Abstract
Vertically transmitted symbionts associate with some of the most ecologically dominant species on Earth, and their fixation has led to major evolutionary transitions (e.g., the development of mitochondria). Theory predicts that exclusive vertical transmission should favor mutualism and generate high frequencies of symbiosis in host populations. However, host populations often support lower-than-expected symbiont frequencies. Imperfect transmission (i.e., symbiont is not transmitted to all offspring) can reduce symbiont frequency, but for most beneficial symbionts it is unknown whether vertical transmission can be imperfect or during which life-history stage the symbiont is lost. Using quantitative natural history surveys of fungal endophytes in grasses, we show that transmission was imperfect in at least one stage for all seven host species examined. Endophytes were lost at all possible stages: within adult plants, from adult tillers to seeds, and from seeds to seedlings. Despite this loss, uninfected seeds failed to germinate in some species, resulting in perfect transmission to seedlings. The type and degree of loss differed among host populations and species and between endophyte genera. Populations with lower endophyte frequencies had higher rates of loss. Our results indicate new directions for understanding cooperation and conflict in symbioses and suggest mechanisms for host sanctions against costly symbionts.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 405-416 |
| Number of pages | 12 |
| Journal | American Naturalist |
| Volume | 172 |
| Issue number | 3 |
| DOIs | |
| State | Published - Sep 1 2008 |
| Externally published | Yes |
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Keywords
- Drought
- Epichloë
- Herbivory
- Mutualism
- Neotyphodium
- Poaceae
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
Cite this
Symbiosis lost : Imperfect vertical transmission of fungal endophytes in grasses. / Afkhami, Michelle; Rudgers, Jennifer A.
In: American Naturalist, Vol. 172, No. 3, 01.09.2008, p. 405-416.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Symbiosis lost
T2 - Imperfect vertical transmission of fungal endophytes in grasses
AU - Afkhami, Michelle
AU - Rudgers, Jennifer A.
PY - 2008/9/1
Y1 - 2008/9/1
N2 - Vertically transmitted symbionts associate with some of the most ecologically dominant species on Earth, and their fixation has led to major evolutionary transitions (e.g., the development of mitochondria). Theory predicts that exclusive vertical transmission should favor mutualism and generate high frequencies of symbiosis in host populations. However, host populations often support lower-than-expected symbiont frequencies. Imperfect transmission (i.e., symbiont is not transmitted to all offspring) can reduce symbiont frequency, but for most beneficial symbionts it is unknown whether vertical transmission can be imperfect or during which life-history stage the symbiont is lost. Using quantitative natural history surveys of fungal endophytes in grasses, we show that transmission was imperfect in at least one stage for all seven host species examined. Endophytes were lost at all possible stages: within adult plants, from adult tillers to seeds, and from seeds to seedlings. Despite this loss, uninfected seeds failed to germinate in some species, resulting in perfect transmission to seedlings. The type and degree of loss differed among host populations and species and between endophyte genera. Populations with lower endophyte frequencies had higher rates of loss. Our results indicate new directions for understanding cooperation and conflict in symbioses and suggest mechanisms for host sanctions against costly symbionts.
AB - Vertically transmitted symbionts associate with some of the most ecologically dominant species on Earth, and their fixation has led to major evolutionary transitions (e.g., the development of mitochondria). Theory predicts that exclusive vertical transmission should favor mutualism and generate high frequencies of symbiosis in host populations. However, host populations often support lower-than-expected symbiont frequencies. Imperfect transmission (i.e., symbiont is not transmitted to all offspring) can reduce symbiont frequency, but for most beneficial symbionts it is unknown whether vertical transmission can be imperfect or during which life-history stage the symbiont is lost. Using quantitative natural history surveys of fungal endophytes in grasses, we show that transmission was imperfect in at least one stage for all seven host species examined. Endophytes were lost at all possible stages: within adult plants, from adult tillers to seeds, and from seeds to seedlings. Despite this loss, uninfected seeds failed to germinate in some species, resulting in perfect transmission to seedlings. The type and degree of loss differed among host populations and species and between endophyte genera. Populations with lower endophyte frequencies had higher rates of loss. Our results indicate new directions for understanding cooperation and conflict in symbioses and suggest mechanisms for host sanctions against costly symbionts.
KW - Drought
KW - Epichloë
KW - Herbivory
KW - Mutualism
KW - Neotyphodium
KW - Poaceae
UR - http://www.scopus.com/inward/record.url?scp=51549107529&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=51549107529&partnerID=8YFLogxK
U2 - 10.1086/589893
DO - 10.1086/589893
M3 - Article
C2 - 18657030
AN - SCOPUS:51549107529
VL - 172
SP - 405
EP - 416
JO - American Naturalist
JF - American Naturalist
SN - 0003-0147
IS - 3
ER -