two-generation analysis of pollen pool genetic structure in flowering dogwood, Cornus florida (Cornaceae), in the Missouri Ozarks

• Published in: American journal of botany Vol. 92; no. 2; pp. 262 - 271
• Main Authors: Sork, V.L, Smouse, P.E, Apsit, V.J, Dyer, R.J, Westfall, R.D
• Format: Journal Article
• Language: English
• Published: United States Botanical Soc America 01-02-2005; Botanical Society of America; Botanical Society of America, Inc
• Subjects: allozymes; anthropogenic activities; Botany; California; clearcutting; Cornaceae; Cornus florida; Ecological genetics; Forest ecology; Forest ecosystems; Forest management; Forest service; forest thinning; gene flow; genetic structure; Genetic variation; genotype; inbreeding; insect pollination; landscape change; Landscapes; plant genetics; Plant reproduction; Pollen; pollen movement; Pollinating insects; Population Biology; silvicultural treatment; stand management; Trees; TwoGener; understory; Missouri; USA, Missouri
• ISSN: 0002-9122; 1537-2197
• DOI: 10.3732/ajb.92.2.262

Anthropogenic landscape change can disrupt gene flow. As part of the Missouri Ozark Forest Ecosystem Project, this study examined whether silvicultural practices influence pollen-mediated gene movement in the insect-pollinated species, Cornus florida L., by comparing pollen pool structure ([Phi][subscript st]) among clear-cutting, selective cutting, and uncut regimes with the expectation that pollen movement should be least in the uncut regime. Using a sample of 1500 seedlings--10 each from 150 seed parents (43 in clear-cut, 74 in selective, and 33 in control sites) from six sites (each ranging from 266 to 527 ha), eight allozyme loci were analyzed with a pollen pool structure approach known as TwoGener (Smouse et al., 2001; Evolution 55: 260-271). This analysis revealed that pollen pool structure was less in clear-cut ([Formula: see text][subscript C] = 0.090, P < 0.001) than in uncut areas ([Formula: see text][subscript U] = 0.174, P < 0.001), with selective-cut intermediate ([Formula: see text][subscript S] = 0.125, P < 0.001). These estimates translate into more effective pollen donors (N[subscript ep]) in clear-cut (N[subscript ep] = 5.56) and selective-cut (N[subscript ep] = 4.00) areas than in uncut areas (N[subscript ep] = 2.87). We demonstrate that [Phi][subscript C] </= [Phi][subscript S] </= [Phi][subscript U], with [Formula: see text][subscript C] significantly smaller than [Formula: see text][subscript U] (P < 0.034). The findings imply that, as long as a sufficiently large number of seed parents remain to provide adequate reproduction and to avoid a genetic bottleneck in the effective number of mothers, silvicultural management may not negatively affect the effective number of pollen parents, and hence subsequent genetic diversity in Cornus florida.