Assessing the diversity of AM fungi in arid gypsophilous plant communities

Abstract

In the present study, we used PCR-Single-Stranded Conformation Polymorphism (SSCP) techniques to analyse arbuscular mycorrhizal fungi (AMF) communities in four sites within a 10 km(2) gypsum area in Southern Spain. Four common plant species from these ecosystems were selected. The AM fungal small-subunit (SSU) rRNA genes were subjected to PCR, cloning, SSCP analysis, sequencing and phylogenetic analyses. A total of 1443 SSU rRNA sequences were analysed, for 21 AM fungal types: 19 belonged to the genus Glomus, 1 to the genus Diversispora and 1 to the Scutellospora. Four sequence groups were identified, which showed high similarity to sequences of known glomalean species or isolates: Glo G18 to Glomus constrictum, Glo G1 to Glomus intraradices, Glo G16 to Glomus clarum, Scut to Scutellospora dipurpurescens and Div to one new genus in the family Diversisporaceae identified recently as Otospora bareai. There were three sequence groups that received strong support in the phylogenetic analysis, and did not seem to be related to any sequences of AM fungi in culture or previously found in the database; thus, they could be novel taxa within the genus Glomus: Glo G4, Glo G2 and Glo G14. We have detected the presence of both generalist and potential specialist AMF in gypsum ecosystems. The AMF communities were different in the plant studied suggesting some degree of preference in the interactions between these symbionts.

Modularity Reveals the Tendency of Arbuscular Mycorrhizal Fungi To Interact Differently with Generalist and Specialist Plant Species in Gypsum Soils

“…This level of richness is higher than that found by a previous study in different gypsum areas (21). However, the results may not be directly comparable, since different primers were used.…”

“…OTUs G24 and G25 are closely related to the Rhizophagus intraradices group (sequence homology, 96%), which represents a ubiquitous generalist fungus, since it is one of the most common taxa and has been found in a broad range of environments (36,53); Ö pik et al (53) proposed that some AMF species occur globally, showing high local abundance and low specificity, and the R. intraradices group clearly falls into this category as a generalist species. The presence of "potential specialist" AMF in gypsum ecosystems has been suggested (21). In the present work, the indicator species analysis showed two OTUs (G10 and G9) that tended to occur in gypsum soils and three OTUs (G8, Cl5, and P5) that tended to occur in marly-limestone soils.…”

“…The most abundant OTUs in this study were Glomus G24 (20.1% of the clones belonged to this OTU), Glomus G25 (17.7%), and Glomus G1 (11.7%), which occurred in all the plant species. They clustered with root-derived sequences of uncultured AMF species, and they have been recorded in other semiarid ecosystems (20,21). OTUs G24 and G25 are closely related to the Rhizophagus intraradices group (sequence homology, 96%), which represents a ubiquitous generalist fungus, since it is one of the most common taxa and has been found in a broad range of environments (36,53); Ö pik et al (53) proposed that some AMF species occur globally, showing high local abundance and low specificity, and the R. intraradices group clearly falls into this category as a generalist species.…”

“…Specifically, plant-AMF symbioses and AMF diversity have been studied recently in gypsum ecosystems, where it has been found that the AMF community is host plant dependent (20,21), such that different AMF communities colonize perennial and annual plant species (22), and gypsovags exhibit a higher AMF infection rate than gypsophytes (5). Despite these previous findings, it still remains unknown whether the community composition of the AMF colonizing the roots of gypsovags differs markedly from that for gypsophytes when both are growing in gypsum soils.…”

Influence of Habitat and Climate Variables on Arbuscular Mycorrhizal Fungus Community Distribution, as Revealed by a Case Study of Facultative Plant Epiphytism under Semiarid Conditions

“…This is a high level of AMF community richness considering that only a single plant species was studied. In previous studies focusing on much more diverse plant communities in semiarid Mediterranean ecosystems (17)(18)(19), we have found values for AMF community richness in individual plant species ranging between 8 and 20. All samples from epiphytic plants showed AMF sequences, thus confirming that S. tenerrimus epiphytic plants establish a symbiotic relationship with AMF.…”