Native microhabitats better predict tolerance to warming than latitudinal macro‐climatic variables in arid‐zone plants

Abstract

Aim Understanding species ability to withstand heat stress is paramount for predicting their response to increasing temperatures and decreasing rainfall. Arid systems are subject to climatic extremes, where plants, being immobile, live on the frontline of climate change. Our aim was to investigate whether: (1) warming tolerance [WT = the difference between a species physiological thermal damage threshold (T 50 ) and the maximum temperature within its distribution (T hab )] for desert plants is higher at high latitudes, as has been shown for terrestrial ectotherms, and (2) if T 50 of desert plants better corresponds with broad climatic indicators or species native microhabitats.Location The Australian Arid Lands Botanic Garden, Port Augusta, South Australia.Methods Using chlorophyll fluorescence techniques, we measured T 50 for 42 Australian arid plant species native to different microhabitats based on water availability. WT was calculated (T 50 ÀT hab ) and each metric was compared against microhabitat and broad-scale climatic variables for each species.Results T 50 was unrelated to macro-scale climate or latitude, whereas WT increased for species whose distributions extend into higher latitudes, a pattern hitherto not shown for terrestrial plants. We also found that species adapted to higher water availability in their native microhabitat had significantly lower T 50 and WT than species from drier microhabitats.Main conclusions (1) Warming tolerance increased with latitude, but the strength of this relationship was related to the way WT was quantified, with T hab and latitude being linked. (2) T 50 did not correlate with latitude, but both T 50 and WT were strongly related to their microhabitats. Specifically, water availability is important, such that even within a desert biome, species associated with 'wetter' microhabitats, may be particularly vulnerable to heat stress. Thus, we show that local-scale patterns better capture plant physiological responses to temperature than broad-scale distributions.

Plasticity of photosynthetic heat tolerance in plants adapted to thermally contrasting biomes

“…Under these heatwave and drought conditions, where adaptive and acclimation dependent changes would be expected to maximize heat tolerance, T crit rarely exceeded 55 °C, with most species exhibiting maximum T crit values near 50 °C. Two other studies on Australian desert plant species during summer (Curtis et al, ; Curtis et al, ) also found the highest thermal tolerance indicated by T 50 of photosynthetic efficiency (50% decline in the maximum quantum yield of PSII of dark‐adapted leaves)—was below 55 °C. Similar results were also reported in studies of 35 desert species of P HT in the USA (Downton et al, ) and 24 savanna woody species in China (Zhang et al, ).…”

“…In a glasshouse study, Knight and Ackerly () compared four pairs of congeneric species from hot desert and cooler coastal regions of northern California but found no inherent differences in T crit . By contrast, a common garden study on Australian desert plants by Curtis et al () found that species adapted to higher water availability experienced thermal damage at lower leaf temperatures than species adapted to low rainfall sites. The contrasting nature of the above studies highlights the need for studies using a wider range of species adapted to several biomes before firm conclusions can be made on whether P HT differs inherently among species adapted to contrasting environments.…”

“…Climate data from Atlas of Living Australia records were extracted using ANUCLIM V6 (Xu & Hutchinson, ). A similar climate‐sourcing approach can be found in Curtis et al ().…”

“…T crit reflects the high temperature threshold at which PSII begins to be damaged. Quantification of the temperature response of F o (i.e., F o ‐T curves)—or similar methods that assess PSII functionality (e.g., temperature dependence of the maximum quantum yield of PSII of dark‐adapted leaves)—therefore provides insights into the heat sensitivity of PSII (Bilger, Schreiber, & Lange, ; Curtis, Gollan, Murray, & Leigh, ; Curtis, Knight, Petrou, & Leigh, ; Krause et al, ; Krause & Weis, ; Krause, Winter, Krause, & Virgo, ; Schreiber & Berry, ; Schreiber, Colbow, & Vidaver, ; Zhang, Poorter, Hao, & Cao, ). Using such approaches, advances have been made in our understanding of the physiological mechanisms (Hüve, Bichele, Rasulov, & Niinemets, ; Hüve, Bichele, Tobias, & Niinemets, ; Yamane, Kashino, Koike, & Satoh, ), broader ecological patterns, and significance of photosynthetic heat tolerance ( P HT ) (Curtis et al, ; Downton, Berry, & Seemann, ; Ghouil et al, ; Knight & Ackerly, ; Knight & Ackerly, ; Knight & Ackerly, ; Krause et al, ; O'Sullivan et al, ; Seemann, Downton, & Berry, ; Zhang et al, ).…”

The vulnerability of developing embryos to simulated climate warming differs between sympatric desert lizards

“…This between‐species difference in embryonic thermal tolerance is likely a result of phylogenetic differences, or physiological adaptation to their respective microhabitats (Curtis, Gollan, Murray, & Leigh, ; Scheers & Van Damme, ). Although our data do not allow us to tease apart these two causes, phylogenetic differences and physiological adaptation may not be mutually exclusive because phylogenetic differences may be a result of physiological adaptation during the evolutionary history of these species (Garland, Bennett, & Rezende, ; Khaliq et al., ).…”