Classical hypotheses in lichenology predict pairs of species in which sexual lineages are ancestral and long-lived evolutionarily and that these give rise to derived, evolutionarily transient asexual lineages. Extensive phylogenetic information generated over the last 20 years regarding relationships within and among various groups of lichens makes possible an investigation of polarity and lability in reproductive mode across diverse clades. To test the long-held hypothesis of asexual reproduction as an evolutionary dead end in lichens, existing phylogenetic data from 23 studies were utilized to reconstruct gains and losses of sexual and asexual reproduction in a model-based statistical framework. Summed across all studies, between 26–44 origins of asexual reproduction from sexual ancestors (forward transitions) and 14–25 origins of sexual reproduction from asexual ancestors (reverse transitions) were identified. However, the higher number of gains of asexual reproduction was concentrated in a relatively low number of clades (e.g. Dirina). The greater number of forward compared to reverse transitions is consistent with dogma in both lichenology and evolutionary biology, but nonetheless this study documents numerous reverse transitions, suggesting that asexual lineages represent a source for evolutionary innovation.

A standardized morphological terminology and descriptive scheme for the sterile asexually reproducing genus Lepraria s. lat. is presented. The contribution includes observations on development and ontogeny of morphological structures and is extensively illustrated with scanning electron and light micrographs. Lepraria has long been considered to be devoid of morphological characters, however the results of extensive micro- and macro-morphological studies strongly refute this hypothesis. The morphological structures of the thallus are defined and described based on their varying degrees of complexity. Thalline morphological variability in the group is categorized into two major types that are further subdivided into six subtypes. Each subtype is described and an artifical key to the subtypes is provided.

Two asexual reproductive strategies of the common lichen Pseudevernia furfuracea are described. Although the species propagates mainly by isidia, some specimens also show the development of soralia. Morphological, chemical and molecular analyses were performed on three such sorediate specimens from the Canary Islands, Morocco and Turkey. Maximum parsimony, maximum likelihood and Bayesian analyses indicate that: a) sorediate samples represent only a morphological variant of the reproductive mode and b) the separation of taxa (at species level or below) on the basis of their containing either olivetoric acid or physodic and oxyphysodic acids is not appropriate. In addition, a phylogenetic reconstruction of the genus Pseudevernia is presented for the first time. The tree shows two sister monophyletic clades, one containing American species (P. intensa, P. cladonia, P. consocians), and the second encompassing the P. furfuracea samples (including sorediate specimens). The biological and taxonomic significance of soralia in sorediate samples is discussed.

Four species of the genus Graphis Adans. are described as new to science, namely G. archeri, G. invisibilis, G. lueckingii and G. paranaensis. These new species were found growing in restinga forest in southern Brazil.

The in-vitro growth rate of soredia from the epiphytic lichen species Physcia tenella was tested at different concentrations of phenols added in an in vitro experiment designed to evaluate the allelopathic effects of bark derived substances in stem flow. The conditions used were designed to resemble those found on bark of Populus×canadensis, as this tree species has been widely used for lichen mapping studies in Germany. Bark phenolic glycosides, flavonoids and tannins undergo hydrolytic decomposition in stem flow, resulting in a variety of monomeric phenolic acids, aldehydes and alcohols. Eleven phenolic substances of different biosynthetic origin in the concentration range between 10−6 M and 10−3 M in the culture medium were tested. IC50 values were calculated for each substance. Inhibition was highest for catechol, substituted phenolic glycosides, benzoic and ellagic acids, moderate for flavonoids, gallic acid, salicylic alcohol, salicylic aldehyde and low for salicylic acid. The tests show that bark phenols in natural concentrations inhibit soredial growth of the test species Physcia tenella and therefore have an influence on the growth of lichens on trees.

Juvenile development has been investigated for the first time in an Antarctic lichen species—Usnea antarctica—in the northern maritime Antarctic, Livingston Island (South Shetland Islands, 62°27′–62°48′S, 59°45′–61°15′W). Here, U. antarctica grows on rocks and forms the dominant vegetation on this site together with a few other macrolichens. This species reproduces mainly by vegetative diaspores (soredia), which include both the photobiont and the mycobiont. To understand the early ontogenetic strategies in U. antarctica, culture experiments were performed in an Antarctic field site where the species occurs naturally. This paper focuses on the different developmental steps seen between the initial colonization of soredia to the formation of a small well-developed thallus, and also on the growth rate of the respective juvenile stages. Compared with growth rates of lichens from temperate European regions the early development of U. antarctica is extraordinarily slow, taking 5–6 years until an adult thallus has been formed. The low photobiont content in the juvenile stages probably limits the growth rate. It is suggested that juvenile development of U. antarctica is controlled by a combination of ecophysiological and morphological adaptations that are required for success in extreme environments such as the terrestrial habitats of the Antarctic.