Genetiken hos svenska fjällgäss - Svenska Jägareförbundet
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Blodprov tas på en vild svensk fjällgås 2010. Dessa prover kommer nu att analyseras och först då vet man om det finns genetiska problem i den svenska populationen.

Genetiken hos svenska fjällgäss

Kontroversen om genetiken går tillbaka till det gamla avelsbeståndet som änvändes fram till år 1999, där studier som genetiska forskare, i samarabete med Projekt Fjällgås, lät utföra i samarbete med genetiska forskare, visade att vissa individer i detta avelsbestånd hade bläsgåsgener i sig. Detta bestånd avskaffades 1999, dvs. för mer än 15 år sedan. Enligt det svenska åtgärdsprogrammet för fjällgås uppskattas att 5-10% av de utsättningsfåglar som härstammade från det gamla avelsbeståndet kunde vara bärare av bläsgås-DNA. Av de totalt 341 fjällgäss som sattes ut 1981-1999, gick mindre än 15 % av fåglarna till häckning och bidrog till den genetiska uppsättningen i den vilda populationen. Om de utsättningsfåglar som häckade hade föräldrar som hade bläsgås-DNA är okänt. Alla utsläppta fåglar från denna avelspopulation är idag döda.

Inga genetiska studier har gjorts på den vilda fjällgåspopulationen som idag häckar i Sverige. Genetiken i den svenska vilda populationen är med andra ord okänd för alla inblandade i debatten. Ändå anser sig BirdLife Norge ha en klar bild över förhållandena.

Upptäckten av bläsgås-DNA och betydelsen av detta har diskuterats länge. För oss i Projekt Fjällgås har dessa rön till stor del styrt vår verksamhet efter upptäckten. Redan tidigt fattades flera beslut baserade på försiktighetsprincipen, även om det innebar betydande avbräck i Projekt Fjällgås´ bevarandearbete. Men till skillnad från BirdLife Norge menar vi, med stöd av utomstående experter och svenska myndigheter, att eventuella problem kan lösas på ett konstruktivt sätt och genom långvarigt och hårt arbete. Vi tror att de åtgärder vi vidtagit är de mest lämpliga:

  1.  Hela det gamla avelsbeståndet avskaffades, som en försiktighetsåtgärd, trots att majoriteten av individer inte hade några påvisbara inslag av bläsgås-DNA.
  2.  Ett helt nytt avelsbestånd av vildfångade ryska fjällgäss har byggts upp med en genetik som följaktligen speglar det västryska beståndet. En population som dessutom har ett naturligt utbyte av individer med det norska beståndet. Utsättningar av dessa fåglar kommer på sikt att späda ut eventuella oönskade genetiska inslag.
  3. Ett avelsprogram med två större avelsstationer i södra Sverige har byggts upp.
  4. Utsättningar av ”ryska fjällgäss” startades upp 2010. När dessa individer parar sig med vilda svenska fjällgäss kommer andelen av, eventuellt, förekommande främmande gener att halveras i avkomman. Av de 6 kända lyckade häckningarna i det vilda beståndet år 2016 var honan i två par en utsättningsfågel (som bildat par med en vild hane).
  5. Under 2016/2017 pågår en omfattande genetisk studie av fjällgäss. Detta har vi ansett nödvändigt då inga studier har gjorts på det vilda beståndet i Sverige.  Med andra ord är det ingen som idag vet om det finns några spår av bläsgåsgener i det svenska beståndet. Från dessa studier kan vi sedan sätta mål för utspädningseffekten med ryska fjällgäss.

Detta åtgärdspaket har kostat, och kostar, mycket pengar och inneburit många års hårt arbete för projektet. Det är först nu vi kan börja hoppas på att dessa ansträngningar ska bära frukt då utsättningsfåglarna börjar nå könsmognad. I de vilda flockarna av fjällgäss i Sverige idag är mer än 40 % fåglar utsatta efter 2012, vilket tyder på att detta metodval är det rätta.

BirdLife Norges inställning

Från norsk sida hävdar man att den svenska populationen utgör ett allvarligt genetiskt hot mot andra populationer. Den norska uppfattningen har dock varierat genom åren och verkar styras av annat än det vetenskapliga underlaget. För att en gång för alla få klarhet om det eventuella genetiska risker, och andra frågor, begärde RECAP-kommittén* ett yttrande från en oberoende genetiker, amerikanen George Amato. Hans utredning presenterades för alla RECAP-medlemmar inklusive Norge och Finland i oktober 2010.  Vid mötet var BirdLife Norge närvarande och godtog slutsatserna som Amato framfört. (Meeting report 3rd Meeting of the Committee for Captive Breeding, Reintroduction and Supplementation of Lesser White-fronted Geese in Fennoscandia 2010:  “All RECAP Committee countries agreed with the conclusions and recommendations of the review”).

