title: The evolution of host associations in the parasitic wasp genus Ichneumon (Hymenoptera: Ichneumonidae): convergent adaptations to host pupation sites.
abstract: BACKGROUND
  The diversification of organisms with a parasitic lifestyle is often tightly linked to the evolution of their host associations. If a tight host association exists, closely related species tend to attack closely related hosts; host associations are less stable if associations are determined by more plastic traits like parasitoid searching and oviposition behaviour. The pupal-parasitoids of the genus Ichneumon attack a variety of macrolepidopteran hosts. They are either monophagous or polyphagous, and therefore offer a promissing system to investigate the evolution of host associations. Ichneumon was previously divided into two groups based on general body shape; however, a stout shape has been suggested as an adaptation to buried host pupation sites, and might thus not represent a reliable phylogenetic character.
  
  
  RESULTS
  We here reconstruct the first molecular phylogeny of the genus Ichneumon using two mitochondrial (CO1 and NADH1) and one nuclear marker (28S). The resulting phylogeny only supports monophyly of Ichneumon when Ichneumon lugens Gravenhorst, 1829 (formerly in Chasmias, stat. rev.) and Ichneumon deliratorius Linnaeus, 1758 (formerly Coelichneumon) are included. Neither parasitoid species that attack hosts belonging to one family nor those attacking butterflies (Rhopalocera) form monophyletic clades. Ancestral state reconstructions suggest multiple transitions between searching for hosts above versus below ground and between a stout versus elongated body shape. A model assuming correlated evolution between the two characters was preferred over independent evolution of host-searching niche and body shape.
  
  
  CONCLUSIONS
  Host relations, both in terms of phylogeny and ecology, evolved at a high pace in the genus Ichneumon. Numerous switches between hosts of different lepidopteran families have occurred, a pattern that seems to be the rule among idiobiont parasitoids. A stout body and antennal shape in the parasitoid female is confirmed as an ecological adaptation to host pupation sites below ground and has evolved convergently several times. Morphological characters that might be involved in adaptation to hosts should be avoided as diagnostic characters for phylogeny and classification, as they can be expected to show high levels of homoplasy.
authors.affiliation: Natural History Museum, Department of Invertebrates, Bernastrasse 15, Bern CH-3005, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Tschopp
authors.forename: Matthias
authors.initials: M
authors.lastname: Riedel
authors.forename: Christian
authors.initials: C
authors.lastname: Kropf
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Nentwig
authors.forename: Seraina
authors.initials: S
authors.lastname: Klopfstein
mesh_terms: D000818:Animals; D057506:Arthropod Antennae / Q000033:anatomy & histology; D005075:Biological Evolution; D017753:Ecosystem; D006790:Host-Parasite Interactions; D007915:Lepidoptera / Q000469:parasitology*; D010802:Phylogeny; D014863:Wasps / Q000033:anatomy & histology / Q000145:classification / Q000235:genetics* / Q000502:physiology
references.citation: Syst Biol. 2004 Oct;53(5):793-808
references.pmid: 15545256
references.citation: Syst Biol. 2008 Oct;57(5):758-71
references.pmid: 18853362
references.citation: Evolution. 2003 Apr;57(4):717-45
references.pmid: 12778543
references.citation: Mol Phylogenet Evol. 1999 Aug;12(3):282-94
references.pmid: 10413623
references.citation: Science. 2006 Apr 21;312(5772):367; author reply 367
references.pmid: 16627724
references.citation: Mol Ecol. 2008 Sep;17(17):3917-27
references.pmid: 18662219
references.citation: BMC Biol. 2009 Jan 15;7:2
references.pmid: 19146674
references.citation: Syst Biol. 2007 Apr;56(2):232-51
references.pmid: 17464880
references.citation: Syst Biol. 2004 Feb;53(1):47-67
references.pmid: 14965900
references.citation: Mol Phylogenet Evol. 1997 Jun;7(3):281-93
references.pmid: 9187088
references.citation: Bioinformatics. 2003 Aug 12;19(12):1572-4
references.pmid: 12912839
references.citation: Mol Biol Evol. 2007 Aug;24(8):1596-9
references.pmid: 17488738
references.citation: J Mol Evol. 2005 Jul;61(1):114-37
references.pmid: 16059751
references.citation: Proc Natl Acad Sci U S A. 2008 Aug 26;105(34):12359-64
references.pmid: 18716001
references.citation: Proc Biol Sci. 2003 Aug 7;270 Suppl 1:S96-9
references.pmid: 12952648
references.citation: PLoS One. 2012;7(2):e32101
references.pmid: 22355411
references.citation: Proc Biol Sci. 2003 Dec 22;270(1533):2623-9
references.pmid: 14728786
references.citation: Syst Biol. 2004 Oct;53(5):673-84
references.pmid: 15545248
references.citation: Arthropod Struct Dev. 2011 Jan;40(1):2-20
references.pmid: 20951828
references.citation: Syst Biol. 2007 Aug;56(4):643-55
references.pmid: 17661232
references.citation: Am Nat. 2006 Jun;167(6):808-25
references.pmid: 16685633
references.citation: BMC Evol Biol. 2008 Dec 04;8:329
references.pmid: 19055825
references.citation: Syst Biol. 2010 Mar;59(2):226-41
references.pmid: 20525632
references.citation: Mol Mar Biol Biotechnol. 1994 Oct;3(5):294-9
references.pmid: 7881515
references.citation: Proc Biol Sci. 2000 Dec 7;267(1460):2403-9
references.pmid: 11133030
references.citation: Mol Ecol. 2011 Jan;20(1):179-86
references.pmid: 21083857
references.citation: Syst Biol. 2005 Jun;54(3):373-90
references.pmid: 16012105
references.citation: Bioinformatics. 2004 Jan 22;20(2):289-90
references.pmid: 14734327
references.citation: Syst Biol. 2012 Oct;61(5):851-69
references.pmid: 22398121
references.citation: Nucleic Acids Res. 1994 Nov 11;22(22):4673-80
references.pmid: 7984417
references.citation: Arthropod Struct Dev. 2003 Oct;32(2-3):277-87
references.pmid: 18089012
references.citation: Mol Ecol. 2009 Nov;18(22):4541-50
references.pmid: 19821901
references.citation: Mol Phylogenet Evol. 1999 Mar;11(2):236-45
references.pmid: 10191068