AOBPreview originally published online on June 7, 2007
Annals of Botany 2007 100(1):91-100; doi:10.1093/aob/mcm077
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Population Genetic Effects of Urban Habitat Fragmentation in the Perennial Herb Viola pubescens (Violaceae) using ISSR Markers
Department of Biological Sciences, University of Cincinnati, 614 Rieveschl Hall, Cincinnati, OH 45221-0006, USA
* For correspondence. E-mail theresa.culley{at}uc.edu
Received: 15 December 2006 Returned for revision: 2 February 2007 Accepted: 2 March 2007 Published electronically: 7 June 2007
Background and Aims: Fragmentation of natural habitats can negatively impact plant populations by leading to reduced genetic variation and increased genetic distance as populations become geographically and genetically isolated from one another. To test whether such detrimental effects occur within an urban landscape, the genetic structure of six populations of the perennial herb Viola pubescens was characterized in the metropolitan area of Greater Cincinnati in southwestern Ohio, USA.
Methods: Using three inter-simple sequence repeat (ISSR) markers, 51 loci amplified across all urban populations. For reference, four previously examined agricultural populations in central/northern Ohio and a geographically distant population in Michigan were also included in the analysis.
Key Results: Urban populations retained high levels of genetic variation (percentage of polymorphic loci, Pp = 80·7 %) with similar genetic distances among populations and an absence of unique alleles. Geographic and genetic distances were correlated with one another, and all populations grouped according to region. Individuals from urban populations clustered together and away from individuals from agricultural populations and from the Michigan population in a principle coordinates analysis. Hierarchical analysis of molecular variance (AMOVA) revealed that most of the genetic variability was partitioned within populations (69·1 %) and among groups (22·2 %) of southwestern Ohio, central/northern Ohio and Michigan groups. Mean Fst was 0·308, indicating substantial population differentiation.
Conclusions: It is concluded that urban fragmentation does not appear to impede gene flow in V. pubescens in southwestern Ohio. These results are consistent with life history traits of this species and the possibility of high insect abundance in urban habitats due to diverse floral resources and nesting sites. Combined with the cleistogamous breeding system of this species, pollinator availability in the urban matrix may buffer populations against detrimental effects of habitat fragmentation, at least in larger forest fragments. Consequently, it may be inappropriate to generalize about genetic effects of fragmentation across landscapes or even across plant species with different pollination systems.
Key words: Habitat fragmentation, ISSR, population genetic structure, urban effects, Viola pubescens