Abstract
The roles of the various potential ecological and evolutionary causes of spatial population genetic structure (SPGS) cannot in general be inferred from the extant structure alone. However, a stage-specific analysis can provide clues as to the causes of SPGS. We conducted a stage-specific SPGS analysis of a mapped population of about 2000 Trillium grandiflorum (Liliaceae), a long-lived perennial herb. We compared SPGS for juvenile (J), nonreproductive (NR), and reproductive (R) stages. Fisher's exact test showed that genotypes had Hardy-Weinberg frequencies at all loci and stage classes. Allele frequencies did not differ between stages. Bootstrapped 99% confidence intervals (99%CI) indicate that F-statistic values are indistinguishable from zero, (except for a slightly negative FIT for the R stage). Spatial autocorrelation was used to calculate f the average kinship coefficient between individuals within distance intervals. Null hypothesis 99%CIs for f were constructed by repeatedly randomizing genotypic locations. Significant positive fine-scale genetic structure was detected in the R and NR stages, but not in the J stage. This structure was most pronounced in the R stage, and declined by about half in each remaining stage: near-neighbor f = 0.122, 0.065, 0.027, for R, NR, and J, respectively. For R and NR, the near-neighbor f lies outside the null hypothesis 99%CI, indicating kinship at approximately the level of half-sibs and first cousins, respectively. We also simulated the expected SPGS of juveniles post dispersal, based on measured R-stage SPGS, the mating system, and measured pollen and seed dispersal properties. This provides a null hypothesis expectation (as a 99%CI) for the J-stage correlogram, against which to test the likelihood that post-dispersal events have influenced J-stage SPGS. The actual J correlogram lies within the null hypothesis 99%CI for the shortest distance interval and nearly all other distance intervals indicating that the observed low recruitment, random mating and seed dispersal patterns are sufficient to account for the disappearance of SPSG between the R and the J stages. The observed increase in SPGS between J and R stages has two potential explanations: history and local selection. The observed low total allelic diversity is consistent with a past bottleneck: a possible historical explanation. Only a longitudinal stage-specific study of SPGS structure can distinguish between historical events and local selection as causes of increased structure with increasing life history stage.
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Claims 12
Claim · model-written summary
Genotypes had Hardy-Weinberg frequencies at all loci and stages.
- Taxon
- Trillium grandiflorum
.png?width=60)
Trillium grandiflorume1 - Outcome
- genotypes had Hardy-Weinberg frequencies at all loci and stage classese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.png?width=500)
Verbatim
e0“Fisher's exact test showed that genotypes had Hardy-Weinberg frequencies at all loci and stage classes”
e1“Trillium grandiflorum”
Claim · model-written summary
Allele frequencies did not differ among stages.
- Taxon
- Trillium grandiflorumTrillium grandiflorume1
- Organ / stage
- stagese0
- Outcome
- Allele frequenciese0
- Direction
- did not differe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Allele frequencies did not differ between stages”
e1“Trillium grandiflorum”
Claim · model-written summary
F-statistics were indistinguishable from zero except a slightly negative reproductive-stage FIT.
- Taxon
- Trillium grandiflorumTrillium grandiflorume1
- Outcome
- F-statistic valuese0
- Direction
- indistinguishable from zeroe0
- Qualifier
- except for a slightly negative FIT for the R stagee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“F-statistic values are indistinguishable from zero, (except for a slightly negative FIT for the R stage)”
e1“Trillium grandiflorum”
Claim · model-written summary
Reproductive and nonreproductive stages had significant positive fine-scale genetic structure; juveniles did not.
- Taxon
- Trillium grandiflorumTrillium grandiflorume1
- Organ / stage
- R and NR stagese0
- Outcome
- fine-scale genetic structuree0
- Direction
- Significant positivee0
- Comparator
- J stagee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Significant positive fine-scale genetic structure was detected in the R and NR stages, but not in the J stage”
e1“Trillium grandiflorum”
Claim · model-written summary
Near-neighbor kinship was 0.122 in reproductive plants.
- Taxon
- Trillium grandiflorumTrillium grandiflorume1
- Organ / stage
- Re0
- Outcome
- near-neighbor fe0
- Value
- 0.122e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“near-neighbor f = 0.122, 0.065, 0.027, for R, NR, and J, respectively”
e1“Trillium grandiflorum”
Claim · model-written summary
Near-neighbor kinship was 0.065 in nonreproductive plants.
- Taxon
- Trillium grandiflorumTrillium grandiflorume1
- Organ / stage
- NRe0
- Outcome
- near-neighbor fe0
- Value
- 0.065e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“near-neighbor f = 0.122, 0.065, 0.027, for R, NR, and J, respectively”
e1“Trillium grandiflorum”
Claim · model-written summary
Near-neighbor kinship was 0.027 in juveniles.
- Taxon
- Trillium grandiflorumTrillium grandiflorume1
- Organ / stage
- Je0
- Outcome
- near-neighbor fe0
- Value
- 0.027e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“near-neighbor f = 0.122, 0.065, 0.027, for R, NR, and J, respectively”
e1“Trillium grandiflorum”
Claim · model-written summary
Near-neighbor reproductive and nonreproductive kinship corresponded approximately to half-sibs and first cousins.
- Taxon
- Trillium grandiflorumTrillium grandiflorume1
- Organ / stage
- R and NRe0
- Outcome
- kinship at approximately the level of half-sibs and first cousinse0
- Qualifier
- outside the null hypothesis 99%CIe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For R and NR, the near-neighbor f lies outside the null hypothesis 99%CI, indicating kinship at approximately the level of half-sibs and first cousins, respectively”
e1“Trillium grandiflorum”
Claim · model-written summary
The juvenile correlogram was within the simulated null expectation at the shortest and nearly all other distances.
- Taxon
- Trillium grandiflorumTrillium grandiflorume1
- Organ / stage
- Je0
- Outcome
- actual J correlograme0
- Comparator
- null hypothesis 99%CIe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The actual J correlogram lies within the null hypothesis 99%CI for the shortest distance interval and nearly all other distance intervals”
e1“Trillium grandiflorum”
Claim · model-written summary
Low recruitment, random mating and seed dispersal could account for loss of spatial genetic structure from reproductive to juvenile stages.
- Taxon
- Trillium grandiflorumTrillium grandiflorume1
- Outcome
- disappearance of SPSG between the R and the J stagese0
- Qualifier
- low recruitment, random mating and seed dispersal patternse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the observed low recruitment, random mating and seed dispersal patterns are sufficient to account for the disappearance of SPSG between the R and the J stages”
e1“Trillium grandiflorum”
Claim · model-written summary
Low total allelic diversity was consistent with a possible past bottleneck.
- Taxon
- Trillium grandiflorumTrillium grandiflorume1
- Outcome
- low total allelic diversitye0
- Qualifier
- past bottlenecke0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The observed low total allelic diversity is consistent with a past bottleneck”
e1“Trillium grandiflorum”
Claim · model-written summary
A longitudinal stage-specific study is needed to distinguish historical events from local selection as causes of increasing structure.
- Taxon
- Trillium grandiflorumTrillium grandiflorume1
- Outcome
- longitudinal stage-specific study of SPGS structuree0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Only a longitudinal stage-specific study of SPGS structure can distinguish between historical events and local selection as causes of increased structure with increasing life history stage”
e1“Trillium grandiflorum”