Large scale patterns of genetic variation and differentiation in sugar maple from tropical Central America to temperate North America.

BACKGROUND: Geological events in the latter Cenozoic have influenced the distribution, abundance and genetic structure of tree populations in temperate and tropical North America. The biogeographical history of temperate vegetation that spans large ranges of latitude is complex, involving multiple latitudinal shifts that might have occurred via different migration routes. We determined the regional structuring of genetic variation of sugar maple (Acer saccharum subsp. saccharum) and its only subspecies in tropical America (Acer saccharum subsp. skutchii) using nuclear and chloroplast data. The studied populations span a geographic range from Maine, USA (46°N), to El Progreso, Guatemala (15°N). We examined genetic subdivisions, explored the locations of ancestral haplotypes, analyzed genetic data to explore the presence of a single or multiple glacial refugia, and tested whether genetic lineages are temporally consistent with a Pleistocene or older divergence. RESULTS: Nuclear and chloroplast data indicated that populations in midwestern USA and western Mexico were highly differentiated from populations in the rest of the sites. The time of the most recent common ancestor of the western Mexico haplotype lineage was dated to the Pliocene (5.9 Ma, 95% HPD: 4.3-7.3 Ma). Splits during the Pleistocene separated the rest of the phylogroups. The most frequent and widespread haplotype occurred in half of the sites (Guatemala, eastern Mexico, southeastern USA, and Ohio). Our data also suggested that multiple Pleistocene refugia (tropics-southeastern USA, midwestern, and northeastern USA), but not western Mexico (Jalisco), contributed to post-glacial northward expansion of ranges. Current southern Mexican and Guatemalan populations have reduced population sizes, genetic bottlenecks and tend toward homozygosity, as indicated using nuclear and chloroplast markers. CONCLUSIONS: The divergence of western Mexican populations from the rest of the sugar maples likely resulted from orographic and volcanic barriers to gene flow. Past connectivity among populations in the southeastern USA and eastern Mexico and Guatemala possible occurred through gene flow during the Pleistocene. The time to the most common ancestor values revealed that populations from the Midwest and Northeast USA represented different haplotype lineages, indicating major divergence of haplotypes lineages before the Last Glacial Maximum and suggesting the existence of multiple glacial refugia.

Trends in access of plant biodiversity data revealed by Google Analytics.

The amount of plant biodiversity data available via the web has exploded in the last decade, but making these data available requires a considerable investment of time and work, both vital considerations for organizations and institutions looking to validate the impact factors of these online works. Here we used Google Analytics (GA), to measure the value of this digital presence. In this paper we examine usage trends using 15 different GA accounts, spread across 451 institutions or botanical projects that comprise over five percent of the world's herbaria. They were studied at both one year and total years. User data from the sample reveal: 1) over 17 million web sessions, 2) on five primary operating systems, 3) search and direct traffic dominates with minimal impact from social media, 4) mobile and new device types have doubled each year for the past three years, 5) and web browsers, the tools we use to interact with the web, are changing. Server-side analytics differ from site to site making the comparison of their data sets difficult. However, use of Google Analytics erases the reporting heterogeneity of unique server-side analytics, as they can now be examined with a standard that provides a clarity for data-driven decisions. The knowledge gained here empowers any collection-based environment regardless of size, with metrics about usability, design, and possible directions for future development.

Phylogenetic evaluation of Xylothamia, Gundlachia, and related genera (Asteraceae, Astereae) based on ETS and ITS nrDNA sequence data.

Previous molecular investigations of the phylogenetic relationship for Xylothamia employed exemplar taxa and indicated its affiliation is either with the Gutierrezia or the Ericameria alliances. The present 3' ETS and ITS nrDNA gene phylogenies yielded the unexpected result that Xylothamia is polyphyletic. Species within its circumscription are placed into two well-supported evolutionary lineages with other genera of Astereae. Of nine species of Xylothamia, four species plus Gundlachia constitute one clade. The other five species are placed in a sister clade with several other genera including Amphiachyris, Bigelowia, Euthamia, Gutierrezia, and others. Except for X. johnstonii and X. palmeri, these five species of Xylothamia have little affinity for one another or for other genera in the same clade. Morphological similarities in foliar features between certain species in both lineages are possibly from a convergence resulting in adaptation to arid habitats. Such similarities were also the basis, in part, for their taxonomic treatment within Xylothamia or their earlier affiliation with Ericameria, which has similar features. The uncharacteristic leaf form in Xylothamia purpursii has a pattern of adaptation considerably different from its allies. Whether the Xylothamia-containing clades are related to Solidaginineae or represent an independently derived lineage remains equivocal because this outcome rested with the choice of data and optimality criteria.