Hotspots of subterranean biodiversity in caves and wells

Abstract

We documented 18 caves and two karst wells that have 20 or more stygobites and troglobites. Crustacea dominated the aquatic fauna. Taxonomic composition of the terrestrial fauna varied, but Arachnida and Insecta together usually dominated. Geographically, the sites were concentrated in the Dinaric Karst (6 caves). Sites tended to have high primary productivity or rich organic input from the surface, be large caves, or have permanent groundwater (phreatic water). Over the past few years, there has been a growing aware-ness and concern with biodiversity worldwide. Books and monographs with a focus on biodiversity have appeared (e.g., Wilson 1992; Master et al. 1998) and a rapidly increasing amount of information is available about patterns of biodiver-sity for many groups of organisms. The same can be said for the fauna of caves and other subterranean habitats. Tabulations and often lists of cave and subsurface-limited species are avail-able for many countries in Stygofauna Mundi (Botosaneanu 1986) and in the multi-volume Encyclopaedia Biospeologica published by the Societe de Biospeologie in Moulis, France. Extensive lists of the caves and wells in which a particular sub-terranean species is found have been published. Prominent examples include Virginia (Holsinger & Culver 1988), the Iberian Peninsula (Belles 1987), and Slovenia (Bole et al. 1993). While not as well studied as temperate areas, similar information exists for many tropical regions (Peck & Finston 1993; Deharveng & Bedos 2000). Understanding patterns of subterranean biodiversity requires an understanding of regional patterns. In general, the number of species found in any one cave or subsurface site is small relative to the number of species in the region. Cave habitats (as opposed to small cavity, interstitial habitats such as the underflow of rivers) are especially fragmented, with differ-ent species occurring in caves only a few kilometers apart. For example, of the more than 500 caves biologically investigated in West Virginia, the maximum number of obligate species in any cave is 14, but the state, with a karst area of 2500 km², has 76 obligate species. It is the documentation of these regional patterns and their explanation that is one of the major tasks of speleobiologists over the next several decades (Peck & Finston 1993; Sket 1999a). Nevertheless, it is important not to neglect diversity pat-terns at individual sites. Even though most subterranean bio-diversity results from the accumulation of different species from nearby sites, there are some outstanding examples of high biodiversity from individual caves and wells that are worth documenting. Protection and concern for the subterranean fauna of a region often begin with protection and concern for a particular cave. It is, after all, individual caves and wells that provide the building blocks for regional biodiversity. The purpose of this short communication is to enumerate those caves and wells that are particularly rich in subterranean species and to offer some preliminary explanations for these biodiversity hotspots, both in terms of their geographic distri-bution and in terms of the types of sites. We use the terms troglobite for terrestrial, cave-limited species and stygobite for aquatic, cave-limited species. Stygobites also include intersti-tial species but they are not considered here.

Full text

Journal of Cave and Karst Studies, April 2000 • 11
David C. Culver and Boris Sket - Hotspots of Subterranean Biodiversity in Caves and Wells. Journal of Cave and Karst Studies 62(1):11-17.
HOTSPOTS OF SUBTERRANEAN
BIODIVERSITY IN CAVES AND WELLS
DAVID C. CULVER
Department of Biology, American University, 4400 Massachusetts Ave., NW, Washington, DC 20016, USA,
dculver@american.edu
BORIS SKET
Department of Biology, Biotechnical Faculty, University of Ljubljana, P.O. Box 2995, 1001 Ljubljana, SLOVENIA,
b.sket@uni-lj.si
We documented 18 caves and two karst wells that have 20 or more stygobites and troglobites. Crustacea
dominated the aquatic fauna. Taxonomic composition of the terrestrial fauna varied, but Arachnida and
Insecta together usually dominated. Geographically, the sites were concentrated in the Dinaric Karst (6
caves). Sites tended to have high primary productivity or rich organic input from the surface, be large
caves, or have permanent groundwater (phreatic water).
