Analysis of genetic diversity in flowering dogwood natural stands using microsatellites: the effects of dogwood anthracnose

Abstract

Flowering dogwood (Cornus florida L.) populations recently have experienced severe declines caused by dogwood anthracnose. Mortality has ranged from 48 to 98%, raising the concern that genetic diversity has been reduced significantly. Microsatellite data were used to evaluate the level and distribution of genetic variation throughout much of the native range of the tree. Genetic variation in areas affected by anthracnose was as high as or higher than areas without die-offs. We found evidence of four widespread, spatially contiguous genetic clusters. However, there was little relationship between geographic distance and genetic difference. These observations suggest that high dispersal rates and large effective population sizes have so far prevented rapid loss of genetic diversity. The effects of anthracnose on demography and community structure are likely to be far more consequential than short-term genetic effects.

Genetic structure and post‐glacial expansion ofCornus floridaL. (Cornaceae): integrative evidence from phylogeography, population demographic history, and species distribution modeling

“…Population genetic structure without large-scale geographic structure suggests that long distance dispersal by migratory birds has not prevented population differentiation, and may explain the wide distribution of haplotypes for the species. Overall, our plastid DNA data agreed with the microsatellite data from Hadziabdic et al (2010) that gene flow has been high for the species and that the majority of the genetic variation occurs within populations. However, the plastid DNA data reveal new genetic patterns not evident in the microsatellite data.…”

“…AMOVA results indicated no discernable differences between the two groups of populations (À2.38%; Table S8). The two groups also showed equivalent levels of genetic diversity (Table S1), similar to the finding by Hadziabdic et al (2010) using microsatellite data. Therefore, data from both plastid DNA and nuclear microsatellite loci support the idea that "... high dispersal rates and large effective population sizes of the species have so far curtailed rapid loss of genetic diversity in affected populations.…”

“…Therefore, data from both plastid DNA and nuclear microsatellite loci support the idea that "... high dispersal rates and large effective population sizes of the species have so far curtailed rapid loss of genetic diversity in affected populations. The effects of anthracnose on demography and community structure are likely far more consequential than on genetic structure over the short term" (Hadziabdic et al, 2010). Therefore, more research is needed to address what the long-term effects this disease will have on the genetic diversity of the species, in addition to its population dynamics.…”

“…Infected smaller trees die in 2-3 years. As a result, C. florida in some local forests of the southern Appalachian Mountain region were reported to have experienced a 48%-98% decline in density due to death of mostly small trees or seedlings (Sherald et al, 1996;Hiers & Evans, 1997;Jenkins & White, 2002).A recent study of several nuclear microsatellite loci on the current populations reported a gene diversity (He) of 0.68, but no significant differences between infected and uninfected populations (Hadziabdic et al, 2010). The study also found little population genetic structure in C. florida.…”

“…This result suggests that frequent gene flow and large effective population sizes might have helped to curb the loss of genetic diversity within the species during recent population decline. Frequent gene flow may be maintained by seed/fruit dispersal by birds as the species produces fleshy red fruits (Hadziabdic et al, 2010). However, this scenario remains uncertain because the nuclear microsatellite data are uninformative regarding gene flow via seeds.…”