Discovering local adaptation, its genetic underpinnings, and environmental drivers is important for conserving forest species. Ecological genomic approaches coupled with next‐generation sequencing are useful means to detect local adaptation and uncover its underlying genetic basis in nonmodel species. We report results from a study on flowering dogwood trees (
Understanding the consequences of exotic diseases on native forests is important to evolutionary ecology and conservation biology because exotic pathogens have drastically altered US eastern deciduous forests.
- NSF-PAR ID:
- 10157180
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Systematics and Evolution
- Volume:
- 58
- Issue:
- 5
- ISSN:
- 1674-4918
- Page Range / eLocation ID:
- p. 546-570
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract Cornus florida L .) using genotyping by sequencing (GBS ). This species is ecologically important to easternUS forests but is severely threatened by fungal diseases. We analyzed subpopulations in divergent ecological habitats within North Carolina to uncover loci under local selection and associated with environmental–functional traits or disease infection. At this scale, we tested the effect of incorporating additional sequencing before scaling for a broader examination of the entire range. To test for biases ofGBS , we sequenced two similarly sampled libraries independently from six populations of three ecological habitats. We obtained environmental–functional traits for each subpopulation to identify associations with genotypes via latent factor mixed modeling (LFMM ) and gradient forests analysis. To test whether heterogeneity of abiotic pressures resulted in genetic differentiation indicative of local adaptation, we evaluatedF stper locus while accounting for genetic differentiation between coastal subpopulations and Piedmont‐Mountain subpopulations. Of the 54 candidate loci with sufficient evidence of being under selection among both libraries, 28–39 were Arlequin–BayeScanF stoutliers. ForLFMM , 45 candidates were associated with climate (of 54), 30 were associated with soil properties, and four were associated with plant health. Reanalysis of combined libraries showed that 42 candidate loci still showed evidence of being under selection. We conclude environment‐driven selection on specific loci has resulted in local adaptation in response to potassium deficiencies, temperature, precipitation, and (to a marginal extent) disease. High allele turnover along ecological gradients further supports the adaptive significance of loci speculated to be under selection. -
Koch, Frank H. (Ed.)Over the past several decades, growth declines and mortality of trembling aspen throughout western Canada and the United States have been linked to drought, often interacting with outbreaks of insects and fungal pathogens, resulting in a “sudden aspen decline” throughout much of aspen’s range. In 2015, we noticed an aggressive fungal canker causing widespread mortality of aspen throughout interior Alaska and initiated a study to quantify potential drivers for the incidence, virulence, and distribution of the disease. Stand-level infection rates among 88 study sites distributed across 6 Alaska ecoregions ranged from <1 to 69%, with the proportion of trees with canker that were dead averaging 70% across all sites. The disease is most prevalent north of the Alaska Range within the Tanana Kuskokwim ecoregion. Modeling canker probability as a function of ecoregion, stand structure, landscape position, and climate revealed that smaller-diameter trees in older stands with greater aspen basal area have the highest canker incidence and mortality, while younger trees in younger stands appear virtually immune to the disease. Sites with higher summer vapor pressure deficits had significantly higher levels of canker infection and mortality. We believe the combined effects of this novel fungal canker pathogen, drought, and the persistent aspen leaf miner outbreak are triggering feedbacks between carbon starvation and hydraulic failure that are ultimately driving widespread mortality. Warmer early-season temperatures and prolonged late summer drought are leading to larger and more severe wildfires throughout interior Alaska that are favoring a shift from black spruce to forests dominated by Alaska paper birch and aspen. Widespread aspen mortality fostered by this rapidly spreading pathogen has significant implications for successional dynamics, ecosystem function, and feedbacks to disturbance regimes, particularly on sites too dry for Alaska paper birch.more » « less
-
more » « less
SUMMARY Sorghum anthracnose caused by the fungus
