Not Knowing, Not Recording, Not Listing: Numerous Unnoticed Mollusk Extinctions

Abstract and Figures

Mollusks are the group most affected by extinction according to the 2007 International Union for Conservation of Nature (IUCN) Red List, despite the group having not been evaluated since 2000 and the quality of information for invertebrates being far lower than for vertebrates. Altogether 302 species and 11 subspecies are listed as extinct on the IUCN Red List. We reevaluated mollusk species listed as extinct through bibliographic research and consultation with experts. We found that the number of known mollusk extinctions is almost double that of the IUCN Red List. Marine habitats seem to have experienced few extinctions, which suggests that marine species may be less extinction prone than terrestrial and freshwater species. Some geographic and ecologic biases appeared. For instance, the majority of extinctions in freshwater occurred in the United States. More than 70% of known mollusk extinctions took place on oceanic islands, and a one-third of these extinctions may have been caused precipitously by introduction of the predatory snail Euglandina rosea. We suggest that assessment of the conservation status of invertebrate species is neglected in the IUCN Red List and not managed in the same way as for vertebrate species.
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Contributed Paper
Not Knowing, Not Recording, Not Listing: Numerous
Unnoticed Mollusk Extinctions
eum National d’Histoire naturelle, D´
epartement Syst´
ematique et Evolution—Malacologie—USM 602, Case postale 51,
55 rue Buffon, 75231 Paris, Cedex 05, France
eum National d’Histoire naturelle, UMR 5173—Conservation des Esp`
eces, Suivi et Restauration des Populations D´
Ecologie et Gestion de la Biodiversit´
e Mus´
eum National d’Histoire Naturelle CP 51, 55 rue Buffon, 75005 Paris, France
Abstract: Mollusks are the group most affected by extinction according to the 2007 International Union for
Conservation of Nature (IUCN) Red List, despite the group having not been evaluated since 2000 and the
quality of information for invertebrates being far lower than for vertebrates. Altogether 302 species and 11
subspecies are listed as extinct on the IUCN Red List. We reevaluated mollusk species listed as extinct through
bibliographic research and consultation with experts. We found that the number of known mollusk extinctions
is almost double that of the IUCN Red List. Marine habitats seem to have experienced few extinctions, which
suggests that marine species may be less extinction prone than terrestrial and freshwater species. Some
geographic and ecologic biases appeared. For instance, the majority of extinctions in freshwater occurred in
the United States. More than 70% of known mollusk extinctions took place on oceanic islands, and a one-third
of these extinctions may have been caused precipitously by introduction of the predatory snail Euglandina
rosea. We suggest that assessment of the conservation status of invertebrate species is neglected in the IUCN
Red List and not managed in the same way as for vertebrate species.
Keywords: conservation status, extinction, geographic bias, islands, IUCN Red List, mollusk, taxonomic bias
No Conocer, No Registrar, No Enlistar: Numerosas Extinciones de Moluscos No Detectadas
Resumen: De acuerdo con la Lista Roja IUCN (Uni´
on Internacional para la Conservaci´
on de la Naturaleza)
2007 los moluscos son el grupo m´
as afectado por la extinci´
on, no obstante que el grupo no ha sido evaluado
desde 2000 y que la calidad de la informaci´
on para invertebrados es mucho menor que para vertebrados.
En total, la Lista Roja IUCN incluye 302 especies y 11 subespecies consideradas extintas. Reevaluamos las
especies de moluscos enlistadas como extintas mediante una investigaci´
on bibliogr´
afica y la consulta con
expertos. Encontramos el que n´
umeros de extinciones de moluscos conocidas es casi el doble del que se˜
la Lista Roja IUCN. Los h´
abitats marinos parecen haber experimentado pocas extinciones, lo que sugiere que
las especies marinas pueden ser menos propensas a la extinci´
on que las especies terrestres y dulceacu´
Aparecieron algunos sesgos geogr´
aficos y ecol´
ogicos. Por ejemplo, la mayor´
ıa de las extinciones en agua
dulce ocurrieron en los Estados Unidos, Mpas de 70% de las extinciones de moluscos conocidas se llevaron a
cabo en islas oce´
anicas, y un tercio de esas extinciones pueden haber sido precipitadas por la introducci´
del caracol depredador Euglandina rosea. Sugerimos que la evaluaci´
on del estatus de conservaci´
on de es-
pecies invertebradas est´
a descuidada en la Lista Roja IUCN y no es manejada de la misma manera que
Palabras Clave: estatus de conservaci´
on, extinci´
on, islas, Lista Roja IUCN, molusco, sesgo geogr´
afico, sesgo
Paper submitted July 4, 2008; revised manuscript accepted December 11, 2008.
Conservation Biology, Volume 23, No. 5, 1214–1221
2009 Society for Conservation Biology
DOI: 10.1111/j.1523-1739.2009.01245.x
egnier et al. 1215
Conservation strategies require knowledge about
extinction-prone groups and good estimates of extinc-
tion risk. The International Union for Conservation of
Nature (IUCN) Red List has become an essential source
of information for conservation action and is widely rec-
ognized as the most comprehensive compilation of ex-
tinct and threatened species (Mace & Lande 1991; Ro-
drigues et al. 2006). Yet IUCN figures do not reflect the
current trend of great losses of biodiversity (Mace 1995;
Lamoreux et al. 2003). The IUCN Red List (IUCN 2007)
shows that 850 species have become extinct since 1500,
which is fewer than two species per year and is the same
order of magnitude of extinctions as background extinc-
tion rates estimated from the fossil record (May et al.
1995). Moreover, there is a huge taxonomic bias in the
assessment of species’ conservation status. According to
Baillie et al. (2004), the conservation status of almost
90% of mammal species and of all bird and amphibian
species has been evaluated, whereas only 3% of mollusk
species and 0.08% of insect species have been assessed.
Indeed, invertebrates receive much less attention than
vertebrates, and our knowledge of them is sparse (Gas-
ton & May 1992; McKinney 1999).
