Comparative phenology of mistletoes shows effect of different host species and temporal niche partitioning

Abstract

The study of plant phenology deals with seasonal events and how these are influenced by environmental factors, including symbiotic interactions. Considering host–mistletoe associations, our goal was to analyze the potential effects of host tree deciduousness on the life cycle of a mistletoe. Thus, Struthanthus martianus Dettke & Waechter was analyzed while growing upon a deciduous host tree and upon an evergreen one. We also compared the phenology of S. martianus with that of a closely related and sympatric species, Struthanthus flexicaulis (Mart. ex Schult. f.) Mart., growing upon a different but also evergreen host. Reproductive and vegetative phenological events were recorded during a three year period following a semiquantitative method. Circular statistical analysis was employed to compare phenological patterns. The peak of leaf production in S. martianus was observed to depend on host deciduousness, as the population infesting a deciduous host showed significant leaf flush during host defoliation. When comparing S. martianus and S. flexicaulis, nearly opposite patterns of flowering and fruiting phenology were recorded. Based on these observations, we conclude that Struthanthus species show niche partitioning to avoid competition. Additionally, we observed that the relationship established with different hosts can alter the mistletoe phenology. This observation highlights the uniqueness of the each host–mistletoe relationship.