Natural hybridization in theAndropogon lateraliscomplex (Andropogoneae, Poaceae) and its impact on taxonomic literature

Abstract

In north‐eastern Argentina, Paraguay and south‐eastern Brazil, morphologically intermediate plants involving Andropogon lateralis, A. bicornis, A. glaziovii, A. arenarius and A. hypogynus were found. The possibility that they were natural hybrids was tested in two ways: (1) where they were sterile, their morphology was compared with that of the putative parents, and their meiosis and reproductive behaviour were studied; (2) where they were fertile, studies of artificial hybrids were also made. Most of the hybrids were sterile. The only fully fertile combination, generating recombination and hybrid swarms, was A. lateralis × A. hypogynus. In spite of apparently normal chromosome pairing, fertility was low in all other combinations on both the male and female sides. Sterility is probably a result of ‘cryptic’ or ‘gametic sterility’, which produces complete sterility of the gametes. Many of the hybrids survive and compete successfully with the parental species in natural populations, but their sterility maintains the genetic isolation of the majority of the taxa involved. Meiotic chromosome behaviour in all the hybrids indicates that the group of species shares slightly different forms of three basic genomes. Several specimens of natural hybrids were found in historical herbarium collections. In the past, they were given the status of type specimens of at least five taxonomic entities (A. lindmanii, A. coloratus, A. lateralis var. subtilior, A. multiflorus and A. lateralis var. bogotensis). The taxonomic consequences of these findings are discussed. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159, 136–154.

Long-term experimental hybrid swarms between nearly incompatible Tigriopus californicus populations: persistent fitness problems and assimilation by the superior population

“…Wild hybridization is often detected by the presence of morphological intermediates (Gompert et al 2006;Norrmann 2009;Ureta et al 2008). However, if swamping occurs, it becomes more difficult to detect an ancestral hybridization event with subsequent generations because individuals with hybrid ancestry may become indistinguishable in morphology from the superior parent.…”

Review of the Genus Andropogon (Poaceae: Andropogoneae) in America Based on Cytogenetic Studies

“…To resolve genomic relationships between Andropogon species, previous studies have successfully made interspecific hybrids among diploids [12], among diploids and triploids [27], among hexaploids [11,19,30,31], between hexaploids with enneaploids and inner aneuploids [19,25] and among diploid and hexaploid species [29]. While the later study suggests that the diploid South American species A. selloanus and A. macrothrix and the North American diploid A. gyrans share a common genome, relationships between the North and South American species are still unclear.…”

“…[2] and two more by Norrmann [11]. Of the ten taxa that comprise the complex in the southern area of South America, five are legitimate species and the others are interspecific hybrids [30]. Norrmann et al [29] performed GISH studies on two hexaploid species of the A. lateralis complex: A. lateralis and A. bicornis.…”

“…Norrmann [30] analyzed the chromosomes and meiotic behavior between interspecific hybrids into the A. lateralis complex and observed that all studied hybrids showed 2n = 60 chromosomes which pair to form up to 30 bivalents per pollen mother cell. The high frequency of bivalents observed in all crosses (30 observed, of 30 maximum) points to the existence of ancient chromosomal homology or homoeology in all species treated, with small differences among the "three" basic genomes (see [29]).…”

Cytogenetic studies in three diploid species of Andropogon (Andropogoneae), section Leptopogon

“…Leptopogon is considered the most advanced section within the genus (Clayton & Renvoize 1986;Campbell & Windisch 1986). In America, the section is mainly represented by two complexes: Andropogon virginicus complex, a monophyletic group with a center of diversity on the Coastal Plain of the southeastern United States (Campbell 1983) and the Andropogon lateralis complex geographically distributed in Central and South America, which is constituted entirely by hexaploid species (Campbell 1983;Norrmann 2009).…”