The Role of Ecotypic Variation in the Distribution of the Central Grassland of North America

McMillan, Calvin

doi:10.2307/1942132

Cited by 183 publications

(150 citation statements)

References 21 publications

(56 reference statements)

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“…A model of two distinct lowland glacial refugia is in complete agreement with McMillan's conclusions based on morpho-geographic analyses of many switchgrass accessions covering much of its distributional area (McMillan 1959(McMillan , 1964. We cannot speculate at this time whether these two refugia were isolated from each other or whether shared boundaries would have allowed some limited gene flow and admixture of their lowland lineages.…”

Section: Geographic Distribution Of Ecotypes and Lineagessupporting

confidence: 83%

“…Group A is directly associated with the ancient broadleaf forest habitat, specifically mixed-mesophytic forest, which included oak savanna dominated by interspersed patches of oak forest and tallgrass prairie (Abrams 1990(Abrams , 1992. Group B likely originated in the western montane refuge, with the greatest long-term adaptation to dryland and semi-arid conditions (McMillan 1959(McMillan , 1964. Group A likely originated somewhere in the greater Gulf Coast refuge.…”

Section: Geographic Distribution Of Ecotypes and Lineagesmentioning

confidence: 99%

“…Pollination facilitated by wind further encourages cross-pollination between geographically and phenotypically diverse strains, leading to potentially heterotic effects from the combination of diverse and complimentary linkage blocks (Lamkey and Edwards 1999;Melchinger 1999;Vogel and Mitchell 2008). These forces resulted in a balance between migration, drift, and selection, creating phenotypic diversity across a broad landscape (McMillan 1959;Casler et al 2007b), but allowing continued migration to balance the effects of drift, maintaining large effective population sizes across a broad landscape. Even with the loss of more than 99% of the tallgrass prairie and savanna ecosystems to habitat loss and fragmentation (Stubbendieck et al 1991), massive amounts of genetic diversity have been preserved in nearly every accession that we have sampled (Casler et al 2007a;Zalapa et al 2011).…”

Section: Geographic Distribution Of Ecotypes and Lineagesmentioning

confidence: 99%

“…These deviations and fluctuations express the environmental amplitude which an individual must tolerate for continued existence, not necessarily involving reproductive processes, within a grassland community. The marked degree of variability within a species-population in grassland vegetation is a visible response to the highly variable nature of the habitat '' McMillan (1959).…”

mentioning

confidence: 99%

“…Switchgrass is thought to have survived repeated glaciation events in three refugia-a western montane refuge in the southwestern USA and Mexico, a Western Gulf Coast refuge, and an Eastern Gulf Coast refuge (McMillan 1959). Although little is known about genetic diversity, spatial differentiation, genetic isolation, or post-glacial migratory patterns of switchgrass, a general pattern has emerged, particularly with reference to woody species.…”

mentioning

confidence: 99%

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Post-glacial evolution of Panicum virgatum: centers of diversity and gene pools revealed by SSR markers and cpDNA sequences

et al. 2011

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Switchgrass (Panicum virgatum), a central and Eastern USA native, is highly valued as a component in tallgrass prairie and savanna restoration and conservation projects and a potential bioenergy feedstock. The purpose of this study was to identify regional diversity, gene pools, and centers-of-diversity of switchgrass to gain an understanding of its post-glacial evolution and to identify both the geographic range and potential overlap between functional gene pools. We sampled a total of 384 genotypes from 49 accessions that included the three main taxonomic groups of switchgrass (lowland 4x, upland 4x, and upland 8x) along with one accession possessing an intermediate phenotype. We identified primary centers of diversity for switchgrass in the eastern and western Gulf Coast regions. Migration, drift, and selection have led to adaptive radiation in switchgrass, creating regional gene pools within each of the main taxa. We estimate that both upland-lowland divergence and 4x-to-8x polyploidization within switchgrass began approximately 1.5-1 M ybp and that subsequent ice age cycles have resulted in gene flow between ecotype lineages and between ploidy levels. Gene flow has resulted in ''hot spots'' of genetic diversity in the southeastern USA and along the Atlantic Seaboard.

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Section: Geographic Distribution Of Ecotypes and Lineagessupporting

confidence: 83%