Growth rates and sexual reproduction in Dolichousnea longissima transplanted along a trans-Himalayan elevational gradient

These datasets provide the underpinning data to the paper:

Worthy FR, Yin AC, Wang LS and Wang XY (2025) Growth rates and sexual reproduction in Dolichousnea longissima transplanted along a trans-Himalayan elevational gradient. The Lichenologist 57(2), 91-112. https://doi.org/10.1017/S0024282925000064.

The work was conducted in Diqing prefecture, Yunnan Province, China. The world’s longest lichen, D. longissima, is usually asexual. We discovered a site with apotheciate thalli, enabling us to address hypotheses in evolutionary biology regarding transitions from asexual to sexual reproduction. For conservation reasons, we also tested length-dependent growth patterns.
D. longissima asexual thallus strands of 10, 20, 40 or 80 cm length were transplanted from higher to lower elevations (≈ 4000 to 3400 m) to simulate climatic change (increased temperatures and VPD, with reduced RH).
We used this field experiment to test the following non-mutually exclusive hypotheses:
1. Dolichousnea longissima shows positive length-dependent growth.
2. Length-dependent growth patterns will be altered by climatic change.
3. Switches from asexual to sexual reproduction are induced by climatic stressors.
4. Greater stress will drive higher reproductive allocation, and reproduction beginning at a smaller thallus size.
5. Raised temperatures, reduced relative humidity and increased vapour pressure deficit will reduce mycobiont growth and photobiont survival.
We also tested the alternative hypothesis that:
6. Apotheciate Dolichousnea specimens from these study sites belong to a genetically and morphologically distinct population.
FINDINGS
Phylogenetic analyses confirmed specimens were D. longissima. Multiple phylogenetic branches included both apotheciate and non-apotheciate thalli. After three-years growth, thallus mortality was highest at the warmest sites. Intact thalli showed negative length-dependent growth. Higher temperatures were associated with initiation of sexual reproduction, reduced Relative Thallus Length Growth rates and lower photobiont abundance, with apparent shifts of photobionts from the main stem to fibrils and reallocation of resources from length to central cord and fibril mass. Probability of switching to sexual production increased with thallus length, but shorter thalli made greater relative investment in apothecia production.
IMPLICATIONS FOR CONSERVATION
Detrimental climatic change impacts could reduce D. longissima range and biomass production, thereby also decreasing food availability for the endangered lichenivorous monkey, Rhinopithecus bieti. Apotheciate populations need protection, because genetic variability could increase resilience to climatic change.