När BirdLife Norge godtog Amatos slutsatser ställde man sig bakom bl.a. följande:

  1. Den svenska populationen utgör inget hot av betydelse för andra populationer
  2. Utsättning av uppfödda fåglar bidrar till att späda ut eventuellt främmande gener
  3. Förstärkning av den svenska populationen med uppfödda fåglar rekommenderas
  4. Inga åtgärder behöver vidtas i form av genetiska analyser som bevis på främmande gener eller genom att avlägsna fåglarna ur sin miljö.

 I den norska rapporten 2016 framför emellertid BirdLife Norge nu helt andra uppfattningar utan att, vad vi känner till, några nya vetenskapliga arbeten utförts på området.:

  1. Den svenska populationen utgör ett allvarligt hot mot den Fennoskandiska
  2. Att utsatta fåglar kan späda ut främmande gener är extremt osannolikt
  3. Pågående utsättningsprojekt riskerar förekomsten av vilda fjällgäss i Fennoskandia. Alla nuvarande och planerade utsättningar av fjällgäss i Europa måste därför avbrytas omedelbart.
  4. Det finns ett starkt behov av att fånga de friflygande svenska fjällgässen för att undersöka deras genetiska status.

BirdLife Norge anser sig nu ha bättre kunskaper inom det genetiska området än den anlitade oberoende experten och frångår därför tidigare överenskommelser inom RECAP-kommittén. Detta trots att inga nya genetiska studier har gjorts.  För många som granskat BirdLife Norges försök att svartmåla det svenska bevarandearbetet med fjällgås står det klart att argumenten inte vilar på vetenskaplig grund utan på en ideologisk uppfattning om vad som är bäst ur norsk synpunkt.

* AEWAs RECAP kommitte: Committee on Captive Breeding, Reintroduction and Supplementation of Lesser White-fronted Geese. Se: http://www.unep-aewa.org/sites/default/files/document/lwfg_recap1_4_terms_reference_adopted.pdf

 

 

Genetics of the Swedish population of Lesser White-fronted Goose

 

Taking blood samples from a wild Swedish Lesser White-fronted Goose in 2010. The collected samples will now be analyzed with new technology and then it will be known if there are any genetic problems in the population.

The controversy about the genetics goes back to the old captive bred population, when researchers, in cooperation with the Project, showed that some individuals carried DNA from Greater White-fronted Geese (GWfG). This population was dismantled in 1999, that is more than 15 years ago.  According to the Swedish Action Plan for LWfG, it was estimated that 5-10% of the birds released could have carried GWfG-DNA. In all 341 LWfG were released 1981-1999. Less than 15% of these birds started to breed, thereby contributing genetically to the wild population. It is not known to what extent those birds carried any GWfG-DNA. All birds released from the old captive population are dead today.

No genetic studies have been conducted on the wild LWfG population breeding in Sweden today. Therefore, the genetics of this population is unknown to everyone involved in the discussion. Still BirdLife Norway and the authors of the report believes it has a clear picture of the situation.

The discovery of GWfG-DNA and the implication of this finding has been discussed since long. The finding of GWfG-DNA in our old captive breeding stock have had crucial implications, and been leading, for our conservation work. Quite early, decisions were made based on the precautionary principle, even if this meant a significant set-back in our project. But in contrast to BirdLife Norway we use the opinion of independent expertise and believe that possible problems can be solved constructively through long-lasting and hard work. Our line is supported by Swedish authorities. We believe that measures taken constitute the most appropriate step forward:

  1. The old captive breeding stock was dismantled as a precautionary step, in spite of the fact that the majority of individuals did not carry any DNA from Greater White-fronted Goose.
  2. A completely new breeding stock based on birds caught in northern Russia has been established. These birds genetically represent the West-Russian population, which has a natural exchange with the birds breeding in Norway. Release from this new captive bred population will gradually “swamp out” possible introgressed genes.
  3. A breeding programme including two major breeding stations in southern Sweden has been developed.
  4. The release of “Russian birds” started in 2010. When such birds mate with wild LWfG in Sweden the proportion of, possible, alien genes be reduced by 50% in the offspring. In 2016, six wild pairs were found breeding successfully.  From these, released females were represented in two pairs, mating wild males.
  5. In 2016/17 a comprehensive genetic study on LWfG is being performed. This is deemed to be necessary, as no genetic studies have been made on the wild population in Sweden. Consequently, there is no one that knows about possible elements of GWfG-DNA in the Swedish population. Based on the result of this study, an objective regarding the dilution of possible alien genes through the release of Russian LWfG can be formulated.