With 302 species and 11 subspecies listed as extinct,
mollusks are the group paying the most severe docu-
mented tribute to the crisis according to IUCN figures
(302 vs. 271 for all terrestrial vertebrates). In this context
mollusks represent an interesting group through which
to address several questions regarding the representative-
ness of the IUCN Red List. What proportion of species
that are known to be extinct by specialists is captured by
the IUCN Red List? Where are the main gaps in terms of
geographical distribution and biomes? Extinct mollusks
on the IUCN Red List have not been evaluated and as-
sessed since 1996, except for 82 North American species
evaluated in 2000. Is this lack of assessment due to the
fact that there have been no other mollusk extinctions
since then, or are mollusks simply not listed? If the latter,
why are they not listed?
Throughout this paper, we focus on extinct species only
and do not deal with species listed as threatened. We re-
viewed all mollusk species listed as extinct on the IUCN
Red List by contacting the assessors of each species and
asking them to provide the source of information that
led to the listing or to a downgrading to threatened sta-
tus if appropriate. As far as possible, we obtained a pub-
lished reference supporting the status for each species.
If no reference was available, we noted the justification
as personal communication. We provisionally considered
species listed as extinct for which we could find no pub-
lished reference to support this status.
We scanned selected references for unlisted cases of
extinct species. These were taxonomic papers (Abdou
& Bouchet 2000; Griffiths & Florens 2004), conserva-
tion papers (Whitten et al. 1987; Fontaine et al. 2007),
and regional checklists of species. This resulted in an
expanded list with additions of extinct (EX) or possi-
bly extinct (PoEX) species. We listed as PoEX species
that may have gone extinct but for which no recent
field surveys had confirmed this, and species cited as
extinct in the literature without any details provided to
support this assertion. This category is not recognized
by the IUCN; rather, these species are listed as criti-
cally endangered with a flag of possibly extinct or as
data deficient (IUCN 2001), depending on the case. We
also listed as PoEX species whose systematic validity was
not clearly established, such as possible synonyms or
For all listed species (those on the IUCN Red List and
those newly assessed as extinct), we asked experts (listed
in the Acknowledgments) to
confirm or contradict the validity of the species listed,
supported by literature references or as personal com-
munication. (Of special interest were cases in which a
taxon was treated by some authors as a valid species
and by others as a valid subspecies or synonym. Our
goal was to distinguish taxonomic extinction from true
confirm or contradict the conservation status of the
species on our list, again supported by literature ref-
erences or supported by as personal communication;
identify species omitted from the expanded list.
Altogether 302 mollusk species and 11 subspecies were
originally listed as extinct on the 2007 IUCN Red List.
Of these, experts recognized 33 species and two sub-
species as still extant. Twenty-seven of these species had
been recently rediscovered in the field, and eight had
to be considered as taxonomic extinctions (synonyms of
other species that still survive). Only 269 species and nine
subspecies were correctly listed as extinct on the IUCN
Red List. Information from the literature and the experts
provided 263 new cases of extinct species and 25 of ex-
tinct subspecies; 17 others had initially been included as
extinct, based on the literature but were removed follow-
ing expert consultation. The full list of extinct mollusk
species and subspecies is available on request from C.R.
New cases of mollusk extinctions should be taken into
account in future releases of the IUCN Red List (M.B.
Seddon, personal communication).
Conservation Biology
Volume 23, No. 5, 2009
1216 Unnoticed Mollusk Extinctions
Figure 1. Geographical distribution of extinct mollusks: Pacific islands (Hawaii, French Polynesia, American
Samoa, Clipperton, Cook Islands, Fiji, Guam, New Caledonia, Mariana Islands, Pitcairn Islands), North America
(United States, Canada), Asia (China, India, Indonesia, Japan, Malaysia, Pakistan, Philippines, Vietnam),
Mascarene Islands (Mauritius, Reunion, Rodrigues), Europe (Austria, Croatia, France, Greece, Montenegro,
Portugal, Serbia), West Indies (Antilles, Cuba, Guadeloupe, Haiti, Jamaica, Martinique, Trinidad), South/Central
America (Argentina, Brazil, Columbia, Ecuador, Mexico, Paraguay, Venezuela), Oceania (Australia, Norfolk
Islands), Macaronesia (Canary Islands, Madeira), Africa (South Africa, Mayotte), others (Bermuda, Israel, Saint
Helena, Seychelles).
Known extinctions of mollusks were unevenly dis-
tributed among geographical areas. The two most im-
portant groups in terms of extinction figures were North
American and Pacific Island species (Fig. 1). All North
American, European, Japanese, and Australian mollusk
extinctions were documented by researchers native to
each of these countries. Among the 334 extinct species
native to countries other than the United States, Europe,
Japan, and Australia, 26% were recorded by North Amer-
ican researchers, 54% by Europeans, and 15% by Aus-
tralians. We documented few extinctions among marine
mollusk species (Fig. 2): only four cases of 566 despite
a wide search by a large number of people (shell collec-
tors). If extinctions had occurred, some would have been
Among the 140 freshwater extinctions we documen-
ted, 83 occurred in the United States (Fig. 3), including
50 in the Alabama River system (Alabama, Cahaba, Coosa,
and Mobile rivers). Balkan species represented another
important group of extinct freshwater mollusks. We
recorded 29 extinctions in this region (Fig. 3). For fresh-
water too, geographical biases were important. Apart
from the two main groups of extinctions (United States
and Balkans), freshwater extinctions were recorded in
small numbers in only a few areas (Fig. 3). This imbal-
ance may be due to a sampling or study artifact. Of
27 known areas of special importance for freshwater
mollusk diversity (Strong et al. 2008), 17 lacked data
on species conservation status, including African great
lakes, Madagascar, and lakes and river basins in Southeast
Another important component of freshwater mol-
luskan biodiversity that remains mostly unknown and for
which very few data were available in terms of species
conservation status is the spring and groundwater snails.