Colletotrichum sublineola (Cs ) is a damaging disease of the crop. Here, we describe the identification ofANTHRACNOSE RESISTANCE GENES (ARG4 andARG5 ) encoding canonical nucleotide‐binding leucine‐rich repeat (NLR) receptors.ARG4 andARG5 are dominant resistance genes identified in the sorghum lines SAP135 and P9830, respectively, that show broad‐spectrum resistance toCs . Independent genetic studies using populations generated by crossing SAP135 and P9830 with TAM428, fine mapping using molecular markers, comparative genomics and gene expression studies determined thatARG4 andARG5 are resistance genes againstCs strains. Interestingly,ARG4 andARG5 are both located within clusters of duplicate NLR genes at linked loci separated by ~1 Mb genomic region. SAP135 and P9830 each carry only one of theARG genes while having the recessive allele at the second locus. Only two copies of theARG5 candidate genes were present in the resistant P9830 line while five non‐functional copies were identified in the susceptible line. The resistant parents and their recombinant inbred lines carrying eitherARG4 orARG5 are resistant to strains Csgl1 and Csgrg suggesting that these genes have overlapping specificities. The role ofARG4 andARG5 in resistance was validated through sorghum lines carrying independent recessive alleles that show increased susceptibility.ARG4 andARG5 are located within complex loci displaying interesting haplotype structures and copy number variation that may have resulted from duplication. Overall, the identification of anthracnose resistance genes with unique haplotype stucture provides a foundation for genetic studies and resistance breeding. -
more » « less
Abstract Range expansions driven by global change and species invasions may have significant genomic, evolutionary, and ecological implications. During range expansions, strong genetic drift characterized by repeated founder events can result in decreased genetic diversity with increased distance from the center of the historic range, or the point of invasion. The invasion of the Indo‐Pacific lionfish,
Pterois volitans , into waters off the US East Coast, Gulf of Mexico, and Caribbean Sea provides a natural system to study rapid range expansion in an invasive marine fish with high dispersal capabilities. We report results from 12,759 single nucleotide polymorphism loci sequenced by restriction enzyme‐associated DNA sequencing for nineP. volitans sampling areas in the invaded range, including Florida and other sites throughout the Caribbean, as well as mitochondrial control region D‐loop data. Analyses revealed low to no spatially explicit metapopulation genetic structure, which is partly consistent with previous finding of little structure within ocean basins, but partly divergent from initial reports of between‐basin structure. Genetic diversity, however, was not homogeneous across all sampled sites. Patterns of genetic diversity correlate with invasion pathway. Observed heterozygosity, averaged across all loci within a population, decreases with distance from Florida while expected heterozygosity is mostly constant in sampled populations, indicating population genetic disequilibrium correlated with distance from the point of invasion. Using anF SToutlier analysis and a Bayesian environmental correlation analysis, we identified 256 and 616 loci, respectively, that could be experiencing selection or genetic drift. Of these, 24 loci were shared between the two methods. -
more » « less
Abstract Previous theoretical work has highlighted the potential for natural enemies to mediate the coexistence of species with similar life histories via density‐dependent effects on survivorship. For plant pathogens to play this role, they must differ in their ability to infect or induce disease in different host plant species. In tropical forests characterized by high diversity, these effects must extend to phylogenetically closely related species pairs. Mortality at the seed and seedling stage strongly influences the abundance and distribution of tropical tree species, but the host preferences and spatial distributions of fungi are rarely determined.
We examined how host species identity, relatedness and seed viability influence the composition of fungal communities associated with seeds of four co‐occurring pioneer trees (
Cecropia insignis ,C. longipes ,C. peltata andJacaranda copaia ). Seeds were buried in mesh bags in five common gardens in the understorey of a lowland tropical forest in Panama and retrieved at intervals from 1 to 30 months. A subset of the seeds in each bag was used to determine germination success. One half of each remaining seed was tested for viability; and the other half was used to culture and identify seed‐infecting fungi.Seeds were infected by fungi after burial. Although fungal communities differed in viable versus dead seeds, and across burial locations, community composition primarily varied as a function of plant species identity (30.7% of variation in community composition vs. 4.5% for viability and location together), even for congeneric
Cecropia species. Phylogenetic reconstruction showed that relatedness of fungi mostly reflected differences betweenJacaranda (Bignoniaceae) andCecropia (Urticaceae).Although the proportion of germinable seeds decreased gradually over time for all species, intraspecific variation in survival was high at the same location (e.g. ranging from 0% to 100% for
C. peltata ) suggesting variable exposure or susceptibility to seed pathogens.Synthesis . Our study provides evidence under field conditions that congeneric tree species with similar life history traits differ markedly in seed‐associated fungal communities when exposed to the same soil‐borne fungi. This is a critical first step supporting pathogen‐mediated coexistence of closely related tree species.
