Germination temperature sensitivity differs between co-occurring tree species and climate origins resulting in contrasting vulnerability to global warming

João C Filipe; Collin C Ahrens; Margaret Byrne; Giles Hardy; Paul D Rymer

doi:10.1002/pei3.10108

Germination temperature sensitivity differs between co-occurring tree species and climate origins resulting in contrasting vulnerability to global warming

Plant Environ Interact. 2023 Apr 24;4(3):146-162. doi: 10.1002/pei3.10108. eCollection 2023 Jun.

Authors

João C Filipe^{1

2}, Collin C Ahrens^{3

4

5

6}, Margaret Byrne¹, Giles Hardy², Paul D Rymer³

Affiliations

¹ Department of Biodiversity, Conservation and Attractions Biodiversity and Conservation Science Perth Western Australia Australia.
² Centre for Terrestrial Ecosystem Science and Sustainability Harry Butler Institute Murdoch University Murdoch Western Australia Australia.
³ Hawkesbury Institute for the Environment Western Sydney University Richmond New South Wales Australia.
⁴ School of Biotechnology & Biomolecular Sciences University of New South Wales Sydney New South Wales Australia.
⁵ Research Centre for Ecosystem Resilience Royal Botanic Gardens and Domain Trust Sydney New South Wales Australia.
⁶ Cesar Australia Brunswick Victoria Australia.

Abstract

Climate change is shifting temperatures from historical patterns, globally impacting forest composition and resilience. Seed germination is temperature-sensitive, making the persistence of populations and colonization of available habitats vulnerable to warming. This study assessed germination response to temperature in foundation trees in south-western Australia's Mediterranean-type climate forests (Eucalyptus marginata (jarrah) and Corymbia calophylla (marri)) to estimate the thermal niche and vulnerability among populations. Seeds from the species' entire distribution were collected from 12 co-occurring populations. Germination thermal niche was investigated using a thermal gradient plate (5-40°C). Five constant temperatures between 9 and 33°C were used to test how the germination niche (1) differs between species, (2) varies among populations, and (3) relates to the climate of origin. Germination response differed among species; jarrah had a lower optimal temperature and thermal limit than marri (T _o 15.3°C, 21.2°C; ED₅₀ 23.4°C, 31°C, respectively). The thermal limit for germination differed among populations within both species, yet only marri showed evidence for adaptation to thermal origins. While marri has the capacity for germination at higher thermal temperatures, jarrah is more vulnerable to global warming exceeding safety margins. This discrepancy is predicted to alter species distributions and forest composition in the future.

Keywords: climate change; conservation; forest ecology; life‐history traits; local adaptation; range shift; safety margin; seed germination; thermal niche.