Among the 566 extinct mollusk species, 400 are from
oceanic islands, representing 71% of all listed mollusk ex-
tinctions. And among these 400 extinct mollusk species,
Figure 2. Number of extinct mollusk species (left)
compared with the number of described species in
marine, freshwater, and terrestrial biotas (right)
(after Bouchet & Lydeard et al. 2004).
Conservation Biology
Volume 23, No. 5, 2009
egnier et al. 1217
Figure 3. Geographical origin and number of extinct
freshwater mollusks.
327 are endemic to the most isolated islands of the world
(UNEP 1998), as ranked by an index of isolation based
on distances to the nearest island, island group, and
continent. The listed extinct island species are mostly
from Hawaii, French Polynesia, and the Mascarene Is-
lands (Fig. 1), where research is very active, and this
introduces a geographical bias within the listing of ex-
tinct island species. Of the 400 extinct species we listed
from oceanic islands, 234 lived on islands to which Eu-
glandina rosea had been introduced, and it is highly
probable that of these 234 extinctions, 134 of them were
ultimately caused by the introduction of E. rosea.
Uneven and Biased Nature of Mollusk Extinctions
The biased distribution of mollusk extinctions we found
has been noted previously. For these poorly known
species (i.e., invertebrate species), knowledge of their
conservation status comes from taxonomists, and 80%
of taxonomists are based in North America or Europe
and few (only 4%) are Latin American or African. How-
ever, biodiversity is richest in countries with fewer tax-
onomists (Gaston & May 1992). These figures match well
with our observations. The sparse knowledge available
for biodiversity-rich countries is partly due to a lack of
local workers. This is not the situation in Europe, where
there are a lot of taxonomists to notice changes in pop-
ulation trends of mollusks and numerous cases of docu-
mented mollusk extinctions are a direct consequence of
a large number of workers in this field. But molluskan
faunas from Pacific islands and North America have an-
other characteristic that makes their extinction figures
stand out. These two faunas (especially freshwater fauna
for North America [Bogan et al. 1995]) have a lot of very
restricted endemics that are much and easily affected by
environmental changes induced by human settlement.
Marine Mollusk Extinctions
Despite the fact that marine mollusks are more diverse
than nonmarine species (Bouchet 2006), only one supple-
mentary case of extinction was found. This trend was not
inherent to the molluskan fauna: only 16 extinct marine
species, from mammals to algae, are listed in the 2007
IUCN Red List. This may be because in published stud-
ies on conservation biology marine habitats are under-
represented (Carlton 1993; Chapman 1999; Reaka-Kudla
1997). This trend may be changing because marine habi-
tats are becoming a topic of concern (Powles et al. 2000;
Dulvy et al. 2003; Hilborn 2007). In papers on this is-
sue, there is conflation of “biological extinction” (our
focus here) and “commercial extinction” (Dulvy et al.
2004; Worm et al. 2006; Hilborn 2007), probably be-
cause of confusion between biodiversity loss (global ex-
tinctions) and declining stocks of commercially valuable
species (Briggs 2007). The lack of quantitative data on
marine invertebrate abundances, ranges, habitat require-
ments, dispersal, and connectedness among populations
prevented us from concluding anything about their con-
servation status (Chapman 1999). This does not mean
marine invertebrates are extinction proof. In vulnerable
marine habitats, such as coral reefs, where species are
part of coevolved associations, worldwide episodes of
coral bleaching probably have serious consequences for
species that are interdependant and may have led to sev-
eral unnnoticed extinctions (Reaka-Kudla 1997). But no
such cases of extinctions have yet been recorded.
It is commonly thought that marine organisms are re-
sistant to human-caused extinction because most of them
have larvae with a long planktonic drifting stage and large
geographic ranges (Carlton 1993; Culotta 1994; McKin-
ney 1998). The very few extinctions listed for marine
organisms and the only additional case of a marine mol-
lusk extinction we documented confirmed this is likely to
be the case. Our general conclusion concerning marine
extinctions is that marine mollusks (and marine species
in general) are likely to be less extinction prone than
nonmarine species.
Freshwater Mollusk Extinctions
Flowing waters are probably the most endangered ecosys-
tem on Earth, and this is because of human activities
(Allan & Flecker 1993; Malmqvist & Rundle 2002). That
mollusks are endangered in river system in the United
States is well known. We illustrated this for the Alabama
River system, which is highly polluted because of infras-
tructure development (Bogan 2006). The effect of habitat
degradation is affecting mollusks all the more because the
freshwater molluskan fauna of North America has a lot of
very restricted endemics.
The Balkan region is rich in freshwater fauna (Griffith
et al. 2004; Glo¨
er et al. 2007). Many gastropod species in
this region have small ranges and are restricted to small
hydrographic systems: rivers, lakes, and springs (Fig. 4).
The high level of endemism in the Balkan freshwater
molluskan fauna is due to the karstic landscape, which is
Conservation Biology
Volume 23, No. 5, 2009
1218 Unnoticed Mollusk Extinctions
Figure 4. Locations of the extinct mollusks of the
Balkan region: 1, Belgrandiella zermanica, Dalmatinella
fluviatilis,Islamia zermanica,Tanousia zrmanjae;2,
Graziana lacheineri adriolitoralis,Vinodolia fiumana;3,
Dianella schlickumi;4,Graecoanatolica vegorriticola;5,
Graecorientalia vrissiana;6,Grossuana serbica vurliana;
7, Heleobia achaja sorella,Turcorientalia hohenackeri
hohenackeri;8,H. steindachneri,I. epirana,Orientalina
curta albanica,Paladilhiopsis janinensis;9,I. graeca,
Pseudoislamia balcanica,Trichonia trichonica,Valvata
klemmi; 10, I. hadei; 11, Pseudamnicola macrostoma;
12, T. kephalovrissonia; 13, G. macedonica; 14,
Antibaria notata,V. gluhodolica; 15, Bracenica spiridoni;
16, V. matjasici; 17, Ohridohauffenia drimica.
characterized by a spring and river hydrography in which
small systems are completely isolated from one another
(Radoman 1985). Narrow ranges and isolation have made
these species more vulnerable to habitat degradation and
in many cases have resulted in extinction.
