Short communication
Novel genes continue to enhance population growth in adders
(Vipera berus)
Thomas Madsen
a,b,
*
, Beata Ujvari
a,b
, Mats Olsson
c
a
School of Biological Sciences A08, University of Sydney, NSW 2006, Australia
b
Department of Animal Ecology, Ecology Building, Lund University, S-223 62 Lund, Sweden
c
Department of Zoology, Animal Ecology, University of Gothenburg, Box 463, S-405 30 Gothenburg, Sweden
Received 20 August 2003; received in revised form 20 January 2004; accepted 21 January 2004
Abstract
In 1999, we published a report on how an introduction of 20 males into a severely inbred and isolated population of adders
(Vipera berus) halted its decline towards extinction, induced a profound change in population genetic variability, resulted in a
dramatic increase in offspring viability and thus in a rapid increase in numbers. Since the publication of our paper we have received
numerous inquiries as to whether we have continued to monitor this population, as this is the case we herein present population
demographic data gathered between 1981 and 2003. The population has continued to increase in numbers and in 2003, we collected
39 adult male adders, more than at any time over the 23-year study. Our continued work, hence, lends strong support to the im-
portance of novel genes in enhancing the viability of inbred populations and supports the importance of preserving genetic vari-
ability in order to maintain viable wild populations.
Ó 2004 Elsevier Ltd. All rights reserved.
Keywords: Novel genes; Genetic variability; Population size; Snake; Vipera berus
1. Introduction
Natural populations are increasingly becoming sub-
ject to the detrimental effects of human influences (e.g.
Walsh et al., 2003). Human activities have unfortunately
not only resulted in the extinction of numerous species
but also in a massive reduction in population numbers
and severe fragmentation of former habitats of vast
numbers of extant species (e.g. Frankham et al., 2002).
One consequence of the two latter factors is loss of ge-
netic diversity and although some authors have argued
that loss of genetic variability poses only a minor threat
to population survival, recent studies have demonstrated
that reduced genetic diversity will indeed increase the
risk of population extinction (e.g. Saccheri et al., 1998;
Madsen et al., 1999; Vil
a et al., 2003).
In 1999, we published a report on how an introduc-
tion of 20 males into a severely inbred and isolated
population of adders (Vipera berus) halted its decline
towards extinction, induced a profound change in pop-
ulation genetic variability, resulted in a dramatic in-
crease in offspring viability and thus a rapid increase in
numbers (Madsen et al., 1999). This type of population
recovery following translocation of animals between
populations has been referred to as genetic rescue
(Richards, 2000; Ingvarson, 2001). However, in a recent
review Fisher and Lindenmayer (2000) demonstrated
that translocations do not necessarily result in genetic
rescue because translocated animals may be poor
breeders or die, thus preventing their novel alleles from
being incorporated into the target population. They
concluded that: ÔRelocations are a commonly used,
popular, and potentially powerful tool for the conser-
vation of biodiversity. However, they are often carried
out in an ad hoc fashion, and are not carefully moni-
tored. In addition, most relocations are poorly docu-
mented in the published literature.Õ Since the publication
of our paper in 1999, the continued monitoring of the
adder population in Smygehuk has been the subject of
numerous inquiries. In this short note, we therefore
*
Corresponding author. Tel.: +46-46-222-3787; fax: +46-46-222-
4716.
E-mail address: thomas.madsen@zooekol.lu.se (T. Madsen).
0006-3207/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.biocon.2004.01.022
Biological Conservation 120 (2004) 145–147
www.elsevier.com/locate/biocon
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