Producción de néctar y flores como rasgos compensatorios al robo de néctar en Bouvardia ternifolia (Rubiaceae): experimentos de campo

Abstract

Resumen: El néctar de fl ores polinizadas por colibríes es usualmente robado por animales no polinizadores, por ello se esperaría que plantas sometidas al robo de néctar presenten distintas estrategias que permitan mitigar los costos asociados. En este estudio, evaluamos la producción de néctar y fl ores como rasgos para mitigar el robo de néctar en la planta diestílica Bouvardia ternifolia (Rubiaceae) en el Parque Nacional la Malinche, Tlaxcala, México. Plantas de ambos morfos fueron sometidas a tres tratamientos: (1) tratamiento de remoción de néctar, (2) tratamiento sin remoción y (3) tratamiento control (plantas sin exclusión ni extracción de néctar). Durante el periodo de fl oración, cuantifi camos semanalmente el volumen de néctar (15 fl ores/planta) y el número de fl ores producidas por planta. Polinizamos manualmente las fl ores focales y los frutos producidos se recolectaron y sus semillas contadas. Las fl ores con y sin remoción de néctar produjeron similar recompensa; contrario a los pequeños volúmenes producidos en fl ores control. Las fl ores del morfo pin mostraron mayores volúmenes y concentraciones de néctar que las thrum. No encontramos efecto de los tratamientos sobre la producción de fl ores en ambos morfos. Las fl ores con y sin remoción de néctar produjeron más semillas que las fl ores control. Nuestros resultados sugieren que Bouvardia puede sobrecompensar el néctar robado, pero no las fl ores; sin afectar el número de semillas producidas. Palabras clave: Bouvardia ternifolia, producción de fl ores y néctar, robo de néctar, Tlaxcala.Abstract:. Nectar of hummingbird-pollinated plants is usually robbed by non-pollinator animals, for that reason it is possible that the robbed plants show different strategies to mitigate the associated costs. In this study, we evaluated the production of nectar and fl owers as traits to mitigate the nectar robbing in the distylous plant Bouvardia ternifolia (Rubiaceae) in the National Park La Malinche, Tlaxcala. Plants of both morphs were subject to three different treatments: (1) treatment with nectar removal, (2) treatment without nectar removal, and (3) treatment control. During the fl owering period, we weekly quantifi ed the nectar volume (15 fl owers/plant) and the number of fl owers per plant. We manually pollinated the focal fl owers and the produced fruits were collected and their seeds counted. Similar volumes of nectar were produce in the fl owers with and without nectar removal; in opposition to the small collected volumes in the control fl owers. Long-styled fl owers (pin morph) produced more nectar volume and sugar than short-styled fl owers (thrum morph). There was not effect of treatments on the fl owers production in both morphs. Flowers with and without nectar removal produced more seeds than control fl owers. Our results showed that Bouvardia can over-compensate the nectar robbed, but not fl owers; without affecting the number produced seeds. Keywords: Bouvardia ternifolia, fl ower and nectar production, nectar robbing, Tlaxcala. L os poliniz...

Evaluation of the symmetric effect of antagonists in the floral morphs of the distylic shrub Bouvardia ternifolia : a field study

“…The LS and SS-morphs produced 24.85 % and 26.76 % more nectar, respectively, with regard to the exclusion treatment. These results are congruent with findings of previous works on Bouvardia ternifolia, in which plants of both floral morphs exposed to various levels of manual nectar extraction seem to equally compensate the experimentally extracted volumes (Salinas-Esquivel et al 2013). This phenomenon of compensation (suggested as a tolerance mechanism) in light of the floral larceny effect has also been documented in Ipomopsis aggregata (Irwin et al 2008).…”

“…In this work, LS and SS flowers with larcenists excluded accumulated a different volume of nectar. Previous work on Bouvardia ternifolia at the same study site agrees with these results (Torres et al 2008, Salinas-Esquivel et al 2013. Likewise, similar results were found on other distylous plant species, such as in Palicourea padifolia (Ornelas et al 2004a).…”

“…It is known that in different distylous plant species some characteristics of the floral morphs related to the attractiveness towards the pollinators, such as the floral display and reward production, are not equal (e.g., Contreras & Ornelas 1999, Barrett 1990, Faivre 2000, Salinas-Esquivel et al 2013, Valois-Cuesta et al 2011. Likewise, it has been suggested that these differences could promote an asymmetrical pollen flow between floral morphs due to a differential attraction of pollinators (Valois-Cuesta et al 2011.…”

“…Flowers of this plant commonly host flower mites of the Tropicoseius (Ascidae) genus, which are important nectar thieves (Salinas-Esquivel 2007). In addition, leaves are commonly consumed by insect herbivores, and fruits damaged by seed predators (Salinas-Esquivel et al 2013). However, levels of natural damage by these antagonists have not been documented throughout the flowering season and differences in the intensity of antagonistic effects between morphs remain unknown.…”

Anatomy of the floral nectaries of selected species of Gardenieae (Rubiaceae)

“…This family have flowers with tetracyclic arrangement, predominantly actinomorphic symmetry, the stamens are epipetalous and in the same number as the number of corolla lobes (the filaments are fused with the corolla-tube), and the ovary is almost always inferior; also, a nectary disc (ND) surrounding the basis of the style with nectarostomata is almost universally present (Robbrecht 1988;Simpson 2010). Despite the uniformity of traits of floral nectaries in the family, the studies in Rubiaceae have mostly focused on nectar composition (Freeman et al 1991), or on ecological aspects of the nectar (Falcão et al 2014;Amorim & Oliveira 2006;Salinas-Esquivel et al 2013;Queiroga & Moura 2017;Avila Jr. & Freitas 2011). There are few studies that describe their anatomy and these are mainly focused on species of the tribe Spermacoceae (subfamily Rubioideae, Galati 1991;Galetto 1998;Florentín et al 2016).…”