Data on the status of groundwater species are rare.
For example, the impact of pollutants and chemical fer-
tilizers on hypogean faunas remains unknown, although
researchers are beginning to address this issue (Canivet
et al. 2001). Conservation studies of subterranean faunas
have been done only in the Balkans (Szarowska & Al-
brecht 2004; Szarowska 2006) and in the Great Artesian
Basin of Australia (Ponder 2003). These studies showed
that drawdown resulting from water extraction leads to
endangerment or extinction of many species. No doubt
the difficulty of reaching these species habitats accounts
for the lack of assessment.
Oceanic Islands
Many more mollusk extinctions have occurred on
oceanic islands than on continents. This imbalance may
be explained by the intrinsic vulnerability of oceanic
island species (island endemics have small ranges and
small populations) and their evolution in isolation from
predators and competitors, which makes them extremely
prone to extinction (Pimm 1991; Purvis et al. 2000). In
addition, it is inherently difficult to record extinctions,
small ranges and small populations. On very small islands
(such as Gambier or Austral islands in French Polynesia),
when an endemic species is not found despite consid-
erable survey efforts, very little doubt remains about its
survival (Abdou & Bouchet 2000).
Extinctions on oceanic islands have been caused
mostly by habitat degradation and introduced species.
Cowie (1997) documented 59 terrestrial and 22 freshwa-
ter snail and slug species that have been recorded as aliens
in the Hawaiian Islands alone. The case of E. rosea de-
serves special attention. E. rosea is a predatory snail that
was introduced to several Pacific islands to control the gi-
ant African snail (Achatina fulica). It has had a dramatic
impact on populations of native land snail. Two cases of
massive extinctions in endemic molluskan faunas caused
by E. rosea have been well documented. In the Society
Islands, E. rosea eradicated 51 endemic species of Partul-
idae in <10 years (Coote & Lo`
eve 2003), and in Hawaii
56 terrestrial species of Amastridae and Achatinellidae
that we list may also have became extinct as a result of
predation by the carnivorous snail (Hadfield 1986; Cowie
1992, 2001a; Hadfield et al. 1993). E. rosea was the pre-
cipitous cause of these extinctions (Griffiths et al. 1993;
Civeyrel & Simberloff 1996; Cowie 2001b), but popula-
tions of these endemic snails were already weakened by
decades of habitat destruction, overcollecting, and pre-
dation by other accidentally introduced species (Hadfield
1986; Cowie 1992). The other extinct species native to
islands where E. rosea was present were extinct in most
cases before introduction of the carnivorous snail.
The current, most serious threat to native island mol-
lusks is probably the introduced flatworm Platydemus
manokwari. The flatworm, native to New Guinea, has
been introduced in attempts to control A. fulica.At
present, it is affecting endemic land snails on Guam
and Rota (Robinson & Hollingsworth 2005), in Samoa
(Cowie & Robinson 2003), and in the Ogasawara Islands
(Okochi et al. 2004). These introduced predators may
Conservation Biology
Volume 23, No. 5, 2009
egnier et al. 1219
Figure 5. Summary of the
updated mollusk species and
subspecies extinctions.
rapidly cause the extinction of many more land snails
native to oceanic islands.
Unlisted but Not Unnoticed
Assessing rates of extinction for invertebrate taxa is ob-
structed by differences in the quality of information about
each group (McKinney 1999) and by uneven numbers
of vertebrate experts and invertebrate experts (Gaston
& May 1992). Moreover, the difficulty of ruling on the
conservation status of species is amplified for inverte-
brate taxonomists because not only are there fewer of
them in relation to terrestrial vertebrate experts but also
the number of species to deal with is colossal (as high
as 99% of animals; Ponder & Lunney 1999). Plus, most
invertebrate species are small. For these two reasons
reaching a decision concerning their conservation sta-
tus involves extensive and detailed survey work that can
take in some cases a lifetime of work. Vertebrate ex-
perts, in contrast, tend to focus on one or a few favorite
species and to go out on targeted field-survey expedi-
tions. Despite these difficulties, some scattered results of
thorough survey works reach the stage of publication,
and our <3 months of bibliographic research and con-
sultation with experts led to a doubling of the number
of listed extinct mollusk species. Why, when monitoring
of the conservation status of mammals and birds is so ac-
curate, were these extinctions not captured by the IUCN
until now? The extinctions we recorded had been known
and published for more than 10 years in many cases. For
mollusks (and all invertebrates) there is a disconnect be-
tween extinctions known to experts or published in the
scientific literature and extinctions on the IUCN Red List,
whereas for birds and mammals, the IUCN Red List is
the scientific reference. The list is designed for verte-
brates and relies on an important task force of ecological
researchers and conservation biologists who are moni-
toring, observing the state of biodiversity, and relaying
their data to the IUCN almost in real time. For inver-
tebrates, taxonomists—not ecological researchers—hold
the knowledge of species population trends. This knowl-
edge is published but does not reach the IUCN. Thus,
there is an additional stage in listing an invertebrate ex-
tinction in the “IUCN way.” For mammals and birds, the
process is (1) knowing and (2) listing, whereas for inver-
tebrates it seems to be (1) knowing and (2) sometimes
recording, or (1) knowing, (2) recording, and (3) not list-
ing and often not knowing. This difference in the way
of documenting extinctions between invertebrates and
terrestrial vertebrates may partly explain the imbalance
in the number of listed extinctions per major taxonomic
At the onset of our study, out of 850 known extinct
species globally, 302 were mollusks, 278 of which
were correctly listed as extinct. Today, the number of
mollusk extinctions has almost doubled (Fig. 5) and
is higher than the number of extinctions in all other
taxa combined. Do mollusks really account for half the
toll? They certainly account for half the toll of docu-
mented extinctions but certainly not for half the toll of
what is really extinct (i.e., both documented and over-
looked extinctions). Invertebrate species receive much
less publicity and attract disproportionately minor re-
search effort relative to vertebrates (Lydeard et al. 2004).
