Local adaptation to different phytogeographic regions: habitat‐related variations in seed germination in response to temperature and salinity for two medicinalSalviaspecies fromJordan

Abstract

AbstractSalvia spinosa L. andSalvia syriaca L. are perennial medicinal herbs that occur in theMediterranean,Irano‐Turanian andSaharo‐Arabian phytogeographic regions ofJordan. With respect to the seed germination requirements, prevailing environmental conditions in each phytogeographic region may promote local adaptation and consequently affect the distribution range of the species. Using seeds of both species collected from populations across the three regions, we tested responses to variations in temperature and salinity under laboratory conditions. Both species showed significant differences in cumulative germination percentages and germination rates (modifiedTimson Index) with temperature, while origin only significantly affectedS. spinosaseeds. Both species germinated best under the highest temperature regime (32/20°C). The low temperature regime (8/4°C) completely inhibited germination inS. syriaca, wheras it led to 80% to 95% germination inS. spinosa, with significant variation being recorded between the phytogeographic regions. For both species, salt solutions of 0, 25 and 50 mMNaCl yielded the highest germination percentages and rates, which sharply and significantly declined at higher concentrations (100 and 200 mMNaCl). Our results provide evidence of local adaptation of the study species to salinity and temperature in the respective maternal environments, particularly in theIrano‐Turanian andSaharo‐Arabian regions. Such differentiation should be accounted for in future conservation planning.