Phalaris arundinacea L. (reed canarygrass) has become one of the most aggressive invaders of North American wetlands. P. arundinacea is native to temperate N. America, Europe, and Asia, but repeated introductions of European genotypes to N. America, recent range expansions, and the planting of forage and ornamental cultivars complicate the resolution of its demographic history. Molecular tools can help to unravel the demographic and invasion history of populations of invasive species. In this study, inter-simple sequence repeat markers were used to analyze the population genetic structure of European and N. American populations of reed canary grass as well as forage and ornamental cultivars. We found that P. arundinacea harbors a high amount of genetic diversity with most of the diversity located within, as opposed to among, populations. Cluster analyses suggested that current populations are admixtures of two formerly distinct genetic groups.

The number of marker loci required to answer a given research question satisfactorily is especially important for dominant markers since they have a lower information content than co-dominant marker systems. In this study, we used simulated dominant marker data sets to determine the number of dominant marker loci needed to obtain satisfactory results from two popular population genetic analyses: STRUCTURE and AMOVA (analysis of molecular variance). Factors such as migration, level of population differentiation, and unequal sampling were varied in the data sets to mirror a range of realistic research scenarios. AMOVA performed well under all scenarios with a modest quantity of markers while STRUCTURE required a greater number, especially when populations were closely related. The popular ΔK method of determining the number of genetically distinct groups worked well when sampling was balanced, but underestimated the true number of groups with unbalanced sampling. These results provide a window through which to interpret previous work with dominant markers and we provide a protocol for determining the number of markers needed for future dominant marker studies.

Urban trees are often more sun- and wind-exposed than their forest-grown counterparts. These environmental differences can impact how many species grow–impacting trunk taper, crown spread, branch architecture, and other aspects of tree form. Given these differences, windthrow models derived from traditional forest production data sources may not be appropriate for urban forest management. Additionally, visual abnormalities historically labeled as “defects” in timber production, may not have a significant impact on tree failure potential. In this study, we look at urban tree failures associated with Hurricane Irma in Tampa, Florida, USA. We used spatial analysis to determine if patterns of failure existed among our inventoried trees. We also looked at risk assessment data to determine which visual defects were the most common and the most likely to be associated with branch or whole-tree failure. Results indicate that there was no spatial pattern associated with the observed tree failures–trees failed or withstood the storm as individuals. While some defects like decay and dead wood were associated with increased tree failure, other defects such as weak branch unions and poor branch architecture were less problematic.

The spread of invasive wetland plants has resulted in a number of negative impacts to wetland habitats including reductions in biodiversity, displacement of native plants, and altered water flow. Phalaris arundinacea L. (Reed canarygrass) is a highly competitive invasive plant in North American wetlands. While research has focused on growth characteristics and competitive ability of P. arundinacea in wetland habitats, little is known about how its growth in upland conditions differs from that in wetlands. To characterize differences in growth between upland and wetland habitats, we conducted a 13-month field experiment of unconstrained growth of P. arundinacea in upland and wetland conditions. A suite of traits was measured in genotypes collected from upland and wetland habitats. Although P. arundinacea most often occurs in wetlands, there was significantly higher growth and fecundity in the dry soil treatment. All of the growth traits measured varied among genotypes, a few varied between the habitats of origin, and significant interactions were found between habitat of origin and soil moisture treatment for several traits. The significant genetic variation observed suggests that there is potential for local adaptation to upland habitats. The higher growth and fecundity in upland conditions highlights the need for additional research to investigate P. arundinacea establishment capacity and competitiveness in upland habitats.

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