Analyzing plant phenology and plant–animal interaction networks can provide sensitive mechanistic indicators to understand the response of alpine plant communities to climate change. However, monitoring data to analyze these processes is scarce in alpine ecosystems, particularly in the highland tropics. The Andean páramos constitute the coldest biodiversity hotspot on Earth, and their species and ecosystems are among the most exposed and vulnerable to the effects of climate change. Here, we analyze for the first time baseline data for monitoring plant phenological dynamics and plant–pollinator networks along an elevation gradient between 4,200 and 4,600 m asl in three mountain summits of the Venezuelan Andes, which are part of the GLORIA monitoring network. We estimated the presence and density of plants with flowers in all the summits and in permanent plots, every month for 1 year. Additionally, we identified pollinators. We calculated a phenological overlap index between species. We summarized the plant–pollinator interactions as a bipartite matrix and represented a quantitative plant–pollinator network, calculating structural properties (grade, connectance, nestedness, and specialization). We also evaluated whether the overall network structure was influenced by differences in sampling effort, changes in species composition between summits, and phenology of the plant species. Finally, we characterized the pollination syndrome of all species. Flowering showed a marked seasonality, with a peak toward the end of the wet season. The overall phenological overlap index was low (0.32), suggesting little synchrony in flowering among species. Species richness of both plants and pollinators decreased along the elevation gradient. Flies, bumblebees, and hummingbirds were the most frequent pollinators in the network, while entomophily and anemophily were the prevailing pollination syndromes. The interaction network in all summits showed high connectance values, significant specialization (H2), and low nestedness. We did not find a significant effect of sampling effort, summit plant species composition, or plant phenology on network structure. Our results indicate that these high tropical alpine plant communities and their plant-pollination networks could be particularly vulnerable to the loss of species in climate change scenarios, given their low species richness and functional redundancy coupled with a high degree of specialization and endemism.
A new species of Heteranthera (Pontederiaceae), H. yucatana, is described, discussed, and iconographically documented based on material from Yucatan state, Mexico. The species is known from a few small ponds along a narrow strip of dry forests and shrublands over limestone outcrops and derived soils along the northwestern edge of the Yucatan Peninsula. The new species is related and has been hitherto confused with H. seubertiana from eastern Brazil but is easily distinguishable by its substantially smaller habit and flowers. Furthermore, the perianth lobes are lilac with a white-greenish basal blotch with yellowish towards the apex (as opposed to yellow lobes with proximal brownish spots). Also, the two lateral filaments are conspicuously inflated obliquely, as in Heteranthera mexicana, from which it differs by its much smaller vegetative size and some floral characters. The conservation status of the new species is assessed as Endangered according to the IUCN criteria. The genus Heteranthera consists of three species in the Yucatan Peninsula: H. dubia, H. limosa, and H. yucatana. Distributional maps for all Heteranthera from the area covered are presented. Finally, we offer a key to Heteranthera of the area.
The associations between morphological fruit types, fruit and seed colors, and functional plant traits: life forms, epiphytism, physiology, nutritional relationships, fruit phenology, and successional stage, were determined for 1,139 plant species from contrasting plant communities. Texture and dehiscence were closely related. Dehiscence is largely associated with dry tissues; indehiscence, however, is an attribute of both dry and fleshy fruits. The number of morphological fruit types was 28 or 55 for Gray's and Spjut's classifications, respectively. Fruits were predominantly dark in color (brown, purple-black, black or green), whilst seeds had both dark and light colors (brown, beige, or black). The most representative associations were mainly found between the more abundant fruit types and the colors most common. Asymmetries in the level of specialization, whereby less common fruit and seed colors tended to be associated with the most common fruit types, were also found. Fleshy fruits showed more variation as regards their coloration, and only drupes and berries showed a tendency towards a specific color: purple-black. The relationships among fruit type and color, seed color, and functional plant traits revealed the following trends: trees produced both fleshy and dry fruits; shrubs produced fleshy fruits; and herbaceous species, dry fruits. Woody species tended to have dark or bright colors, depending on their seed dispersal mechanisms and phylogenetic relations. Epiphytes were associated with dry-dehiscent fruits and brown seeds, and parasitic-hemiparasitic species had predominantly fleshy-indehiscent fruits. Pioneer species were more likely to have dry fruits, whereas fleshy fruits tended to be more frequent in late successional stage species. The C4 species, mostly herbs, had mainly one-seeded dry fruits, but multi-seeded fruits in succulent-CAM species showed morphologically diverse fruit types. Unripe and ripe fruits showed seasonal changes, especially during the rainy-dry transition period for the most abundant morphological fruit types, dry fruits during the dry period and fleshy fruited species was positively associated with the rainy season. All these trends are discussed with regard to their environmental significance and the relationships between fruit morphology, colors and functional groups. .
