Biología floral y compuestos volátiles de tres especies de herbáceas en el cerro de Xochitepec, Xochimilco, Ciudad de México Public Deposited
Salvia polystachia Cav., Leonotis nepetifolia (L.) R. Br. y Tithonia tubiformis (Jacq.) Cass. son tres herbáceas arvenses ruderales que cohabitan en un relicto de vegetación natural de la Ciudad de México. No se cuenta con estudios de su fenología y morfología floral, ni de sus atrayentes y recompensas florales relacionadas con sus visitantes florales. El objetivo del presente trabajo fue conocer algunos aspectos de la biología reproductiva (fenología y morfología floral, néctar, compuestos orgánicos volátiles y visitantes florales) de tres herbáceas silvestres presentes en el Cerro de Xochitepec, Xochimilco, CDMX. En las tres especies de estudio la fenología fue agregada, se observó alta coincidencia en la floración intrapoblacional e interespecífica. Las flores de S. polystachia y de L. nepetifolia tienen una longevidad de tres días, no se logró determinar la longevidad floral de T. tubiformis. La relación polen/óvulo por flor de Cruden (1977) sugiere xenógamia obligada para las tres especies. Los granos de polen de las especies estudiadas se presentan en mónadas, y son isopolares y radiosimétricos. La forma del grano de polen en S. polystachia y L. nepetifolia essubprolata y en T. tubiformis es oblato-esferoidal. El néctar de S. polystachia fuedominante en sacarosa (80.07 %) con un volumen promedio de 0.74 μL por flor, el néctar de L. nepetifolia fue rico en glucosa (37.80 %) con un volumen promedio de 3.56 μL por flor. No se encontraron cantidades medibles de néctar en T. tubiformis. Las flores de las tres especies de estudio emiten α-copaeno, sin embargo, cada especie emite COVs particulares y a diferentes abundancias. S. polystachia fue visitada principalmente por himenópteros (32.14 %), L. nepetifolia por coleópteros (25.64 %) y hemípteros (23.08 %), mientras que T. tubiformis por coleópteros (32.43 %). La red de interacción planta-visitante floral es de tipo bipartita, con tres especies núcleo (Apis mellifera, Sphenarium sp. y una especie de la familia Curculionidae). La variación en la estructura de la comunidad de visitantes florales entre estas plantas que coexisten, podría ser explicada porque presentan rasgos morfológicos florales y ofrecen recompensas distintas para los visitantes florales. Por lo cual es importante mantener una comunidad diversa de herbáceas ya que representan un recurso importante para los insectos visitantes de flores. Palabras clave: biología reproductiva, compuestos orgánicos volátiles, flores, herbáceas, néctar, polen, visitantes florales.
Salvia polystachia Cav., Leonotis nepetifolia (L.) R. Br. and Tithonia tubiformis (Jacq.) Cass. are three herbaceous ruderal weeds that coexist in a relict of natural vegetation in Mexico City. There are no studies of its floral phenology and morphology, neither of its attractants and floral rewards related to its floral visitors. The objective of this work was to know some aspects of the reproductive biology (phenology and floral morphology, nectar, volatile organic compounds and floral visitors) of three wild herbaceous plants present in the Cerro of Xochitepec, Xochimilco, CDMX. In the three study species, the phenology was aggregated, a high coincidence was observed in intrapopulation and interspecific flowering. The flowers of S. polystachia and L. nepetifolia have a longevity of three days, it was not possible to determine the floral longevity of T. tubiformis. Cruden's (1977) pollen/ovule per flower ratio suggests obligate xenogamy for all three species. The pollen grains of the studied species occur in monads, and are isopolar and radiosymmetric. The shape of the pollen grain in S. polystachia and L. nepetifolia is subprolate and in T. tubiformis it is oblate-spheroidal. The nectar of S. polystachia was dominant in sucrose (80.07 %) with an average volume of 0.74 μL per flower, the nectar of L. nepetifolia was rich in glucose (37.80 %) with an average volume of 3.56 μL per flower. No measurable amounts of nectar were found in T. tubiformis. The flowers of the three study species emit α-copaene, however, each species emits particular VOCs and at different abundances. S. polystachia was visited mainly by hymenopterous (32.14 %), L. nepetifolia by beetles (25.64 %) and hemipterans (23.08 %), while T. tubiformis by beetles (32.43 %). The plant-floral visitor interaction network is bipartite, with three core species (Apis mellifera, Sphenarium sp. and a species from the Curculionidae family). Salvia polystachia Cav., Leonotis nepetifolia (L.) R. Br. and Tithonia tubiformis (Jacq.) Cass. are three herbaceous ruderal weeds that coexist in a relict of natural vegetation in Mexico City. There are no studies of its floral phenology and morphology, neither of its attractants and floral rewards related to its floral visitors. The objective of this work was to know some aspects of the reproductive biology (phenology and floral morphology, nectar, volatile organic compounds and floral visitors) of three wild herbaceous plants present in the Cerro of Xochitepec, Xochimilco, CDMX. In the three study species, the phenology was aggregated, a high coincidence was observed in intrapopulation and interspecific flowering. The flowers of S. polystachia and L. nepetifolia have a longevity of three days, it was not possible to determine the floral longevity of T. tubiformis. Cruden's (1977) pollen/ovule per flower ratio suggests obligate xenogamy for all three species. The pollen grains of the studied species occur in monads, and are isopolar and radiosymmetric. The shape of the pollen grain in S. polystachia and L. nepetifolia is subprolate and in T. tubiformis it is oblate-spheroidal. The nectar of S. polystachia was dominant in sucrose (80.07 %) with an average volume of 0.74 μL per flower, the nectar of L. nepetifolia was rich in glucose (37.80 %) with an average volume of 3.56 μL per flower. No measurable amounts of nectar were found in T. tubiformis. The flowers of the three study species emit α-copaene, however, each species emits particular VOCs and at different abundances. S. polystachia was visited mainly by hymenopterous (32.14 %), L. nepetifolia by beetles (25.64 %) and hemipterans (23.08 %), while T. tubiformis by beetles (32.43 %). The plant-floral visitor interaction network is bipartite, with three core species (Apis mellifera, Sphenarium sp. and a species from the Curculionidae family). The variation in the structure of the floral visitor community among these coexisting plants could be explained because they present floral morphological traits and offer different rewards for floral visitors. Therefore, it is important to maintain a diverse community of herbaceous plants, given that they represent an important resource for flower-visiting insects. key words: floral visitors, flowers, herbaceous, nectar, pollen, reproductive biology, volatile organic compounds.
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