How much genetic variation is stored in the endangered and fragmented shrubTetraena mongolicaMaxim?

Abstract

Tetraena mongolica Maxim (Zygophyllaceae) is an endangered species endemic to western Inner Mongolia and China, and is currently threatened by habitat loss and human over-exploitation. We explored the genetic background, its genetic diversity, population structure, and demographic history, based on 12 polymorphic nuclear microsatellite loci. Our results indicated high genetic diversity in extant populations, but no distinguishable gene cluster corresponding with a specific biogeography. Population demography analysis using a MSVAR indicated a strong, recent population decline approximately 5,455 years ago. These results suggest that the Yellow River and Zhuozi Mountain range may not prevent pollination between populations. Finally, we surmised that the population demography of T. mongolica was likely to have been affected by early mankind activities.

Identification of Genic SSRs Provide a Perspective for Studying Environmental Adaptation in the Endemic Shrub Tetraena mongolica

“…The average H E and H O were 0.587 and 0.418, respectively ( Table 3 and Figure 4). Although these genic SSRs may have low levels of polymorphism compared with the levels in genome SSRs (mean number of alleles per locus was 26.0, and mean H E and H O were 0.868 and 0.840, respectively [24]) in the T. mongolica genome, the genic SSRs have some intrinsic advantages (e.g., high transferability and functional importance) that make them a valuable resource that can be used for genetic and evolutionary studies of the species or its phylogenetically closed species and genus, such as species Larrea tridentata and genus Viviania marifolia [8,9]. In addition, Zhi et al (2018) indicated that the highly polymorphic nuclear microsatellites might be over-estimating the genetic diversity of the present demography of T. mongolica [24], thus we considered that a rational genetic variation reserve could further be evaluated in T. mongolica by combing genetic data obtained from either the nuclear or genic SSRs.…”

“…Although these genic SSRs may have low levels of polymorphism compared with the levels in genome SSRs (mean number of alleles per locus was 26.0, and mean H E and H O were 0.868 and 0.840, respectively [24]) in the T. mongolica genome, the genic SSRs have some intrinsic advantages (e.g., high transferability and functional importance) that make them a valuable resource that can be used for genetic and evolutionary studies of the species or its phylogenetically closed species and genus, such as species Larrea tridentata and genus Viviania marifolia [8,9]. In addition, Zhi et al (2018) indicated that the highly polymorphic nuclear microsatellites might be over-estimating the genetic diversity of the present demography of T. mongolica [24], thus we considered that a rational genetic variation reserve could further be evaluated in T. mongolica by combing genetic data obtained from either the nuclear or genic SSRs. However, analyses of gene regions rather than non-coding genome regions evenly revealed a high level of genetic diversity in this endangered species [5,24], suggesting that the genome of the species is highly heterozygous to some extent and saturated with plenty of genetic variations that are potentially important for environmental adaptation and ongoing survival of the species.…”

“…This pioneering work includes the studies of systematic, geographic, and taxonomic aspects [7-9]; morphology and anatomy [10][11][12]; physiological ecology [13][14][15][16]; chemometrics and biochemistry [17,18]; population genetics [5]; conservation biology [19][20][21]; abiotic stress response [3]; and medicinal phytochemistry [22,23]. In recent decades, the plant has suffered from serious habitat destruction in size and has even disappeared, leading to the general decline of the species and making the survival of T. mongolica much harder than before [24]. Correspondingly, one consideration for the ongoing survival of the species that has been paid much attention recently is an apparent decrease in genetic diversity due to loss of demographics, inbreeding depression, stochastic events, and other factors [5,24].…”

“…In recent decades, the plant has suffered from serious habitat destruction in size and has even disappeared, leading to the general decline of the species and making the survival of T. mongolica much harder than before [24]. Correspondingly, one consideration for the ongoing survival of the species that has been paid much attention recently is an apparent decrease in genetic diversity due to loss of demographics, inbreeding depression, stochastic events, and other factors [5,24]. However, contrary to the assumption of diversity loss, it has been observed that the species has an intermediate or high level of genetic diversity as detected from analyses of inter-simple sequence repeats and nuclear microsatellites, respectively [5,24].…”

“…Correspondingly, one consideration for the ongoing survival of the species that has been paid much attention recently is an apparent decrease in genetic diversity due to loss of demographics, inbreeding depression, stochastic events, and other factors [5,24]. However, contrary to the assumption of diversity loss, it has been observed that the species has an intermediate or high level of genetic diversity as detected from analyses of inter-simple sequence repeats and nuclear microsatellites, respectively [5,24]. Therefore, further exploration of these hereditary characteristics and a potential link to adaptation strategies of the species is needed.Genic simple sequence repeats (SSRs) (also called genic microsatellites or expressed sequence tag (EST)-SSRs), a relatively newly established concept, are simple sequence repeats located in genes, including protein-coding genes (CDSs) and their untranslated regions (UTRs) [25].…”