Propagule size is not a good predictor for regional population subdivision or fine-scale spatial structure in lichenized fungi

Regionally Varying Habitat Relationships in Lichens: The Concept and Evidence with an Emphasis on North-Temperate Ecosystems

Habitat ecology of lichens (lichen-forming fungi) involves diverse adaptations to stressful environments where lichens use specific habitat conditions. Field observations confirm that such habitat ‘preferences’ can vary significantly across species’ distribution ranges, sometimes revealing abrupt changes over short distances. We critically review and generalize such empirical evidence as broad ecological patterns, link these with the likely physiological mechanisms and evolutionary processes involved, and outline the implications for lichen conservation. Non-replicated correlative studies remain only suggestive because the data are frequently compromised by sampling bias and pervasive random errors; further noise is related to unrecognized cryptic species. Replicated evidence exists for three macroecological patterns: (a) regional limiting factors excluding a species from a part of its microhabitat range in suboptimal areas; (b) microhabitat shifts to buffer regionally adverse macroclimates; (c) substrate suitability changed by the chemical environment, notably air pollution. All these appear to be primarily buffering physiological challenges of the adverse conditions at the macrohabitat scale or, in favorable environments, coping with competition or predation. The roles of plasticity, adaptation, dispersal, and population-level stochasticity remain to be studied. Although lichens can inhabit various novel microhabitats, there is no evidence for a related adaptive change. A precautionary approach to lichen conservation is to maintain long-term structural heterogeneity in lichen habitats, and consider lichen ecotypes as potential evolutionarily significant units and a bet-hedging strategy for addressing the climate change-related challenges to biodiversity.

Functional Traits in Lichen Ecology: A Review of Challenge and Opportunity

Community ecology has experienced a major transition, from a focus on patterns in taxonomic composition, to revealing the processes underlying community assembly through the analysis of species functional traits. The power of the functional trait approach is its generality, predictive capacity such as with respect to environmental change, and, through linkage of response and effect traits, the synthesis of community assembly with ecosystem function and services. Lichens are a potentially rich source of information about how traits govern community structure and function, thereby creating opportunity to better integrate lichens into 'mainstream' ecological studies, while lichen ecology and conservation can also benefit from using the trait approach as an investigative tool. This paper brings together a range of author perspectives to review the use of traits in lichenology, particularly with respect to European ecosystems from the Mediterranean to the Arctic-Alpine. It emphasizes the types of traits that lichenologists have used in their studies, both response and effect, the bundling of traits towards the evolution of life-history strategies, and the critical importance of scale (both spatial and temporal) in functional trait ecology.

Deep divergence between island populations in lichenized fungi

Macaronesia is characterized by a high degree of endemism and represents a noteworthy system to study the evolutionary history of populations and species. Here, we compare the population-genetic structure in three lichen-forming fungi, the widespread Lobaria pulmonaria and two Macaronesian endemics, L. immixta and L. macaronesica, based on microsatellites. We utilize population genetic approaches to explore population subdivision and evolutionary history of these taxa on the Canary Islands, Madeira, Azores, and the western Iberian Peninsula. A common feature in all species was the deep divergence between populations on the Azores, a pattern expected by the large geographic distance among islands. For both endemic species, there was a major split between archipelagos. In contrast, in the widespread L. pulmonaria, divergent individuals were distributed across multiple archipelagos, suggesting a complex evolutionary history involving repeated migration between islands and mainland.

How do genes flow? Identifying potential dispersal mode for the semi-aquatic lichen Dermatocarpon luridum using spatial modelling and photobiont markers

Background

Landscape genetics is an interdisciplinary field that combines tools and techniques from population genetics with the spatially explicit principles from landscape ecology. Spatial variation in genotypes is used to test hypotheses about how landscape pattern affects dispersal in a wide range of taxa. Lichens, symbiotic associations between mycobionts and photobionts, are an entity for which little is known about their dispersal mechanism. Our objective was to infer the dispersal mechanism in the semi-aquatic lichen Dermatocarpon luridum using spatial models and the spatial variation of the photobiont, Diplosphaera chodatii. We sequenced the ITS rDNA and the β-actin gene regions of the photobiont and mapped the haplotype spatial distribution in Payuk Lake. We subdivided Payuk Lake into subpopulations and applied four spatial models based on the topography and hydrology to infer the dispersal mechanism.

