Linnaea

Abstract: Linnaeoideae is a small subfamily of erect or creeping shrubs to small trees in Caprifoliaceae that exhibits a wide disjunct distribution in Eurasia, North America and Mexico. Most taxa of the subfamily occur in eastern Asia and Mexico but the monospecific genus Linnaea has a circumboreal to north temperate distribution. In this study, we conducted phylogenetic and biogeographic analyses for Linnaeoideae and its close relatives based on sequences of the nuclear ribosomal ITS and nine plastid (rbcL, trnS-G, matK, trnL-F, ndhA, trnD-psbM, petB-D, trnL-rpl32 and trnH-psbA) markers. Our results support that Linnaeoideae is monophyletic, consisting of four eastern Asian lineages (Abelia, Diabelia, Dipelta and Kolkwitzia), the Mexican Vesalea, and Linnaea. The Mexican Vesalea was formerly placed in Abelia, but it did not form a clade with the eastern Asian Abelia; instead Vesalea and Linnaea are sisters. The divergence time between the eastern Asian lineages and the Mexican Vesalea plus the Linnaea clade was dated to be 50.86 Ma, with a 95% highest posterior density of 42.8 Ma (middle Eocene) to 60.19 Ma (early Paleocene) using the Bayesian relaxed clock estimation. Reconstructed ancestral areas indicated that the common ancestor of Linnaea plus Vesalea may have been widespread in eastern Asia and Mexico or originated in eastern Asia during the Eocene and likely migrated across continents in the Northern Hemisphere via the North Atlantic Land Bridges or the Bering Land Bridge. The Qinling Mountains of eastern Asia are the modern-day center of diversity of Kolkwitzia-Dipelta-Diabelia clade. The Diabeliaclade became highly diversified in Japan and eastern China. Populations of Diabelia serrata in Japan and eastern China were found to be genetically identical in this study, suggesting a recent disjunction across the East China Sea, following the last glacial event.

Abstract: This study was based on two years of field observations of a Linnaea borealis population in a coniferous forest in Sweden. Detailed information on performance and survivorship of shoots were gathered from consecutively made drawings of 90 individually marked shoot systems of Linnaea distributed among 15 plots in the forest. Branching of the shoot systems was correlated to growth of the main shoot. Increasing light flux negatively affected growth of Linnaea. A tendency for a competitive effect on Linnaea of Vaccinium spp. was also found. In contrast, the surrounding mosses, and intraspecific density of Linnaea had no significant effect on the shoot systems. The growth rate of the shoot population was analysed by matrix models. Population growth rate was most dependent on survivorship and growth of main shoots in Linnaea, while the survivorship of lateral shoots was of less importance. In spite of an average decrease in the population size as revealed by the matrix model simulation, the incorporation of the observed spatial variation in shoot growth increment, branching and shoot survivorship, yielded varying population growth rates. Parts of the population increased in size. The importance of choice of spatial scale in population analyses of forest understory plants is emphasized.