Abstract Detail

Reproductive Processes

Wenzell, Katherine [1], Fant, Jeremie [2], Skogen, Krissa [3].

Floral divergence in color and corolla length in relation to major pollinators within Castilleja.

INTRODUCTION: As many flowering plants rely on animal pollinators to reproduce, pollinators directly influence plant evolution, as agents of both gene flow (pollen movement) and selection (fecundity). Most models of pollinator-driven plant speciation invoke geographic variation in pollinators driving local adaptation in floral traits. Despite this, few studies actually measure range-wide variation in either plant traits or pollinators. Furthermore, uncertainty remains regarding the importance of different floral traits—such as color or morphology—in facilitating or deterring pollination by certain pollinator groups. Here, our study tests whether variation in floral color and morphology may relate to differences in major pollinator groups within and among closely related species of Castilleja.
Study system: Castilleja sessiliflora displays intraspecific variation in floral color and morphology across its wide range in the central US. The closely related C. purpurea species complex comprises three species that differ in inflorescence color across narrow geographic clines in the south-central US. This study examines ecological consequences of variation in floral color and morphology at contrasting geographic scales. We ask the questions: 1. What is the geographic pattern of floral trait variation in C. sessiliflora and the C. purpurea complex? 2. Do major pollinators vary within and among these groups? 3. If so, does variation in major pollinators correlate to variation in certain floral traits?
METHODS: We sampled 10 populations of C. sessiliflora and 11 populations of the C. purpurea complex to measure floral traits (color and morphology) and observe pollinators. Visitation rate was recorded and compared among pollinator groups and correlated with population mean floral trait values.
RESULTS: Geographic variation in floral traits was apparent in floral morphology, particularly corolla length, in C. sessiliflora, and in inflorescence color in C. sessiliflora and the C. purpurea complex. Pollinator visitation varied among populations and regions. In C. sessiliflora, longer corollas were associated with less diverse floral visitors, indicating corolla length may restrict visitation by some pollinators. In the C. purpurea complex, differences in inflorescence color do not confer complete differences in pollinator groups, but we find some evidence of associations between floral color and major pollinators. While additional study is needed, we find early evidence that variation in certain floral traits may drive differences in the diversity and identity of major pollinators, hinting at the potential for pollinator-mediated selection as a driver of floral divergence in this system.

1 - Northwestern University and Chicago Botanic Garden, Plant Science Center, Chicago Botanic Garden, 1000 Lake Cook Road, Glencoe, Illinois, 60022, United States
2 - Chicago Botanic Gardens, Plant Biology And Conservation , 1000 Lake Cook Rd, Glencoe, IL, 60022, United States
3 - Chicago Botanic Garden, Conservation Scientist, 1000 Lake Cook Road, Glencoe, IL, 60022, United States

Keywords:
floral divergence
Castilleja
pollinator-mediated selection
reproductive isolation.

Presentation Type: Oral Paper
Session: REP1, Reproductive Processes 1
Location: San Luis 2/Starr Pass
Date: Wednesday, July 31st, 2019
Time: 8:30 AM
Number: REP1003
Abstract ID:122
Candidate for Awards:None