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The earth is experiencing major changes in global and regional climates and changes are predicted to accelerate in the future. Many species will be under considerable pressure to evolve, to migrate, or be faced with extinction. Clonal plants would appear to be at a particular disadvantage due to their limited mobility and limited capacity for adaptation. However, they have outlived previous environmental shifts and clonal species have persisted for millenia. Clonal spread offers unique ecological advantages, such as resource sharing, risk sharing, and economies of scale among ramets within genotypes. We suggest that ecological attributes of clonal plants, in tandem with variation in gene regulation through epigenetic mechanisms that facilitate and optimize phenotype variation in response to environmental change may permit them to be well suited to projected conditions.

• Pear cultivars responded to temperature changes in winter less than expected. • Shoots rehardened but buds did not reharden after a warm spell during the dormancy. • Pear cultivars responded similarly to the temperature changes. • Frost hardiness of shoot by DTA was much higher than by REL and VD. The rates of dehardening and rehardening in response to rapid temperature changes in winter are important traits that affect the survival, growth and productivity of the European pear (Pyrus communis [L.]) cultivars in northern countries. The frost hardiness (FH) of shoots of three pear cultivars were studied by a series of freezing tests, after sampling in natural conditions, after dehardening in a growth chamber at 5 °C for 3–4 days (D1) and 16 days (D2), and then after rehardening at −7 °C for 5–7 days (R1 and R2). The FH was assessed by a differential thermal analysis (DTA) to measure the low temperature exotherm (LTE) of shoots, by relative electrolyte leakage (REL) of shoots and by visual damage scoring (VD) of shoots and buds. According to the DTA, the FH of the cultivars varied between −38 °C ('Conference' in D2) and −41 °C ('Pepi' in R2). The shoots of the cultivar 'Pepi' and 'Conference' had the highest and the lowest FH, respectively, in all conditions and methods. All the cultivars had the lowest shoot FH after dehardening in either D1 (between −26 °C and −30 °C by REL and between −28 °C and −30 °C by VD) or D2 (between −38 °C and −40 °C by DTA), and the highest FH after rehardening (R1) preceded by D1 (between −30 °C and −34 °C by REL, and between −29 °C and −32 °C by VD). After the dehardening in D1, the buds did not reharden but continued to deharden (the average FH by VD − 24.5 °C). In the forcing conditions, bud growth was resumed most rapidly in 'Conference', indicating a shallower dormancy in this cultivar than in 'Pepi' or 'Clara Frijs'. We conclude that the pear cultivars responded to temperature changes in mid-winter, but less than expected, and the responses were similar in all cultivars. [ABSTRACT FROM AUTHOR]