An Evaluation of Putative Sympatric Speciation within Limnanthes (Limnanthaceae)

Abstract

Limnanthes floccosa ssp. floccosa and L. floccosa ssp. grandiflora are two of five subspecies within Limnanthes floccosa endemic to vernal pools in southern Oregon and northern California. Three seasons of monitoring natural populations have quantified that L. floccosa ssp. grandiflora is always found growing sympatrically with L. floccosa ssp. floccosa and that their flowering times overlap considerably. Despite their subspecific rank within the same species crossing experiments have confirmed that their F1 hybrids are sterile. An analysis of twelve microsatellite markers, with unique alleles in each taxon, also shows exceedingly low levels of gene flow between populations of the two subspecies. Due to the lack of previous phylogenetic resolution among L. floccosa subspecies, we used Illumina next generation sequencing to identify single nucleotide polymorphisms from genomic DNA libraries of L. floccosa ssp. floccosa and L. floccosa ssp. grandiflora. These data were used to identify single nucleotide polymorphisms in the chloroplast, mitochondrial, and nuclear genomes. From these variable loci, a total of 2772 bp was obtained using Sanger sequencing of ten individuals representing all subspecies of L. floccosa and an outgroup. The resulting phylogenetic reconstruction was fully resolved. Our results indicate that although L. floccosa ssp. floccosa and L. floccosa ssp. grandiflora are closely related, they are not sister taxa and therefore likely did not diverge as a result of a sympatric speciation event.

Mitochondrial Capture Misleads about Ecological Speciation in the Daphnia pulex Complex

“…Although theoretical models have deemed sympatric ecological speciation plausible [3,4], compelling examples are scarce and evidence often controversial [7–9,66]. Speciation by divergent selection between sympatric habitats was considered a parsimonious scenario to explain the distribution and ecological divergence of D .…”

The plastid genome of the mycoheterotrophicCorallorhiza striata(Orchidaceae) is in the relatively early stages of degradation

“…Any nuclear copies of plastid genes would typically occur at orders of magnitude lower coverage than genes residing in the plastome (for which there are typically numerous copies per cell) and are therefore not an issue if initial PCR‐based enrichment is not undertaken. This approach has been highly successful in previous studies of monocots (Givnish et al, 2010; Delannoy et al, 2011; Steele and Pires, 2011; Barrett et al, in press), and eudicots (Straub et al, 2011; Meyers et al, 2012; Straub et al, 2012), for acquiring complete or nearly complete plastid genomes. Nevertheless, contigs (and short‐read pileups) were carefully screened for potential extraplastid reads.…”

A Simulation Study of the Ecological Speciation Conditions in the Galician Marine Snail Littorina saxatilis

“…This idea has produced controversy between theoretical studies that show that natural selection can overcome the effects of gene flow ( Dieckmann and Doebeli, 1999 ; Gavrilets, 2004 ; Barluenga et al, 2006 ; Hey, 2006 ; Bolnick and Fitzpatrick, 2007 ; Rolán-Alvarez, 2007 ; Debarre and Gandon, 2011 ; Weissing et al, 2011 ; Savolainen et al, 2013 ; Butlin et al, 2014 ; Richardson et al, 2014 ; Getz et al, 2016 ; Rettelbach et al, 2016 ; Servedio and Boughman, 2017 ; Kopp et al, 2018 ) and those that admit that this is feasible but that the conditions necessary for it to occur make it difficult to observe in the real world. ( Jiggins, 2006 ; Babik et al, 2009 ; Meyers et al, 2012 ; Martin, 2013 ; Savolainen et al, 2013 ; Martin et al, 2015 ; Fernández-Meirama et al, 2017a ; Foote, 2018 ).…”