Abstract
Post-fire recruitment by seeds is regarded as an adaptive response in fire-prone ecosystems. Nevertheless, little is known about which heritable seed traits are functional to the main signals of fire (heat and smoke), thus having the potential to evolve. Here, we explored whether three seed traits (pubescence, dormancy and shape) and fire regime modulate seed response to fire cues(heat and smoke). As a model study system, we used Helenium aromaticum (Asteraceae), a native annual forb from the Chilean matorral, where fires are anthropogenic. We related seed trait values with fitness responses (germination and survival) after exposure to heat-shock and smoke experimental treatments on seeds from 10 H. aromaticum wild populations. We performed a phenotypic selection experiment to examine the relationship of seed traits with post-treatment fitness within a population (adaptive hypothesis). We then explored whether fire frequency in natural habitats was associated with trait expression across populations, and with germination and survival responses to experimental fire-cues. We found that populations subjected to higher fire frequency had, in average, more rounded and pubescent seeds than populations from rarely burned areas. Populations with more rounded and pubescent seeds were more resistant to 80°C heat-shock and smoke treatments.There was correlated selection on seed traits: pubescent-rounded or glabrouscent-elongated seeds had the highest probability of germinating after heat-shock treatments. Seed pubescence and shape in H. aromaticum are heritable traits that modulate adaptive responses to fire. Our results provide new insights into the process of plant adaptation to fire and highlight the relevance of human-made fires as a strong evolutionary agent in the Anthropocene.
Highlights
Fire has influenced terrestrial plant communities since their appearance on earth [1,2,3] and has played a key role in the geographic expansion of large groups of plants, such as angiosperms during the Cretaceous [4] and C4 grasses during the Miocene [5]
Pubescence reduced the percentage of seed germination and survival of all H. aromaticum populations, while seed shape had no effects on these response variables (Table 1)
These results confirm the idea proposed by Gómez-González et al [28] of rapid evolution of seed traits driven by anthropogenic fires, and deepen into the mechanisms implicated in this process by showing that heat shock and smoke are involved in the adaptive responses
Summary
Fire has influenced terrestrial plant communities since their appearance on earth [1,2,3] and has played a key role in the geographic expansion of large groups of plants, such as angiosperms during the Cretaceous [4] and C4 grasses during the Miocene [5]. All MTC regions, except Central Chile, have been subjected to natural fire regimes ever since [8, 9] and fire has played a role in the evolutionary history of their floras [10] Plant species in these ecosystems show fire-response traits such as resprouting [11], fire-stimulated seed release (i.e. serotiny [12, 13]), thick bark [14], fire-stimulated flowering [15], flammability [16, 17] and firecued seed germination through heat-shock and/or smoke [18,19,20,21]). These traits are considered adaptations to fire ([22], and references therein), some authors have argued that their evolution might have been caused by other selective forces (e.g. drought, herbivory) and they should be regarded as exaptations [6]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
