Vertical Distribution of Floracarus perrepae (Acariformes: Eriophyidae) Galls on the Invasive Fern Lygodium microphyllum (Schizeales: Lygodiaceae) and a Potential Productivity - Reproduction Tradeoff

Old World climbing fern, Lygodium microphyllum (Schizeales: Lygodiaceae) invades and negatively impacts natural areas throughout south Florida. Its invasiveness is attributed, in part, to its fast growth rate that allows it to climb rapidly on neighboring vegetation and large reproductive output via aerially distributed spores that are borne on fertile leaves. We conducted a field study to determine the within-plant distribution of the biological control agent, Floracarus perrepae (Acariformes: Eriophyidae), the vertical distributions of fertile leaves, and to evaluate the potential productivity-reproduction tradeoff in L. microphyllum. The 3 m vertical trellises were spatially segregated with galls formed by F. perrepae at the bottom of the trellises and reproduction (i.e., the development of fertile leaves) at the top of the trellises. Galling occurred on 81% of leaves in the bottom stratum versus 40% of leaves in the uppermost stratum of the trellis. Conversely, only 16% of leaves in the bottom stratum versus 76% in the upper stratum were fertile (bore sori). With increasing biomass (i.e., larger plants) fewer reproductive leaves were noted, indicating a trade-off between growth and reproduction. This association was twice as strong in the very largest plants versus the smaller plants. Further, the potential for this productivity-reproduction tradeoff to be impacted by biological control agents may be illustrated by the strong negative correlation between galled leaves and fertile leaves. Lygodium microphyllum thus appears to compensate for mite damage by redirecting energy to regrowth instead of reproduction.