DOI: 10.5061/dryad.k6djh9wgp
title: Ornithophily in the trumpet creeper: floral metric data from the Ozark Mountains

description: The diversification of hummingbirds (Trochilidae) has shaped the
 pollination strategies and floral trait evolution in at least 68 families
 of flowering plants in the Western Hemisphere. The trumpet creeper
 (Bignoniaceae) is the quintessential example of ornithophily in eastern
 North America. The mutualistic relationship between this
 flamboyantly-flowered liana and the ruby-throated hummingbird (Archilochus
 colubris) was illustrated as early as 1731. However, neither historical
 nor modern accounts accurately describe the feeding behavior of
 ruby-throats at trumpet creeper flowers or the floral adaptations for
 ornithophily. This paper explores their surprisingly immersive mode of
 foraging at trumpet creeper flowers and quantitatively assesses floral
 traits in two populations in the Ozark Mountains. The ruby-throat's
 bill is approximately one-third the length of the trumpet-shaped flowers,
 which counters the tendency for the corolla length of ornithophilous
 plants to match the bill length of their principal hummingbird pollinator.
 To reach the nectary, ruby-throats cling to the ventral petal lobe of the
 corolla with their claws and thrust their head and neck deeply into the
 flower. This immersive “floral-diving” has not been previously described
 among the 356 species of hummingbirds. The didynamous anthers and stigma
 are strategically positioned inside the corolla to brush the crown
 feathers when the ruby-throat inserts its head. A narrow stricture in the
 corolla, about a third of the way up, allows the bill and tongue of
 hummingbirds to pass, but blocks bees from reaching the nectary. None of
 the bee species native to eastern North American have tongues long enough
 to access floral nectar. Consequently, the abundant sucrose-rich floral
 nectar appears to be reserved for hummingbird pollinators. This dataset
 presents measurements for 238 trumpet creeper flowers from two populations
 in the Ozark Mountains in Baxter County, Arkansas: (1) White River (36°
 11.7ʹ N, 92° 16.9ʹ W; elevation 110 m) and (2) Norfork Lake (36° 22.5ʹ N,
 92° 13.9ʹ W; elevation 177 m).  
description: <strong>Overview of trumpet creeper floral
 traits</strong> The sympetalous, zygomorphic
 flowers (60-90 mm in length) are arranged in terminal inflorescences
 composed of 12–35 flowers organized in 3-flowered dichasial cymes. The
 campanulate corolla widens from a narrow elongated cylindrical base. The
 floral tube terminates in five rounded petal lobes that unfold at
 anthesis. The ventral petal lobe functions as a landing platform for
 hummingbirds and bees. The pentagonal corolla opening is vertically
 compressed, wider horizontally than it is tall. The base of the corolla,
 which encloses the basal nectary and superior ovary, is protected by a
 leathery cup-shaped calyx. Most corollas curve subtly downward above the
 calyx. The corollary stricture marks the point where the trumpet-shaped
 corolla narrows abruptly, forming a narrow basal tube. The four staminal
 filaments and a short curled staminode emerge from the interior wall at
 the corollary stricture and curve along the inner walls toward the
 opening. The anthers are arranged in a didynamous configuration, with a
 proximal and distal pair. The dorsifixed anthers are positioned along the
 dorsal wall inside the corolla opening. The style protrudes through and
 partially blocks the aperture of the stricture. The flattened,
 approximately diamond-shaped stigma usually lies between the proximal and
 distal pairs of anthers along the dorsal wall of the floral
 tube. <strong>Floral
 data</strong> I stored newly opened flowers in
 plastic bags and transported them in a refrigerated cooler for later
 measurement and dissection. Insect-damaged flowers were culled in the
 field, while undersized flowers were retained in the population samples.
 Most floral measurements were made with digital calipers to the nearest
 0.1 mm. The width of the corolla opening (horizontal plane) was measured
 first. The corolla was then split distally along the ventral midline far
 enough to measure the position of the stigma in relation to the proximal
 and distal pairs of anthers. The calyx, nectary, and stigma were then
 removed as a single unit. Corolla length (minus calyx) was measured from
 the base, which approximates the position of the nectary, to the notches
 flanking the ventral petal lobe at the mouth of the floral tube. The
 corolla was then split from end to end along the ventral midline, pressed
 flat under a thin sheet of glass, and photographed alongside a scale bar.
 The distance from the corolla base to the corollary stricture
 (stricture-nectary distance), approximated by the base of the distal
 anther filaments, was measured from scaled photographs (to the nearest
 mm). I also measured the distance from the corolla base to the filament
 tips of the longest proximal (proximal anther-nectary distance) and distal
 pairs of anthers
description: # Ornithophily in the trumpet creeper: floral metric data from the Ozark
 Mountains
 [https://doi.org/10.5061/dryad.k6djh9wgp](https://doi.org/10.5061/dryad.k6djh9wgp) ## Description of the data and file structure #### File: Ornithophily\_in\_the\_trumpet\_creeper--floral\_metrics\_(8-27-2024).pdf **Description:** The spreadsheet includes field number, date, location, corolla length, corolla width at the mouth, stricture-nectary distance, proximal anther-nectary distance, distal anther-nectary distance, and stigma-nectary distance of trumpet creeper flowers (*Campsis radicans*) from two populations in the Ozark Mountains, Baxter County, Arkansas. All measurements are in millimeters.  Missing data points are indicated by blank cells.