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With ca. 2500 species, Myrteae is the largest tribe of Myrtaceae and one of the most diverse groups of flowering plants in the tropical Americas. In light of recent systematics adjustments, the present study is a review and provides new insights into floral diversity and evolution in Myrteae. General aspects of floral ontogeny and morphology for the fifty currently accepted genera plus all accepted sections within the large genera Eugenia and Myrcia are summarized based on current morphological data. The discussion provides a broader understanding of the floral diversity across the tribe, highlighting developmental modes, ecological traits, and specializations in reproductive strategies. Hypotheses to be tested in future studies are also presented and discussed. [ABSTRACT FROM AUTHOR]

Summary: Changes in floral morphology are expected across evolutionary time and are often promoted as important drivers in angiosperm diversification. Such a statement, however, is in contrast to empirical observations of species‐rich lineages that show apparent conservative floral morphologies even under strong selective pressure to change from their environments.Here, we provide quantitative evidence for prolific speciation despite uniform floral morphology in a tropical species‐rich tree lineage. We analyse floral disparity in the environmental and phylogenetic context of Myrcia (Myrtaceae), one of the most diverse and abundant tree genera in Neotropical biomes.Variation in floral morphology among Myrcia clades is exceptionally low, even among distantly related species. Discrete floral specialisations do occur, but these are few, present low phylogenetic signal, have no strong correlation with abiotic factors, and do not affect overall macroevolutionary dynamics in the lineage.Results show that floral form and function may be conserved over large evolutionary time scales even in environments full of opportunities for ecological interactions and niche specialisation. Species accumulation in diverse lineages with uniform flowers apparently does not result from shifts in pollination strategies, but from speciation mechanisms that involve other, nonfloral plant traits. [ABSTRACT FROM AUTHOR]

• Eugenia is monophyletic including related genera previously segregated. • Calyx fused species evolved several times in the evolution of Eugenia. • Deep morphological assessment revealed five development patterns of calyx fusion. • Apparently six-petal species are the result of modification of two petaloid sepals. • Eugenia feijoi group can be recognized by the membranisepalous pattern. Eugenia has a pantropical distribution and comprises ca. 1000 species found mostly in the Neotropics. Recent DNA based phylogenies show that unusual flower morphology of 'eugenioid' collections, e.g. fused calices that open by tearing, consistently emerged within Eugenia. These results emphasize a demand to revaluate flower morphology in a phylogenetic context within the genus. A reassessment of calyx fusion in Eugenia and traditionally related genera is here focused on clarification of the systematic relevance of this apparently recurrent characteristic. Twenty-four Eugenia species with some level of calyx fusion in the bud were newly used (one nuclear and four plastid markers) in conjunction with a representative sample of previously sequenced species to recover a time-calibrated Eugenia phylogeny of 86 accessions. Development of the fused calyx was analysed using scanning electron microscopy, differing patterns were re-coded and subsequently phylogenetic character reconstruction was performed. Eugenia was recovered as monophyletic including the traditionally segregated genera Calycorectes and Catinga. Ancestral character reconstruction uncovered free calyx lobes as the ancestral condition. Five development patterns leading to calyx fusion are reported in Eugenia including species with apparently six petals, which contrast with the standard tetramerous flowers. This condition is interpreted as the petaloid pattern, where two external fused calyx lobes cover the bud while two internal calyx lobes are free and petaloid. The fused calyx condition is homoplastic and evolved independently, several times in Eugenia, as did the different development patterns. Data presented here show that systematic incongruence resulting from multiple, independent origins of the fused calyx in Eugenia is further aggravated by an inability to distinguish parallelism and convergence within the recovered patterns. [ABSTRACT FROM AUTHOR]

Premise: There is little direct evidence linking floral development and pollination biology in plants. We characterize both aspects in plain and ornamented flowers of Trimezieae (Iridaceae) to investigate how changes in floral ontogeny may affect their interactions with pollinators through time. Methods: We examined floral ontogeny in 11 species and documented pollination biology in five species displaying a wide range of floral morphologies. We coded and reconstructed ancestral states of flower types over the tribal phylogeny to estimate the frequency of transition between different floral types. Results: All Trimezieae flowers are similar in early floral development, but ornamented flowers have additional ontogenetic steps compared with plain flowers, indicating heterochrony. Ornamented flowers have a hinge pollination mechanism (newly described here) and attract more pollinator guilds, while plain flowers offer less variety of resources for a shorter time. Although the ornamented condition is plesiomorphic in this clade, shifts to plain flowers have occurred frequently and abruptly during the past 5 million years, with some subsequent reversals. Conclusions: Heterochrony has resulted in labile morphological changes during flower evolution in Trimezieae. Counterintuitively, species with plain flowers, which are endemic to the campo rupestre, are derived within the tribe and show a higher specialization than the ornamented species, with the former being visited by pollen‐collecting bees only. [ABSTRACT FROM AUTHOR]