Abstract
Host-specialized pathogens are credited with the maintenance of tropical forest diversity under the Janzen-Connell hypothesis. Yet, in diverse forests, selection may favor pathogens with broad host ranges, given their passive dispersal and the relative rarity of tree species. We surveyed the host associations of potential pathogens isolated from symptomatic seedlings in forests in Panama and used inoculations to assess the pathogenicity and host ranges of 27 fungal isolates, and differences among tree species in susceptibility. Thirty-one of the 33 nonsingleton operational taxonomic units (OTUs) isolated from seedlings are multi-host. All 31 multi-host OTUs exhibit low to moderate specialization, and we observed phylogenetically overdispersed host use for 19 OTUs. The pathogenicity of 10 isolates was experimentally confirmed; nine caused disease in seedlings in multiple families. However, the outcome of infection differs among tree species susceptible to a given multi-host pathogen. Furthermore, some tree species were seemingly resistant to all fungi tested, while others were susceptible to multiple fungi. Tree species adapted to environments with lower disease pressure were most likely to exhibit disease. Our results suggest that generalist pathogens contribute to the maintenance of local and regional forest diversity via host-specific impacts and the exclusion of disease-sensitive trees from disease-prone habitats.
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Claims 10
Claim · model-written summary
Thirty-one of the 33 nonsingleton OTUs isolated from seedlings are multi-host
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OtusOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
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Verbatim
e0“We surveyed the host associations of potential pathogens isolated from symptomatic seedlings in forests in Panama”
e1“Thirty-one of the 33 nonsingleton operational taxonomic units (OTUs) isolated from seedlings are multi-host”
Claim · model-written summary
All 31 multi-host OTUs exhibit low to moderate specialization
Verbatim
e0“We surveyed the host associations of potential pathogens isolated from symptomatic seedlings in forests in Panama”
e2“All 31 multi-host OTUs exhibit low to moderate specialization”
Claim · model-written summary
Phylogenetically overdispersed host use was observed for 19 OTUs
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We surveyed the host associations of potential pathogens isolated from symptomatic seedlings in forests in Panama”
e3“we observed phylogenetically overdispersed host use for 19 OTUs”
Claim · model-written summary
The pathogenicity of 10 isolates was experimentally confirmed
Verbatim
e0“We surveyed the host associations of potential pathogens isolated from symptomatic seedlings in forests in Panama”
e4“The pathogenicity of 10 isolates was experimentally confirmed”
Claim · model-written summary
Nine isolates caused disease in seedlings in multiple tree families
Verbatim
e0“We surveyed the host associations of potential pathogens isolated from symptomatic seedlings in forests in Panama”
e4“The pathogenicity of 10 isolates was experimentally confirmed”
e5“nine caused disease in seedlings in multiple families”
Claim · model-written summary
The outcome of infection differs among tree species susceptible to a given multi-host pathogen
Verbatim
e6“the outcome of infection differs among tree species susceptible to a given multi-host pathogen”
Claim · model-written summary
Some tree species were seemingly resistant to all fungi tested
Verbatim
e7“some tree species were seemingly resistant to all fungi tested, while others were susceptible to multiple fungi”
Claim · model-written summary
Other tree species were susceptible to multiple fungi
Verbatim
e7“some tree species were seemingly resistant to all fungi tested, while others were susceptible to multiple fungi”
Claim · model-written summary
Tree species adapted to environments with lower disease pressure were most likely to exhibit disease
Verbatim
e0“Tree species adapted to environments with lower disease pressure were most likely to exhibit disease”
Claim · model-written summary
Generalist pathogens are suggested to maintain local and regional forest diversity via host-specific impacts and exclusion of disease-sensitive trees from disease-prone habitats
Verbatim
e0“generalist pathogens contribute to the maintenance of local and regional forest diversity via host-specific impacts and the exclusion of disease-sensitive trees from disease-prone habitats”