Selective sweeps and intercontinental migration in the cosmopolitan moss Ceratodon purpureus (Hedw.) Brid.

Abstract

The moss Ceratodon purpureus has long been used as a model system in plant development and physiology. However, the molecular population genetics of the species remains virtually unexplored. In this study, we used population genetic analyses of DNA sequence data from three unlinked loci (atpB-rbcL spacer, adk, and phy2) to examine biogeographical patterns in a global sample of this species. The three loci differed significantly in mutation frequency spectra and implied population structure. Pairs of haplotypes from single populations were frequently more divergent than haplotypes sampled from widely disjunct populations. In the atpB-rbcL spacer and adk samples, Australasian haplotypes were more closely related to Northern Hemisphere haplotypes than to haplotypes found in the equatorial regions. In contrast, the phy2 sample showed that the north and south temperate regions were genetically divergent, with the equatorial regions intermediate. Maximum-likelihood estimates (MLE) of the rates of migration between the two hemispheres were significantly different for the two nuclear genes. The frequency spectra of mutations indicated that differences in implied population structure among the three loci resulted from directional selection on the chloroplast genome and on the chromosomal segment containing adk. Collectively, these data suggest that long-distance migration within the Northern Hemisphere and Australasian regions is common (relative to the mutation rate) and that migration between these two regions, potentially via equatorial populations, is more frequent than migration among equatorial populations.

A Linkage Map Reveals a Complex Basis for Segregation Distortion in an Interpopulation Cross in the Moss Ceratodon purpureus

“…As a first step toward understanding the genetic basis of these phenotypic differences, we generated recombinant progeny from a cross between isolates of C. purpureus from Ithaca, New York, and Otavalo, Ecuador. Taxonomically these populations belong to different subspecies (Burley and Pritchard 1990), although in previous molecular population genetic analyses we found no genealogical support for this arrangement (McDaniel and Shaw 2005). Here we describe widespread segregation distortion in the progeny of a cross between these two populations, which we suggest results from spore mortality.…”

“…Development and analysis of molecular markers: Genomic DNA was extracted from sterile protonemal tissue from the two parents and all of progeny, using a cetyl trimethyl ammonium bromide extraction, described in McDaniel and Shaw (2005), modified for 1-ml extractions using a Genogrinder 2000 bead shaker (SPEX CertiPrep, Metuchen, NJ). The DNA was resuspended in 30 ml of TE.…”

“…Brid. is used as a model system for the study of several biological processes (Shaw and Gaughan 1993;Shaw et al 1997;Shaw and Beer 1999;McDaniel 2005;McDaniel and Shaw 2005;Thornton et al 2005;. However, progress toward identifying genes underlying traits of interest in C. purpureus is limited (Cove et al 1996;Wagner et al 1997;Esch et al 1999;Kern and Sack 1999;; but see Brucker et al 2005), largely because classical forward genetic approaches have not been developed.…”

Insolation and disturbance history drive biocrust biodiversity in Western Montana rangelands

“…Biocrusts are assemblages of lichens, bryophytes, algae, cyanobacteria, fungi, and microfauna that form on and stabilize dryland soil surfaces (reviewed by Belnap and Lange 2003;Rosentreter et al 2016;Seppelt et al 2016). One way in which biocrusts are different from plant and animal communities is that they may not be strongly dispersal-limited due to the existence of small propagules such as spores that can plausibly disperse across long distances, even continent to continent (Muñoz et al 2004;McDaniel and Shaw 2005). Consequently, there are multiple biocrust species that have multi-continental distributions or broad ranges within a single continent.…”

Australian mosses - new chromosome numbers and a compilation of chromosome data

“…DNA studies based on population genetic analyses using three unlinked loci to examine biogeographical patterns by McDaniel & Shaw (2005) showed that in Ceratodon purpureus "Australasian haplotypes were more closely related to northern hemisphere haplotypes than to haplotypes found in the equatorial regions. Collectively these data suggest that long distance migration within the northern hemisphere and Australasian regions is common (relative to mutation rate) and that migration between these two regions, potentially via equatorial populations, is more frequent than migration among equatorial populations".…”