An official website of the United States government
Abstract AimAngiosperm epiphytes have long been reported to have larger geographic ranges than terrestrial species, despite evidence of their outstanding diversity and endemism. This apparent contradiction calls for further investigation of epiphytes' poorly understood range size patterns. Here, we address the question of whether epiphytes have larger geographic ranges and different vulnerability to extinction than terrestrial species. LocationThe Atlantic Forest of Brazil, a global centre of tropical epiphyte diversity with relatively well‐known flora, where we can estimate the geographic ranges of a large number of species with reasonable confidence. Time periodOccurrence records from the 17th century to the year 2021. Major taxa studiedFlowering plants (angiosperms). MethodsWe downloaded, processed and cleaned all occurrence records for the angiosperm species native to the Atlantic Forest of Brazil available in the speciesLink network and the Global Biodiversity Information Facility. We estimated the extent of occurrence and area of occupancy of 12,679 native flowering plants, including 1251 epiphytic species. We compared the geographic ranges of epiphytes and other life forms at broad (e.g. Angiosperms, Monocots) and more restricted taxonomic scales (e.g. individual families), assuming species are independent entities and also when accounting for species phylogenetic dependence. ResultsWe found that epiphytes have among the smallest geographic ranges of flowering plants. We found no consistent evidence that epiphytism leads to differences in geographic ranges between close relatives. However, both epiphytes and non‐epiphytes in epiphyte‐rich lineages have small ranges and likely a high vulnerability to extinction. Main ConclusionsOur findings contrast with the long‐held hypothesis that epiphytes have larger geographic ranges than terrestrial species. Epiphytes and their close relatives share many diversification mechanisms and ecological adaptations (‘epiphyte‐like traits’), which probably explain why both sets of species have small range sizes and high vulnerability to extinction.
more »
« less
Source height and contact with terrestrial soil drive transplanted epiphyte performance
Abstract 1. Epiphytes are characterized by their ability to survive without a root connection to the ground, but many basic life-history traits and ecological trade-offs of this unique aerial growth habit remain largely uncharacterized. Mortality causes are still not well understood, but falling from the host tree has been suggested as a leading cause of epiphyte mortality and community dynamics. Little empirical ev- idence exists for why epiphytes do not survive when forced to become terrestrial, and few studies exist that transplant epiphytes between high- and low-forest strata to test trade-offs between thriving in canopy environments and survival in the forest understorey. 2. Here, we experimentally test two hypotheses regarding the drivers of epiphyte mortality in a cloud forest of central Panama. We test whether simple contact with terrestrial soil is deleterious to epiphytes, preliminarily testing the epiphyte enemy escape hypothesis, and test the vertical niche differentiation hypothesis, wherein epiphytes are specifically adapted for microsites throughout the vertical forest strata. By monitoring survival, leaf loss and health status of 270 trans- planted epiphytes for a year and a half, we pinpoint the extent to which soil con- tact and height of origin regulate epiphyte performance. 3. We found that contact with terrestrial soil itself was detrimental to epiphytes in situ, providing some of the first empirical data to explain why falling onto the ground, versus falling into the understorey, is particularly fatal to epiphytes. However, we also found that mortality rates vary substantially among taxonomic groups and among epiphytes that originally came from different height strata. 4. Synthesis. Plants that are adapted for the canopy experience a trade-off with higher mortality when in contact with terrestrial soil. Follow-up studies should explore the role of terrestrial soil microbes and physiological constraints as po- tential drivers of decreased grounded epiphyte survival.
