Low reproductive success of hay-scented fern (Dennstaedtia punctilobula) regardless of inbreeding level or time since disturbance

Self-fertilization can facilitate the colonization of new habitats because it allows a single individual to found a population. Here we investigated the relationship between mating systems and colonization in hay-scented fern (Dennstaedtia punctilobula (Michx.) T.Moore). Throughout eastern North America, this species has been called a 'native invasive' for its tendency to dominate forest understories disturbed by logging, inhibiting tree regeneration. Thus, it is important to understand the mechanisms of its spread. We hypothesized that if populations were founded through selfing, then populations disturbed more recently would retain higher selfing ability; this pattern would demonstrate an important link between mating systems and colonization. For four populations logged at different times in the past, we compared the sporophyte production of gametophytes at different levels of inbreeding (intragametophytic selfing, intergametophytic selfing, and outcrossing) using laboratory crosses. Across all treatments, only 9.8% of gametophytes formed sporophytes (N = 400 gametophytes). Neither inbreeding level nor time since disturbance affected sporophyte production. Selfing ability did not differ across populations logged at different times; there was no interaction between inbreeding level and time since disturbance. The low reproductive success of D. punctilobula, regardless of inbreeding level or time since disturbance, suggests that population establishment and expansion via sexual reproduction may be relatively rare in this clonal species. Key words: inbreeding depression, invasive species, mating systems, reproductive assurance, self-fertilization. L'auto-fertilisation peut faciliter la colonisation de nouveaux habitats car elle permet a un seul individu de fonder une population. Les auteurs ont examine ici la relation entre les systemes de croisement et la colonisation de la fougere odorante (Dennstaedtia punctilobula (Michx.) T.Moore). A travers tout l'est de l'Amerique du Nord, cette espece a ete identifiee comme indigene envahissante a cause de sa tendance a dominer les sous-etages forestiers perturbes par l'exploitation forestiere, inhibant la regeneration des arbres. Il est alors important de comprendre les mecanismes de sa dissemination. Les auteurs ont emis l'hypothese que si des populations etaient fondees par autofecondation, alors les populations perturbees plus recemment pourraient conserver plus longtemps leur capacite d'autofecondation; ce patron demontrerait un lien important entre les systemes de croisement et la colonisation. Les auteurs ont compare chez quatre populations exploitees a differentes periodes dans le passe, la production sporophyte des gametophytes a differents niveaux d'endogamie (autofecondation intragametophyte, autofecondation inter-gametophyte et croisement eloigne) a l'aide de croisements en laboratoire. A travers tous les traitements, 9.8% des gametophytes seulement formaient des sporophytes (N = 400 gametophytes). Aucun niveau d'endogamie, ni le temps ecoule depuis la perturbation n'affectait la production de sporophytes. La capacite d'autofecondation ne differait pas d'une population a l'autre, exploitees a des periodes differentes; il n'y avait pas d'interaction entre le niveau d'endogamie et le temps ecoule depuis la perturbation. Le faible succes reproducteur de D. punctilobula, peu importe le niveau d'endogamie ou le temps ecoule depuis la perturbation, suggere que l'etablissement et l'expansion de la population par la reproduction sexuee peut etre relativement rare chez cette espece clonale. [Traduit par la Redaction] Mots-cles : depression d'endogamie, espece envahissante, systemes de croisement, assurance reproductive, auto-fertilisation.
Introduction Self-fertilization should facilitate plant invasions by providing reproductive assurance in new habitats, where mates or pollinators may be scarce (Darwin 1876; Baker 1955). In fact, introduced species often have [...]