Several hummingbird-pollinated plant lineages have been demonstrated to show increased rates of diversification compared to related insect-pollinated lineages. It has been argued that this pattern is produced by a higher degree of specialization on part of both hummingbirds and plants. We here test an alternative hypothesis: The often highly territorial hummingbirds may on average carry pollen over shorter distances than other pollinators and drive diversification by reducing gene flow distances. We present experimental data from pollen analogue tracking showing shorter dispersal distances in hummingbird- than in bee-pollinated species among ten neotropical species of Justicia (Acanthaceae).
Observations of powder dye carryover in flowers of Bolivian Justicia (Acanthaceae)
Observation data of stigmata carrying fluorescent powder dye one day after application of dye to anthers of five flowers of a focus plant, in 2 m distance classes from the focus plant (ten replicates). Asterisks indicate hummingbird pollinated species, their absence indicates bee pollinated species.
data_SchmidtLebuhn_etal_Justicia_powder_dye.tsv
Observed flower visitors to ten Bolivian species of Justicia (Acanthaceae)
Pollinator observations in ten species of Bolivian Justicia to establish pollination syndromes. Visitors were registered for one visit whenever they entered the observed area and visited the first flower, and not counted again while they stayed on the patch, regardless of the number of flowers visited. As hummingbirds avoid approaching human observers too closely but visited flowers at ca. 2 m distance from the observers, a hummingbird visit was scored for every time the bird foraged in the perimeter of the patch. Visitor behaviour was classified as “using the flowers as intended”, i.e. entering the corolla orifice to probe for nectar, “pollen thief”, i.e. emptying the anthers without touching the stigma, or “nectar thief”, i.e. piercing the corolla base or using holes made by other such thieves. In the first case, it was noted whether the visitor would actually touch the reproductive organs, in which case they were considered a pollinator. If a pollinator showed two different types of behaviour, both were recorded and the predominant behaviour was noted as such, but no percentages were recorded.
data_SchmidtLebuhn_etal_Justicia_flower_visitors.tsv