Geographic patterns of clonal propagation
Having detected extensive clonality among the wild-collected P. vaginatum samples, we next assessed the distribution of geographic and environmental distances between clones of the same genotype in our wild collections. Specifically, we investigated the extent to which they showed patterns consistent with a “frozen-niche” strategy (multiple geographically and environmentally restricted clones) or a “general-purpose genotype” strategy (a few broadly distributed clones). For the fine-textured ecotype, the four genotypes with multiple clones in the wild tended to have relatively small geographic ranges; two of the four had genotypes restricted to a single location, while the two found in multiple locations had a maximum range of 126 km (Table S1; Fig. 1; Fig. 2A). Consistent with their narrow geographical distributions, assessments of pairwise environmental distances among locations (based on local climatic and salinity conditions; see Methods) indicated a low level of environmental dispersion (Fig. 2B). These patterns are generally consistent with a “frozen-niche” reproductive strategy for fine-textured P. vaginatum .
In contrast to the fine-textured ecotype, genotypes of the coarse-textured ecotype showed patterns more consistent with a “general purpose genotype” strategy. Not only did a handful of unique genotypes make up the majority of wild accessions (Table 1), but these genotypes showed broad distributions with respect to both geography and environmental variables. With the exception of one genotype that was restricted to a 1 km area (coarse_06), the narrowest geographical range of any coarse-textured clonal genotype was 750 km (coarse_04), and the three most common genotypes (coarse_01, coarse_02 and coarse_03) all had ranges >1400 km (Fig. 1; Fig. 2A). Pairwise environmental distance measures were similarly higher for the coarse-textured ecotype compared to fine-textured accessions (Fig. 2B); this indicates that clonal propagules of these widely dispersed genotypes are not specializing on particular environments in the locations where they occur.