This action package has involved large sums of money and meant years of hard work for people involved in the Swedish LWfG Project. Not until now we can hope to see these efforts bear fruit as the released birds reach sexual maturity. More than 40% of the wild LWfG flocks in Sweden today consist of birds released after 2012, indicating that this method is effective.

The opinion of BirdLife Norway
According to BirdLife Norway, the Swedish LWfG population pose a serious genetic threat to other populations. The Norwegian attitude, however, has varied over time and the opinion seems to be based on non-scientific knowledge. To solve the controversials regarding the genetic issue, the RECAP* Committee requested a second opinion from an independent expert, the American geneticist George Amato. His review was presented to all RECAP members, including Norway and Finland in October 2010. BirdLife Norway was present at this meeting and accepted the conclusions presented by Amato. (Meeting report 3rd Meeting of the Committee for Captive Breeding, Reintroduction and Supplementation of Lesser White-fronted Geese in Fennoscandia 2010:  “All RECAP Committee countries agreed with the conclusions and recommendations of the review”).

When BirdLife Norway agreed with the conclusions made by Amato it accepted the following statements:

  1. Reinforcement of the Fennoscandian population with Swedish birds is beneficial
  2. The Swedish population does not pose a significant threat to other populations
  3. Release of captive bred birds will reduce possible introgressed genes
  4. Reinforcement of the Swedish population with captive bred birds is recommended
  5. No action needs to be initiated in terms of screening wild birds for evidence of hybrid genes or in removing birds from the ecosystem

In the Norwegian report 2016 BirdLife Norway now presents a quite different opinion but, to our knowledge, no new scientific work have been conducted on the subject:

  1. No reinforcement of the Fennoscandian population should take place
  2. The Swedish population poses a serious threat to the Fennoscandian population
  3. That release of captive bred birds will “swamp out” introgressed genes is extremely unlikely
  4. Ongoing release project is jeopardizing the existence of LWfG as a wild bird in Fennoscandia. All current and planned releases of LWfG in Europe should be halted immediately. Contact between the populations should be prevented
  5. There is a pressing need to capture the Swedish Lesser White‐fronted Geese for screening to examine the genetic make‐up of the birds at large.

Consequently, BirdLife Norway consider its own knowledge about LWfG genetics to be superior to the independent expert engaged and therefore abandons its previous agreement within the RECAP Committee. It should be noted that no additional genetic studies have been carried out. Many who have looked into the efforts by BirdLife Norway to defame LWfG conservation work in Sweden have come to the conclusion that the argument is based on an ideological conception about what is best from Norwegian point of view, rather than founded on scientific ground.

* AEWAs RECAP Committe: Committee on Captive Breeding, Reintroduction and Supplementation of Lesser White-fronted Geese. See: http://www.unep-aewa.org/sites/default/files/document/lwfg_recap1_4_terms_reference_adopted.pd

 

Scientific framework with references for interested readers.

No genetic studies have been conducted on the population currently breeding in the wild in the Swedish mountains.  The genetics of this population is thus unknown. All published studies that dealt with the genetic structure of the Swedish population are based on samples from the old captive population that was dismantled in 1999/2000.

None of the two independent genetic experts that reviewed the issue have found the introgression of GWfG-genes to be the cause of drastic actions. Both Lacy (2005) and Amato (2010) based their recommendations on the assumption that the numbers (36% of individuals) presented in Ruokonens papers were applicable to describe genetics of the released birds.

In the Swedish National Action Plan it was estimated, based on parental analysis, that 5-10% of the birds released 1981-1999 could be carriers of GWfG-genes.

Introgression of DNA from Greylag Geese has never been detected in the stocks used to produce birds for release in Sweden. It is not known which source BirdLife Norway uses as a base for such statement.

The majority of the released individuals 1981-1999 was lost and few birds have been observed to reproduce (less than 10% males and less than 15% females) and hence contribute to the genetics of the population (report from Swedish LWfG Project in prep).

Several specimens of hybrids LWfGxGWfG are reported to occur in museums (Voous & Wattel 1967, McCarthy 2006, Kampe-Persson & Lerner 2007, Nijman et al. 2010). Thus, hybridizations between Greater and Lesser White-fronted Geese have occurred, and may still occur in nature, independent of restocking programs.

