Abstract
Temperature is one of the climatic factors that shape the geographic distribution of plant populations. Mangroves are temperature-sensitive plants, and their distributions are severely limited by low temperatures. It is unknown, however, to what extent temperature contributes to their population differentiation and evolution. Kandelia obovata (Rhizophoraceae) is a mangrove species with high cold tolerance in the Northern Hemisphere. We investigated the phenotypic responses of an artificial population of K. obovata, with plants transplanted from different source populations, to extremely low temperatures during winter of 2015–2016 in Yueqing County (28°20′N), Zhejiang Province of China. Using two binary traits, “with/without leaves alive on the branches” and “with/without alive buds on the tips of branches,” we classified plants in this artificial population into strong, moderate and poor cold resistance groups. We further assessed the genetic diversity, structure and differentiation of these three groups, as well as five natural populations along a latitudinal gradient using ten nuclear and six plastid microsatellite markers. Microsatellite data revealed genetic differentiation among the natural populations along the latitudinal gradient. Molecular data indicated that the cold tolerance of three groups in the artificial population was associated with their geographic origins, and that the most cold-tolerant group came from the northernmost natural population. Our study thus indicates that natural populations of K. obovata may have evolved divergent capacity of cold tolerance.
Highlights
Climate is one of the primary factors that shape the natural distribution, genetic and geographic structures of plant populations (MacArthur, 1984; Woodward, 1987; Etterson, 2004; Lomolino et al, 2010)
Based on the phenotypic response of individuals to chilling event in the YQ population during the winter of 2015–2016, we could classify them into three categories of cold resistance: the group with strong resistance to cold (SRC), the group with moderate resistance to cold (MRC) and the group with poor resistance to cold (PRC) (Figure 2)
The chilling event that occurred during the winter of 2015–2016 in Yueqing provided us with an ideal opportunity to obtain data of phenotypic response of K. obovata to low temperature and to compare the cold-resistant capability between populations of different geographic origins
Summary
Climate is one of the primary factors that shape the natural distribution, genetic and geographic structures of plant populations (MacArthur, 1984; Woodward, 1987; Etterson, 2004; Lomolino et al, 2010). Both the annual coldest air temperature and the winter sea surface temperature can directly or indirectly affect mangroves (Chapman, 1977; Duke et al, 1998; Lovelock et al, 2016) Their distributions appear to be strongly limited by temperature in spite of some outliers, such as Avicennia marina var. Australasica (Acanthaceae) in New Zealand (38◦45 S), Avicennia germinans (Acanthaceae) in Bermuda (32◦20 N), and Kandelia obovata in Japan (31◦N), which may move from mangrove-rich regions to their latitudinal limits by the aids of warm ocean currents (Tomlinson, 2016) According to their adaptability to temperature, mangroves can be grouped into three thermal categories: thermophilic stenotopic species, thermophilic eurytopic species, and winter-resistant eurytopic species (Li and Lee, 1997; Hu et al, 2012). We currently lack evidence that populations of a single mangrove species may differentiate under temperature control
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