Esa Huhta

Publications (3)6.55 Total impact

• Article: Evolution of defences against cuckoo (Cuculus canorus) parasitism in bramblings (Fringilla montifringilla): a comparison of four populations in Fennoscandia

  Johan Reinert Vikan, Bård Gunnar Stokke, Jarkko Rutila, Esa Huhta, Arne Moksnes, Eivin Røskaft
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  ABSTRACT: The brood parasitic common cuckoo Cuculus canorus has a history of coevolution that involves numerous passerine hosts, but today only a subset is known to be regularly parasitised in any area. In some hosts, there is significant variation in the occurrence of parasitism between populations, but still individuals in non-parasitised populations show strong antiparasite defences. In the present study we compared the strength of egg rejection of four distant Fennoscandian brambling Fringilla montifringilla populations experiencing different levels of cuckoo parasitism (0–6%). Egg rejection ability was in general very well developed and we did not find any population differences in the relationship between egg rejection probability and similarity between host and experimental parasitic eggs. Furthermore, bramblings very rarely made errors in rejection, indicating that selection against rejection behaviour is likely to be very weak. The brambling-cuckoo system therefore differs from other well studied systems which are characterised by pronounced spatial and temporal variation in the host’s level of defence. This result is unlikely to reflect independent replication of the same evolutionary trajectory because the weak breeding site tenacity of bramblings should result in an extreme amount of gene flow within the distribution area and thus strongly impede localised responses to selection. Instead, lack of geographic variation has more likely arisen because bramblings respond to selection as one evolutionary unit, and because the average parasitism pressures have been high enough in the past to cause regional fixation of rejection alleles and evolution of clutch characteristics that facilitate cost free egg recognition. KeywordsCoevolution-Brood parasitism-Egg rejection- Cuculus canorus
  Evolutionary Ecology 04/2012; 24(5):1141-1157. · 2.45 Impact Factor
• Source

  Available from: Arne Moksnes

  Article: Outcomes of brood parasite-host interactions mediated by egg matching: common cuckoos Cuculus canorus versus Fringilla finches.

  Johan Reinert Vikan, Frode Fossøy, Esa Huhta, Arne Moksnes, Eivin Røskaft, Bård Gunnar Stokke
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  ABSTRACT: Antagonistic species often interact via matching of phenotypes, and interactions between brood parasitic common cuckoos (Cuculus canorus) and their hosts constitute classic examples. The outcome of a parasitic event is often determined by the match between host and cuckoo eggs, giving rise to potentially strong associations between fitness and egg phenotype. Yet, empirical efforts aiming to document and understand the resulting evolutionary outcomes are in short supply. We used avian color space models to analyze patterns of egg color variation within and between the cuckoo and two closely related hosts, the nomadic brambling (Fringilla montifringilla) and the site fidelic chaffinch (F. coelebs). We found that there is pronounced opportunity for disruptive selection on brambling egg coloration. The corresponding cuckoo host race has evolved egg colors that maximize fitness in both sympatric and allopatric brambling populations. By contrast, the chaffinch has a more bimodal egg color distribution consistent with the evolutionary direction predicted for the brambling. Whereas the brambling and its cuckoo host race show little geographical variation in their egg color distributions, the chaffinch's distribution becomes increasingly dissimilar to the brambling's distribution towards the core area of the brambling cuckoo host race. High rates of brambling gene flow is likely to cool down coevolutionary hot spots by cancelling out the selection imposed by a patchily distributed cuckoo host race, thereby promoting a matching equilibrium. By contrast, the site fidelic chaffinch is more likely to respond to selection from adapting cuckoos, resulting in a markedly more bimodal egg color distribution. The geographic variation in the chaffinch's egg color distribution could reflect a historical gradient in parasitism pressure. Finally, marked cuckoo egg polymorphisms are unlikely to evolve in these systems unless the hosts evolve even more exquisite egg recognition capabilities than currently possessed.
  PLoS ONE 01/2011; 6(4):e19288. · 4.09 Impact Factor
• Source

  Available from: Craig Ryan Jackson

  Article: Fixed rejection responses to single and multiple experimental parasitism in two Fringilla hosts of the common cuckoo

  Johan R Vikan, Bå Rd, G Stokke, Frode Fossøy, Craig Jackson, Esa Huhta, Jarkko Rutilaà, Arne Moksnes, Eivin Røskaft