Ülle Reier

The online database MaarjAM reveals global and ecosystemic distribution patterns in arbuscular mycorrhizal fungi (Glomeromycota).

• Here, we describe a new database, MaarjAM, that summarizes publicly available Glomeromycota DNA sequence data and associated metadata. The goal of the database is to facilitate the description of distribution and richness patterns in this group of fungi. • Small subunit (SSU) rRNA gene sequences and available metadata were collated from all suitable taxonomic and ecological publications. These data have been made accessible in an open-access database (http://maarjam.botany.ut.ee). • Two hundred and eighty-two SSU rRNA gene virtual taxa (VT) were described based on a comprehensive phylogenetic analysis of all collated Glomeromycota sequences. Two-thirds of VT showed limited distribution ranges, occurring in single current or historic continents or climatic zones. Those VT that associated with a taxonomically wide range of host plants also tended to have a wide geographical distribution, and vice versa. No relationships were detected between VT richness and latitude, elevation or vascular plant richness. • The collated Glomeromycota molecular diversity data suggest limited distribution ranges in most Glomeromycota taxa and a positive relationship between the width of a taxons geographical range and its host taxonomic range. Inconsistencies between molecular and traditional taxonomy of Glomeromycota, and shortage of data from major continents and ecosystems, are highlighted.

Global assessment of arbuscular mycorrhizal fungus diversity reveals very low endemism

Cosmopolitan plant root symbionts The aboveground lives of plants are only sustainable because of the symbiotic soil fungi that encase their roots. These fungi swap nutrients with plants, defend them from attack, and help them withstand abrupt environmental changes. Out of necessity, fungal symbionts in the soil would appear to be restricted and local to certain plant species. Davison et al., however, discovered that some taxa are globally distributed. How these underground fungi have dispersed so widely remains a mystery; perhaps human farmers have had something to do with it. Science, this issue p. 970 The wide distribution of plant-root fungal symbionts seems to be driven by recent dispersal rather than ancient tectonics. The global biogeography of microorganisms remains largely unknown, in contrast to the well-studied diversity patterns of macroorganisms. We used arbuscular mycorrhizal (AM) fungus DNA from 1014 plant-root samples collected worldwide to determine the global distribution of these plant symbionts. We found that AM fungal communities reflected local environmental conditions and the spatial distance between sites. However, despite AM fungi apparently possessing limited dispersal ability, we found 93% of taxa on multiple continents and 34% on all six continents surveyed. This contrasts with the high spatial turnover of other fungal taxa and with the endemism displayed by plants at the global scale. We suggest that the biogeography of AM fungi is driven by unexpectedly efficient dispersal, probably via both abiotic and biotic vectors, including humans.

Global sampling of plant roots expands the described molecular diversity of arbuscular mycorrhizal fungi.

We aimed to enhance understanding of the molecular diversity of arbuscular mycorrhizal fungi (AMF) by building a new global dataset targeting previously unstudied geographical areas. In total, we sampled 96 plant species from 25 sites that encompassed all continents except Antarctica. AMF in plant roots were detected by sequencing the nuclear SSU rRNA gene fragment using either cloning followed by Sanger sequencing or 454-sequencing. A total of 204 AMF phylogroups (virtual taxa, VT) were recorded, increasing the described number of Glomeromycota VT from 308 to 341 globally. Novel VT were detected from 21 sites; three novel but nevertheless widespread VT (Glomus spp. MO-G52, MO-G53, MO-G57) were recorded from six continents. The largest increases in regional VT number were recorded in previously little-studied Oceania and in the boreal and polar climatic zones — this study providing the first molecular data from the latter. Ordination revealed differences in AM fungal communities between different continents and climatic zones, suggesting that both biogeographic history and environmental conditions underlie the global variation of those communities. Our results show that a considerable proportion of Glomeromycota diversity has been recorded in many regions, though further large increases in richness can be expected in remaining unstudied areas.

Past and present effectiveness of protected areas for conservation of naturally and anthropogenically rare plant species.

The Global Strategy of Plant Conservation states that at least 60% of threatened plant species should be within protected areas. This goal has been met in some regions with long traditions of plant protection. We used gap analysis to explore how particular groups of species of conservation interest, representing different types of natural or anthropogenic rarity, have been covered by protected areas on a national scale in Estonia during the last 100 years. Species-accumulation curves indicated that plant species that are naturally rare (restricted global or local distribution, always small populations, or very rare habitat requirements) needed almost twice as many protected areas to reach the 60% target as plant species that are rare owing to lack of suitable management (species depending on grassland management, moderate forest disturbances, extensive traditional agriculture, or species potentially threatened by collecting). Temporal analysis of the establishment of protected areas suggested that grouping plant species according to the predominant cause of rarity accurately reflected the history of conservation decision making. Species found in very rare habitats have previously received special conservation attention; species dependent on traditional extensive agriculture have been largely ignored until recently. Legislative initiative and new nature-protection schemes (e.g., Natura 2000, network of protected areas in the European Union) have had a positive influence on all species groups. Consequently, the species groups needing similar action for their conservation are sensitive indicators of the effectiveness of protected-area networks. Different species groups, however, may not be uniformly conserved within protected areas, and all species groups should fulfill the target of 60% coverage within protected areas.

