Abstract

Truffle-like fruit body forms have evolved independently at least 59 times from aboveground ancestors in most major fungal lineages. They can be found in a broad range of habitats, are important food sources for native mammals, and functionally significant as mycorrhizae or saprotrophs. Australasia is a global diversity hotspot, with over 400 described, and a further 500-800 estimated species in 55 genera. Extreme variation in truffle-like fruit body forms make it difficult to determine ancestors or sister taxa without supporting molecular data, and large gaps in phylogenetic and distribution data make estimating patterns of evolution and diversification problematic.

Phylogenetic analyses were conducted for exemplars of all known Australasian truffle-like genera, utilising existing and novel sequence data, to provide an updated classification of global application, and fill gaps in phylogenetic data. Fifty ‘known novel’ taxa were also included: seven endemic Australasian genera in the Hysterangiales and Boletales, the first recorded truffle-like species in Lactifluus, and 10-12 species of Lactarius. This data formed the basis for several different lines of enquiry.

Cryptic diversity. Three widespread species from different lineages were examined in an attempt to look at biogeographic patterns. However, all three taxa turned out to be species complexes, in every case going from one to more than seven species. Some of which have highly restricted known distributions, and plant host associations.

Diversification of evolution. The Hysterangiales, Russulales, and Bolbiteaceae are diverse lineages in Australasia, with particularly high levels of truffle-like genera and species richness. We refined molecular clock analyses of the timing of emergence of truffle-like forms and rates of diversification. The Hysterangiales is still one of the oldest lineages with truffle-like forms appearing early on, while Russulales is intermediate in timing of emergence of truffle-like forms. Significant gaps still exist for Australasian mushroom-like sister taxa in the Russulales lineage.

Acquisition of truffle-like habit. We are sequencing the genomes of 14 sister pairs of truffle + mushrooms, and comparing expression of genes both between species pairs and within species pairs to identify those associated with morphological development and the origins of animal attracting odours. Three of the truffle taxa are ‘secotioid’ or more mushroom-like in habit. Incomplete phylogenies and luck of the draw with fruiting and seasonality, means the closest possible species pairs have been sampled.

Abstract

Truffle-like fungi form a heterogeneous group of diverse origin and they are common in temperate ectomycorrhizal (ECM) forests worldwide. The Nothofagaceae forests are restricted to the southern hemisphere and host a high diversity of fungi that are symbiotically associated with a relatively low number of related tree species. This unusual richness includes genera where the transition to hypogeous or subhypogeous forms is known to have occurred many times in their evolutionary history. Different degrees of hymenium exposure, stipe reduction, and loss of forcible spore discharge occur in many lineages of sequestrate ECM fungi in southern temperate forests. Among the hypothetical driving forces of this process are the adaptation to mycophagy, the closeness of the inoculum reservoir to the roots, and an increased resistance to drought or other climatic stressors. Since these factors are the result of biogeographical processes (climate changes, distribution of ECM hosts, and mycophagous animals), different selective pressures might explain differences in the sequestration process. Lineage specific traits in fungi of restricted distribution are an alternative explanation to biogeographical selective pressures leading to sequestration. Here we use newly generated sequences from Patagonian specimens within the Agaricomycetidae to examine the phylogenetic component of sequestration and compare it to biogeographic, climatic, and geologic influences. We discuss the influence of alternative hosts (e.g. Myrtaceae spp.) as well as hypotheses regarding putative historical host shifts and their implications on the evolution of sequestrate fungi.

Abstract

Compared to temperate and boreal ecosystems, little is known about ectomycorrhizal (EM) fungal diversity and evolution in tropical rainforests. For instance, it remains unknown whether tropical EM fungi have a common ancient origin, or have codispersed with their EM host plants and subsequently evolved. Tropical EM fungal communities with a common, ancient origin should exhibit similar structures, in terms of generic and species richness, in regions now separated by Gondwanan break up. Conversely, if tropical EM fungi have codispersed with their host plants, then the generic and species richnesses may vary between now-separated Gondwanan EM communities. To address these questions, we intensively examined two northern Gondwana EM fungal communities now separated for ~100 million years. Monodominant forests of Dicymbe corymbosa in the South American Guiana Shield and Gilbertiodendron dewevrei in Central Africa were the targets of our sampling efforts. These closely related EM host plant species of the Fabaceae subfam. Detarioideae form ecologically similar forest types in both regions. Multi-year matched sporocarp and root tip sampling was conducted in three plots in both forest types. Sporocarps and root tips were sequenced at the fungal barcode and clustered at a 97% sequence identity threshhold. Preliminary results suggest that while EM fungal generic richness and composition is similar at both sites, the species diversity is much higher in the Gilbertiodendron forests. Such results lend early support to an Africa to South America plant/fungal codispersal hypothesis. Phylogeographic analyses and divergence dating of target EM fungal clades will also be discussed.

