Highly coevolved pollination mutualism accompanied by reciprocal diversification has been known in only two plant genera, Ficus (Moraceae) and Yucca (Agavaceae), which are pollinated exclusively by obligate seed-parasitic wasps and moths, respectively. An additional, highly diversified, species-specific pollination mutualism between a monoecious tree genus, Glochidion (Euphorbiaceae), and a moth genus, Epicephala (Gracillariidae), is presented here. At night, the small female moth actively deposits pollen on the cryptic stigma of the female flower by using its proboscis, then oviposits into the style. The moth larva infests only a portion of the developing seeds within fruit. We confirmed that at least three Glochidion species are pollinated only by their respective seedparasitic moth species, which could be distinguished by genitalic morphology and mitochondrial DNA sequences. These results and widespread evidence of limited seed infestation by the moths associated with Glochidion species suggest that speciation based on the highly specialized Glochidion stylar structure and moth oviposition behavior have promoted species diversification in Glochidion and its pollinators.
Species-specific obligate pollination mutualism between Glochidion trees (Euphorbiaceae) and Epicephala moths (Gracillariidae) involves a large number of interacting species and resembles the classically known fig-fig wasp and yucca-yucca moth associations.To assess the extent of parallel cladogenesis in Glochidion-Epicephala association, we reconstruct phylogenetic relationships of 18 species of Glochidion using nuclear ribosomal DNA sequences (internal and external transcribed spacers) and those of the corresponding 18 Epicephala species using mitochondrial (the cytochrome oxidase subunit I gene) and nuclear DNA sequences (the arginine kinase and elongation factor-1␣ genes). Based on the obtained phylogenies, we determine whether Glochidion and Epicephala have undergone parallel diversification using several different methods for investigating the level of cospeciation between phylogenies. These tests indicate that there is generally a greater degree of correlation between Glochidion and Epicephala phylogenies than expected in a random association, but the results are sensitive to selection of different phylogenetic hypotheses and analytical methods for evaluating cospeciation. Perfect congruence between phylogenies is not found in this association, which likely resulted from host shift by the moths. The observed significant discrepancy between Glochidion and Epicephala phylogenies implies that the one-to-one specificity between the plants and moths has been maintained through a complex speciation process or that there is an underestimated diversity of association between Glochidion trees and Epicephala moths.
Species-specific obligate pollination mutualism between Glochidion trees (Euphorbiaceae) and Epicephala moths (Gracillariidae) involves a large number of interacting species and resembles the classically known fig-fig wasp and yucca-yucca moth associations. To assess the extent of parallel cladogenesis in Glochidion-Epicephala association, we reconstruct phylogenetic relationships of 18 species of Glochidion using nuclear ribosomal DNA sequences (internal and external transcribed spacers) and those of the corresponding 18 Epicephala species using mitochondrial (the cytochrome oxidase subunit I gene) and nuclear DNA sequences (the arginine kinase and elongation factor-1alpha genes). Based on the obtained phylogenies, we determine whether Glochidion and Epicephala have undergone parallel diversification using several different methods for investigating the level of cospeciation between phylogenies. These tests indicate that there is generally a greater degree of correlation between Glochidion and Epicephala phylogenies than expected in a random association, but the results are sensitive to selection of different phylogenetic hypotheses and analytical methods for evaluating cospeciation. Perfect congruence between phylogenies is not found in this association, which likely resulted from host shift by the moths. The observed significant discrepancy between Glochidion and Epicephala phylogenies implies that the one-to-one specificity between the plants and moths has been maintained through a complex speciation process or that there is an underestimated diversity of association between Glochidion trees and Epicephala moths.
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