Published online by Cambridge University Press: 05 September 2012
A high percentage of lichen-forming ascomycetes reproduce sexually and thus are assumed to disperse primarily via ascospores, which have to relichenize. However, one should keep in mind that even fertile lichens have options for vegetative dispersal in the symbiotic state, either via symbiotic propagules such as soredia, blastidia or isidia, or via thallus fragmentation. Viable fungal and algal cells were shown to be contained in fecal pellets of lichenivorous slugs (McCarthy and Healey 1978; Fröberg et al. 2001) and of the ever-present lichenivorous mites (Meier et al. 2002). Thus, it is not known how often relichenization occurs in natural habitats.
A detailed knowledge of sexual reproductive strategies is required for understanding evolutionary traits and population genetics. Zoller et al. (1999) were the first to recognize that lack of ascomata in strongly fragmented and geographically isolated populations of Lobaria pulmonaria (“lungwort”) might be due to missing mating partners. As this species produces abundant isidiate soredia, one might conclude that ascospores are unnecessary. However, recombination as the centrally important element of sexual reproduction has an impact on genetic stability, whereas favorable and unfavorable mutations are transmitted to the offspring in clonal (vegetative) dispersal. As pointed out by Hestmark (1992), sexual reproduction may often be a mode of escape from old, severely parasitized thalli (Seymour et al. 2005b). It remains to be seen how often new thalli are formed from germinating ascospores in rarely fertile species with efficient dispersal via vegetative symbiotic propagules, such as Pseudevernia furfuracea, Hypogymnia physodes and others.
To save this book to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.