Reproductive biology of three fern species may contribute to differential colonization success in post-agricultural forests.

Because selfing enables a single individual to reproduce in a new location, the ability to self-fertilize should enhance plants' capacity for colonization. This study examined whether selfing ability correlated with successful migration in three fern species, Dryopteris carthusiana, Dryopteris intermedia, and Polystichum acrostichoides, which vary in their ability to colonize forests on abandoned agricultural lands in central New York, USA. Polystichum acrostichoides is much more frequent in forests that were never cleared for agriculture, D. carthusiana is more frequent in forests that developed on former fields, and D. intermedia is equally frequent in the two forest types. To test the hypothesis that better-colonizing species and post-agricultural forest populations have greater selfing ability, I assessed the sporophyte production of gametophytes grown in isolation and in pairs of varying relatedness. Dryopteris carthusiana had the highest reproductive success and selfing ability and P. acrostichoides the lowest. These results support the hypothesis that selfing may facilitate colonization in these species. They also exemplify the general pattern that polyploid fern species have higher rates of self-fertilization than related diploids, as the allotetraploid D. carthusiana had greater selfing ability than both diploid species.