Indeed, there is a mismatch between the number of
scientists working on birds and mammals and the very
few taxonomists specializing in invertebrate taxa. If one
adds to this the unbalanced repartition of human ef-
fort and funding in relation to the richest biodiversity
locations, it becomes clear that these two phenom-
ena are influencing this uneven number of documented
Yet, the difficulties encountered in recording mollusk
extinctions are less critical than those faced in recording
extinctions in other invertebrate taxa, such as insects.
Recording mollusk extinctions in the field is facilitated
by the fact that one can still find dead shells from species
that became extinct during the 19th century (Bouchet &
Abdou 2003; Griffiths & Florens 2006). Compared with
mollusks, the number of documented insect extinctions
is amazingly small: 60 according to the 2007 IUCN Red
List (IUCN 2007) of about 950,000 described species.
Baillie et al. (2004) estimated that the conservation status
Conservation Biology
Volume 23, No. 5, 2009
1220 Unnoticed Mollusk Extinctions
of 771 insect species had been evaluated and that 73% of
them are listed as threatened by the IUCN. This provides
a good idea of the huge number of extinctions being
missed and makes it clear how much the present listing of
extinctions is biased. If “[m]ost extinctions estimated to
have occurred in the historical past, or predicted to occur
in the future, are of insects” (Dunn 2005), then no doubt
a huge number of insect extinctions have gone unnoticed
since 1500. The same work we did for mollusks could be
applied to insects and would surely increase dramatically
the number of documented extinctions on the IUCN Red
J. P. Rodriguez for their constructive comments on the
manuscript. We also thank the following experts who
checked extinction data and provided new data: C. Al-
O. Griffiths, M. Haase, M. G. Hadfield, D. Herbert, M.
Ibanez, M. C. Mansur, I. Muratov, S. Panha, G. Rosen-
berg, M. Schilthuizen, M. Seddon, L. Ricardo, L. Simone,
F. G. Thompson, K. Tomiyama, A. War´
en, F. Wesselingh,
and T. de Winter.
Supporting Information
An updated list of mollusk extinctions (Appendix S1) and
sources for updating the extinct species list (Appendix
S2) are available as part of the on-line article. The authors
are responsible for the content and functionality of these
materials. Queries (other than absence of the material)
should be directed to the corresponding author.
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... Despite their diversity, Pacific land snails are among the most threatened taxa in the world, with more recorded extinctions since 1600 than any other group of fauna (Regnier et al. 2009). Estimates of extinction rates in Hawaii range from 50%-75% (Solem 1990), although the true rate is likely to be at the higher end of the scale; according to Solem, the lower bound of this estimate is "wildly optimistic". ...
... The discovery of a new species, Auriculella gagneorum, discovered in 2020 in the Waianae mountains, Oahu, also gives some hope for conservation efforts (Yeung et al. 2020). Despite occasional discovery/rediscovery, continued habitat destruction and introduction of non-native predators necessitate the development and deployment of effective conservation strategies to save the remainder of the Auriculella genus before it is lost entirely (Solem 1990, Regnier et al. 2009, Yeung and Hayes 2018. ...
The study of both animal colouration and patterning across the natural world has been imperative for understanding some of the key principles of biology throughout the past century, particularly with respect to evolution and genetics. Generally, colour and pattern have each been described qualitatively, often being binned into discrete groups relying on human perception of colour or pattern, rather than being considered in a biologically relevant context. ‘Binning’ traits into discrete groups has the consequence that variation within discrete morphs is often overlooked. Terrestrial gastropods, such as the selected study genera Cepaea and Auriculella, provide an ideal system for the study of polymorphisms and colour variation due to the extreme variety of morphs present across the taxa, as well as the nature of shell growth providing a complete ontogeny of an individual. The aims of this thesis are threefold; firstly, I aimed to understand finescale variation within and between established banding pattern morphs in Cepaea, to allow inferences to be made regarding the genetic mechanisms responsible for this variation. The implementation of two quantitative methods for measuring variation in band position and width in individual shells found that individual band absence has a minor but significant effect on the position of the remaining bands, implying that the locus controlling band presence/absence acts mainly after the position of bands is determined. I establish a method which is useful for comparative studies of quantitative banding variation in snail shells, and for extraction of growth parameters and morphometrics, highlighting the importance and usefulness of gastropod shells in the understanding of how variation is established and maintained in a population. Secondly, I aimed to understand the shell colour variation present in both Cepaea nemoralis and Cepaea hortensis by using spectrophotometry and psychophysical modelling in tandem. It was revealed that colour variation in Cepaea hortensis is continuous, with no detectable effects of geographic location with the exception of an association of the paleness of yellow shells with latitude. Differences between the colour of Cepaea hortensis and Cepaea nemoralis, both in terms of exact shade and overall colour were revealed; Cepaea hortensis are generally paler, and less pink-toned, but slightly more brown-toned. Precise shade variation of yellow individuals from genetically diverse lineages of Cepaea nemoralis were also detected. The results presented have significance in furthering the understanding of the precise nature of the colour polymorphism displayed in Cepaea spp., and the nature of the selection which acts upon it, as well as highlighting the importance of considering colour as a continuous trait, rather than binning it into discrete groups. Thirdly, I aimed to investigate colour variation across a number of scales in the Hawaiian land snail genus Auriculella, to allow inferences about the genetic architecture responsible for the variation, and to highlight the usefulness of museum collections of gastropod shells in understanding variation in extinct or endangered species. I demonstrated that there are differences in colour within single shells of Auriculella, similar to variation displayed by other Pacific Island snails. I described significant variation between isolated populations of the same species, and determined that there is no difference in colour variation between shells on the islands of Maui and Oahu. Finally, I demonstrated that there is no difference in colour between shell chiralities, suggesting that interchiral mating is not uncommon, and that the loci responsible for colour variation and chirality are not closely linked. By describing the variation present in Auriculella in a biologically relevant context, inference regarding genetic mechanisms of variation becomes possible in a taxa of conservation concern. By achieving these aims, and synthesising conclusions drawn from their achievement, I have highlighted the importance of accurately defining phenotypes for the purposes of evolutionary ecology and genetics. Defining phenotypes and investigating variation present within morphs has allowed inferences to be made regarding the underpinning genetic mechanisms which control variation in two gastropod genera, although the principles are applicable to other taxonomic groups. Finally, and more broadly, I have demonstrated the usefulness of gastropods as study systems, particularly where large collections of shells are available.
