• Specific orchid–fungal associations are known for nonphotosynthetic orchids but fungal diversity in photosynthetic orchids is thought to be quite broad. Specific fungal associations will figure prominently in conservation efforts, while diverse associations may require less attention. We combined culture techniques with ITS and mtLSU sequences and phylogenetic analysis to determine the genetic diversity of mycorrhizal fungi associated with an evergreen, a spring-green, and a winter-green orchid and compared this diversity with that published for a nonphotosynthetic orchid. • Mycorrhizal diversity in two of the three photosynthetic orchids was lower than for the nonphotosynthetic orchid. Mycorrhizal diversity in protocorms of the third species was also equal to, or less than, the fungal diversity associated with the nonphotosynthetic species, but adult fungal diversity was greater. • We found that photosynthetic orchids do not necessarily have more diverse mycorrhizal associations than nonphotosynthetic orchids. Similarly, evergreen orchids do not necessarily have greater mycorrhizal diversity than seasonally green orchids. Thus, orchid mycorrhizal diversity may not be determined by adult photosynthetic capacity.

Although coevolution is acknowledged to occur in nature, coevolutionary patterns in symbioses not involving species‐to‐species relationships are poorly understood. Mycorrhizal plants are thought to be too generalist to coevolve with their symbiotic fungi; yet some plants, including some orchids, exhibit strikingly narrow mycorrhizal specificity. Here, we assess the evolutionary history of mycorrhizal specificity in the lady's slipper orchid genus, Cypripedium. We sampled 90 populations of 15 taxa across three continents, using DNA methods to identify fungal symbionts and quantify mycorrhizal specificity. We assessed phylogenetic relationships among sampled Cypripedium taxa, onto which we mapped mycorrhizal specificity. Cypripedium taxa associated almost exclusively with fungi within family Tulasnellaceae. Ancestral specificity appears to have been narrow, followed by a broadening after the divergence of C. debile. Specificity then narrowed, resulting in strikingly narrow specificity in most of the taxa in this study, with no taxon rewidening to the same extant as basal members of the genus. Sympatric taxa generally associated with different sets of fungi, and most clades of Cypripedium‐mycorrhizal fungi were found throughout much of the northern hemisphere, suggesting that these evolutionary patterns in specificity are not the result of biogeographic lack of opportunity to associate with potential partners. Mycorrhizal specificity in genus Cypripedium appears to be an evolvable trait, and associations with particular fungi are phylogenetically conserved.

The number of patches of non-native Phragmites australis in brackish tidal wetlands in the Rhode River subestuary increased from 5 in 1971–72 to 212 in 2007, and the area covered by the patches increased more than 25 times during the same time interval. Genetic analysis of the patches showed that the expansion has primarily been from seed, and genetic similarities between patches indicate that most cross-pollination occurs within a distance of 50 m. Comparison of patches in different parts of the subestuary indicate that the expansion of Phragmites australis has occurred at the scale of the entire subestuary and not the scale of subsections of the subestuary dominated by differing upland land-uses.