Yucca moths (Tegeticula spp.) are the exclusive pollinators of Joshua trees (Yucca brevifolia s. l.). The moths actively pollinate the Joshua tree flowers and lay their eggs in the style. Recent studies have revealed that the plants commonly known as Joshua trees include two distinct, sister-species of plant: Yucca brevifolia Engelm. and Yucca jaegeriana McKelvey, each pollinated by two sister-species of yucca moth Tegeticula synthetica Riley and Tegeticula antithetica Pellmyr, respectively. A number of studies have argued that the moths have coevolved with their hosts, producing a pattern of phenotype matching between moth ovipositor length and floral style length. However, the only known descriptions of yucca moth pollination and oviposition behavior on Joshua trees are observations of T. synthetica made in 1893. The behavior of T. antithetica has never been observed before. We produced the first video recordings of the behavior of T. antithetica, and measured the points of oviposition and egg placement within the floral style. We found a number of differences between the behaviors of T. antithetica and T. synthetica, which appear to be a consequence of differences in floral morphology between Y. jaegeriana and Y. brevifolia. We also found that variation in floral style length strongly influences the placement of eggs within the flower, which may explain patterns of phenotype matching described previously. However, unlike in other yucca moths, we find that the mode of oviposition is unlikely to wound the floral ovules, and thus that oviposition by T. antithetica is unlikely to prompt floral abscission.
Keywords: behavior; coevolution; oviposition; pollination; yucca-moth.