Clonality and genetic variation in Amylostereum areolatum and A. chailletii from northern Europe

Abstract

Genetic variation within and between vegetative compatibility groups (VCGs) of Amylostereum areolatum (Fr.) Boid. and Amylostereum chailletii (Pers. : Fr.) Boid. isolates was investigated. DNA fingerprints were made using the M13 core sequence as a primer. A total of 53 isolates of A. areolatum and 57 isolates of A. chailletii from Lithuania, Sweden, Denmark and Great Britain were studied. In all cases isolates belonging to the same VCG showed identical DNA banding patterns, suggesting that VCGs correspond to clones. In A. areolatum the vast majority of the isolates (spread by Sirex juvencus L.) were assigned to dispersive clones, that have wide geographical distribution (i.e. the same genotypes were detected in Lithuania, Sweden and Denmark), with low genetic variation between the different clones. By contrast, A. chailletii population structure was consistent with the spread of airborne basidiospores produced by outcrossing. Only a small fraction of A. chailletii isolates studied, could be assigned to dispersal clones with a local distribution, spread by Urocerus gigas L. Overall, M13 fingerprinting detected low genetic differentiation in both species in the samples we studied.

Lack of fidelity revealed in an insect–fungal mutualism after invasion

“…Similarly, S. noctilio specimens carrying A. chailletii emerged from logs that were not infested with S. nigricornis. However, these wasps could have entered trees pre-infected via wind dispersed spores (as can occur with A. chailletii in Europe [20]), un-emerged woodwasp infestation or aborted woodwasp attacks. Important questions which should be addressed by further studies are whether carrying the 'wrong' symbiont influences wasp or fungal fitness, and whether novel symbiont associations are stable over longer time periods.…”

Diversity, population genetics, and evolution of macrofungi associated with animals

“…The relative roles of two types of spores spread by wasps vary among the fungal species. Vasiliauskas et al (Vasiliauskas et al 1998; Vasiliauskas and Stenlid 1999), Margrete Thomsen and Koch (1999) (Table 1), and Slippers et al (2005) investigated the genetic structure of A. areolatum and A. chailletii . They found that the isolates of both A. areolatum and A. chailletii can be spread clonally by woodwasps.…”

Mutualism and asexual reproduction influence recognition genes in a fungal symbiont

“…In this relationship, the fungus is necessary for the development of the larvae, while the woodwasp spreads the asexual spores and/or mycelium of the fungus (Vasiliauskas et al 1998, Thomsen andKoch 1999), thereby facilitating vertical transmission of A. areolatum (Madden 1981). Like other fungal symbionts of insects (Chapela et al 1994;Judson and Normark 1996), A. areolatum can also reproduce sexually and has a tetrapolar mating system, i.e., the genes governing sexual recognition in the fungus are present on two unlinked mating type loci (mat-A and mat-B) (Boidin and Lanquetin 1984;van der Nest et al 2008;.…”

“…The sexual sporocarps of these fungi are, however, rarely found in nature and usually only in the native range of the insect and fungus (Vasiliauskas and Stenlid 1999;Slippers et al 2003;Nielsen et al 2009). The population biology of these fungi also suggests that, like other insect symbionts, they rely on the woodwasp for the effective spread of asexual spores (Vasiliauskas et al 1998;Vasiliauskas and Stenlid 1999;Thomsen and Koch 1999).…”

“…The rab1 gene has been demonstrated previously to be involved in sexual recognition in A. areolatum (van der Nest et al 2008). For comparison, we included data from the closely related species A. chailletii that more frequently reproduces sexually (Vasiliauskas et al 1998;Vasiliauskas and Stenlid 1999;Slippers et al 6 2 0 0 1 ) . F i n a l l y , t h e s e s y s t e m s w e r e a l s o c o m p a r e d w i t h t h o s e o f o t h e r f r e e -l i v i n g Agaricomycetes.…”