... Among these faunas and floras, land molluscs show the highest levels of endemism and the highest rates of extinction ( Lydeard et al. , 2004 ). Of all known molluscan extinctions, 70% have occurred on oceanic islands ( Régnier et al. , 2009 ;Cowie et al ., 2017 ), and in particular cases extinction rates may be greater than 75% ( Solem, 1990 ;Régnier et al. , 2015b ). The scale of species endangered, extirpated or extinct is certainly underestimated by the International Union for Conservation of Nature (IUCN) ( Régnier et al. , 2009( Régnier et al. , , 2015b , and the full extent of species loss may be concealed by uncertainties in the discovery and recording of snail extinctions before the fauna was first described. ...
... Of all known molluscan extinctions, 70% have occurred on oceanic islands ( Régnier et al. , 2009 ;Cowie et al ., 2017 ), and in particular cases extinction rates may be greater than 75% ( Solem, 1990 ;Régnier et al. , 2015b ). The scale of species endangered, extirpated or extinct is certainly underestimated by the International Union for Conservation of Nature (IUCN) ( Régnier et al. , 2009( Régnier et al. , , 2015b , and the full extent of species loss may be concealed by uncertainties in the discovery and recording of snail extinctions before the fauna was first described. In the absence of accurate estimates of such extinction events and knowledge of the taxa involved, biogeographical inferences such as those of Chiba & Cowie (2016) and Triantis et al. (2016b) can be compromised. ...
Late Quaternary deposits containing fossil snail shells were sampled from nine sites on Deserta Grande and three on Bugio, two of the three Desertas Islands in the oceanic Madeiran archipelago. In total, 3,432 shells representing 45 species or subspecies were retrieved. Calibrated amino acid racemization yielded ages ranging from > 45 to 6 ka, with variation by site often confounded by reworking of mostly colluvial deposits. The assemblages found are compared with the extant fauna, itself a subject of intensive recent study. Of the 45 taxa, 18 are apparently extinct, and a further 5 no longer survive on the Desertas. A similar pattern emerges when each island is considered separately. The level of local extinction ( c. 50%) is greater than seen on the larger, nearby islands of Madeira and Porto Santo. There are few endemic species in the extant fauna not represented in the fossil assemblages, but there are a number of possibly adventitious species, some with wide distributions in Europe. There is little evidence of faunal change within the limits of the age range available, and extinction seems to be concentrated in the later Holocene. It is attributed to the massive habitat destruction that occurred subsequent to human occupation from the 15th century CE onwards. The study emphasizes the depauperate nature of many extant island faunas subject to human disturbance.
... Invertebrates are being lost from many ecosystems; as illustrations, molluscs (Régnier et al. 2009), insects (Fonseca 2009;Hallmann et al. 2017;Forister et al. 2019) and decapods (De Grave et al. 2015) are all in rapid decline (Eisenhauer et al. 2019). Yet the proportion of invertebrate species that is actually listed by IUCN is far lower than for vertebrates. ...
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Coconut crabs Birgus latro have recently been reclassified from Data Deficient to Vulnerable on the IUCN Red List. This is a somewhat unusual case of temporal and spatial information being used to change the IUCN status of an arthropod and it draws attention to the paucity of biological data on most invertebrate species. To be listed, two or more scientific criteria need to be documented but such data are unavailable for many invertebrates. This raises the question as to whether certain invertebrates receive more scientific attention and are hence more likely to be listed if, like the coconut crab, they are large, slow-reproducing or a dual-biome species (characteristics which make them inherently vulnerable) and whether being an indicator or a flagship species is important.
... Land mollusks are sensitive to moisture differences, and their low dispersing abilities and shell's persistence after death make them useful tools in assessing environmental health within the terrestrial ecosystem. That several mollusks are under the threats of extinction with many unaccounted for [1,7] and the pressure to use hitherto unused habitats [4], informed the need to investigate the mollusk species in Cross River. ...
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Ecosystem characteristics affect the composition, richness, diversity of species, and their ability to recolonize disturbed habitats. Here in Nigeria, two localities Mfamosing limestone hills and Odukpani lowland forest with different exposures to human activities were sampled in 2017. The study was aimed at creating inventories, comparing and evaluating the diversity of mollusk species in leaf litters and topsoil sourced from eleven 20x20m plots per locality. Results revealed a total of 593 individuals belonging to 26 species in 18 genera and ten families, and 282 individuals belonging to 18 species from 10 genera in 5 families at Mfamosing and Odukpani respectively. The mollusk composition at Mfamosing was significantly different from those at Odukpani, although they had eleven common species. In further assessing these findings against similar assessments conducted no less than a decade ago in the neighboring Oban hill and Odukpani, previously abundant species were now numerically depauperate species, while some were completely absent. While the key drivers responsible for their population decline remain unknown, how changes in habitats-due to human use over time-impinge on the mollusk species is worthy of further investigation.
... Continued exploration of terrestrial and marine life has witnessed a proliferation of new species with many still undiscovered. It is estimated, for instance, that 70% of life in the seas are not even known to science (Régnier et al, 2009). The identi cation of newly discovered species and determination of their phylogeny have indeed become a daunting task. ...
