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Vascular epiphytes are a diverse and conspicuous component of biodiversity in tropical and subtropical forests. Yet, the patterns and drivers of epiphyte assemblages are poorly studied in comparison with soil-rooted plants. Current knowledge about diversity patterns of epiphytes mainly stems from local studies or floristic inventories, but this information has not yet been integrated to allow a better understanding of large-scale distribution patterns. EpIG-DB, the first database on epiphyte assemblages at the continental scale, resulted from an exhaustive compilation of published and unpublished inventory data from the Neotropics. The current version of EpIG-DB consists of 463,196 individual epiphytes from 3,005 species, which were collected from a total of 18,148 relevés (host trees and 'understory' plots). EpIG-DB reports the occurrence of 'true' epiphytes, hemiepiphytes and nomadic vines, including information on their cover, abundance, frequency and biomass. Most records (97%) correspond to sampled host trees, 76% of them aggregated in forest plots. The data is stored in a TURBOVEG database using the most up-to-date checklist of vascular epiphytes. A total of 18 additional fields were created for the standardization of associated data commonly used in epiphyte ecology (e.g. by considering different sampling methods). EpIG-DB currently covers six major biomes across the whole latitudinal range of epiphytes in the Neotropics but welcomes data globally. This novel database provides, for the first time, unique biodiversity data on epiphytes for the Neotropics and unified guidelines for future collection of epiphyte data. EpIG-DB will allow exploration of new ways to study the community ecology and biogeography of vascular epiphytes. K E Y W O R D S biodiversity, community ecology, database, forest plot, hemiepiphytes, Neotropics, nomadic vines, taxonomic diversity, vascular epiphytes, vegetation relevé 520 |

Background: Cacao is an umbrophile species and therefore the handling of shade by producers can cause a microclimatic modification that influences the physiology of the plant. Questions: Can canopy management influence the microclimate of the crop area and the water content of cacao? Species of study: Theobroma cacao L. (Malvaceae). Study site: Comalcalco, Tabasco, Mexico; dry and rainy season 2018. Methods: Three sites were selected with an open canopy (OC) and three with a closed canopy (CC), where we determined air temperature and humidity, soil temperature, vapor pressure deficit, photosynthetically active radiation, soil water potential and leaf water potential in 15 cacao trees and the sap flow density in 12 trees, by canopy condition and by season. Results: Higher values of solar radiation, air and soil temperature, vapor pressure deficit and lower relative humidity were recorded under OC compared to CC, in both seasons. Differences in soil water potential between 10 and 60 cm depth in CC were recorded during the dry season. There was a lower sap flow density and daily water use in OC. The leaf water potential was similar between canopy conditions, in both seasons. Conclusions: Changes in canopy coverage significantly modify the microclimate of the crop area, a less stressful environment being generated under closed canopy conditions, influencing the sap flow density of cacao trees.

4Autor para la correspondencia: andrade@cicy.mxResumen: El dosel de las selvas secas presenta cambios anuales drásticos de luz y disponibilidad de agua, debido a que la mayoría de los árboles pierde sus hojas durante la temporada de sequía. Las epífi tas que ahí habitan presentan una morfología y fi siología adecuadas para tolerar la escasez de agua y el exceso de luz. Se estudiaron las respuestas fi siológicas de cinco especies de orquí-deas epífi tas en relación con la variación vertical del microambiente y a la estacionalidad en una selva baja caducifolia y en una selva mediana subcaducifolia, durante las temporadas de lluvias, nortes y sequía. Los cambios fi siológicos en las orquídeas fueron debido al efecto de los cambios estacionales en ambas selvas. Las orquídeas mostraron diferentes estrategias de tolerancia a la sequía: las hojas de Encyclia nematocaulon, Cohniella yucatanensis y Laelia rubescens, de la selva baja, mantuvieron su estado hídrico constante durante el año, pero disminuyeron su tasas de fotosíntesis durante la sequía. Aunque el estado hídrico foliar de E. nematocaulon y Lophiaris oerstedii, de la selva mediana, disminuyó durante las sequía, la fotosíntesis no disminuyó en L. oerstedii. Cohniella ascendens no mostró variación fi siológica estacional en sus hojas; se sugiere que esto fue debido a su baja densidad estomática y a la inclinación de las mismas, porque ello evita la perdida de agua y la exposición directa a la radiación. La especie más abundante, E. nematocaulon, mostró reducción foliar y estomas pequeños, lo que le confi rió gran plasticidad morfológica y fi siológica para tolerar la alta radiación y la sequía en ambas selvas. Palabras clave: contenido relativo de agua, fotoinhibición, metabolismo ácido de las crasuláceas, potencial osmótico, selvas secas.Abstract: Dry forest canopies exhibit drastic changes of light and water availability throughout the year, because most trees drop their leaves during the dry season. Epiphytes that inhabit there show a suit of morphological and physiological traits to tolerate water scarcity and light excess. We studied the physiological responses of fi ve epiphyte orchid species in relation to their vertical microenvironment and the seasonality in a deciduous tropical forest and a semi-deciduous tropical forest, during the wet, early dry and dry seasons. Physiological variation of orchids was mainly seasonal in both forests. Orchids showed different strategies to cope with drought: Encyclia nematocaulon, Cohniella yucatanensis and Laelia rubescens from the deciduous forest maintained their leaf water status constant throughout the year, with reduced photosynthetic rates during the dry season. Although the leaf water status of both, E. nematocaulon and Lophiaris oerstedii from the semi-deciduous forest, diminished during the dry season, photosynthesis did not decline in L. oerstedii. Leaves of Cohniella ascendens did not show signifi cant seasonal physiological variation, arguably due to low stomatal density and tilted leaf orientation, which ...

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