Results

Genetic variation corresponded with the topography of the lake and the net flow of water through the waterbody. A lack of isolation-by-distance suggests high gene flow or dispersal within the lake. We infer the dispersal mechanism in D. luridum could either be by wind and/or water based on the haplotype spatial distribution of its photobiont using the ITS rDNA and β-actin markers.

Conclusions

We inferred that the dispersal mechanism could be either wind and/or water dispersed due to the conflicting interpretations of our landscape hypotheses. This is the first study to use spatial modelling to infer dispersal in semi-aquatic lichens. The results of this study may help to understand lichen dispersal within aquatic landscapes, which can have implications in the conservation of rare or threatened lichens.

Genetic variation and factors affecting the genetic structure of the lichenicolous fungus Heterocephalacria bachmannii (Filobasidiales, Basidiomycota)

Heterocephalacria bachmannii is a lichenicolous fungus that takes as hosts numerous lichen species of the genus Cladonia. In the present study we analyze whether the geographical distance, the host species or the host secondary metabolites determine the genetic structure of this parasite. To address the question, populations mainly from the Southern Europe, Southern Finland and the Azores were sampled. The specimens were collected from 20 different host species representing ten chemotypes. Three loci, ITS rDNA, LSU rDNA and mtSSU, were sequenced. The genetic structure was assessed by AMOVA, redundance analyses and Bayesian clustering methods. The results indicated that the host species and the host secondary metabolites are the most influential factors over the genetic structure of this lichenicolous fungus. In addition, the genetic structure of H. bachmannii was compared with that of one of its hosts, Cladonia rangiformis. The population structure of parasite and host were discordant. The contents in phenolic compounds and fatty acids of C. rangiformis were quantified in order to test whether it had some influence on the genetic structure of the species. But no correlation was found with the genetic clusters of H. bachmannii.

Discovery of long-distance gamete dispersal in a lichen-forming ascomycete

Accurate estimates of gamete and offspring dispersal range are required for the understanding and prediction of spatial population dynamics and species persistence. Little is known about gamete dispersal in fungi, especially in lichen-forming ascomycetes. Here, we estimate the dispersal functions of clonal propagules, gametes and ascospores of the epiphytic lichen Lobaria pulmonaria. We use hierarchical Bayesian parentage analysis, which integrates genetic and ecological information from multiannual colonization and dispersal source data collected in a large, old-growth forest landscape. The effective dispersal range of gametes is several hundred metres to kilometres from potential paternal individuals. By contrast, clonal propagules disperse only tens of metres, and ascospores disperse over several thousand metres. Our study reveals the dispersal distances of individual reproductive units; clonal propagules, gametes and ascospores, which is of great importance for a thorough understanding of the spatial dynamics of ascomycetes. Sexual reproduction occurs between distant individuals. However, whereas gametes and ascospores disperse over long distances, the overall rate of colonization of trees is low. Hence, establishment is the limiting factor for the colonization of new host trees by the lichen in old-growth landscapes.

Microsatellite loci in two epiphytic lichens with contrasting dispersal modes: Nephroma laevigatum and N. parile (Nephromataceae)

PREMISE OF THE STUDY

Microsatellite markers were characterized for two epiphytic cyanolichens, Nephroma laevigatum and N. parile (Nephromataceae), and will be used to investigate population structure and estimate gene flow among populations of these two closely related species with contrasting dispersal modes. •

METHODS AND RESULTS

Twelve and 14 microsatellite loci were characterized for N. laevigatum and N. parile, respectively. Allele number in N. laevigatum ranged from three to 13 per locus, while in N. parile there were from two to six alleles per locus. As expected, the sexually reproducing N. laevigatum had higher genetic diversity than the predominantly asexual N. parile. •

CONCLUSIONS

This new set of markers is suitable for studying population structure and providing insights into gene flow among populations and for understanding processes of diversification. Compared between the species, they will facilitate an understanding of the influence of contrasting reproductive strategies on population and community structure.