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Mature eastern hemlock-northern hardwood forest cover decreased drastically in the upper Midwest following European settlement and has yet to rebound substantially. Previous studies show that stands retaining substantial hemlock canopy coverage have low hemlock seedling and sapling densities. Results from various geographically restricted studies suggest several possible mechanisms that could cause low seedling or sapling density. We examined the relative importance of these proposed mechanisms in the Southern Superior Uplands Section of the Laurentian Forest Province. We surveyed 294-m2plots in 100 hemlock stands in northern Wisconsin and western upper Michigan to assess how these proposed mechanisms affect the number of hemlock seedlings and saplings in four sequential size classes. Seedling and sapling abundance increases with greater light availability and differs significantly among geographically distinct ecological units (ecological subsections). In contrast, the abundance of medium and large saplings (30-99 and 100-300 cm tall) appears unrelated to light and geographic factors but declines as deer browsing increases, diminishing rccruitment of larger saplings. The abundance of seedlings and saplings in each size class also depends strongly on the number of seedlings or saplings in the next smaller size class at the same site, reflecting demographic inertia. Path analysis integrates and separates these effects, explaining 24% of the regional variation in seedling abundance, 63% of small sapling abundance, and ∼80% of medium and large sapling abundance. Light and ecological subsection directly affect the number of seedlings and small saplings, whereas deer browsing directly affects the number of medium saplings. Demographic inertia remains important for all larger size classes. These results imply that restoring hemlock populations requires both appropriate microsites for seedling establishment and sanctuary from excessive browse for successful recruitment.

Abstract Polyploidy, which is common in plants, can confound taxon recognition and hence conservation assessments. In the taxonomically complex genus Rhododendron, 25 % of the over 1,300 taxa are considered under threat and 27 % Near Threatened or Data Deficient, with their taxonomy needing to be resolved urgently. Although ploidy levels of Rhododendron taxa range from diploid (2x) to dodecaploid (12x) according to previous reports, the extent of polyploidy across the genus has not been examined. We first summarized the taxonomic distribution of polyploids in the genus based on the literature. Then as a case study, we estimated ploidy levels of 47 taxa in subsection Maddenia (subgenus Rhododendron, section Rhododendron) using flow cytometry, together with verification of meiotic chromosome counts for representative taxa. The summary of reported ploidy in Rhododendron indicates that polyploidy is most common in subgenera Pentanthera and Rhododendron. In subsection Maddenia, all examined taxa are diploids except for the R. maddenii complex that shows a high ploidy variation (2–8x, 12x). We investigated ploidy level of 12 taxa in subsection Maddenia for the first time, and estimated genome sizes of two Rhododendron species. Knowledge of ploidy levels will inform phylogenetic analysis of unresolved species complexes. Overall, our study of subsection Maddenia provides a model for examining multiple issues including taxonomic complexity, ploidy variation and geographic distribution in relation to biodiversity conservation. Rhododendron is a woody plant genus of over 1,300 species. Although primarily native to the Himalayan mountains, many species are cultivated in botanic gardens around the world because of their spectacular floral diversity. In many plant species, variation in chromosome numbers (ploidy level) is a key aspect of genetic diversity for biodiversity conservation. Our paper examines the taxonomic distribution of reported ploidy levels in Rhododendronand investigates the ploidy level of 47 taxa in subsection Maddenia(~65 taxa). Using flow cytometry with chromosome count validation, we report ploidy of 12 taxa for the first time, and verify that taxa in subsection Maddeniaare all diploids except for the R. maddeniicomplex. Our future study on species geography and phylogenetics will help to understand the rich diversity and resolve the complex taxonomy of subsection Maddeniaand eventually of the genus Rhododendron.

The infraspecific taxon Anthurium willdenowii Kunth var. pohlii Engl. is elevated to the rank of species and is given the new name Anthurium maxakali Theófilo, Sakur. & Mayo. Comments about its taxonomy, ecology, and geographic distribution are discussed.

Geographers have developed and refined a set of strategies to organize time in their research. This study outlines the strengths and weaknesses of these temporal strategies and suggests diagrammatic interpretations and examples of each. Also offered are class activities through which secondary and college teachers can give their students a fuller understanding of the organization of time in geographic studies.