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The impact of climate change on biodiversity needs to be understood from a multidisciplinary approach. Using an analytical framework, we investigate the species response to rising temperatures. Common traits and characteristics among species that allow classification at different taxonomic levels imply an underlying symmetry that gives rise to invariances behind the biodiversity observed in nature. Changing temperatures that go beyond a critical limit break this underlying symmetry which could lead to enhanced speciation.
... And finally, snails are an important piece of the puzzle that makes the planet work. Understanding their role in the grand scheme of things can also help us to better understand how to avoid their extinction (Régnier et al., 2009;Haponski et al., 2017;Hirano et al., 2018), and in a roundabout way, ours as well. From our experience of utilizing snails as a vehicle to engage in scientific thinking, we have identified ways in which the natural accessible environment can be experienced and then understood at a deeper level through technological enhancements and supports, which ultimately lead to student learning. ...
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Snails have occupied an important role in the ideology and religion of the ancient American peoples, who considered them to be magical and used them in ritual ceremonies as ornaments, musical instruments, and architectural elements. Today, they are a valuable study system for understanding biodiversity and evolution due to their remarkable ecological and morphological diversity. Given that many endemic snails are of conservation concern, and that most South American species are poorly studied, there is a need to engage the public through understandable and scientifically based language, conveying the importance of biodiversity. However, not all biodiversity can be seen with the naked eye. Herein, we describe how we utilize snails and their shells to engage citizens and train teachers to promote the many different facets of biodiversity. Through design-based research oriented toward educational innovation, we created a teaching–learning sequence with immersive technology through the following stages of work: (1) produce a teaching–learning sequence and accompanying mobile device application (for Android on GooglePlay), (2) evaluate the impact of the educational resource, and (3) conduct research through a pre- and posttest design on the learning outcomes of participants. In this work, we first present the field experience where scientists, teachers, and pre-service teachers worked together to find snails from northern Chile to Chiloé Island. Some results from this research stage are: criteria for designing a teaching–learning sequence (e.g., how to utilize place as an opportunity for learning science with developmentally appropriate technologies identified for every phase of the sequence), modeling relevant phenomena about biodiversity and ecosystems through snails, scaffolding for teachers implementing the sequence, and activities that enhance STEM education. A teaching–learning sequence that addresses snails as study objects for 4th grade is presented and validated, allowing us to continue the next phase of our research with schools. A second article will propose results from implementation, iterations, and their implications.
... Freshwater mussels (Mollusca: Bivalvia: Unionida) are benthic macroinvertebrates that are among the most endangered animals in the world (Lydeard et al., 2004;Régnier, Fontaine & Bouchet, 2009;Lopes-Lima et al., 2017;Lopes-Lima et al., 2018). These remarkable molluscs have a life history that includes a parasitic larval stage, a juvenile stage that lives buried within the stream or lake sediment, and a filter-feeding adult stage that provides and contributes towards a number of ecosystem services (Vaughn & Hakenkamp, 2001;Howard & Cuffey, 2006;Vaughn, 2018). ...
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The decline of endangered freshwater pearl mussel (FPM, Margaritifera margaritifera) has been attributed to juvenile mortality caused by low concentrations of dissolved oxygen in the stream substrate resulting from fine sediments (siltation) that impede water exchange in the interstitial microhabitat of juveniles. If low oxygen concentration causes recruitment failure of FPMs, knowledge on the oxygen tolerance of juvenile FPMs is essential for the conservation of the species, as it will justify conservation efforts improving water exchange in the bottom gravel. However, the tolerance of low oxygen of FPM juveniles has not been directly studied. Juvenile FPMs (9–11 months old) were exposed in individual chambers equipped with optical oxygen measurement spots to different levels of dissolved oxygen at 19 °C and their viability was monitored for 10 days to assess the acute oxygen tolerance of juvenile FPMs. Oxygen concentration ranged between 8.8 and 6.2 mg L−1 in the high oxygen treatment (control), 5.0–0.4 mg L−1 in the medium treatment, and 1.3–0.04 mg L−1 in the low oxygen treatment (near‐anoxic conditions). Viability of juvenile FPMs depended on the concentration of available dissolved oxygen, such that all juveniles exposed to near‐anoxic conditions were classified as non‐viable, whereas all mussels exposed to high and medium concentrations were viable at the end of the 10 day experiment. Juveniles differed in their ability to tolerate near‐anoxic conditions, so that some individuals survived only 1 day and others survived up to 9 days. This study provides the first direct experimental evidence on the oxygen sensitivity of FPM juveniles and suggests that >10‐day events of very low dissolved oxygen at summer temperatures are fatal to juvenile FPMs, supporting the view that actions preventing low oxygen episodes in the substrate are essential for recruitment, and conservation, of FPMs.
... En attendant, l'absence de stabilité taxonomique pour ces taxons limite le développement des connaissances sur leur cycle de vie, autoécologie, répartition géographique et statut de menace. C'est donc tout un pan de connaissances au sujet des mollusques continentaux qui nous échappe (CAMERON 2015), et ce, dans un contexte global d'érosion massive de la biodiversité (PIMM et al. 2014) qui affecte particulièrement les mollusques continentaux (RÉGNIER et al. 2009, COWIE et al. 2017). ...
