Abstract
Seed biology in the annual herbaceous flora of ecologically stressful, seasonally wet habitats remains largely unexplored. Temporal and spatial species turnover among these habitats is often high, yet little is known about how fine-scale habitat variation drives intraspecific variability in seed dormancy depth and seed germination requirements. The present study characterised seed dormancy and investigated the germination biology of six closely related herbaceous annual species of Byblis from northern Australia. We assessed variation in the response of seeds of all species to temperature cues, as well as light and the naturally occurring germination stimulants karrikinolide (KAR1) and ethylene. We also examined intraspecific variation in germination response and seed-dormancy depth for three widely distributed species with overlapping distribution occurring in habitats with differing soil thermal and hydrological conditions. Seed germination in all six species was significantly increased by exposure to either KAR1 or ethylene, with this effect being amplified in two species (B. filifolia and B. rorida) following a period of warm, dry after-ripening. Seed-dormancy depth and the germination response of seeds to both KAR1 and ethylene were partitioned more strongly among habitats than among species. Populations on shallow (<20-cm soil depth) sandy soils produced less dormant seeds than did populations of the same species on deeper sandy soils (40+ cm) or on heavy cracking clays. The upper soil profile of shallow soil habitats was exposed to higher average temperatures, greater diurnal temperature fluctuation and greatly reduced moisture persistence compared with deeper soils. Fine-scale differences in the thermal and hydrological conditions of seasonally wet habitats appear to be strong drivers of dormancy depth in seeds of tropical Byblis. Widely distributed species exhibit high levels of plasticity in seed-dormancy depth and germination response among different habitats, with similar responses being observed for sympatric species. So as to fully understand species turnover in tropical ephemerals, future studies should examine phenotypic plasticity and the rate of local adaptation of seed traits in greater detail.
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Claims 15
Claim · model-written summary
Karrikinolide significantly increased germination in all six Byblis species.
ByblisNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seed germination in all six species was significantly increased by exposure to either KAR1 or ethylene”
e1“species of Byblis”
Claim · model-written summary
Ethylene significantly increased germination in all six Byblis species.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seed germination in all six species was significantly increased by exposure to either KAR1 or ethylene”
e1“species of Byblis”
Claim · model-written summary
Warm dry after-ripening amplified the stimulant response in B. filifolia.
- Taxon
- B. filifolia
Byblis filifoliae0 - Treatment
- warm, dry after-ripeninge0
- Outcome
- this effecte0
- Direction
- amplifiede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this effect being amplified in two species (B. filifolia and B. rorida) following a period of warm, dry after-ripening”
Claim · model-written summary
Warm dry after-ripening amplified the stimulant response in B. rorida.
- Taxon
- B. rorida
Byblis roridae0 - Treatment
- warm, dry after-ripeninge0
- Outcome
- this effecte0
- Direction
- amplifiede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this effect being amplified in two species (B. filifolia and B. rorida) following a period of warm, dry after-ripening”
Claim · model-written summary
Seed dormancy depth was partitioned more strongly among habitats than among species.
- Outcome
- Seed-dormancy depthe0
- Direction
- more stronglye0
- Comparator
- among speciese0
- Setting
- among habitatse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seed-dormancy depth and the germination response of seeds to both KAR1 and ethylene were partitioned more strongly among habitats than among species”
e1“species of Byblis”
Claim · model-written summary
Germination response to KAR1 was partitioned more strongly among habitats than species.
- Treatment
- KAR1e0
- Outcome
- germination response of seedse0
- Direction
- more stronglye0
- Comparator
- among speciese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the germination response of seeds to both KAR1 and ethylene were partitioned more strongly among habitats than among species”
e1“species of Byblis”
Claim · model-written summary
Germination response to ethylene was partitioned more strongly among habitats than species.
- Treatment
- ethylenee0
- Outcome
- germination response of seedse0
- Direction
- more stronglye0
- Comparator
- among speciese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the germination response of seeds to both KAR1 and ethylene were partitioned more strongly among habitats than among species”
e1“species of Byblis”
Claim · model-written summary
Shallow sandy soil populations produced less dormant seeds than deeper sand or cracking clay populations.
- Outcome
- dormant seedse0
- Direction
- lesse0
- Comparator
- deeper sandy soils (40+ cm) or on heavy cracking clayse0
- Setting
- shallow (<20-cm soil depth) sandy soilse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Populations on shallow (<20-cm soil depth) sandy soils produced less dormant seeds than did populations of the same species on deeper sandy soils (40+ cm) or on heavy cracking clays”
e1“species of Byblis”
Claim · model-written summary
Shallow soil habitats had higher average upper-soil temperatures.
Not reportedTaxon
Verbatim
e0“The upper soil profile of shallow soil habitats was exposed to higher average temperatures”
Claim · model-written summary
Shallow soil habitats had greater diurnal temperature fluctuations.
Not reportedTaxon
Verbatim
e0“greater diurnal temperature fluctuation”
Claim · model-written summary
Shallow soil habitats had reduced moisture persistence.
Not reportedTaxon
Verbatim
e0“greatly reduced moisture persistence”
Claim · model-written summary
Habitat thermal and hydrological differences appear to drive Byblis seed dormancy depth.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Fine-scale differences in the thermal and hydrological conditions of seasonally wet habitats appear to be strong drivers of dormancy depth in seeds of tropical Byblis”
Claim · model-written summary
Widely distributed Byblis species show high plasticity in dormancy depth and germination responses among habitats.
- Outcome
- high levels of plasticity in seed-dormancy depth and germination responsee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Widely distributed species exhibit high levels of plasticity in seed-dormancy depth and germination response among different habitats”
e1“species of Byblis”
Claim · model-written summary
Sympatric species showed similar responses.
- Outcome
- similar responsese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“similar responses being observed for sympatric species”
e1“species of Byblis”
Claim · model-written summary
The authors recommend further study of plasticity and local adaptation of seed traits.
- Outcome
- examine phenotypic plasticity and the rate of local adaptation of seed traits in greater detaile0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“future studies should examine phenotypic plasticity and the rate of local adaptation of seed traits in greater detail”
e1“species of Byblis”