Geese are among the bird taxa most likely to hybridize in nature (e.g. Randler 2008, Nijman et al. 2010) and recurrent hybridizations may account for the low level of genetic differentiation within the genus Anser (Ruokonen et. al. 2000, Gonzalez et. al. 2009, Ottenburghs et. al. 2016a). There are some recent works that have tried to give an overall picture of the phenomena (eg. Kampe-Person & Lerner 2007, Ottenburghs et.al. 2016a). Lesser White-fronted Geese have been reported to hybridize with Greater White-Fronted Goose, Snow Goose (A. caerulescens), Bar-headed Goose (A. indicus), Brent Goose (Branta bernicla), Barnacle Goose, and Red-breasted Goose (B. ruficollis) in the wild (summarized from McCarthy 2006, Kampe-Persson & Lerner 2007 and Ottenburghs et. al. 2016b).

There are no data to prove the claimed reproductive and genetic separation between the Swedish and Norwegian breeding populations of the Lesser White-fronted Goose in the past or at present.

Recent works on genetics and relationship analyses, applying new technology, within the genus Anser suggest that methods used earlier may be misleading. One example is Ruokonen's findings that LWfG may be closer to Taiga Bean and Pink-footed Geese than to GWfG.  This opinion is probably a result of “analytical shortcomings, incomplete lineage sorting and/or hybridization” (Ottenburghs et. al. 2016b).

Reference list

AEWA. 2008. International Single Species Action Plan for the Conservation of the Lesser White-fronted Goose (Western Palearctic population). Technical series

Amato, G. 2010. A Review of the Conservation Genetics Issues Confronting the Lesser White-fronted Goose Recovery Program. Expertise on behalf of he AEWA Secretariat.

Gonzalez J., Duttman H. & Wink M. 2009. Phylogenetic relationships based on two mitochondrial genes and hybridization patterns in Anatidae. J. Zool. 279: 310-318

Lacy, R C. 2005. Comments on the genetic issues related to the new Action Plan for the Lesser White-fronted Goose (L WfG). Expertise on behalf of he AEWA secretariat.

Madsen, J., Cracknell G. & Fox T. 1999. Goose Populations of the Western Palearctic. A review of status and distribution. Wetlands International Publication 48, NERI, Wageningen/Kalø.

Naturvårdsverket. 2011. Åtgärdsprogram för Fjällgås 2011-2015. Rapport 6434. Naturvårdsverket. Stockholm.

Nijman V.  Aliabadian, M. & C.S. Roselaar. 2010. Wild hybrids of Lesser White-fronted Goose (Anser erythropus) X Greater White-fronted Geese (A. albifrons) (Aves: Anseriformes) from the European migratory flyway. Zoologischer Anzeiger 248: 265-271.

Ottenburghs, J. Megens, H-J. Kraus, R.H.S. Madsen, Ole. van Hooft, P. van Wieren, S.E. Crooijmans, P.M.A. Ydenberg, R.C. Groenen, M.A.M. Prins, H.H.T. 2016a. A tree of geese: A phylogenomic perspective in the evolutionary history of true geese. Molecular phylogenetics and evolution 101: 303-313

Ottenburghs, J. van Hooft, P. van Wieren, S E. Ydenberg, R C. Prins, H H T. 2016b. Hybridization in geese: a review. Frontiers in Zoology 13: 20

Randler, C. 2008. Hybrid Wildfowl in Central Europe - an Overview. Waterbirds 31(1): 143-146.

Ruokonen, M. &  J. Lumme 1999. Phylogeography and population genetic structure of the Lesser White-fronted Goose. Fennoscandian Lesser White-fronted Goose conservation project. Annual report 1998. WWF Finland Report No. 10, NOF Rapportserie Report No. 1-1999.

Ruokonen, M., Kvist, L., Tegelström, H. & Lumme, J. 2000. Goose hybrids, captive breeding and restocking of the Fennoscandian populations of the Lesser White-fronted goose (Anser erythropus). Conservation Genetics.

Ruokonen, M. 2001. Phylogeography and conservation genetics of the Lesser White-fronted Goose (Anser erythropus). PhD Thesis, University of Oulu.

Ruokonen, M., Aarvak, T., Chesser, R.K., Lundqvist, A.-C. & Merilä, J. 2010. Temporal increase in mtDNA diversity in a declining population. Molecular Ecology 19: 2408-2417.

Voous, K.H. & J. Wattel 1967. Waarschijnlijke bastaard Kolgans x Dwerggans uit de natuur. – Limosa 40: 9-11.

 

 

 

 


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2017-01-04 2017-02-16