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The dispersion and detection patterns of mtDNA-assigned red fox Vulpes vulpes scats in Tasmania are anomalous.

Marks CA, Obendorf D, Pereira F, Edwards I, Hall GP - J Appl Ecol (2014)

Bottom Line: The majority of assigned mtDNA positive scats were found in urban and peri-urban environments corresponding to small mainland fox home ranges (30-45 ha) that imply higher scat density and more certain replication.Synthesis and applications.Type I error, which may have various sources, should be considered when scat mtDNA data are few, accumulated over many years, uncorroborated by observations of extant specimens, inadequately replicated in independent surveys within an expected spatiotemporal scale and reported in geographically isolated environments unlikely to have been colonized.

View Article: PubMed Central - PubMed

Affiliation: Nocturnal Wildlife Research Pty Ltd Wattletree Rd, Malvern, VIC, 3144, Australia.

ABSTRACT

Models used for resource allocation in eradication programmes must be based on replicated data of known quality and have proven predictive accuracy, or they may provide a false indication of species presence and/or distribution. In the absence of data corroborating the presence of extant foxes Vulpes vulpes in Tasmania, a habitat-specific model based upon mtDNA data (Sarre et al. 2012. Journal Applied Ecology, 50, 459-468) implied that foxes were widespread. Overall, 61 of 9940 (0·6%) surveyed scats were assigned as mtDNA fox positive by the fox eradication programme (FEP). We investigated the spatiotemporal distribution of the 61 mtDNA-assigned fox scats and modelled the probability of replicating scat detection in independent surveys using detection dogs based upon empirically derived probabilities of scat detection success obtained by the FEP using imported fox scats. In a prior mainland study, fox genotypes were recurrently detected in a consecutive four-day pool of scats. In Tasmania, only three contemporaneously collected scat pairs of unknown genotype were detected by the FEP within an area corresponding to a conservatively large mainland fox home range (639 ha) in a decade. Nearest neighbour pairs were widely spaced (mean = 7·0 km; circular area = 153 km(2)) and generated after a mean of 281 days. The majority of assigned mtDNA positive scats were found in urban and peri-urban environments corresponding to small mainland fox home ranges (30-45 ha) that imply higher scat density and more certain replication. Using the lowest empirically determined scat detection success for dogs, the failure to replicate fox scat detection on 34 of 36 occasions in a large (639 ha) home range is highly improbable (P = 0·00001) and suggestive of Type I error. Synthesis and applications. Type I error, which may have various sources, should be considered when scat mtDNA data are few, accumulated over many years, uncorroborated by observations of extant specimens, inadequately replicated in independent surveys within an expected spatiotemporal scale and reported in geographically isolated environments unlikely to have been colonized.

No MeSH data available.


Related in: MedlinePlus

Location of 61 mtDNA-assigned fox-positive scats in Tasmania relative to major highways (double lines), railway tracks (black line) and the urban centres of Burnie (B), Devonport (D), Launceston (L), Conara (C) and Hobart (H).
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fig01: Location of 61 mtDNA-assigned fox-positive scats in Tasmania relative to major highways (double lines), railway tracks (black line) and the urban centres of Burnie (B), Devonport (D), Launceston (L), Conara (C) and Hobart (H).

Mentions: The European red fox Vulpes vulpes established in mainland Australia after at least nine separate introductions after 1845 (Abbott 2011) and presently inhabits much of continental Australia where it threatens the conservation status of a range of fauna (Bennett, Lumsden & Menkhorst 1989; Dickman 1996; Priddel & Wheeler 1997). Since 1843, a number of historical and anecdotal reports implied that red foxes were also released in Tasmania, yet no reports of a potentially establishing population were made until 2001 (Marks et al. 2014) when it was reported that 11–19 foxes had been deliberately released (Dennis 2002; Saunders et al. 2006; Sarre et al. 2007; Marshall 2011). Soon after, opportunistically acquired fox carcasses presented by members of the public, some of which were quickly attributed to hoaxing using foxes sourced from mainland Australia (Saunders et al. 2006; Marks et al. 2014), prompted the Tasmanian government to conclude that a fox eradication programme (FEP) was warranted (Wilkinson 2009). Molecular survey techniques targeting red fox mitochondrial DNA (mtDNA) were used after 2005 in an attempt to detect red fox scats in the Tasmanian environment (Berry et al. 2007) in contrast to the use of microsatellites that had previously been used to identify genotypes on the mainland (Piggott et al. 2008; Marks et al. 2009). Between 2002 and 2012, coordinated searches using volunteers and trained fox scat detection dogs (Smith et al. 2003; Vynne et al. 2011) collected 9940 putative fox scats of which 61 (0·6%) were initially assigned as mtDNA fox positive (Anon 2012) (Fig.1). Thereafter, Sarre et al. (2012) retrospectively reported that from 7658 predator scats from which DNA was amplified, 56 had produced fox indicative sequences. Together with 9 unspecified cases of opportunistically acquired post-mortem evidence that are of equivocal evidentiary quality (Marks et al. 2014), the authors produced a habitat-specific model and concluded that foxes were now widespread in Tasmania. In the absence of data confirming the presence of extant foxes or independent data permitting the predictive capacity of the model to be tested, we undertook a qualitative analysis (Vaughan & Ormerod 2005) of the molecular data collected by the FEP.