Abstract

Current understanding of fungal biodiversity is particularly limited in South America, yet global studies have identified many unique fungal lineages that are present in the Southern Hemisphere but absent from other regions. The ectomycorrhizal tree family Nothofagaceae is one striking example of vicariance associated with the final breakup of Southern Gondwana (part of the supercontinent that included South America, Antarctica and Australia) and the onset of Antarctic glaciation at the Eocene/Oligocene boundary (ca. 32 mya). However, conflicting evidence suggests that long-distance dispersal or migration has continued long after the fragmentation of Southern Gondwana. As expected from previous studies, we detected strong biogeographic connections between South America and Australasia within many ectomycorrhizal fungal lineages collected in our biodiversity assessment of the Patagonian region (Chile and Argentina). We traced the most recent common ancestors of several southern temperate lineages of Basidiomycota and Ascomycota using dated phylogenies built from nuclear ribosomal loci ITS and LSU as well as RPB2 and EF1-alpha markers. We tested alternative hypotheses of vicariance or long distance-dispersal while taking into account the spore dispersal abilities, responses to disturbance, and whether taxa are early or late successional in Nothofagaceae forests. We also tested whether taxa with sequestrate fruiting bodies are more likely to have a restricted distribution and show evidence of a Southern Gondwanan origin. Our global approach using basidiomycete and ascomycete fungi with various life-history strategies will highlight common patterns for ectomycorrhizal fungi in the Patagonian region.

Abstract

Compared with other groups of macro-organisms, the evolutionary histories of most groups of fungi are still largely unknown. Fungal molecular phylogenies, which serve as the base of evolutionary history reconstructions, are often incomplete. Fungal fossils are scarce, which makes it hard to make accurate estimates of divergence times. Furthermore, observed distribution patterns are often difficult to explain. Many ectomycorrhizal fungi display disjunct distribution patterns that might be explained by vicariance or long-distance dispersal events.

The ectomycorrhizal milkcap genus Lactifluus (Russulaceae) is mainly represented in the tropics and is characterized by a high genetic variability combined with a conserved morphology, which is supported by the occurrence of cryptic species complexes and species with isolated phylogenetic positions. The genus displays disjunct distributions and is characterised by many evolutionary divergent lineages in sub-Saharan Africa.

In this study, we aim to construct a global phylogeny of the genus Lactifluus, reconstruct its evolutionary history and test whether it has originated in the Afrotropics.

We carried out an extensive global sampling and assembled a dataset of 1306 Lactifluus collections. A four-gene molecular phylogeny was constructed and compared with morphological data. Species delimitation was performed using the GMYC method in R. Divergence times were estimated in BEAST, using a secondary calibration procedure on a dataset containing species from several Basidiomycota orders. Biogeographical ranges were inferred using BioGeoBEARS in R.

Our molecular phylogeny confirms the monophyly of Lactifluus and supports the division of the genus into four subgenera. Due to an extensive sampling, ten new clades are discovered, which highlight the high diversity in this genus. The traditional infrageneric classification is only partly maintained and nomenclatural changes are proposed. Morphological synapomorphies were verified for five characteristics and appear important at different evolutionary levels.

Species delimitation resulted in 369–461 possible Lactifluus species, of which the majority are Asian and African species. Only 162 of these species are already described. Our dating analysis estimated the origin of the Russulaceae in the early Cretaceous and its major genera, Lactifluus, Lactarius and Russula, originated near the mid-Cenozoic. Biogeographical analyses indicated an Afrotropical origin for Lactifluus to be most likely, with multiple on-land migrations and long-distance dispersal events to other continents.

Abstract

Conditions for terrestrial life in Antarctica are frequently described as being amongst the most extreme and challenging on Earth. Coping with these conditions, fungi have been shown to be one of the most diverse elements of the Antarctic biota, with approx. 1350 species listed so far. Among fungi, species associating symbiotically with an autotrophic partner (i.e. lichens) show a high diversity, with about 550 species (ca. 2.8% of all known species worldwide). They constitute the most conspicuous component of terrestrial macrobiota even in areas considered analogs for Mars because of their cold and dry climate and topography, such as the McMurdo Dry Valleys (Victoria Land, Continental Antarctica). From a biogeographic perspective, more than a third of the current Antarctic lichen diversity is shared with the Arctic and Sub-Arctic regions (bipolar distribution). Long-distance dispersion has been commonly invoked to explain this strikingly disjunct distribution pattern, but it is still unknown whether those species originated in or arrived to Antarctica. Similarly, there is also a considerable percentage of endemic Antarctic lichens (ca. 33%) whose origin some authors claimed to be ancient, pre-dating the last glaciations, which implies that these species may have taken refuge in ice-free areas. We selected several phylogenetically-unrelated species of both endemic and bipolar lichen-forming fungi to determine which historical processes may be responsible for the contemporary geographical distribution of alleles. Molecular data from several markers were obtained and analyses included the inference of genetic clusters based on mixture and admixture models, exploration of genealogical relationships between haplotypes, estimation of divergence times and evaluation of migration models under a Bayesian framework. Herein, through these phylogeography analyses, we provide evidence for the colonization of Antarctica in the Pleistocene by some bipolar species, and point to endemics as long-term inhabitants of this continent.