Multiple factors influence population sex ratios in the Mojave Desert moss Syntrichia caninervis

Abstract

Premise of research: Natural populations of many mosses appear highly female-biased based on the presence of reproductive structures. This bias could be caused by increased male mortality, lower male growth rate, or a higher threshold for achieving sexual maturity in males. Here we test these hypotheses using samples from two populations of the Mojave Desert moss Syntrichia caninervis.Methods: We used double digest restriction-site associated DNA (RAD) sequencing to identify candidate sex-associated loci in a panel of sex-expressing plants. Next, we used putative sex-associated markers to identify the sex of individuals without sex structures.Key results: We found an 18:1 phenotypic female: male sex ratio in the higher elevation site (Wrightwood), and no sex expression at the low elevation site (Phelan). In contrast, based on genetic data we found a 2:1 female bias in the Wrightwood site and only females in the Phelan site. The area occupied by male and female genets was indistinguishable.Conclusions: These data suggest that both differential mortality and sexual dimorphism in thresholds for sex expression likely contribute to population genetic and phenotypic sex ratio biases, and that phenotypic sex expression alone fails to capture the extent of actual sex ratio bias present in natural populations of S. caninervis.

What do tropical cryptogams reveal? Strong genetic structure in Amazonian bryophytes

“…Significant IBD patterns are thus reported here despite the comparatively lower number of SNPs than in recent population genetic studies based on RADseq in bryophytes (Baughman et al ., 2017; Lewis et al ., 2017) and angiosperms, wherein 2000–3000 independent SNPs are commonly reported for phylogeographic studies (e.g. Prunier et al ., 2017; Bell et al ., 2018).…”

A pseudomolecule‐scale genome assembly of the liverwort Marchantia polymorpha

“…Subsequent to DNA extraction, we performed double‐digest RAD (ddRAD) library preparation for Illumina sequencing, following a modified protocol described in (Baughman et al , ). In brief, the genomic DNA was digested by Eco RI and Mse I, resulting in sticky‐end fragments that were labelled by using 92 unique Eco RI adaptors containing an in‐line barcode.…”

Do motile spermatozoids limit the effectiveness of sexual reproduction in bryophytes? Not in the liverwort Marchantia polymorpha

“…Even with surface water films likely to be less effective than in Marchantia and with neither splash dispersal nor explosive antheridial dehiscence, fertilization distances in Sphagnum of over at least 1 m must still be commonplace. Numerous examples of genetic heterogeneity between bryophytes clones, even in taxa which rarely or only sporadically produce sporophytes, including diverse Sphagna (Cronberg, ; Stenøien & Såstad, ; Thingsgaard, ; Cronberg & Natcheva, ; Gunnarsson et al, ; Provan & Wilson, ; Shaw et al, ) desert acrocarps (Baughman et al, ) and a range of pleurocarps (Økland, ; Cronberg, ; Cronberg et al, ; Rosengren et al, ) further underline the effectiveness of sexual reproduction. On the other hand, Hughes () suggests that polysety in Dicranum may be an adaptation to compensate for an insufficient supply of spermatozoids or their inefficient dispersal.…”

“…Also indicating that motile spermatozoids are far from ineffective sexual propagules in terrestrial environments is the ability of antheridia to retain viable gametes through periods of desiccation (Abel, ; Shortlidge et al, ; Stark et al, ; Döbbeler, ) and the abundance of sporophytes in many bryophytes, including taxa of dry habitats (Goffinet & Shaw, ), although here drought may have profound effects on sporophyte production and maturation (Stark, ). Further underlining successful sexual reproduction has been the discovery of remarkable and often unexpected genetic diversity from population studies on taxa ranging from Sphagnum to pleurocarpous mosses (Eriksson, ; Stenøien & Såstad, ; Økland, ; Thingsgaard, ; Cronberg, ; Cronberg & Natcheva, ; Cronberg et al, ; Gunnarsson et al, ; Provan & Wilson, ; Shaw et al, ; Rosengren et al, ; Baughman et al, ).…”