000). Rock 
pool specialists such as the various branchiopods, 
ostracods and cladocerans are typically passive 
dispersers. These passive dispersers do not have the 
ability for active dispersal to another habitat patch and 
are dependent on other media such as wind (Brendonck 
& Riddoch 1999) and water (Brendonck et al. 1998). This 
results in strong dispersal limitation of populations 
between outcrops, so that the populations over time each 
evolve in their own direction and might differentiate to 
different species. Long-distance dispersal limitation in 
this habitat type in Botswana was found for 
Branchipodopsis wolfi (Anostracan) by Hulsmans et al. 
(2007) and probably applies also to the fairy shrimp and 
possibly otlier passive dispersers of local rock pools. 
The active dispersers such as beetles and corixids are 
often generalist species of temporary waters with high 
dispersal capacities and easily spread over large areas, 
and also not particularly restricted to rock pools (joeque 
et al. 2006). In particularly wet winters as in our study 
period, pools have a relatively long inundation cycle and 
the longer exposure time results in more species and 
species from (more) permanent water bodies, which are 
absent in drier years (Jeffries 1994). 
Despite the occurrence of the frequently encountered 
species discussed above, the most characteristic 
inhabitants of these gnammas are indeed the large 
branchiopods —Spinicaudata, together with Anostraca 
and Notostraca (Bayly, 1997; Timms, 2006). While the 
spincaudatan Limnadia badia was common and 
widespread, this study hardly encountered another clam 
shrimp (Caenestheriella mariae) and fairy shrimp 
Branchinella longirostris, yet in other years both were 
common (Timms 2006, and unpublished data). Anostraca 
are specialists of temporary pools and highly sensitive to 
predation, mostly from insects immigrating to the pools 
(Brendonck et al. 2002). Increasing predator pressure 
over time reduces Anostracan populations and could 
explain why B. longirostris completes its life cycle early 
in a pool's seasonal existence, so that after a few weeks 
individuals are no longer present. In 2004 the pools of 
Wave Rock filled early in the season (April-May), but in 
2006 they filled late (July). In 2004, none were present on 
Wave Rock in August (Table 1), but in 2006 most pools 
had extant populations (Timms, unpublished data). 
Finder et al. (2000) did not mention any Anura. In 
several pools we found large densities of tadpoles of 
Crinia sp. Tadpoles may have an important role in rock 
pools as competitors or predators and they are also 
known to increase the nutrient availability in a rock pool 
by processing the sediment (0.sborne & McLachlan 1985) 
and hence indirectly influence the primary productivity 
and richness of the community. Besides their ecological 
role, the presence of amphibians in rock pools also has 
serious implications for conservation. Amphibian 
diversity in Australia and on a global scale is declining 
dramatically (Fechmann & Wilbur 1994). When 
evaluating the conservation value of a rock pool system, 
attention should be devoted to the presence and diversity 
of amphibian populations. 
The cumulative richness curve shows that the most 
common species are collected after sampling about 10 
pools. This was the sampling intensity used by Finder et 
al. (2000) and it provides information on the core species 
of the system and allows a good estimate of the total 
richness on these outcrops. If more complete information 
is needed on the diversity in a rock pool system, a large 
number of additional pools should be sampled. Most of 
the rare species collected on Wave Rock occurred in one 
of the deeper (and often also larger) pools with more 
permanent inundation, indicating that for an intensive 
sampling campaign aimed at finding the rare species in a 
rock pool system, it is best to focus on these deeper and 
larger pools, if present. However it should be noted that 
most of the rare species occurring in the pools with a 
longer inundation cycle are insects (e.g., almost all were 
beetles and odonates) and appear to be generalist species 
of temporary habitats, also occurring in other types of 
freshwater wetlands. The later are declining in 
availability in the Wheatbclt of WA (Halse et al., 2003), 
so that gnammas are becoming more important in their 
survival, but it is the crustaceans unique to gnammas for 
which this habitat should be evaluated to establish the 
primary conservation value. 
As shown above, the rock pools and the entire rocky 
outcrops are unique habitats with a high diversity of 
specialist and endemic species. Frotection of these 
habitats is essential but establishment of a conservation 
strategy will not be straightforward (Mawson 2000). The 
strong isolation of the communities on these outcrops 
potentially makes them sensitive for extinctions through 
140 
