Proceedings of the Third International Conference on Invasive ...

Chapter 1: Spartina Biology<strong>Proceedings</strong> <strong>of</strong> <strong>the</strong> <strong>Third</strong> <strong>International</strong> <strong>Conference</strong> on Invasive Spartina180.00160.00140.00Total Dry Biomass (g)120.00100.0080.0060.0040.0020.000.002-15(foli)S. foli 1-9 S. alt 3-7 3-2 3-4 2-5 2-17 1-5 2-13 3-13 3-1 3-10 3-5 2-6 1-17 2-8 2-16 3-8 2-11Spartina GenotypeLow Medium HighFig. 3. Total biomass <strong>of</strong> Spartina genotypes at each salinity level, in increasing order <strong>of</strong> total biomass achieved by each genotype(low + medium + high salinities).RESULTSHybrid Spartina genotypes exhibited great variability inmorphological traits, response to salinity stress andcompetitive suppression by Sa. virginica. Salinity reducedtotal biomass <strong>of</strong> most Spartina genotypes. Several hybridcordgrass genotypes exhibited more robust growth than <strong>the</strong>parental species at both low and high salinity levels (Fig. 3).Results <strong>of</strong> <strong>the</strong> field experiment indicated that shootdensity <strong>of</strong> hybrid cordgrasses was highly sensitive to Sa.virginica removal, increasing an average <strong>of</strong> 105% (range =39-211%; Table 1). End-<strong>of</strong>-season biomass <strong>of</strong> cordgrassgenotypes increased an average <strong>of</strong> 64% in response to Sa.virginica removal (range = 2-144%; Table 1). Genotypes inTable 1 are listed in order <strong>of</strong> appearance on Fig. 3.CONCLUSIONSCertain hybrids (e.g., genotypes 1-5 and 2-8) showed acombination <strong>of</strong> competitive vigor in <strong>the</strong> field and relativelystronger performance in higher salinity conditions,exhibiting <strong>the</strong> potential to successfully expand into highermarsh zones. The native S. foliosa has weaker competitiveabilities and tolerance for salinity. Our results support apositive association between hybridization and invasionability. The genetic heterogeneity <strong>of</strong> Spartina hybrids willlead to <strong>the</strong> evolution <strong>of</strong> even more invasive hybridpopulations.Table 1. Genotype means and percent change between plots with S. virginica "clipped" vs. unclipped, end-<strong>of</strong>-season shoot densityand aboveground dry biomass.Spartina Shoot Density (#/m 2 ) Dry Biomass (g/m 2 )Genotype Unclipped Clipped % Change Unclipped Clipped % Change2-15 (S. foli) 41 84 104 107 206 931-9 107 235 119* 212 330 562-17 84 117 39 234 243 41-5 67 136 103* 695 1360 96*3-13 77 173 126* 277 426 543-1 74 117 59 464 471 21-17 65 104 60 512 1251 144*2-8 62 139 124* 501 556 113-8 46 142 211* 159 342 115* Significant difference (P < 0.05)-30-