Evolutionary shifts to bird pollination (ornithophily) have occurred independently in many lineages of flowering plants. This shift affects many floral features, particularly those responsible for the attraction of birds, deterrence of illegitimate flower visitors (particularly bees), protection from vigorous foraging by birds, and accurate placement of pollen on bird's bodies. Red coloration appears to play a major role in both bee-deterrence and bird-attraction. Other mechanisms of bird-attraction include the production of abundant dilute nectar and the provision of secondary perches (for non-hovering birds). As a result of selection for similar phenotypic traits in unrelated bird-pollinated species, a floral syndrome of ornithophily can be recognized, and this review surveys the component floral traits. The strong convergent evolution evident in bird-pollinated flowers raises a question about the nature of the genetic mechanisms underlying such transitions and whether the same gene systems are involved in most cases. As yet there is too little information to answer this question. However, some promising model systems have been developed that include closely related bee and bird-pollinated flowers, such as Ipomoea, Mimulus, and Lotus. Recent studies of floral developmental genetics have identified numerous genes important in the development of the floral phenotype, which are also potential candidates for involvement in shifts between bee-pollination and bird pollination. As more whole-genome information becomes available, progress should be rapid.

Un reciente análisis filogenético de cuatro regiones de ADN para ca. 354 especies de la subtribu Maxillariinae indican fuertemente que el género Maxillaria, en su circunscripción tradicional, es altamente polifilético. Presentamos una nueva clasificación filogenética para Maxillariinae que reconoce 17 géneros.Los cambios necesarios incluyen: 1) la resurrección de los géneros Camaridium, Heterotaxis, y Ornithidium; 2) el reconocimiento de los recientes segregados genéricos Brasiliorchis (=Maxillaria secciónRepentes), Christensonella (=Maxillaria sección Urceolatae), Nitidobulbon (en prensa), y una Sauvetrea recircunscrita (=Maxillaria sección Trigonae); 3) la adopción de los nuevos géneros Inti (=Maxillaria secciónPolyphyllae), Mapinguari, Maxillariella (=Maxillaria secciones Ebulbes y Erectae), y Rhetinantha; 4) transferencias de Maxillaria sección Reflexae a Ornithidium, y Maxillaria sección Rufescens a Mormolyca; y 5) puesta en sinonimia de los géneros Adamanthus, Pseudomaxillaria,  Psittacoglossum y Sepalosaccus (bajo Camaridium), Anthosiphon (bajo Cryptocentrum), Chrysocycnis (bajo Mormolyca), Dicrypta, Marsupiaria y Pentulops (bajo Heterotaxis), y Laricorchis, Neo-Urbania, y Siagonanthus (bajo Ornithidium). Algunos sinónimos nuevos al nivel de especie también son presentados.

Strong micromorphological variation between different petals in the flower is exclusive to the subfamily Papilionoideae. Both major and minor epidermal types can be used as micromorphological markers of petal identity, at least in papilionoids, and they are important characters of flower evolution in the whole family. The molecular developmental pathway between specific epidermal micromorphology and the expression of petal identity genes has yet to be established.

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