o_19ko2dt161ng2j4e1tgnoqv1s45a.pdf

MALAYSIAN FRESHWATER CRABS: CONSERVATION PROSPECTS AND CHALLENGES
LC status was awarded to taxa that were evaluated against the criteria and did not qualify for
CR, EN, VU or NT; in general, these taxa are widespread (Extent of Occurrence greater than
20,000 km 2 ) and abundant.
RESULTS
The results are presented in Table 1, which is a checklist of the freshwater crabs of Malaysia,
showing available data relevant to the IUCN (2001) Red List criteria together with the
conservation outcomes. The assessment shows that of the 102 Malaysian species known, 16
taxa are Critically Endangered, 46 Endangered, 28 Vulnerable, 10 of Least Concern and 2 are
Data Deficient. None of the species evaluated here qualified for the Near Threatened category
as defined above.
DISCUSSION
Based on the conservation status assigned to the Malaysian freshwater crabs in the present
study, a few patterns have emerged that should be noted. The restricted distributions of most
of the freshwater crab species in Malaysia pose serious problems for conservation. It is
somewhat fortunate that the species with the most restricted distributions are those which
inhabit offshore islands or mountains (see later, however). These areas are generally less
disturbed or not scheduled for development, at least for the moment. The serious loss of
natural forest as a result of land development and agriculture has generally affected the lowlands
more severely. The species which do occur in lowlands, e.g., Parathelphusa maculata and
Sayamia sexpunctata, are still common in relatively unpolluted plantation waterways and
ricefields. These lowland species also have relatively much wider distributions, and are least
at risk. Ten species (e.g., Perithelphusa borneensis) reported here with an Extent of Occurrence
of approximately 1,500 to 2,000 km 2 are categorized as Least Concern. Aquatic species (e.g.,
Isolapotamon collinsi and Thelphusula baramensis) in general appear to be faring better than
their terrestrial kin, as only 22 out of 51 primarily aquatic species (43%) are categorized under
Critically Endangered or Endangered. On the other hand, terrestrial or semi-terrestrial species
like Geosesarma katibas and Thelphusula granosa seem to be under much greater threat, with
36 out of 47 such species (77%) being regarded as Critically Endangered or Endangered.
Perhaps not surprisingly, the results also indicate that specialist species, e.g., the obligate
cave-dwelling crab, Cerberusa caeca, are also more threatened, with most such taxa being
Critically Endangered or Endangered. Interestingly, highland taxa, despite their relative
inaccessibility, seem to also be at higher risk, with all 10 highland species in Peninsular Malaysia
(e.g., Johora grallator) being Critically Endangered or Endangered. Many of the potamids
and smaller parathelphusids are especially vulnerable to development and pollution. The limited
distribution of most of these species with very restricted ranges is not an anomaly. Johora
johorensis for example, is only known from Gunung Pulai, and despite much collecting around
the hill and other areas, has not been recorded elsewhere. In neighbouring hills, it is replaced
by two very different taxa: J. intermedia to the north and J. murphyi to the east. Any
development of Gunung Pulai would thus have dire consequences for J. johorensis. Finally,
the isolated nature of small islands also appears to put the island endemic species at a
disadvantage, as illustrated by the eight species (five Johora, one Parathelphusa, two
Geosesarma) known only from Pulau Tioman, all of which are regarded as Endangered.
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