Over the past few years, there has been a growing aware-
ness and concern with biodiversity worldwide. Books and
monographs with a focus on biodiversity have appeared (e.g.,
Wilson 1992; Master et al. 1998) and a rapidly increasing
amount of information is available about patterns of biodiver-
sity for many groups of organisms. The same can be said for
the fauna of caves and other subterranean habitats. Tabulations
and often lists of cave and subsurface-limited species are avail-
able for many countries in Stygofauna Mundi (Botosaneanu
1986) and in the multi-volume Encyclopaedia Biospeologica
published by the Societe de Biospeologie in Moulis, France.
Extensive lists of the caves and wells in which a particular sub-
terranean species is found have been published. Prominent
examples include Virginia (Holsinger & Culver 1988), the
Iberian Peninsula (Belles 1987), and Slovenia (Bole et al.
1993). While not as well studied as temperate areas, similar
information exists for many tropical regions (Peck & Finston
1993; Deharveng & Bedos 2000).
Understanding patterns of subterranean biodiversity
requires an understanding of regional patterns. In general, the
number of species found in any one cave or subsurface site is
small relative to the number of species in the region. Cave
habitats (as opposed to small cavity, interstitial habitats such as
the underflow of rivers) are especially fragmented, with differ-
ent species occurring in caves only a few kilometers apart. For
example, of the more than 500 caves biologically investigated
in West Virginia, the maximum number of obligate species in
any cave is 14, but the state, with a karst area of 2500 km², has
76 obligate species. It is the documentation of these regional
patterns and their explanation that is one of the major tasks of
speleobiologists over the next several decades (Peck & Finston
1993; Sket 1999a).
Nevertheless, it is important not to neglect diversity pat-
terns at individual sites. Even though most subterranean bio-
diversity results from the accumulation of different species
from nearby sites, there are some outstanding examples of high
biodiversity from individual caves and wells that are worth
documenting. Protection and concern for the subterranean
fauna of a region often begin with protection and concern for a
particular cave. It is, after all, individual caves and wells that
provide the building blocks for regional biodiversity.
The purpose of this short communication is to enumerate
those caves and wells that are particularly rich in subterranean
species and to offer some preliminary explanations for these
biodiversity hotspots, both in terms of their geographic distri-
bution and in terms of the types of sites. We use the terms
troglobite for terrestrial, cave-limited species and stygobite for
aquatic, cave-limited species. Stygobites also include intersti-
tial species but they are not considered here.
M
ETHODS AND MATERIALS
We used an arbitrary cutoff of 20 or more obligate subter-
ranean species for a site to be included. This resulted in a man-
ageable number of sites to enumerate, representing less than
one-tenth of one per cent of the sites sampled. We limited our
attention to large cavities—caves and wells that intersect large
cavities. According to Curl (1964), proper caves are large
enough for humans to enter (and proper entrances are
entrances large enough for humans to enter). We restricted our
attention to proper caves, whether they do or do not have prop-
er entrances, since many wells in carbonate rock intersect
proper caves that lack proper entrances. What constitutes a
single cave is a matter of considerable debate and confusion.
We restricted our attention to connected voids, either water- or
air-filled, regardless of how many separate entrances or names
Dokumentirala sva 18 jam in dva kraška vodnjaka, iz katerih je znanih 20 ali vec vrst troglobiontov in
stigobiontov. V vodni favni preladujejo raki. Taksonomski sestav kopenske favne je raznolik, vendar
pajkovci in zuzelke skupaj navadno prevladujejo. Najvec takšnih jam (šest) je v Dinarskem krasu.
Nadpovprecno so zastopane jame z lastno primarno produkcijo ali bogatim vnosom hrane s površja,
obsezne jame in jame, ki vkljucujejo tudi freatsko plast.

12 • Journal of Cave and Karst Studies, April 2000
HOTSPOTS OF SUBTERRANEAN BIODIVERSITY IN CAVES AND WELLS
the cave had. We specifically excluded porous aquifers—they
have been less thoroughly studied and are likely to have a pat-
tern very different than that of proper caves. We also exclud-
ed the few known fungal parasites.
