TY - JOUR
T1 - A fungus among us
T2 - Broad patterns of endophyte distribution in the grasses
AU - Rudgers, Jennifer A.
AU - Afkhami, Michelle E.
AU - Rúa, Megan A.
AU - Davitt, Andrew J.
AU - Hammer, Samantha
AU - Huguet, Valérie M.
N1 - Copyright:
Copyright 2009 Elsevier B.V., All rights reserved.
PY - 2009/6
Y1 - 2009/6
N2 - Plant-associated microbes have been increasingly recognized for influencing host populations, plant communities, and even herbivores and predators. Thus, understanding factors that affect the distribution and abundance of microbial symbioses may be important for predicting the ecological dynamics of communities. Using endophytic fungi-grass symbioses, we explored how intrinsic traits of the symbiosis, specifically transmission mode, may influence symbiont frequencies in host populations. Combining published literature with new field surveys, we compared Epichloë endophytes, which had mixed horizontal and vertical transmission, with Neotyphodium endophytes, which were exclusively vertically transmitted from host plants to seeds. Exclusively vertical transmission should select against pathogenicity because symbionts depend entirely on hosts for reproduction. Across 118 host species, we found that Neotyphodium hosts had 40-130% higher symbiont frequencies than Epichloë hosts. In field surveys, endophyte frequency was positively correlated with the local density of hosts, but only for Epichloë, suggesting that contagiously spread Epichloë may attain higher frequencies when hosts are more abundant. Epichloë endophytes were also more likely than Neotyphodium to have imperfect vertical transmission; thus, hosts may reduce the transmission of more pathogenic symbionts to seeds. Results are consistent with the conclusion that the evolutionary transition to exclusively vertical transmission can alter patterns of symbiont frequency in nature.
AB - Plant-associated microbes have been increasingly recognized for influencing host populations, plant communities, and even herbivores and predators. Thus, understanding factors that affect the distribution and abundance of microbial symbioses may be important for predicting the ecological dynamics of communities. Using endophytic fungi-grass symbioses, we explored how intrinsic traits of the symbiosis, specifically transmission mode, may influence symbiont frequencies in host populations. Combining published literature with new field surveys, we compared Epichloë endophytes, which had mixed horizontal and vertical transmission, with Neotyphodium endophytes, which were exclusively vertically transmitted from host plants to seeds. Exclusively vertical transmission should select against pathogenicity because symbionts depend entirely on hosts for reproduction. Across 118 host species, we found that Neotyphodium hosts had 40-130% higher symbiont frequencies than Epichloë hosts. In field surveys, endophyte frequency was positively correlated with the local density of hosts, but only for Epichloë, suggesting that contagiously spread Epichloë may attain higher frequencies when hosts are more abundant. Epichloë endophytes were also more likely than Neotyphodium to have imperfect vertical transmission; thus, hosts may reduce the transmission of more pathogenic symbionts to seeds. Results are consistent with the conclusion that the evolutionary transition to exclusively vertical transmission can alter patterns of symbiont frequency in nature.
KW - Endophytic fungi-grass symbioses
KW - Epichloe spp.
KW - Neotyphodium spp.
KW - Plant-microbe
KW - Poaceae
KW - Symbiosis
KW - Vertical transmission
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U2 - 10.1890/08-0116.1
DO - 10.1890/08-0116.1
M3 - Article
C2 - 19569368
AN - SCOPUS:67449124359
VL - 90
SP - 1531
EP - 1539
JO - Ecology
JF - Ecology
SN - 0012-9658
IS - 6
ER -