Molecular diversity of arbuscular mycorrhizal fungi and patterns of host association over time and space in a tropical forest

Abstract

We have used molecular techniques to investigate the diversity and distribution of the arbuscular mycorrhizal (AM) fungi colonizing tree seedling roots in the tropical forest on Barro Colorado Island (BCI), Republic of Panama. In the first year, we sampled newly emergent seedlings of the understory treelet Faramea occidentalis and the canopy emergent Tetragastris panamensis , from mixed seedling carpets at each of two sites. The following year we sampled surviving seedlings from these cohorts. The roots of 48 plants were analysed using AM fungal-specific primers to amplify and clone partial small subunit (SSU) ribosomal RNA gene sequences. Over 1300 clones were screened for random fragment length polymorphism (RFLP) variation and 7% of these were sequenced. Compared with AM fungal communities sampled from temperate habitats using the same method, the overall diversity was high, with a total of 30 AM fungal types identified. Seventeen of these types have not been recorded previously, with the remainder being similar to types reported from temperate habitats. The tropical mycorrhizal population showed significant spatial heterogeneity and nonrandom associations with the different hosts. Moreover there was a strong shift in the mycorrhizal communities over time. AM fungal types that were dominant in the newly germinated seedlings were almost entirely replaced by previously rare types in the surviving seedlings the following year. The high diversity and huge variation detected across time points, sites and hosts, implies that the AM fungal types are ecologically distinct and thus may have the potential to influence recruitment and host composition in tropical forests.

Arbuscular mycorrhizal mycelial respiration in a moist tropical forest

“…Further information is now required on mycorrhizal respiration in different tropical forests where nutrient limitation of plant growth and community composition of mycorrhiza may vary (e.g. Husband et al, 2002cf. Lovelock et al, 2003, and on how increased concentrations of atmospheric CO 2 will affect the allocation of C from plants to mycorrhizal fungi in tropical forests.…”

Mycorrhizal responses to biochar in soil – concepts and mechanisms

“…Studies to date have focused on quantifying potential responses in fungal abundance measures, primarily root colonization and spore numbers (see Table 1). However, mycorrhizal fungi occur as species assemblages in ecosystems and in roots of individual plants (Johnson et al 1992;Husband et al 2002;Vandenkoornhuyse et al 2003;Mummey et al 2005). The species composition of a mycorrhizal fungal assemblage can be important to mycorrhizal functioning (e.g., van der Heijden et al 1998).…”

Six-year fertilization modifies the biodiversity of arbuscular mycorrhizal fungi in a temperate steppe in Inner Mongolia

“…However, some studies showed that highly diverse plant communities may not supported a higher AMF diversity compared with depauperate plant communities (Johnson et al, 2003a;Börstler et al, 2006), suggesting that factors other than plant diversity are also important in determining AMF communities. Distinctions between AMF communities may be partially caused by ecological specificity among fungale plant pairs (Helgason et al, 1998;Vandenkoornhuyse et al, 2003) or effects of season and host plant development stage (Husband et al, 2002a), and also possibly a result of environmental disturbance. For example, farming practices may play a key role in determining the AMF communities at both the local and regional scales (van der Gast et al, 2011).…”