In order to generate the list, we consulted with many col-
leagues throughout the world with the request for information
about any particular cave or well fauna. We consulted avail-
able species lists from throughout the world. An Excel file of
the species list is available from the authors. We are aware of
the fact that a number of caves may be missing from our list
because we lack a faunal list. We also expect some species to
be shown eventually not to be limited to caves. However, none
of the sites enumerated here is likely to be excluded from the
list owing to such changes.
R
ESULTS
Eighteen caves and two wells have 20 or more obligate
species. Of the 20 sites, fourteen are from Europe (five of
them from Slovenia and five from France), three from North
America, one from Australia, one from southeast Asia, and one
from an island in the Atlantic (Fig. 1). The major taxonomic
composition of these faunas is listed in Table 1. Each site is
briefly described below.
San Marcos Spring, Texas, USA—This artesian spring
serves as an exit point for water from the Edwards Aquifer.
Two-thirds of its aquatic species are crustaceans, of which 11
are amphipods (Holsinger & Longley 1980, Table 1).
Endemism is high, with 11 endemics representing 40% of the
fauna. The aquifer itself is about 280 km long and 8-64 km
wide. Oil and peat deposits above the aquifer may be the pri-
mary energy input into the system (Longley 1981). The
aquifer is threatened by excessive drawdown, both by agricul-
tural interests and the City of San Antonio.
Shelta Cave, Alabama, USA—Slightly over 700 m long,
Shelta Cave consists of three large rooms of considerable vol-
ume that intersect permanent groundwater. Pioneering biolog-
ical studies by Cooper (1975) led to the purchase of the
entrance sink by the National Speleological Society. Half of
the species are aquatic (Table 1). No group dominates the ter-
restrial fauna, but crustaceans dominate the aquatic fauna.
Installation of a bat-unfriendly gate apparently led not only to
a loss of bats, but to a major decline in the population sizes of
the aquatic species (Hobbs & Bagley 1989; Culver 1999).
Mammoth Cave, Kentucky, USA—Mammoth Cave is the
longest known cave in the world, with over 500 km of sur-
veyed passages. Most of the cave is within the boundaries of
Mammoth Cave National Park. It rivals the Postojna-Planina
Cave system of Slovenia in the amount of study devoted to the
biota. Major discussions of the fauna of Mammoth Cave
include Packard (1888), Barr (1967), and Poulson (1992).
One-third of the fauna is aquatic, two-thirds terrestrial.
Figure 1. Location of hotspots of subterranean biodiversity: 1—San Marcos Spring,Texas; 2—Shelta Cave,Alabama; 3—
Mammoth Cave, Kentucky; 4—Walsingham Caves, Bermuda; 5—Triadou Wells, France; 6—Baget/Grotte de Sainte
Catherine, France; 7—Goueil di Her/Reseau Trombe, France; 8—Résurgence de Sauve/Vidourle souterrain, France; 9—
Cent-fons, France; 10—Grotta dell’Arena, Italy; 11—Buso della Rana, Italy; 12—Sistem Postojna-Planina; 13—Šica-Krka
Sistem, Slovenia; 14—Jama Logarcek, Slovenia; 15—Grad (Osapka Jama), Slovenia; 16—Krizna Jama, Slovenia; 17—
Vjetrenica Jama, Bosnia & Hercegovina; 18: Pestera de la Movile, Romania; 19—Salukkang-Kallang/Towakkalak,
Indonesia; 20—Bayliss Cave, Australia.

Journal of Cave and Karst Studies, April 2000 • 13
CULVER AND SKET
Taxonomically, arachnids dominate the terrestrial fauna and
crustacea dominate the aquatic fauna (Table 1). Noteworthy is
the co-occurrence of five species of trechine beetles in the
closely related genera Neaphaenops and Pseudanophthalmus.
Walsingham Caves, Bermuda—This complex of anchiha-
line caves (ones with a direct connection to the sea), including
Walsingham Sink Cave, Walsingham Cave, and Tuckers Town
Cave, is ~1 km long, with most of the passages submerged.
With a freshwater lens and a redox boundary between fresh
and saltwater, Walsingham Cave likely has considerable sec-
ondary and possibly primary productivity. The fauna is entire-
ly aquatic and dominated by Crustacea from many orders (Sket
& Iliffe 1980, Table 1). Some of the micro-crustacean species
may occur outside the hypogean realm.
