Niche Differentiation in Tank and Atmospheric Epiphytic Bromeliads of a Seasonally Dry Forest

Abstract

Factors influencing the niche differentiation of epiphytes have been determined for the epiphytic bromeliads that coexist in the seasonally dry forest of Chamela, Mexico. Over 40 percent of the bromeliad epiphytes were distributed in only 5 percent of the trees. The occurrence of compound leaves in host trees was highly correlated with abundance of epiphytes, as these allow scattered light to penetrate throughout the canopy. The effect of leaf type overrides the effect of bark type, the main factor determining seedling establishment in moist forests. Eight species had the atmospheric life form, while only two species had tanks, formed by overlapping leaf bases and associated to a lower drought tolerance. Distribution in the canopy is counter to that observed in moist forests, since tank species occur in the upper canopy. Tank life forms showed most annual carbon gain during the rainy season, when the newly leafed out trees provide shade to the lower canopy. Atmospheric species had photosynthetic activity for longer into the dry period, possibly supported by dew and fog events. Leaf angles, orientation, trichome, and stomata densities are discussed in relation to water and light use among the species with contrasting ecological strategies.

Evaluating factors that predict the structure of a commensalistic epiphyte–phorophyte network

“…Caesalpinia sclerocarpa's architecture, with ramifications high on the trunk and fairly horizontal branches may favour the establishment of epiphytes. Species with dense wood are capable of growing taller [65], and this is one of the tallest species in the forest; Tillandsia are light demanding [66] and may be more successful high in the canopy. By contrast, the most abundant woody species, Apoplanesia paniculata, interacted with 10 Tillandsia spp., but was found interacting less frequently than expected by its abundance, bark texture, wood density, spatial overlap and tree sizes, with two Tillandsia species.…”

Adaptive radiation, correlated and contingent evolution, and net species diversification in Bromeliaceae

“…Dense arrays of tillandsioid trichomes are highly efficient at capturing moisture from fog when combined with narrow leaves that efficiently intercept fine droplets (Martorell and Ezcurra, 2007). Atmospherics tolerate desiccation better than tank species but have lower rates of photosynthesis per unit leaf mass (Benzing and Burt, 1970;Benzing and Renfrow, 1974;Reyes-Garcia et al, 2008), and almost all have CAM photosynthesis (Crayn et al, 2004). Many tank bromeliads exhibit developmental heterophylly, with juveniles starting as atmospherics (Adams and Martin, 1986;Benzing, 2000;Zotz et al, 2011) and then later forming tanks as body size increases.…”

Fog interception by Ball moss (<i>Tillandsia recurvata</i>)

“…Although the atmospheric bromeliads do not have roots to absorb water or a tank to capture rainfall, the number of narrow leave are enough to capture the fog and help satisfy their water requirements (Martorell and Ezcurra, 2007). Reyes-García et al (2008a) suggested that dew and fog interception are important mechanisms because the main photosynthetic activity of atmospheric bromeliads is during the rainless time of the year.…”