Conservation genetics and phylogeography of endangered and endemic shrub Tetraena mongolica (Zygophyllaceae) in Inner Mongolia, China

Abstract

BackgroundTetraena mongolica (Zygophyllaceae), an endangered endemic species in western Inner Mongolia, China. For endemic species with a limited geographical range and declining populations, historical patterns of demography and hierarchical genetic structure are important for determining population structure, and also provide information for developing effective and sustainable management plans. In this study, we assess genetic variation, population structure, and phylogeography of T. mongolica from eight populations. Furthermore, we evaluate the conservation and management units to provide the information for conservation.ResultsSequence variation and spatial apportionment of the atpB-rbcL noncoding spacer region of the chloroplast DNA were used to reconstruct the phylogeography of T. mongolica. A total of 880 bp was sequenced from eight extant populations throughout the whole range of its distribution. At the cpDNA locus, high levels of genetic differentiation among populations and low levels of genetic variation within populations were detected, indicating that most seed dispersal was restricted within populations.ConclusionsDemographic fluctuations, which led to random losses of genetic polymorphisms from populations, due to frequent flooding of the Yellow River and human disturbance were indicated by the analysis of BEAST skyline plot. Nested clade analysis revealed that restricted gene flow with isolation by distance plus occasional long distance dispersal is the main evolutionary factor affecting the phylogeography and population structure of T. mongolica. For setting a conservation management plan, each population of T. mongolica should be recognized as a conservation unit.

Evidence for intragenic recombination and selective sweep in an effector gene of Phytophthora infestans

“…More than 50 nucleotide haplotypes were detected in 96 sequences, and the combined nucleotide diversity was 0.017 (Table 1). Effector genes are critical for the invasion, colonization, and reproduction of pathogens on hosts, and the finding of high genetic diversity in the effector gene Avr3a is consistent with the evolutionary hypothesis postulating that genes involving in antagonistic host‐pathogen coevolution have higher evolutionary rates compared to other genes as documented both in P. infestans (Cárdenas et al., 2011; de Vries et al., 2017) and many other species (Allen et al., 2004, 2008; Raffaele, Win, Cano, & Kamoun, 2010). This high evolutionary rate may well contribute to the rapid “breakdown” of many host resistances mediated by major genes (Cooke et al., 2012; Pilet et al., 2005).…”

“…These primers were originally designed for Pex147 (Armstrong et al., 2005) but were successfully used to amplify Avr3a in a previous study (Cárdenas et al., 2011). PCRs were carried out in a 25 μl reaction volume using Gene Cycler ™ (Bio‐Rad, Shanghai).…”

“…Silencing Avr3a compromised the pathogenicity of P. infestans in a susceptible potato cultivar and Nicotiana benthamiana (Bos et al., 2010; Vetukuri et al., 2011). Although both virulent and avirulent types of Avr3a existed in P. infestans , the former are more frequent, accounting for 60%–100% of Avr3a in natural populations (Armstrong et al., 2005; Cárdenas et al., 2011; Wu et al., 2016). Recently, several main groups of isoforms have been functional analyzed.…”

Population size, center–periphery, and seed dispersers’ effects on the genetic diversity and population structure of the Mediterranean relict shrub Cneorum tricoccon

“…However, experimental evidence has not always supported this generalization (see Peakall, Ebert, Scott, Meagher, & Offord, 2003; Vanden‐Broeck et al., 2011). Low rates of evolution, genetic stability, and habitat reliability have been proposed as some of the factors that may influence the genetic patterns of relict species (Hampe & Petit, 2007).…”

“…For instance, species with long‐range seed dispersal mechanisms, such as zoochory, often have higher within‐population genetic diversity and lower population differentiation than species with limited dispersal (Avise, 2004; Hamrick, Murawski, & Nason, 1993; Vanden‐Broeck et al., 2011). Therefore, the loss of local vertebrate frugivores can have detrimental genetic effects on plants that depend upon them (Babweteera & Brown, 2009; Christian, 2001).…”