Triadou Wells, France—Two wells (F1 and P1) only a few
meters apart in the Lez Basin in southern France at a depth of
50 m yielded a variety of stygobites, especially crustaceans
(Malard et al. 1994, Table 1). Located in a major karst area,
the wells tap a network of fissures and solution tubes begin-
ning at a depth of ~35 m.
Baget—Sainte Catherine System, France—This subter-
ranean system is situated in the Pyrenees, near Moulis, in the
small valley of Lachein. The basin occupies an area of 13.25
km². The object of intense study by R. Rouch and his col-
leagues for more than 20 years (e.g., Rouch & Danielopol
1997), three components have been extensively sampled—the
outlet of the subterranean stream, a mostly flooded conduit
(Aven de la Peyrere), and Grotte de Sainte-Catherine. The
aquatic fauna is especially diverse, with 21 species of
Crustacea (Table 1).
Goueil di Her/Reseau Trombe, France—The Trombe sys-
tem is located in the Pyrenees in the Arbas Massif. The sub-
terranean system consists of over 100 km of air- and water-
filled passages, with numerous pits providing access to the
submerged part of the system. The most extensively studied
part of the system is Goueil di Her and its resurgence. The ter-
restrial and aquatic fauna are about equally diverse (Table 1),
with Crustacea and Coleptera predominating.
Resurgence de Sauve and subterreanean Vidourle,
France—The fountain of Sauve, near Montpelier, is the resur-
gence of the subterranean Vidourle River, which drains about
75 km² of area. The fountain is well known on account of the
violence of its floods. Twenty stygobites have been collected
from the watercourse, and most of these are crustaceans
(Juberthie & Juberthie-Jupeau 1975, Table 1).
Cent-fons, France—The cave, which is flooded, and its
resurgence are located at the southern border of the Massif
Central. There are ten resurgences. The populations are
diverse (Table 1) and abundant—about 16,500 crustaceans
have been ejected out of the resurgence in ten weeks (C.
Juberthie, pers. comm., October, 1999).
Grotta dell’Arena, Italy—This fossil cave is located in an
alpine pasture (1512 m msl) and consists of a single large
gallery less than 100 m long with the floor covered by large
blocks of limestone. Percolating water forms some small, per-
manent pools at the end of the gallery. The stygobitic fauna
consists of six, mostly tiny crustaceans (Table 1). Beetles and
archnids dominate the richer terrestrial fauna.
Cave Buso della Rana, Italy—This large and complex cave
system, with more than 20 km of passage, shows a high habi-
tat diversity, with an alternation of inactive and active branch-
es. A small permanent brook flows along the main passage and
emerges at the entrance. During the rainy season, most of the
cave may be flooded. Crustaceans dominate the aquatic fauna
(Table 1). None of the terrestrial groups is particularly diverse.
Grad (Osapska Jama), Slovenia—The entrance is a boiling
spring with 1070 m of passage accessible during the dry sea-
son. After rains, the water can rise 50 m and flood most of the
cave. There is no connection with a surface stream except at
the periodically emerging spring. Terrestrial fauna is largely
un-investigated, and the stygobitic fauna includes 17 crus-
taceans (including two amphibious Oniscoidea) and among
them the large cirolanid isopod Sphaeromides virei (Brancelj
1992, Table 1).
Krizna Jama, Slovenia—This is a hydrologically active but
nevertheless beautifully decorated cave of more than 8000 m
length. It is isolated from permanent surface rivers and, there-
fore, has very few non-stygobitic animals. The fauna is very
scarce but species rich. Crustaceans (Table 1) dominate the
rich aquatic fauna. Remarkable is the high number of gas-
tropods: 2 terrestrial and 6 aquatic species have been found.
Jama Logarcek, Slovenia—A multi-level cave with a river
in its deepest corridors; it measures 2300 m. It is situated close
to Postojna-Planina Cave System, but with less apparent habi-
tat diversity. Two-thirds of the fauna is aquatic, with gastropod
and crustacean species predominating (Table 1). There also is
an exceedingly rich epizoic ciliate protozoan fauna, described
from one specimen of the bizarre isopod Monolistra spinosis-
sima (Hadzi 1940).
