Long-term isolation of the coastal plant Calystegia soldanella (Convolvulaceae) in ancient freshwater Lake Biwa, Japan

Abstract

Lake Biwa is an ancient freshwater lake that was formed approximately 4 Mya and harbours many coastal plants that commonly inhabit the seashore. We used chloroplast DNA haplotype analysis using two spacer sequences and simple sequence repeat (SSR) analysis using eight nuclear microsatellite markers to detect genomic signatures indicating long-term isolation of inland populations of Calystegia soldanella in Lake Biwa from coastal populations. We used 348 samples from 63 populations for haplotype analysis and 478 samples from 27 populations for SSR analysis covering the inland and coastal distribution of the species. We detected seven haplotypes, and the distribution pattern of these haplotypes was geographically highly structured between Lake Biwa and the coast. Nuclear SSR analysis also supported genetic differentiation between Lake Biwa and coastal populations (analyses of molecular variance, 43%), and the grouping of Lake Biwa and coastal populations by a Neighbour-joining tree. In addition, genetic diversity of the inland populations (mean HE = 0.153) was significantly lower than that of coastal populations (mean HE = 0.328). These results suggested that inland populations at Lake Biwa have been isolated from coastal populations for a very long time. The inland populations most likely experienced a bottleneck effect, resulting in sufficient in situ genetic divergence to clearly distinguish them from coastal populations.

Recent colonization by a coastal plant of inland habitats at an ancient freshwater lake, Lake Biwa: multilocus sequencing and a demographic history of Lathyrus japonicus (Fabaceae)

“…700–32,000; Table ) corresponds to the postglacial period, contradicting the previous inference of long‐term isolation of inland (Lake Biwa) and coastal populations (Noda et al. ; Ohtsuki et al. ) of L. japonicus and Calystegia soldanella .…”

“…Those also detected significantly lower genetic diversity in Lake Biwa's populations than in coastal populations. These results were likely to have been caused by founder events or genetic drift in the inland populations during the long-term isolation of Lake Biwa (Noda et al 2011; However, given that the Lake Biwa populations harbored a single haplotype of cpDNA sharing with the coastal populations in L. japonicus , such a shared haplotype might be interpreted as recent divergence between inland and coastal populations. Because if inland populations have been isolated from coastal populations for long time, they were expected to have unique haplotypes.…”

“…) and C. soldanella (Noda et al. ), found in both Lake Biwa and coastal site, detected unambiguous genetic differentiation between the Lake Biwa's and coastal populations using chloroplast DNA (cpDNA) and nuclear DNA microsatellite (nDNA SSR) loci. Those also detected significantly lower genetic diversity in Lake Biwa's populations than in coastal populations.…”

“…These results were likely to have been caused by founder events or genetic drift in the inland populations during the long‐term isolation of Lake Biwa (Noda et al. ; Ohtsuki et al. ).…”

Low functional diversity promotes niche changes in natural island pollinator communities

“…We tested the effect of long-tongued pollinator abundances on pollination in the same plant species because coastal sand dune vegetation includes similar species across the study region, perhaps due to the prevalence of sea-drifted (long-distance dispersed) plants [39][40][41] and harsh environmental conditions including high salinity and frequent disturbance [42]. Examining niche changes with and without increased niche breadth, that is, niche expansion and shift, respectively (figure 1), we asked the following questions.…”