
Geographic Patterns In Pollen Production In The Plant Ring Species Euphorbia tithymaloides In The Caribbean
Abstract—
We examine investment in male function in the context of geography and floral morphology in the plant ring species Euphorbia tithymaloides, which colonized the Caribbean from Mexico/Guatemala along two fronts that roughly correspond to the Greater and the Lesser Antilles and that meet in the vicinity of the Anegada Passage. Our results on investment in pollen relative to ovule production are consistent with E. tithymaloides relying on pollinators for reproduction across its range in the Caribbean. We document a geographic pattern of reduction in anther number and pollen:ovule ratios in populations of E. tithymaloides towards the Anegada Passage, which is consistent with a possible geographic transition towards a mixed breeding system where selfing has increased importance in this area where its two expansion fronts meet. The reduction in pollen production is correlated with inflorescence morphology, which converges to relatively shorter cyathia towards the Anegada Passage along both fronts. We discuss alternative scenarios and potential drivers of the patterns we document.
We examine investment in male function in the context of geography and floral morphology in the plant ring species Euphorbia tithymaloides, which colonized the Caribbean from Mexico/Guatemala along two fronts that roughly correspond to the Greater and the Lesser Antilles and that meet in the vicinity of the Anegada Passage. Our results on investment in pollen relative to ovule production are consistent with E. tithymaloides relying on pollinators for reproduction across its range in the Caribbean. We document a geographic pattern of reduction in anther number and pollen:ovule ratios in populations of E. tithymaloides towards the Anegada Passage, which is consistent with a possible geographic transition towards a mixed breeding system where selfing has increased importance in this area where its two expansion fronts meet. The reduction in pollen production is correlated with inflorescence morphology, which converges to relatively shorter cyathia towards the Anegada Passage along both fronts. We discuss alternative scenarios and potential drivers of the patterns we document.
Keywords: Breeding systems; Euphorbiaceae; convergence; divergence; male investment; outcrossing; pollen:ovule ratios; reproductive isolation; selfing; speciation
Document Type: Research Article
Publication date: December 8, 2020
- Systematic Botany is the scientific journal of the American Society of Plant Taxonomists and publishes four issues per year.
2011 Impact Factor: 1.517
2011 ISI Journal Citation Reports® Rankings: 87/190 - Plant Sciences
34/45 - Evolutionary Biology - Editorial Board
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