Sistem Postojna-Planina, Slovenia—There are 17 km and 6
km of passages connected by 2 km of flooded corridors. The
sinking river in the main passages is inhabited by a rich assort-
ment of stygobites, stygophiles, and accidental surface species
(Sket 1979). Hydrologically inactive parts of the system con-
tain other aquatic and terrestrial habitats. This is the type
locality of a number of “first cave” animals, including the first
described troglobite, the beetle Leptodirus hochenwarti and
the European cave salamander, Proteus anguinus. It also is a
site of long-term ecological studies (Sket & Velkovrh 1981).
Slightly over half of the species are aquatic, with a rich crus-
tacean, snail and oligochaete fauna. Beetles dominate the ter-
restrial troglobitic fauna (Table 1). Some of the cave has been
heavily visited by tourists since 1818.
Šica-Krka Sistem, Slovenia—Šica-Krka Sistem consists of
two caves 1700 m and 250 m long, hydrologically connected
by 5 km of underground flow. This sinking river is inhabited
mostly by surface animals at the sink and mostly by stygobites
at the resurgence. Most parts of the cave are hydrologically
active and more than 70 percent of the cave fauna is aquatic,
primarily crustacean (Table 1).

14 • Journal of Cave and Karst Studies, April 2000
HOTSPOTS OF SUBTERRANEAN BIODIVERSITY IN CAVES AND WELLS
Higher Groups San Marcos Spring Shelta Cave Mammoth Cave Walsingham Caves Triadou Wells F1 & P1
TX, USA AL, USA KY, USA Bermuda France
AQUATIC
Protista: Ciliata (epizoic)
Cnidaria
Aschelminthes: Nematoda
Rotatoria
Nemertini
Turbellaria: Tricladida 1 1 2
Temnocephala
Annelida: Hirudinea
Oligochaeta 1 3
Polychaeta 4
Mollusca: 5 1 3 3
Crustacea: 18 8 11 29 28
Arachnida: Acarina 1
Insecta: 1
Vertebrata: Amphibia 2 1
Pisces 1
Aquatic Subtotal 27 12 15 37 34
TERRESTRIAL
Annelida: Oligochaeta
Mollusca: Gastropoda 1 1
Crustacea: Isopoda 1
Arachnida: 2 12
Symphyla:
Diplopoda: 1 2
Chilopoda:
Insecta: Collembola 2 4
Coleoptera 3 5
Other 2 2
Terrestrial Subtotal 12 26
TOTAL 27244137 34
Table 1. Taxonomic summary of stygobites and troglobites found in the 20 caves and karst wells. See Figure 1 for their
location.
Higher Groups
Baget—Ste. Catherine Goueil di Her Resurgence de Sauve Cent-fons Grotta dell’Arena
System Reseau Vidourle souterrain France Italy
France Trombe, France France
AQUATIC
Protista: Ciliata (epizoic)
Cnidaria
Aschelminthes: Nematoda
Rotatoria
Nemertini
Turbellaria: Tricladida 1
Temnocephala
Annelida: Hirudinea
Oligochaeta 1 1
Polychaeta
Mollusca: 2131
Crustacea: 21 11 14 20 6
Arachnida: Acarina 3 1
Insecta:
Vertebrata: Amphibia
Pisces
Aquatic Subtotal 24 14 20 22 6
TERRESTRIAL
Annelida: Oligochaeta
Mollusca: Gastropoda 1
Crustacea: Isopoda 1 1
Arachnida: 1 2 5
Symphyla:
Diplopoda: 1 2 1
Chilopoda:
Insecta Collembola 3 1
Coleoptera 4 6 6
Other
Terrestrial Subtotal 9 12 14
TOTAL 33262022 20

Higher Groups Buso della Rana Grad (Osapka Jama) Krizna Jama Jama Logarcek Sistem Postojna-Planina
Italy Slovenia Slovenia Slovenia Slovenia
AQUATIC
Protista:Ciliata (epizoic) 1 9 1
Cnidaria 1
Aschelminthes: Nematoda
Rotatoria
Nemertini
Turbellaria: Tricladida 1 1