more »
« less
- Award ID(s):
- 1907190
- PAR ID:
- 10464430
- Date Published:
- Journal Name:
- Journal of Ecology
- ISSN:
- 0022-0477
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
The interspecific trade‐off between growth versus mortality rates of tree species is thought to be driven by functional biology and to contribute to species ecological niche differentiation. Yet, functional trait variation is often not strongly correlated with growth and mortality, and few studies have investigated the relationships of both traits and niches, specifically encompassing above and belowground resources, to the trade‐off itself. These relationships are particularly relevant for seedlings, which must often survive resource limitation to reach larger size classes.We investigated the functional basis of the interspecific growth–mortality trade‐off and its relationship with ecological niches for seedlings of 14 tree species in a tropical forest in southwest China.We found evidence for an interspecific growth–mortality trade‐off at the seedling stage using 15 functional traits and 15 ecological niche variables. None of the organ‐level traits correlated with growth, mortality, nor the trade‐off, whereas specific stem length (SSL), a biomass allocation trait, was the only trait to have a significant correlation (positive). Moreover, light‐defined niches were not correlated with growth, mortality or the trade‐off, but soil‐defined niches did. Species at the faster growth/higher mortality end of the trade‐off were associated with higher fertility defined by lower soil bulk density and slope, and higher soil organic matter concentration and soil total nitrogen.Our findings indicate the importance of stem elongation and soil fertility for growth, mortality and their trade‐off at the seedling stage in this Asian tropical forest. Our findings contrast with analogous studies in neotropical forests showing the importance of photosynthesis‐related leaf traits related to insolation. Therefore, the functional drivers of demographic rates and trade‐offs, as well as their consequences for ecological niches, can vary among forests, likely owing to differences in biogeography, canopy disturbance rates, topography and soil properties. Moreover, the effects of functional trait variation on demographic rates and trade‐offs may be better revealed when biomass allocation is accounted for in a whole‐plant context. Read the freePlain Language Summaryfor this article on the Journal blog.more » « less
-
Liverworts and mosses are a major component of the epiphyte flora of tropical montane forest ecosystems. Canopy access was used to analyse the distribution and vertical stratification of bryophyte epiphytes within tree crowns at nine forest sites across a 3400 m elevational gradient in Peru, from the Amazonian basin to the high Andes. The stable isotope compositions of bryophyte organic material ( 13 C/ 12 C and 18 O/ 16 O) are associated with surface water diffusive limitations and, along with C/N content, provide a generic index for the extent of cloud immersion. From lowland to cloud forest δ 13 C increased from −33‰ to −27‰, while δ 18 O increased from 16.3‰ to 18.0‰. Epiphytic bryophyte and associated canopy soil biomass in the cloud immersion zone was estimated at up to 45 t dry mass ha −1 , and overall water holding capacity was equivalent to a 20 mm precipitation event. The study emphasizes the importance of diverse bryophyte communities in sequestering carbon in threatened habitats, with stable isotope analysis allowing future elevational shifts in the cloud base associated with changes in climate to be tracked.more » « less
-
Abstract Both tree size and life history variation drive forest structure and dynamics, but little is known about how life history frequency changes with size. We used a scaling framework to quantify ontogenetic size variation and assessed patterns of abundance, richness, productivity and light interception across life history strategies from >114,000 trees in a primary, neotropical forest. We classified trees along two life history axes: a fast–slow axis characterized by a growth–survival trade‐off, and a stature–recruitment axis with tall, long‐lived pioneers at one end and short, short‐lived recruiters at the other.Relative abundance, richness, productivity and light interception follow an approximate power law, systematically shifting over an order of magnitude with tree size. Slow saplings dominate the understorey, but slow trees decline to parity with rapidly growing fast and long‐lived pioneer species in the canopy.Like the community as a whole, slow species are the closest to obeying the energy equivalence rule (EER)—with equal productivity per size class—but other life histories strongly increase productivity with tree size. Productivity is fuelled by resources, and the scaling of light interception corresponds to the scaling of productivity across life history strategies, with slow and all species near solar energy equivalence. This points towards a resource‐use corollary to the EER: the resource equivalence rule.Fitness trade‐offs associated with tree size and life history may promote coexistence in tropical forests by limiting niche overlap and reducing fitness differences. Synthesis . Tree life history strategies describe the different ways trees grow, survive and recruit in the understorey. We show that the proportion of trees with a pioneer life history strategy increases steadily with tree size, as pioneers become relatively more abundant, productive, diverse and capture more resources towards the canopy. Fitness trade‐offs associated with size and life history strategy offer a mechanism for coexistence in tropical forests.more » « less
-
Tropical montane cloud forests (TMCFs) are ecosystems with high biodiversity that are threatened by deforestation, land use changes, and climate change. One of the unique aspects of TMCFs is the high biomass and diversity of epiphytes. Epiphytes are vascular and non-vascular plants that live in tree canopies, creating arboreal micro-ecosystems. They provide ecological services by capturing and retaining allochthonous nutrients from rain and fog, and by supporting the presence of canopy pollinators and other fauna. Predicted changes in cloudiness and land conversion threaten the abundance of epiphytes, and thus their capacity to contribute to ecosystem functions. However, how losses in epiphyte abundance will affect microclimate and host tree water status is still unclear and requires the ability to simulate the role of epiphytes in canopy water storage dynamics. We developed a water balance model for epiphytes in TMCFs. We consider epiphytes in the host tree as a water store inside the canopy that is filled via precipitation from both rain and fog, and depleted via evapotranspiration and host tree water uptake. The model was used to simulate water and energy fluxes between the epiphytes and their surroundings under idealized and real dry season conditions for TMCFs near Monteverde, Costa Rica. Results from the idealized and real simulations capture how epiphytes retain water under dry-down conditions, leading to small diurnal variability in temperature, low evapotranspiration rates, and enhanced dew deposition at night. We find that dew deposition recharges up to 34 % of epiphyte water storage lost due to evapotranspiration over a 3-day dry-down event. Our results provide the first quantitative demonstration of the importance of epiphyte water storage on temperature and dew formation in TMCFs. This work sets the foundation for developing a process-based understanding of the effects of epiphyte loss on TMCF ecohydrology.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1111/1365-2745.14187
