Browsing by Author "Tate JA"
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- ItemCytonuclear Coordination Is Not Immediate upon Allopolyploid Formation in Tragopogon miscellus (Asteraceae) Allopolyploids.(2015) Sehrish T; Symonds VV; Soltis DE; Soltis PS; Tate JAAllopolyploids, formed by hybridization and chromosome doubling, face the immediate challenge of having duplicated nuclear genomes that interact with the haploid and maternally inherited cytoplasmic (plastid and mitochondrial) genomes. Most of our knowledge of the genomic consequences of allopolyploidy has focused on the fate of the duplicated nuclear genes without regard to their potential interactions with cytoplasmic genomes. As a step toward understanding the fates of nuclear-encoded subunits that are plastid-targeted, here we examine the retention and expression of the gene encoding the small subunit of Ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco; rbcS) in multiple populations of allotetraploid Tragopogon miscellus (Asteraceae). These polyploids formed recently (~80 years ago) and repeatedly from T. dubius and T. pratensis in the northwestern United States. Examination of 79 T. miscellus individuals from 10 natural populations, as well as 25 synthetic allotetraploids, including reciprocally formed plants, revealed a low percentage of naturally occurring individuals that show a bias in either gene (homeolog) loss (12%) or expression (16%), usually toward maintaining the maternal nuclear copy of rbcS. For individuals showing loss, seven retained the maternally derived rbcS homeolog only, while three had the paternally derived copy. All of the synthetic polyploid individuals examined (S0 and S1 generations) retained and expressed both parental homeologs. These results demonstrate that cytonuclear coordination does not happen immediately upon polyploid formation in Tragopogon miscellus.
- ItemOn the road to diploidization? Homoeolog loss in independently formed populations of the allopolyploid Tragopogon miscellus (Asteraceae)(BioMed Central, 2009) Tate JA; Joshi P; Soltis KA; Soltis P; Soltis DBackground: Polyploidy (whole-genome duplication) is an important speciation mechanism,particularly in plants. Gene loss, silencing, and the formation of novel gene complexes are some ofthe consequences that the new polyploid genome may experience. Despite the recurrent natureof polyploidy, little is known about the genomic outcome of independent polyploidization events.Here, we analyze the fate of genes duplicated by polyploidy (homoeologs) in multiple individualsfrom ten natural populations of Tragopogon miscellus (Asteraceae), all of which formedindependently from T. dubius and T. pratensis less than 80 years ago.Results: Of the 13 loci analyzed in 84 T. miscellus individuals, 11 showed loss of at least one parentalhomoeolog in the young allopolyploids. Two loci were retained in duplicate for all polyploidindividuals included in this study. Nearly half (48%) of the individuals examined lost a homoeologof at least one locus, with several individuals showing loss at more than one locus. Patterns of losswere stochastic among individuals from the independently formed populations, except that the T.dubius copy was lost twice as often as T. pratensis.Conclusion: This study represents the most extensive survey of the fate of genes duplicated byallopolyploidy in individuals from natural populations. Our results indicate that the road to genomedownsizing and ultimate genetic diploidization may occur quickly through homoeolog loss, but withsome genes consistently maintained as duplicates. Other genes consistently show evidence ofhomoeolog loss, suggesting repetitive aspects to polyploid genome evolution.
- ItemThe compounding effects of high pollen limitation, selfing rates and inbreeding depression leave a New Zealand tree with few viable offspring.(2015-10) Van Etten ML; Tate JA; Anderson SH; Kelly D; Ladley JJ; Merrett MF; Peterson PG; Robertson AWBACKGROUND AND AIMS: Interactions between species are especially sensitive to environmental changes. The interaction between plants and pollinators is of particular interest given the potential current global decline in pollinators. Reduced pollinator services can be compensated for in some plant species by self-pollination. However, if inbreeding depression is high, selfed progeny could die prior to reaching adulthood, leading to cryptic recruitment failure. METHODS: To examine this scenario, pollinator abundance, pollen limitation, selfing rates and inbreeding depression were examined in 12 populations of varying disturbance levels in Sophora microphylla (Fabaceae), an endemic New Zealand tree species. KEY RESULTS: High pollen limitation was found in all populations (average of 58 % reduction in seed production, nine populations), together with high selfing rates (61 % of offspring selfed, six populations) and high inbreeding depression (selfed offspring 86 % less fit, six populations). Pollen limitation was associated with lower visitation rates by the two endemic bird pollinators. CONCLUSIONS: The results suggest that for these populations, over half of the seeds produced are genetically doomed. This reduction in the fitness of progeny due to reduced pollinator service is probably important to population dynamics of other New Zealand species. More broadly, the results suggest that measures of seed production or seedling densities may be a gross overestimate of the effective offspring production. This could lead to cryptic recruitment failure, i.e. a decline in successful reproduction despite high progeny production. Given the global extent of pollinator declines, cryptic recruitment failure may be widespread.