Temnocephala 32
Annelida: Hirudinea 1
Oligochaeta 6 7
Polychaeta 1
Mollusca: 1167 8
Crustacea: 14 15 15 8 26
Arachnida: Acarina
Insecta:
Vertebrata: Amphibia 11
Pisces
Aquatic Subtotal 15 17 29 28 48
TERRESTRIAL
Annelida: Oligochaeta
Mollusca: Gastropoda 1 2 4 3
Crustacea: Isopoda 2 1 1 2
Arachnida: 1 4 3 9
Symphyla:
Diplopoda: 11 2
Chilopoda:
Insecta: Collembola 1 9
Coleoptera 3166 8
Other 1
Terrestrial Subtotal 5 3 16 15 36
TOTAL 20204543 84
Journal of Cave and Karst Studies, April 2000 • 15
CULVER AND SKET
Higher Groups
Sica-Krka Sistem Vjetrenica Jama Pestera de la Movile Salukkang Kallang Bayliss Cave
Slovenia Bosnia- Romania Towakkalak N. Queensland
Herzegovina Indoesia Australia
AQUATIC
Protista: Ciliata (epizoic)
Cnidaria 1 1
Aschelminthes: Nematoda 3 3
Rotatoria 2
Nemertini 1
Turbellaria: Tricladida 1 1
Temnocephala 3 3
Annelida: Hirudinea 1 1
Oligochaeta 1 2
Polychaeta 1
Mollusca: 6 8 1
Crustacea: 12 23 7 4
Arachnida: Acarina
Insecta: 1
Vertebrata: Amphibia 1 1
Pisces 2
Aquatic Subtotal 27 39 18 7
TERRESTRIAL
Annelida: Oligochaeta 1
Mollusca: Gastropoda 3 2
Crustacea: Isopoda 1343 2
Arachnida: 2 4 10 8 5
Symphyla: 1
Diplopoda: 3 1 3 4
Chilopoda: 1 3 1
Insecta: Collembola 1 3 4 1
Coleoptera 1641 3
Other 1 2 2 8
Terrestrial Subtotal 7 21 29 21 24
TOTAL 34604728 24

16 • Journal of Cave and Karst Studies, April 2000
HOTSPOTS OF SUBTERRANEAN BIODIVERSITY IN CAVES AND WELLS
Vjetrenica Jama in Popovo polje, Bosnia and
Hercegovina—This complex cave system has 7.6 km of pas-
sages, which include a number of small streams, pools, and
trickles of water. There are no sinking streams but there are
extensive opportunities for the import of organic debris
through crevices and shafts. About two-thirds of the fauna is
aquatic, and dominated by Crustacea (Pretner 1963, Sket
1999a, Table 1). Noteworthy are the amphibious catopid bee-
tle and amphipod species that occupy rock walls covered by a
film of water trickling from above (hygropetric habitat).
Movile Cave, Romania—Movile Cave is a small, mostly
water filled cave near the coast of the Black Sea. Slightly more
than a third of its fauna is aquatic. No one taxonomic group
dominates either the aquatic or terrestrial fauna (Table 1), and
the fauna, as a whole, has the remarkably high level of over
65% endemism (Sarbu 2000). Extensive chemoautotrophic
production occurs in the cave system (Sarbu, Kane et al. 1996).
The cave is threatened by extensive trash dumping in the sink-
hole in which the entrance is located.
Gua Salukkan Kallang—Towakkalak, Indonesia—This
immense river cave system has over 20 km of passage, a large
bat population, and 25% of the obligate cave fauna is aquatic.
Comprising mostly undescribed species, crustaceans predomi-
nate in the aquatic fauna and arachnids in the terrestrial cave
fauna (Deharveng & Bedos 2000, Table 1).
Bayliss Cave, Australia—Bayliss Cave is a small (900 m)
cave formed in lava. It is a “bad-air” cave, with up to 200
times the ambient atmospheric level of carbon dioxide
(Howarth & Stone 1990), likely the result of in situ production
of CO
2 from the oxidation of organic matter (James 1977).
