Abstract
Fungal populations that reproduce sexually are likely to be genetically more diverse and have a higher adaptive potential than asexually reproducing populations. Mating systems of fungal species can be self-incompatible, requiring the presence of isolates of different mating-type genes for sexual reproduction to occur, or self-compatible, requiring only one. Understanding the distribution of mating-type genes in populations can help to assess the potential of self-incompatible species to reproduce sexually. In the locally threatened epiphytic lichen-forming fungus Lobaria pulmonaria (L.) Hoffm., low frequency of sexual reproduction is likely to limit the potential of populations to adapt to changing environmental conditions. Our study provides direct evidence of self-incompatibility (heterothallism) in L. pulmonaria. It can thus be hypothesized that sexual reproduction in small populations might be limited by an unbalanced distribution of mating-type genes. We therefore assessed neutral genetic diversity (using microsatellites) and mating-type ratio in 27 lichen populations (933 individuals). We found significant differences in the frequency of the two mating types in 13 populations, indicating a lower likelihood of sexual reproduction in these populations. This suggests that conservation translocation activities aiming at maximizing genetic heterogeneity in threatened and declining populations should take into account not only presence of fruiting bodies in transplanted individuals, but also the identity and balanced representation of mating-type genes.
Highlights
Sexual reproduction is an important factor for introducing genetic variation in populations, providing the basis for longterm adaptation and population survival [1]
Combining this sequence with the 454 sequence data we obtained a total of 900 bp sequence of MAT1-1. tBLASTx showed the presence of a conserved alpha box motif and high homology with MAT1-1 protein of various ascomycetes fungi: Xanthoria polycarpa (32%), Fusarium pseudograminearum, Fusarium lunulosporum, Fusarium culmorum (30%), Aspergillus parasiticus, A. flavus, A. oryzae (34%)
Our study provides genetic evidence of heterothallism in L. pulmonaria, i.e. the existence of a dimictic mating system with two idiomorphs, MAT1-1 and MAT1-2 located on a single locus
Summary
Sexual reproduction is an important factor for introducing genetic variation in populations, providing the basis for longterm adaptation and population survival [1]. Reshuffling gene combinations in sexual reproduction can potentially improve the adaptability of populations by producing progeny with enhanced abilities to cope with changing environmental conditions. Sexual populations have higher chances of survival and evolutionary potential than asexual populations [2]. In contrast, leads to genetic uniformity and is favorable for well-adapted populations in stable habitats as it preserves locally adapted genotypes. Genetic uniformity is the basis of vulnerability to epidemics and to biotic and abiotic stress [3] as it limits the ability of species to respond to these threats in both short and long terms. A population with low genetic diversity may have a low adaptive potential
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