Threatened herbaceous species dependent on moderate forest disturbances: A neglected target for ecosystem-based silviculture

Abstract Biodiversity conservation should be considered in forest management. Most forests have a long history of moderate human disturbances. In the temperate region this coevolution has resulted in high species diversity since many threatened herbaceous species depend on moderate forest disturbances. This study considered these species in Estonia. One-third of Estonian threatened herbaceous species were estimated to be dependent on moderate forest disturbances. All of these species are favoured by small-scale gaps through partial cutting or allowing natural uprooting of trees to occur. Several species are favoured by moderate soil disturbances (paths, horseriding, etc.) and clearing of undergrowth. A smaller number of species are favoured by grazing or by prescribed fires. Disturbance-dependent species ranked high in the national Red Data Book and they were particularly characteristic in dry forests. Disturbance-dependent herbaceous species should be considered as a target group for ecosystem-based forest management. Moderate disturbances are required in both managed and protected forests to conserve forest biodiversity.

Comparative Study of Seed Germination and Genetic Variation of Rare Endemic Rhinanthus osiliensis and Related Widespread Congener R. rumelicus (Orobanchaceae)

Genetic diversity is affected by breeding systems, life history traits and the distribution of species. Generally, inbred species with restricted geographic distribution have lower genetic variation compared to common outbreeding plant species. Rhinanthus osiliensis is a narrow endemic growing in calcareous spring fens on the island Saaremaa, Estonia. Presumably the closest congener of R. osiliensis is R. rumelicus, which is widely distributed in Eastern and Central Europe and the Balkan Peninsula. Isozymes were used to describe the mating system, levels of genetic variation and differentiation between the populations of R. osiliensis and R. rumelicus. Genetic diversity was found to be higher in widespread R. rumelicus compared to the endemic R. osiliensis. A significantly higher inbreeding coefficient with a low germination rate indicated substantial autogamy in R. osiliensis, whereas R. rumelicus displayed a mixed mating mode with a moderate inbreeding coefficient and a high germination rate. The low genetic differentiation between R. osiliensis and R. rumelicus confirmed their close affinity and the short evolutionary period of both taxa after the postglacial colonization. Considering the restricted geographic range and inbreeding in populations of R. osiliensis, this species may face a loss of genetic variation in the future.

Intra-individual ITS polymorphism and hybridization in Pulmonaria obscura Dumort. and Pulmonaria angustifolia L. (Boraginaceae)

Internal transcribed spacer (ITS) is used as a molecular marker in most phylogenetical analyses in Boraginaceae, an unplaced group in the current angiosperm phylogeny. However, there is no knowledge on intra-individual polymorphism of ITS in Boraginaceae. Difficulties in PCR and sequencing of ITS in Pulmonaria species mentioned in the literature may be seen as indirect evidence of intra-individual polymorphism. This study aims to detect intra-individual polymorphism of ITS1–5.8S–ITS2 in rare species Pulmonariaangustifolia L. and common species Pulmonariaobscura Dumort. Cloning of ITS sequences of P. angustifolia, P. obscura and putative hybrid specimens from mixed population showed intra-individual polymorphism of ITS1–5.8S–ITS2 in all specimens, whereas most of them also contained pseudogenic sequences. Intra-individual sequence divergence of ITS1 and ITS2 spacers was similar in the P. angustifolia and mixed population and significantly higher than in P. obscura. P. angustifolia specimens had nucleotide polymorphisms characteristic to both P. angustifolia and P. obscura and part of P. angustifolia sequences clustered into mostly P. obscura clade on the neighbour-joining trees based on ITS1 sequence and ITS2 sequence and structure data. These results suggest a hybrid origin of all P. angustifolia populations studied. Thus, outbreeding depression is a likely explanation for the decline in populations near the northern border of distribution area of rare species P. angustifolia. Hybrid origin of the whole P. angustifolia is also probable; the central population from Poland showed a similar pattern of polymorphism as distribution edge populations.

Microbial island biogeography: isolation shapes the life history characteristics but not diversity of root-symbiotic fungal communities

Island biogeography theory is one of the most influential paradigms in ecology. That island characteristics, including remoteness, can profoundly modulate biological diversity has been borne out by studies of animals and plants. By contrast, the processes influencing microbial diversity in island systems remain largely undetermined. We sequenced arbuscular mycorrhizal (AM) fungal DNA from plant roots collected on 13 islands worldwide and compared AM fungal diversity on islands with existing data from mainland sites. AM fungal communities on islands (even those >6000 km from the closest mainland) comprised few endemic taxa and were as diverse as mainland communities. Thus, in contrast to patterns recorded among macro-organisms, efficient dispersal appears to outweigh the effects of taxogenesis and extinction in regulating AM fungal diversity on islands. Nonetheless, AM fungal communities on more distant islands comprised a higher proportion of previously cultured and large-spored taxa, indicating that dispersal may be human-mediated or require tolerance of significant environmental stress, such as exposure to sunlight or high salinity. The processes driving large-scale patterns of microbial diversity are a key consideration for attempts to conserve and restore functioning ecosystems in this era of rapid global change.

Do Landscape Dissimilarity and Environmental Factors Affect Genetic and Phenotypic Variability in Myosotis laxa s. lato (Boraginaceae)

Myosotis laxa s. lato (Boraginaceae) is a morphologically highly variable taxon. We examined whether, in the Baltic Sea region, the coastal form of M. laxa has a single centre of origin or if it has emerged due to landscape dissimilarity (sea/land ratio) and environmental factors independently in different regions. We used partial Mantels test to investigate correlations between the genetic and phenotypic variability of M. laxa and the mentioned habitat factors. Although the correlation between genetic distance and the sea/land ratio existed (p < 0.01), it was not strong (r = 0.34). Phenotypic distance among populations was not correlated with habitat factors. Similarly, there was no correlation between geographic distance and morphological characteristics of the studied populations. As neither phenotypic nor genetic dissimilarity between sampled locations was correlated with geographic distance, we suggest that the coastal form can arise independently in suitable habitats and its development may be caused by epigenetic regulation. However, gene flow among the coastal and mainland populations most likely prevents stronger adaptive and genetic divergence.