Niche divergence between diploid and autotetraploid Tolmiea.

PREMISE OF STUDY: Polyploidy is common in eukaryotes and is of major evolutionary importance over both short and long time-scales. Compared to allopolyploids, autopolyploids remain understudied; they are often morphologically cryptic and frequently remain taxonomically unrecognized, although there is increasing recognition of the high frequency of autopolyploidy in angiosperms. While autopolyploidy can serve as an instant speciation mechanism, little is known about the ecological consequences of this process. We describe the ecological divergence of a diploid-autotetraploid species pair in Tolmiea. METHODS: We investigated whether abiotic niche divergence has shaped the current allopatric distribution of diploid T. diplomenziesii and its autotetraploid derivative, T. menziesii, in the Pacific Northwest of North America. We employed field measures of light availability, as well as niche modeling and a principal component analysis of environmental space. Within a common garden, we also investigated physiological responses to changes in soil moisture. KEY RESULTS: Diploid and autotetraploid Tolmiea inhabit significantly different climatic niche spaces. The climatic niche divergence between these two species is best explained by a shift in precipitation availability, and we found evidence of differing physiological response to water availability between these species. CONCLUSIONS: We found that spatial segregation of T. diplomenziesii and T. menziesii was accompanied by adaptation to changes in climatic regime. Tolmiea menziesii is not a nascent autotetraploid, having persisted long enough to be established throughout the Pacific Northwest, and therefore both polyploidization and subsequent evolution have contributed to the observed differences between T. menziesii and T. diplomenziesii.

The report of my death was an exaggeration: A review for researchers using microsatellites in the 21st century.

Microsatellites, or simple sequence repeats (SSRs), have long played a major role in genetic studies due to their typically high polymorphism. They have diverse applications, including genome mapping, forensics, ascertaining parentage, population and conservation genetics, identification of the parentage of polyploids, and phylogeography. We compare SSRs and newer methods, such as genotyping by sequencing (GBS) and restriction site associated DNA sequencing (RAD-Seq), and offer recommendations for researchers considering which genetic markers to use. We also review the variety of techniques currently used for identifying microsatellite loci and developing primers, with a particular focus on those that make use of next-generation sequencing (NGS). Additionally, we review software for microsatellite development and report on an experiment to assess the utility of currently available software for SSR development. Finally, we discuss the future of microsatellites and make recommendations for researchers preparing to use microsatellites. We argue that microsatellites still have an important place in the genomic age as they remain effective and cost-efficient markers.