1,
Dept. of Biological Sciences, National Univ. of Singapore, 14 Science
Drive 4, Singapore 117543
2, Present address: Dept. of Ecology and Evolutionary Biology, Princeton
Univ., Princeton, NJ 08544-1003, USA
3, Dept. of Ecol. & Evol.Biology, Univ. of Tennessee, 1416 Circle
Drive, 569 Dabney Hall, Knoxville, TN 37996-1610, USA
4, Dept. of Ecol. &
Evol.Biology, Univ. of Connecticut, Storrs,
CT 06269-3043, USA
5, Dept. of Biological Sciences, University of Alberta, Edmonton,
Alberta Canada, T6G 2E9
6, Institute of Biomedical and Life Sciences, Univ. of Glasgow, Glasgow,
Scotland, G12 8QQ, UK. (Present address: Illinois Natural History
Survey, 607 East Peabody Drive, Champaign, IL 61820-6970, USA)
Joint First Authors*: Lian Pin Koh and Robert R. Dunn Corresponding Author&: Navjot S. Sodhi e-mail: dbsns@nus.edu.sg
Status: Published 10th Sept. 2004 in Science,
vol. 305, no. 5690. pp. 1632-1634.
Mini Press Release
Species co-extinction: till
death do us part?
Of the 12,200 species of plants and animals currently listed as threatened or
endangered, a further 6,300 affiliate species should be classified as “co-endangered”.
This is the bleak assessment offered by a new study attempting to quantify the
phenomenon of co-extinction – the loss of an “affiliate” species
when its host goes extinct.
Many plants and animals have a diverse selection of insects, fungi, and other
organisms associated with them that are uniquely adapted to their host. This
specialization makes these affiliate species vulnerable to host extinction.
Using estimates of host specificity, Lian Pin Koh, Robert R. Dunn and colleagues
calculated the expected levels of co-extinction across a diverse selection of
host and associate systems. For the groups examined, the authors show that at
least 200 affiliate species have historically been lost through co-extinction,
and a further 6,300 are co-endangered with their hosts. These processes have
been widely overlooked, perhaps because some of the most susceptible organisms
are uncharismatic parasites. For example, many herald the success of conservation
efforts to save the Californian condor from extinction, but who mourns the condor
louse that went extinct as a result of efforts by well-meaning conservation
biologists to rid the birds of their parasites? The authors suggest that co-extinction
is a largely unexamined and potentially substantial contributor to the present
global extinction crisis and that estimates of species extinction should be
re-calibrated, taking estimates of co-extinction into account.
Abstract
The co-extinction of species (the loss of a species upon the loss of another)
remains a critical process. We present a probabilistic model, scaled with empirical
data, to examine the relationship between co-extinction levels (proportion of
species extinct) of affiliates and their hosts across a wide range of coevolved
interspecific systems: pollinating Ficus-wasps and Ficus, parasites and their
hosts, butterflies and their larval hostplants, and ant-butterflies and their
host ants. Applying a nomographic method based on mean host specificity (number
of host species per affiliate species), we estimate that 6300 affiliate species
are “co-endangered” with host species currently listed as endangered.
Current extinction estimates need to be re-calibrated by taking species co-extinctions
into account.
These is available to download as an Adobe Acrobat PDF file. To view these
you need Adobe Acrobat, which is available for Macs, PCs, and Unix from here.
Lian
Pin Koh has compiled a
PDF containing articles written by the 70+ news organizations that the reported
this paper between 10-13 Sept. 2004. The complete PDF is available
here (note this is a very large file - 6.6MB). Thomas Brooks of Washinton
based Conservation International
said of this study "The team has done the conservation community a
great favour by synthesizing the theory and data on the co-extinction crisis."
(11 Sept, 04, New Scientist).
Sept '04
Promotional Fig.
2 (High Res
TIFF File)
A pair of feather mites (Rhytidelasma punctata), from the pale-headed
rosella (Platycercus adscitus). Image by David
Evans Walter. Copyright information available from Heather
Proctor.
Promotional Fig.
3 (High
Res TIFF File)
This feather mite is known only from the threatened southern cassowary,
Casuarius casuarius, in Australia. Copyright information available
from Heather Proctor.
Promotional Fig.
4 (High Res TIFF
File)
The locally extinct butterfly hostplant (Tylophora sp.) and
its co-extinct affiliate butterfly species (Parantica aspasia)
from Singapore. Copyright information available from Lian
Pin Koh.
Promotional Fig.
5 (High Res TIFF File)
Hummingbird flower mites can go extinct if either the hummingbirds they
use for transport or flowers on which the mites depend for nectar and
pollen go extinct. In the illustration, the mite Tropicoseius uniformis,
monophagous on its host plant Psychotria poepegiana, is phoretic
on the hummingbird Amazilia tobaci in Trinidad, West Indies.
Credits - Amazilia tobaci (hummingbird), Rick and Nora Bowers;
Tropicoseius uniformis (mite): Shahid Naeem; Psychotria
poepegiana (host plant), R. K. Colwell. Copyright information available
from Robert Colwell.
* Note that these figures
do not constitute part of the publication and are intended for promotional use
of this paper. High resolution images are available in TIFF format from the
links above. Copyright permission must be sought from the relevant contact listed
by each figure BEFORE use. Requests for use of multiple figures can be directed
to Vince Smith in the first instance.
Figures from
the Paper
Figure 3
(High Res TIFF File)
Predictions of affiliate extinctions from the nomographic and combinatorial
models. (A) Estimated numbers of historically extinct affiliate species
based on the number of host species recorded as extinct. (B) Projected
numbers of affiliate species extinctions, were all currently endangered
hosts to go extinct. The first value in parentheses represents the absolute
number and the second value the percentage of species extinct or endangered
as predicted by the nomographic model; the second set of values in parentheses
represents predictions from the combinatorial model for selected affiliate-host
groups where affiliation matrices are available. See ref. 10 within
the manuscript for details on datasets. Copyright information available
from Lian Pin Koh.
