United in difference: on the divergence in floral preferences between Galápagos birds and insects

<b>Dataset</b><br><br>Sixteen morphological and nectar traits of 31 Galápagos plant species studied in the arid zone between March 2016 and April 2017. <br><br> <b>Study Abstract</b>The characteristic scarcity of insects on remote oceanic islands has driven non-flower specialized vertebrates to broaden their trophic niches and explore floral resources. From our previous studies in the Galápagos, we know that native insectivorous and frugivorous Galápagos birds visit a wide range of typical entomophilous flowers and can also act as effective pollinators. Here, we tested whether opportunistic Galápagos birds show any preference for specific floral traits, and if this preference differs from that of insects.<b> </b>Sixteen morphological and nectar traits of 31 Galápagos plant species were studied, as well as their visitation frequency by birds and insects. Non-metric multidimensional scaling (NMDS) was used to evaluate the dispersal of flower trait values along two main dimensions and measure the similarity between the plants visited mostly by birds versus those by insects.<em><b> </b></em>A NMDS of floral traits resulted in two species groups: i) larger, bell-shaped flowers with slight larger nectar volume, associated with high bird visitation rates; and ii) smaller, bowl-shaped flowers with lower nectar volume, associated with high insect visitation rates. Galápagos birds preferred species with floral traits intermediate between those of insect- and bat-pollination syndromes. This finding is coherent with the existence of a transitional or bet-hedging phenotype between insect and bird pollination and underscores the importance of coevolution and floral diversification in non-specialized plant-pollinator mutualisms.<em><b> <br></b></em><em></em><br>