The dispersion and detection patterns of mtDNA-assigned red fox Vulpes vulpes scats in Tasmania are anomalous.

Marks CA, Obendorf D, Pereira F, Edwards I, Hall GP - J Appl Ecol (2014)

Location of 61 mtDNA-assigned fox-positive scats in Tasmania relative to major highways (double lines), railway tracks (black line) and the urban centres of Burnie (B), Devonport (D), Launceston (L), Conara (C) and Hobart (H).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4301185&req=5

fig01: Location of 61 mtDNA-assigned fox-positive scats in Tasmania relative to major highways (double lines), railway tracks (black line) and the urban centres of Burnie (B), Devonport (D), Launceston (L), Conara (C) and Hobart (H).
Mentions: The European red fox Vulpes vulpes established in mainland Australia after at least nine separate introductions after 1845 (Abbott 2011) and presently inhabits much of continental Australia where it threatens the conservation status of a range of fauna (Bennett, Lumsden & Menkhorst 1989; Dickman 1996; Priddel & Wheeler 1997). Since 1843, a number of historical and anecdotal reports implied that red foxes were also released in Tasmania, yet no reports of a potentially establishing population were made until 2001 (Marks et al. 2014) when it was reported that 11–19 foxes had been deliberately released (Dennis 2002; Saunders et al. 2006; Sarre et al. 2007; Marshall 2011). Soon after, opportunistically acquired fox carcasses presented by members of the public, some of which were quickly attributed to hoaxing using foxes sourced from mainland Australia (Saunders et al. 2006; Marks et al. 2014), prompted the Tasmanian government to conclude that a fox eradication programme (FEP) was warranted (Wilkinson 2009). Molecular survey techniques targeting red fox mitochondrial DNA (mtDNA) were used after 2005 in an attempt to detect red fox scats in the Tasmanian environment (Berry et al. 2007) in contrast to the use of microsatellites that had previously been used to identify genotypes on the mainland (Piggott et al. 2008; Marks et al. 2009). Between 2002 and 2012, coordinated searches using volunteers and trained fox scat detection dogs (Smith et al. 2003; Vynne et al. 2011) collected 9940 putative fox scats of which 61 (0·6%) were initially assigned as mtDNA fox positive (Anon 2012) (Fig.1). Thereafter, Sarre et al. (2012) retrospectively reported that from 7658 predator scats from which DNA was amplified, 56 had produced fox indicative sequences. Together with 9 unspecified cases of opportunistically acquired post-mortem evidence that are of equivocal evidentiary quality (Marks et al. 2014), the authors produced a habitat-specific model and concluded that foxes were now widespread in Tasmania. In the absence of data confirming the presence of extant foxes or independent data permitting the predictive capacity of the model to be tested, we undertook a qualitative analysis (Vaughan & Ormerod 2005) of the molecular data collected by the FEP.

Bottom Line: The majority of assigned mtDNA positive scats were found in urban and peri-urban environments corresponding to small mainland fox home ranges (30-45 ha) that imply higher scat density and more certain replication.Synthesis and applications.Type I error, which may have various sources, should be considered when scat mtDNA data are few, accumulated over many years, uncorroborated by observations of extant specimens, inadequately replicated in independent surveys within an expected spatiotemporal scale and reported in geographically isolated environments unlikely to have been colonized.

View Article: PubMed Central - PubMed

Affiliation: Nocturnal Wildlife Research Pty Ltd Wattletree Rd, Malvern, VIC, 3144, Australia.

ABSTRACT

Models used for resource allocation in eradication programmes must be based on replicated data of known quality and have proven predictive accuracy, or they may provide a false indication of species presence and/or distribution. In the absence of data corroborating the presence of extant foxes Vulpes vulpes in Tasmania, a habitat-specific model based upon mtDNA data (Sarre et al. 2012. Journal Applied Ecology, 50, 459-468) implied that foxes were widespread. Overall, 61 of 9940 (0·6%) surveyed scats were assigned as mtDNA fox positive by the fox eradication programme (FEP). We investigated the spatiotemporal distribution of the 61 mtDNA-assigned fox scats and modelled the probability of replicating scat detection in independent surveys using detection dogs based upon empirically derived probabilities of scat detection success obtained by the FEP using imported fox scats. In a prior mainland study, fox genotypes were recurrently detected in a consecutive four-day pool of scats. In Tasmania, only three contemporaneously collected scat pairs of unknown genotype were detected by the FEP within an area corresponding to a conservatively large mainland fox home range (639 ha) in a decade. Nearest neighbour pairs were widely spaced (mean = 7·0 km; circular area = 153 km(2)) and generated after a mean of 281 days. The majority of assigned mtDNA positive scats were found in urban and peri-urban environments corresponding to small mainland fox home ranges (30-45 ha) that imply higher scat density and more certain replication. Using the lowest empirically determined scat detection success for dogs, the failure to replicate fox scat detection on 34 of 36 occasions in a large (639 ha) home range is highly improbable (P = 0·00001) and suggestive of Type I error. Synthesis and applications. Type I error, which may have various sources, should be considered when scat mtDNA data are few, accumulated over many years, uncorroborated by observations of extant specimens, inadequately replicated in independent surveys within an expected spatiotemporal scale and reported in geographically isolated environments unlikely to have been colonized.

No MeSH data available.


Related in: MedlinePlus