Host genus and rainfall drive the population dynamics of a vascular epiphyte

Abstract

Abstract. Vascular epiphytes constitute up to 25% of tropical plant diversity and play an important role in providing food, water, and shelter to many organisms. However, the factors that drive their population dynamics, including the influence of their host plants (phorophytes) and of climatic factors, are still poorly understood. We provide the first test of whether host tree genus can affect population dynamics of an epiphytic species, and assess the interactive effects of host tree and rainfall. We carried out a five-year study of the demography of >1000 plants of the endemic bromeliad, Tillandsia macdougallii L. B. Sm, growing on pine and oak trees in a Mexican montane forest. We tested for differences in vital rates and used integral projection models to test whether these scaled up to differences in long-term population growth rates between the two host genera and as a function of rainfall. T. macdougallii survival and growth were higher on pines than on oaks for larger plants but not for seedlings. The probability of producing capsules was higher for T. macdougallii on oaks than on pines. Increasing dry season rainfall was significantly correlated with increased survival of individuals, but not of ramets, growing on both oaks and pines. The probability of clonal reproduction increased significantly with increasing dry season rainfall for T. macdougallii growing on oaks, but not on pines. Projected long-term population growth rates, λ, for T. macdougallii on pines were higher than on oaks. Lambda increased steeply as a function of dry season rainfall for T. macdougallii populations on both host tree genera, but the increase was steeper for populations on oaks, likely because the former are deciduous. Our results show that host tree genus can affect the long-term dynamics of epiphyte populations and suggest that these effects may depend on rainfall. The high sensitivity of this species to changes in dry season rainfall suggests that a better understanding of how rainfall may drive vascular epiphyte populations will be critical for understanding the effects of climate change on species persistence.

La precipitación está asociada con la fenología de Rodriguezia granadensis (Lindl.) Rchb. f. en Fusagasugá, Cundinamarca

“…Los resultados mostraron que la fenofase vegetativa para el número de individuos registrados predominó durante todo el lapso evaluado, presentando una leve disminución en los períodos lluviosos y un aumento en la época seca (Figura 2), obteniendo una correlación negativa (Spearman, p<0,05) con la precipitación (r=-0,79), lo que indicaría la disminución del número de individuos vegetativos, cuando se presentan las épocas de mayor precipitación en la zona de la hacienda Betania. Este resultado contrasta con el reportado por Ticktin et al (2016), en la bromelia Tillandsia macdougallii L. B. Sm. (epífita), en Oaxaca, México, donde la estación seca hizo que las plantas fueran más sensibles a la desecación, aumentando su tasa de mortalidad.…”

Vascular epiphyte populations with higher leaf nutrient concentrations showed weaker resilience to an extreme drought in a montane cloud forest

“…2011; Ticktin et al . 2016). The leaf C:N ratio is positively associated with δ 13 C, indicating that species with a high leaf C:N ratio have high water use efficiency (Prieto et al .…”

Vascular Epiphytes: The Ugly Duckling of Phenological Studies

“…The diversity of microhabitats could favor phenological variation among epiphytic individuals. While this effect has not been measured on phenology itself, it has been proven that different micro-habitats cause variation in the growth, reproductive potential, and flower production of vascular epiphytes (Cervantes et al, 2005;Ticktin et al, 2016;Ramírez-Martínez et al, 2018).…”

“…It is known that epiphytes have an intimate relationship with their host trees (Einzmann et al, 2015;Wagner et al, 2015;Ticktin et al, 2016;Ramírez-Martínez et al, 2018;Rasmussen and Rasmussen, 2018) so it is fundamental to understand how these hosts affect epiphyte phenology. If we consider a population as the group of individuals growing on the same tree (Overton, 1994), the effect of the host tree could be evaluated in two levels: a) interpopulation variation among populations on different hosts, and b) intrapopulation variation between individuals growing on the same tree.…”