Population genetics under the Massenerhebung effect: the influence of topography on the demography of Acer morrisonense (Sapindaceae)

The sampling range mainly focused on CMR following Chiou et al. (2010), and the SMR was also considered for its second-largest mountain range in Taiwan. Thirteen populations with 286 individuals (Table 1) and 12 populations with 200 individuals of A. morrisonense (Table 2) surrounding the SMR and CMR in Taiwan were sampled for nuclear SSR genotyping and cpDNA sequencing, respectively (Fig. 2). The spacing between sampled individuals was at least 20 m. The altitudes of the sampling sites ranged from 1,280 m to 2,700 m a.s.l. Based on the altitudinal distribution pattern of A. morrisonense (Fig. 1), the populations SKR, LLS, and TPS in the north and JBS, LD, and STC in the south were respectively defined as northern and southern peripheral populations compared to the rest of the core populations (Fig. 2). Fresh leaves of each individual were collected and dried immediately in silica gel to prevent DNA degradation. Voucher specimens of each sample were deposited at National Taiwan Normal University. Total genomic DNA was extracted from dried leaf tissue following a modified cetyltrimethylammonium bromide (CTAB) method (Doyle & Doyle, 1987). The extracted DNA was dissolved in 1× TE buffer and stored at −20 °C. The expressed sequence tag-simple sequence repeats (EST-SSRs) used for genotyping for the genetic diversity analyses were developed from transcriptomic assemblies of Acer saccharum Marshall (Accession: Acer saccharum 010515, Hardwood Genomics Project, http://www.hardwoodgenomics.org/) and Acer negundo L. (Accession: VFFP, One Thousand Plants (1KP) Consortium, https://sites.google.com/a/ualberta.ca/onekp/). A total of 17 polymorphic EST-SSR loci were developed and used in this study (Table S1). For genotyping, the PCR products were analyzed by capillary electrophoresis on an Applied Biosystems 3730 DNA Analyzer (Applied Biosystem, USA). The fragment size was analyzed by Peak Scanner version 1.0 (Applied Biosystem, USA) at the National Center for Genome Medicine, Academia Sinica, Taiwan, and determined by reference to size standard ABI GS500 LIZ (Applied Biosystems, USA). For peak picking and noise reduction, a minimum peak height of 100 was adopted for allelic calling. Those peaks with sizes falling into the expected range were manually checked and adjusted.