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The stems of some myrmecophytes in Piper are used as domatia by resident ant colonies. Hollow, ant-occupied stems were previously known only in four species of southern Central American Piper, all members of Section Macrostachys. Here we present two additional, unrelated, hollow-stemmed myrmecophytes from Ecuador: P. immutatum and P. pterocladum (members of sections Radula and Peltobryon, respectively). Although similar superficially, stem cavities of the Ecuadorian Piper species differ morphologically and developmentally from those of Central American taxa. The stem cavities of P. immutatum, and possibly P. pterocladum, are formed during stem development, and begin forming only a few millimeters behind the apical meristem. This mode of cavity formation differs markedly from myrmecophytes in section Macrostachys, where the stems remain solid unless excavated by the specialized ant partner Pheidole bicornis. The stems of P. immutatum and P. pterocladum do not produce wound-response tissue around the cavity, unlike the stems in section Macrostachys. The entrance holes in stems of P. immutatum are formed through apoptotic processes and are located at each node below the petiole, whereas those in section Macrostachys are excavated by the ants in the leaf axil. This study documents convergent evolution of ant-plant associations in Piper, and emphasizes the need for careful comparison of apparently homologous, ant-associated structures in specialized myrmecophytes.

The relationship of seasonal variation in isozymes to systematic studies at the infraspecific level is evaluated. Isozyme variation in peroxidases, esterases, and α‐terpineol dehydrogenases was evaluated monthly for one year in J. scopulorum Sarg. Zymograms of α‐terpineol dehydrogenases showed one nonvariable band. Isoperoxidases varied quantitatively but not qualitatively, this variation being correlated with seasonal growth and dormancy. Isoesterases showed qualitative variation, with two types of esterases being produced. One type showed seasonal variation and a second was nonvariable. The presence of two types of isoesterases may reflect differing physiological roles for each. The esterase results showed that care should be taken during investigations of isozymes at the population level to assure phenological similarity.

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