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NOTE La liste de référence des mollusques d'Alsace de DEVIDTS (1977) : 40 ans de malacologie régionale par Jean-Michel BICHAIN* RÉSUMÉ Joseph DEVIDTS publiait en 1977, dans ce bulletin, la première liste de référence commentée des mollusques d'Alsace. Il recense alors 155 espèces à travers la littérature, les collections régionales et ses propres observations. Aujourd'hui, 210 taxons terminaux sont listés pour notre région. Néanmoins, l'évolution des concepts et des outils en taxonomie subit aujourd'hui une mutation en profondeur. Les limites spécifiques pour nombre de taxons restent encore largement discutées et la part des données naturalistes pour ce groupe reste encore faible. Par conséquent, la liste de référence régionale aujourd'hui disponible ne donne qu'une vue partielle de la réalité biologique et sera amenée à évoluer en profondeur dans les prochaines années. MOTS-CLÉS : Liste de référence, mollusques continentaux, Alsace, Joseph DEVIDTS, évaluation de la biodiversité. ABSTRACT Joseph DEVIDTS published in 1977, in this bulletin, the first annotated checklist of the molluscs from Alsace. He then recorded 155 species through the literature, regional collections and his own observations. Today, 210 terminal taxa are listed for our region. However, the evolution of concepts and tools in taxonomy is undergoing an in-depth mutation. Many species boundaries are still widely discussed and the natural history data for this group is still low. Therefore, the new regional checklist currently available gives a partial view of the biological reality and will have to evolve in depth in the coming years.
In both scientific and popular circles it is often said that we are in the midst of a sixth mass extinction. Although the urgency of our present environmental crises is not in doubt, such claims of a present mass extinction are highly controversial scientifically. Our aims are, first, to get to the bottom of this scientific debate by shedding philosophical light on the many conceptual and methodological challenges involved in answering this scientific question, and, second, to offer new philosophical perspectives on what the value of asking this question has been — and whether that value persists today. We show that the conceptual challenges in defining ‘mass extinction’, uncertainties in past and present diversity assessments, and data incommensurabilities undermine a straightforward answer to the question of whether we are in, or entering, a sixth mass extinction today. More broadly we argue that an excessive focus on the mass extinction framing can be misleading for present conservation efforts and may lead us to miss out on the many other valuable insights that Earth’s deep time can offer in guiding our future.
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La Caragouille globuleuse, Cernuella virgata (da Costa, 1778), est une espèce méditerranéenne et ouest-européenne et par ailleurs introduite en Australie et aux États-Unis. En France, elle occupe une vaste répartition sur l'ensemble du territoire à l'exclusion du quart nord-est. Aucune donnée récente ou historique ne mentionne la présence de l'espèce en Alsace ou dans les régions limitrophes. Une petite population d'une trentaine d'animaux actifs a été découverte en avril 2018 à proximité de la gare de Herrlisheim, commune du Bas-Rhin située à une vingtaine de kilomètres au nord de Strasbourg. Au regard de son statut d'espèce à fort potentiel invasif, la dynamique d'expansion de l'espèce est à surveiller localement, non seulement dans les habitats naturels de la région, mais aussi dans les espaces verts urbains et périurbains ainsi que dans les milieux agricoles. ABSTRACT The vineyard snail, Cernuella virgata (da Costa, 1778), is a Mediterranean and western European species. Also introduced in Australia and the United States, the species is listed as a crop pest. In France, it occupies a large distribution over the whole territory excluding the northeast quarter. No recent or historical data mentions its presence in Alsace or in adjacent immediate areas. However, a small population of about thirty active animals was discovered in April 2018 near the station of Herrlisheim, a town located about twenty kilometers north of Strasbourg. Given its status of species with high invasive potential, the populations' expansion should be monitored locally, not only in the natural habitats, but also in urban and peri-urban green spaces as well as in agricultural environments.
Balkan Biodiversity is the first attempt to synthesise our current understanding of biodiversity in the great European hot spot. The conservation of biodiversity is one of today’s great ecological challenges but Balkan biodiversity is still poorly understood, in a region with complex physical geography and a long history of political conflict. The Balkans exhibit outstanding levels of endemism, particularly in caves and ancient lakes such as Ohrid; lying at the crossroads of Europe and Asia they are also renowned as a focus of Pleistocene glacial refugia. This volume unites a diverse group of international researchers for the first time. Its interdisciplinary approach gives a broad perspective on biodiversity at the level of the gene, species and ecosystem, including contributions on temporal change. Biological groups include plants, mammals, spiders and humans, cave-dwelling organisms, fish, aquatic invertebrates and algae. The book should be read by zoologists, botanists, speleobiologists, palaeoecologists, palaeolimnologists and environmental scientists.
This report is the first product of the Status and Trends Program in the National Biological Service. It is the first of a series of reports on the status and trends of the nation's plants, animals, and ecosystems. The report compiles information on many species and the ecosystems on which they depend. It provides information about causes for the decline of some species and habitats. It also gives insight into successful management strategies that have resulted in recovery of others. The report represents an effort to bridge the gap between scientists and resource managers, policy makers, and the general public.
The heterobranch gastropod family Glacidorbidae (?Pulmonata) is known only from temperate Australia and Chile. The Australian taxa are reviewed and three new genera, Benthodorbis, Striadorbis and Tasmodorbis are described based on differences in their shells, especially the protoconchs, and in their opercula and radulae. Nineteen species of Australian glacidorbids are recognised, all but four of them new. Of the four Australian species previously included in Glacidorbis, only two, G. hedleyi (Iredale) from New South Wales and Victoria, and G. occidentalis Bunn & Stoddart from south Western Australia, are retained in that genus. Eleven new species of Glacidorbis are described, seven from Tasmania (G. bicarinatus, G. catomus, G. atrophus, G. decoratus, G. costatus, G. tasmanicus and G. circulus), one (G. isolatus) from New South Wales, two (G. otwayensis and G. rusticus) from Victoria and one (G. troglodytes) from South Australia. Striadorbis contains the Tasmanian S. pedderi (Smith), and two new species, S. spiralis from western Victoria and S. janetae from Tasmania. Benthodorbis contains two species, both from old lakes in Tasmania; B. pawpela (Smith) from Great Lake and B. fultoni from Lake Sorell. Tasmodorbis contains a single species found in western Tasmania, T. punctatus, unique in having internal shell pores. Glacidorbis costatus is known only from Pulbeena Swamp in NW Tasmania and appears to be recently extinct, possibly as a result of draining of the swamp in the early part of this century. A cladistic analysis with the South American member of the family, Gondwanorbis, as the outgroup, supports the monophyly of the genera recognised.