Seed-based approach for identifying flora at risk from climate warming

Abstract

In obligate seeding species, the germination niche is crucial for colonization and population survival. It is a high-risk phase in a plant's life cycle, and is directly regulated by temperature. Seeds germinate over a range of temperatures within which there is an optimum temperature, with thresholds above and below which no germination occurs. We suggest that abrupt changes in temperature associated with a warming climate may cause a disconnect between temperatures seeds experience and temperatures over which germination is able to occur, rendering obligate seeding species vulnerable to decline and extinction. Using a bidirectional temperature gradient system, we examined the thermal constraints in the germination niche of some geographically restricted species from the low altitude mountains of the Stirling Range, southern Western Australia, including seedlots from lowland populations of four of these species. We demonstrated that high temperatures are not a limiting factor for germination in some restricted species, signifying a lack of relationship between geographic range size and breadth of the germination niche. In contrast, we identified other restricted species, in particular Sphenotoma drummondii, as being at risk of recruitment failure as a consequence of warming: seeds of this species showed a strong negative relationship between percentage germination and increasing temperature above a relatively low optimum constant temperature (13°C). We found some ecotypic differences in the temperature profiles between seeds collected from montane or lowland populations of Andersonia echinocephala, and while specific populations may become more restricted, they are perhaps at less risk of extinction from climate warming.This seed-based approach for identifying extinction risk will contribute tangibly to efforts to predict plant responses to environmental change and will assist in prioritizing species for management actions, directing limited resources towards further investigations and can supplement bioclimatic modelling.

Seed dormancy responses to temperature relate toNothofagusspecies distribution and determine temporal patterns of germination across altitudes in Patagonia

“…), suggesting a link between physiological functional traits and elevation. The relationships between germination temperature and altitude predicted by our models are largely in concordance with some (Mariko et al ., ; Cochrane et al ., ), although not all (Linington, ; Cavieres & Arroyo, ; Rosbakh & Poschlod, ), previous data based on laboratory assessments. Studies that, in contrast to ours, report a negative relationship between germination temperature and altitude, propose that relatively high germination temperatures are required in colder environments to prevent seedling loss in high‐elevation habitats, because germination would be triggered solely by warm soil temperatures in late spring or early summer to reduce the risk of seedling frost (Billings & Mooney, ).…”

Seed germination and rising atmospheric CO2 concentration: a meta‐analysis of parental and direct effects

“…Identifying general patterns of similarities and differences in germination success responses between functional groups and life histories is a valuable first step in our ability to better understand how rising CO 2 concentrations (Huxman et al ., ) and other components of global change (Cochrane et al ., ) affect life transition from one generation to the next. We believe, however, that the most revealing pattern emerging from this meta‐analysis is the large degree of variability among species that transcends functional group and/or life form boundaries.…”

Distinct germination response of endangered and common arable weeds to reduced water potential

“…Temperature as a local trigger has a major impact on plants because it allows seedlings to germinate when the most favourable environmental conditions prevail (Cochrane et al . ). The importance of temperature for the germination process and the corresponding vulnerability of plants in this life cycle stage are highlighted in numerous studies ( e.g .…”