Characterization of microsatellite loci in the endangered grand spider orchid Caladenia huegelii (Orchidaceae)

The orchid genus Caladenia is species rich with many threatened and endangered taxa. We report on the isolation and characterization of microsatellite loci in the rare Caladenia huegelii for molecular evaluation of this and the closely related C. thinicola as part of the development of conservation initiatives. Eight di- and trinucleotide loci were screened using 30 samples from each species. All loci were highly variable, with similar levels of heterozygosity and number of alleles across both species. These markers will be highly informative for population studies in both species

Continental scale distribution and diversity of Ceratobasidium orchid mycorrhizal fungi in Australia

Background and aims: Mycorrhizal fungi are a critical component of the ecological niche of most plants and can potentially constrain their geographic range. Unlike other types of mycorrhizal fungi, the distributions of orchid mycorrhizal fungi (OMF) at large spatial scales are not well understood. Here, we investigate the distribution and diversity of Ceratobasidium OMF in orchids and soils across the Australian continent.MethodsWe sampled 217 Ceratobasidium isolates from 111 orchid species across southern Australia and combined these with 311 Ceratobasidium sequences from GenBank. To estimate the taxonomic diversity of Ceratobasidium associating with orchids, phylogenetic analysis of the ITS sequence locus was undertaken. Sequence data from the continent-wide Australian Microbiome Initiative was used to determine the geographic range of Operational Taxonomic Units (OTUs) detected in orchids, with the distribution and climatic correlates of the two most frequently detected OTUs modelled using MaxEnt.Key resultsWe identified 23 Ceratobasidium OTUs associating with Australian orchids, primarily from the orchid genera Pterostylis, Prasophyllum, Rhizanthella and Sarcochilus. OTUs isolated from orchids were closely related to, but distinct from, known pathogenic fungi. Data from soils and orchids revealed that ten of these OTUs occur on both east and west sides of the continent, while 13 OTUs were recorded at three locations or less. MaxEnt models suggested that the distributions of two widespread OTUs are correlated with temperature and soil moisture of the wettest quarter and far exceeded the distributions of their host orchid species.ConclusionsCeratobasidium OMF with cross-continental distributions are common in Australian soils and frequently have geographic ranges that exceed that of their host orchid species, suggesting these fungi are not limiting the distributions of their host orchids at large spatial scales. Most OTUs were distributed within southern Australia, although several OTUs had distributions extending into central and northern parts of the continent, illustrating their tolerance of an extraordinarily wide range of environmental conditions.Marc W Freestone, Nigel D Swarts, Noushka Reiter, Sean Tomlinson, Frances C Sussmilch, Magali M Wright ... et al