Ownbey's Tragopogons: 40 Years Later

Abstract

Two of the classic examples of recent allopolyploid speciation are Tragopogon mirus and T. miscellus. Previous studies have documented that both allotetraploids originated within the past 50-60 years; the diploid parents of T. mirus are T. dubius and T. porrifolius; those of T. miscellus are T. dubius and T. pratensis. It has now been 40 years since these allotetraploids were first described by Ownbey in 1950. To assess whether population size (the absolute number of plants) and population number of these species have changed during the past 40 years, we determined their distribution and numbers in the Palouse region of eastern Washington and northern Idaho in the spring of 1990. We visited 90 localities, 60 in Washington and 30 in Idaho. Tragopogon mirus is found in nine locations, with eight of these sites located in eastern Whitman County, Washington. Tragopogon miscellus is much more widespread, occurring in 38 of90 locations. The latter species is now one of the most common weeds in the vicinity of Spokane, Washington. Comparison of the current distributions of these species with historical records indicates that both allotetraploids, especially T. miscellus, have increased substantially in both geographic range and numbers. These Tragopogon species offer an excellent model system for testing questions concerning the ecology and population biology of recently derived allotetraploid species and their diploid progenitors.

Concerted Evolution of rDNA in Recently Formed Tragopogon Allotetraploids Is Typically Associated With an Inverse Correlation Between Gene Copy Number and Expression

“…Perhaps T. mirus population 2602 remains unstable because it is relatively young (recently formed) with incompletely established epigenetic patterns. However, Ownbey collected plants of T. mirus in Palouse, WA (the collection site of 2602) in 1949 (Ownbey 1950;Novak et al 1991).…”

Ecological studies of polyploidy in the 100 years following its discovery

“…In Spartina, growth performance and phenotypic plasticity of allopolyploid S. anglica plants were evaluated experimentally for plants grown in different environments, though without comparison to its progenitors S. maritima and S. alterniflora [270,271]. In Tragopogon, field surveys of the allopolyploids T. mirus and T. miscellus were conducted to determine spatial distributions and population sizes 40 years after their initial description in the 1940s and 1950s [265], while isozymes were used to evaluate mating systems of allotetraploid T. mirus and one of its diploid progenitors, T. dubius [239]. More recently, neopolyploids of T. mirus and T. miscellus were produced by colchicine treatment, enabling studies of these plants' morphology, cytogenetic behaviour and gene expression immediately following genome duplication [272,273].…”

Gene loss and silencing in Tragopogon miscellus (Asteraceae): comparison of natural and synthetic allotetraploids

“…The five natural populations of T. miscellus all formed independently and included lineages of reciprocal origin: the short-liguled form (with T. pratensis as the maternal parent) from Moscow, ID, and Garfield, Oakesdale and Spangle, WA, USA, and the long-liguled form (with T. dubius as the maternal parent) from Pullman, WA, USA (Soltis and Soltis collection numbers for all populations are given in Table 1). Samples of T. dubius and T. pratensis were obtained from the same locations (except Pullman, where T. pratensis is not currently found (Novak et al, 1991)) and analysed with their progeny to ensure that the parents of the allopolyploid lineages were not heterozygous for the markers surveyed. Fieldcollected seeds were used from Oakesdale, Spangle and Garfield populations; seeds used from Moscow and Pullman populations were derived from plants grown in the greenhouse (at Washington State University, Pullman, WA, USA) from field-collected seeds and allowed to self-fertilise for one generation.…”