The cave-limited fauna is entirely terrestrial with no one group
dominating (Table 1).
D
ISCUSSION
It is worthy reiterating that, compared to surface habitats,
diversity in caves is low (Sket 1999a) and that most diversity
in caves and wells is expressed regionally rather than locally.
Sket (1999a) gives a variety of reasons for the low diversity
compared to surface habitats, including reduced area of eco-
tonal regions between surface and subsurface, reduced subter-
ranean habitat diversity, and reduced food resources. The frag-
mented nature of the cave habitat and restricted opportunities
for dispersal keep local diversity much lower than regional
diversity.
One obvious difference, even among the caves and wells
listed in Table 1, is the breadth of taxonomic scrutiny. In only
a scattering of caves have epizoic ciliates been collected, let
alone described (Walsingham Cave and Logarèek Cave in
Table 1). Likewise, microcrustaceans have not been collected
from all sites; even those listed in Table 1. It seems that
Copepoda in North American subterranean waters have been
nearly completely ignored. Nonetheless, most of the species in
all sites listed in Table 1 are easily observed and collected.
What in the way of generalities can be gleaned from the list
of caves and wells with high species diversity? First, there is
a remarkable concentration of sites in the Dinaric karst of
Slovenia, Croatia, and Bosnia-Herzegovina, which is also the
richest region of subterranean biodiversity (Sket 1999b). This
is particularly evident in the stygobitic fauna. Of the ten sites
with 25 or more stygobites (Table 1), six are in the Dinaric
karst. France also has a concentration of sites, although, in
general, diversity at these sites is slightly less than that at
Dinaric karst sites. Sket (1996) points out that the Dinaric
Karst in general, and the Slovenia karst in particular, is exten-
sive in areal extent and with a rich geologic history. Poulson
(1992) makes a similar argument for Mammoth Cave. Second,
sites with high productivity, especially chemoautotrophy, com-
pared to other subsurface sites are well represented. These
include Washingham Cave, Movile Cave, Bayliss Cave, and
San Marcos Springs. Such high productivity caves are rare.
This reinforces the widely held view that caves are resource
poor (e.g. Sket 1999a). Gua Salukkang Kallang Towakkalak
and Sistem Postojna-Planina also can be counted as caves with
high (secondary) productivity, but the scarcity of high diversi-
ty caves in the tropics is still a puzzle. Another example of a
high diversity cave with high productivity is Cabaret Cave in
Western Australia. This small cave has extensive root mats
penetrating the aquatic habitat, with over 40 species in a 20 m
reach of stream (Jasinska et al. 1996; Jasinska & Knott 2000).
We did not include it in the list of hotspots because the major-
ity of species are probably not strictly stygobitic.
Nevertheless, it is a striking example of high diversity in a very
small cave. Third, caves and wells that intersect the perma-
nently saturated (phreatic) zone also are well represented.
These include Movile Cave, Shelta Cave, San Marcos Spring,
all six caves in the Dinaric karst, and all six caves in France.
This is an especially intriguing result, and suggests that there
are a great many undiscovered species at such sites. Finally,
many of the caves are long caves. Seven of the caves listed in
Table 1 (Mammoth Cave, Buso della Rana, Krizna Jama,
Sistem Postojna-Planina, Vjetrenica Jama, Reseau Trombe,
and Gua Salukkan Kallang—Towakkalak) are over 5 km long,
yet less than 1% of caves are this long, at least based on U.S.
cave data (Culver, unpublished). A longer cave usually means
a higher number of different habitats.
More complete explanations of the patterns of subterranean
biodiversity must await a more detailed regional analysis, but
we hope that this report sparks an increased interest in hotspots
of subterranean biodiversity.
A
CKNOWLEDGMENTS
Several colleagues, including T. Iliffe, C. Juberthie, S.
Sarbu, J. Holsinger, T. Kane, S. Peck, and F. Stoch, helped with
the compilation of the lists. F. Stoch provided descriptions of
the Italian caves and C. Juberthie provided descriptions of the
French caves. C. Belson provided Figure 1.

Journal of Cave and Karst Studies, April 2000 • 17
CULVER AND SKET
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