Salamander Longshanks – breed them out

3 02 2010

© M. Dawson

Patrick McGoohan in his role as the less-than-sentimental King Edward ‘Longshanks’ in the 1995 production of ‘Braveheart’ said it best in his references to the invocation of ius primæ noctis:

If we can’t get them out, we’ll breed them out

What a charmer.

Dabbling in molecular ecology myself over the past few years with some gel-jockey types (e.g., Dick Frankham [author of Introduction to Conservation Genetics], Melanie Lancaster, Paul Sunnucks, Yuji Isagi inter alios), I’m quite fascinated by the application of good molecular techniques in conservation biology. So when I came across the paper by Fitzpatrick and colleagues entitled Rapid spread of invasive genes into a threatened native species in PNAS, I was quite pleased.

When people usually think about invasive species, they tend to think ‘predator eating naïve native prey’ or ‘weed outcompeting native plant’. These are all big problems (e.g., think feral cats in Australia or knapweed in the USA), but what people probably don’t think about is the insidious concept of ‘genomic extinction’. This is essentially a congener invasive species breeding with a native one, thus ‘diluting’ the native’s genome until it no longer resembles its former self. A veritable case of ‘breeding them out’.

Who cares if at least some of the original genome remains? Some would argue that ‘biodiversity’ should be measured in terms of genetic diversity, not just species richness (I tend to agree), so any loss of genes is a loss of biodiversity. Perhaps more practically, hybridisation can lead to reduced fitness, like we observed in hybridised fur seals on Macquarie Island.

Fitzpatrick and colleagues measured the introgression of alleles from the deliberately introduced barred tiger salamander (Ambystoma tigrinum mavortium) into threatened California tiger salamanders (A. californiense) out from the initial introduction site. While most invasive alleles neatly stopped appearing in sampled salamanders not far from the introduction site, three invasive alleles persisted up to 100 km from the introduction site. Not only was the distance remarkable for such a small, non-dispersing beastie, the rate of introgression was much faster than would be expected by chance (60 years), suggesting selection rather than passive genetic drift. Almost none of the native alleles persisted in the face of the three super-aggressive invasive alleles.

The authors claim that the effects on native salamander fitness are complex and it would probably be premature to claim that the introgression is contributing to their threatened status, but they do raise an important management conundrum. If species identification rests on the characterisation of a specific genome, then none of the native salamanders would qualify for protection under the USA’s Endangered Species Act. They believe then that so-called ‘genetic purity’ is an impractical conservation goal, but it can be used to shield remaining ‘mostly native’ populations from further introgression.

Nice study.

CJA Bradshaw

ResearchBlogging.orgFitzpatrick, B., Johnson, J., Kump, D., Smith, J., Voss, S., & Shaffer, H. (2010). Rapid spread of invasive genes into a threatened native species Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0911802107

Lancaster, M., Bradshaw, C.J.A., Goldsworthy, S.D., & Sunnucks, P. (2007). Lower reproductive success in hybrid fur seal males indicates fitness costs to hybridization Molecular Ecology, 16 (15), 3187-3197 DOI: 10.1111/j.1365-294X.2007.03339.x

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4 responses

11 03 2012
» Butterfly Drawings Butterfly Facts

[…] Salamander Longshanks – breed them out « – What a charmer. Dabbling in molecular ecology myself over the past few years with some gel-jockey types (e.g., Dick Frankham [author of Introduction to Conservation Genetics], Melanie Lancaster, Paul Sunnucks, Yuji Isagi … […]


4 02 2010
Marty Deveney

All the seemingly irrelevant things I’ve done circle around me like echoes and return at the most unexpected moments.

The following is from experience and hearsay only – it is what I saw and was told more than a decade ago. I checked on the referenced aspects but the rest is merely experience and therefore subject to the normal biases and errors.

In some groups of religious Ashkenazic jews, women shave their heads the night before they get married and keep their hair shaved for the rest of their lives. They can and do wear wigs, but they continue to shave their heads.

Before I was a scientist I worked on Kafka. It was a good way to spend some time in Prague, which is a place that I love. There, I met some of these Ashkenazi, some of whom told me that the head shaving links back to the droit de signeur with the idea that the lord would not find a shaved woman attractive.

Whether the droit de signeur ever existed is doubtful; mediaeval researchers have found very limited evidence that it ever existed (Boureau 1998; Wettlaufer, 1999 – see links below), although Barsoumian (2004) stated that Kurdish khafirs retained this dubious right over Armenian brides until the early 20th century.

Like biological evolution, societies can evolve in ways that historical pressures continue to manifest after the selective process no longer exists. In this case, the the social pressure may not have ever existed, leaving open the fascinating possibilities that the real reason that this behaviour started has been lost (forgotten), that social factors in the group mean that it is improper to tell an outsider the real reason or origin, or that the droit de signeur existed but was poorly documented, or that evidence of its existence was lost. If the droit de signeur never existed and what I was told was correct, then it points to the social power of suggestion and rumour, useful for green- or blackwashing, returning us to conservation.




4 02 2010

Great comment, Marty. Thanks.


3 02 2010
Mary Ellen Ryall

Hi Corey, You are right on time with the invasive species article and reference to spotted knapweed. We hand eradicate it from the Monarch Butterfly Habitat in Shell Lake, Wisconsin and of course wear gloves. This plant is “Chemical Warfare” according to National Geographic. I published an article on the invasive plant in 2006. Only recently has the Department of Natural Resources (DNR) published an article that the plant is invasive in Michigan.

Cheers, Mary Ellen


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