NEWS 2014

Inferring ploidy variation in natural populations, and its implications for species conservation

Jennifer DEWOODY¹, Valerie HIPKINS¹, Julie K NELSON², Deborah L ROGERS³
Botany 2014 - The Boise Centre, Boise, Idaho, USA

¹USDA Forest Service, National Forest Genetics Lab, 2480 Carson Road, Placerville, CA, 95667, USA
²USDA Forest Service, Shasta-Trinity National Forest, 3644 Avtech Parkway, Redding, CA, 96002, USA
³Center for Natural Lands Management, 27258 Via Industria, Suite B, Temecula, CA, 92590, USA

Botany 2014


A large percentage of angiosperm species have been described as polyploid (having more than two copies of each chromosome) or of variable ploidy (individuals of the same species displaying different ploidy levels).  Differences in ploidy may correlate with differences in fitness or community interactions, and may indicate limitations in sexual compatibility. Yet the ploidy of natural populations, whether or not known, is rarely considered in conservation or management strategies.  Confirming the relative ploidy of seed or germplasm collections is often of low priority given the limited funds available for most research and management efforts.  The National Forest Genetics Lab (NFGEL) is a central genetics laboratory within the USDA Forest Service that serves government and private collaborators.  In the 25 years that NFGEL has been providing molecular genetic data to land managers, the ploidy level of focal species have been examined either as part of the study design (i.e. via flow cytometry) or as a by-product of the data collection (e.g. inferred from isozyme banding patterns). Examining relative DNA content using flow cytometry provides a direct comparison of ploidy between samples. Inferring ploidy from allozyme banding patterns may be possible by scoring dosage effects or the presence of multiple alleles, but cannot quantify DNA content.  Here we present case studies from diverse genera (Fritillaria and Acanthomintha) where genetic data identified variable ploidy levels within or among populations. In one study, direct estimates of DNA content corroborated polyploidy inferred from isozyme banding patterns. The patterns are part of a larger study of species identification, and complicate the inferred relationships in one sympatric site.  In the other study, while polyploidy was suspected based on the natural history of the system, the inferred levels revealed a complex pattern of variable ploidy across populations. These data will be used to inform management and restoration plans (e.g. when or how to pool seed for outplanting efforts). Overall, the frequency of variable ploidy in angiosperm species indicates that relative ploidy levels should routinely be assessed and included in germplasm collection and species management plans.

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