Evolution of brood-site mimicry in Madagascan Impatiens (Balsaminaceae)

• Published in: Perspectives in plant ecology, evolution and systematics evolution and systematics, 2021-04, Vol.49, p.125590, Article 125590
• Main Authors: Abrahamczyk, Stefan, Humphreys, Aelys M., Trabert, Felix, Droppelmann, Fabian, Gleichmann, Maria, Krieger, Vera, Linnartz, Marius, Lozada-Gobilard, Sissi, Rahelivololona, Marie Elisette, Schubert, Marian, Janssens, Steven B., Weigend, Maximilian, Fischer, Eberhard
• Format: Article
• Language: English
• Subjects: Autogamy; Brood-site deception; Evolution; Fly pollination syndrome; Fungus mimicry; Impatiens; Madagascar; Trimorphopetalum
• ISSN: 1433-8319; 1618-0437; 1618-0437
• DOI: 10.1016/j.ppees.2021.125590

•Evolution of smaller flowers with lower amounts of nectar in Trimorphopetalum.•A sophisticated form of brood-site mimicry in Impatiens section Trimorphopetalum.•No indication of other major drivers of floral evolution in this clade. The species-rich flora of Madagascar is well known for a range of unusual floral ecologies. One example is Impatiens section Trimorphopetalum with its unique combination of floral traits: small, spur-less, cup- or lip-shaped, greenish or brownish flowers. So far no hypotheses on floral function or pollination of this peculiar group have been proposed. We analysed six reproductive traits in relation to pollination syndromes for 34 Madagascan Impatiens species, including 18 species of section Trimorphopetalum plus six outgroup species, in a phylogenetic framework. Further, we present pollinator observations for one additional species of Trimophopetalum. All pollination syndromes occurring in the African species are also present in Madagascan Impatiens. In addition, species of Trimorphopetalum represent two unique floral types, possibly corresponding to two different types of fly pollination. The evolution of these flower types corresponds to a strong decrease in nectar production, flower display size, pollen grain and ovule number. Autogamy is found in one derived sub-clade of the otherwise largely pollinator-dependent Trimorphopetalum. We find evidence consistent with the evolution of brood-site deception and fungus mimicry in combination with fly pollination in one clade of Trimorphopetalum and the stepwise evolution of autogamy in the second clade. The evolution of these very different reproductive strategies may have been triggered by pollinator limitation in the dense, humid forest undergrowth of Madagascar.