Antecedentes y Objetivos: La biología floral de comunidades tropicales bajo clima estacional ha mostrado el predominio de caracteres relacionados con la polinización generalista. En este contexto, se describe la biología floral de 48 especies de un bosque inundable con el propósito de explorar la relación entre atributos florales, examinar la diversidad de síndromes de polinización y evaluar la efectividad de este concepto para predecir clases de polinizadores. Además, se analizó el solapamiento de los períodos de floración de las especies con síndromes de polinización y/o clases de polinizadores comunes en búsqueda de un patrón que pudiese reflejar efectos adversos del solapamiento en cuanto a polinizadores. Métodos: En cada especie se describió el sistema sexual, la existencia de dicogamia y/o hercogamia, el tipo de unidad de polinización, las dimensiones, forma, simetría y orientación espacial de las flores, los atrayentes y recompensas florales, el horario de antesis, la longevidad floral, el síndrome de polinización y las clases de polinizadores. El solapamiento interespecífico fue estimado mediante el índice de Pianka y contrastado con valores generados aleatoriamente. Resultados clave: Las especies en su mayoría fueron hermafroditas, adicógamas y no hercógamas; mostraron unidades de polinización individuales, de dimensiones pequeñas, formas abiertas, simetría radial, orientación horizontal, color blanco y néctar como recompensa principal. La antesis fue principalmente diurna y la longevidad floral corta, generalmente de un día. La melitofilia fue el síndrome predominante y las abejas la principal clase de polinizadores, aunque varias especies fueron polinizadas por más de un tipo de agente. La distribución temporal de los períodos de floración no difirió a la de un esquema aleatorio. Conclusiones: Los resultados permiten concluir que más allá de lo predicho por los síndromes florales, en la comunidad prevalece un sistema alofílico que posiblemente redunda en mayores oportunidades de polinización para las especies de plantas.
La relación fruto/flor, relación semilla/óvulo y fecundidad relativa fueron evaluadas en 25 especies de un bosque inundable en la cuenca del lago de Maracaibo (Venezuela) y correlacionadas con el número y costo de las estructuras reproductivas. Estos estimadores, junto con la biomasa asignada a frutos y semillas y la relación pericarpio/semilla, fueron analizados entre formas de vida, sistemas reproductivos y síndromes de dispersión de semillas. En general, la relación fruto/flor y la fecundidad relativa fueron bajas mientras que la relación semilla/óvulo fue alta. La relación fruto/flor estuvo asociada negativamente con el número de flores por inflorescencia, y al igual que la fecundidad relativa, con el peso del fruto y de la semilla. La relación semilla/óvulo estuvo negativamente relacionada con el número de óvulos por flor y con el peso del fruto. La relación fruto/flor y la fecundidad relativa fueron mayores en especies herbáceas, autógamas y/o de dispersión abiótica que en sus contrapartes leñosas, xenógamas y/o zoocoras las cuales presentaron mayor peso semilla, y en el caso de las especies xenógamas, también mayor relación pericarpio/semilla que las autógamas. La relación semilla/óvulo fue mayor en especies de dispersión abiótica que en las zoocoras. Estos resultados sugieren una fuerte influencia del número y costo de las estructuras reproductivas en la eficiencia reproductiva de las especies.
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