Functional Diversity in Tropical High Elevation Giant Rosettes

Clinal variation in drought resistance shapes past population declines and future management of a threatened plant

“…Young plants averaged a Ψ tlp of −1.17 MPa, which is more similar to global means of species from wet tropical rather than dry tropical environments (Bartlett et al. ), but is also similar to that of other tropical alpine rosette plants (Rada ). This indicates that these plants cannot tolerate very low stem water potentials before loss of leaf turgor and cessation of gas exchange.…”

“…(Carlquist , Robichaux and Morse ). Taken together, the ecohydrologic characteristics of silverswords, like many Andean giant rosette species (Rada ), indicate a strategy more aligned with drought avoidance than with drought tolerance (see Appendix S3 for additional information).…”

“…After adjusting for size, plants grown at low elevation perished more quickly when experiencing drought at high elevation, despite the down‐regulation of stomatal conductance, which presumably occurred in response to the higher VPD prevailing in the upper greenhouse (e.g., Schulze et al. , Rada ). Stomatal control, therefore, appeared to be insufficient to prevent elevated transpirational water loss under the drier atmospheric conditions at higher elevation, which also led to higher rates of soil water evaporation.…”

Phylogenetic signatures of ecological divergence and leapfrog adaptive radiation inEspeletia

“…The ecological and historical setting of these high‐elevation plant radiations likely implies some sort of ecological opportunities provided by mountain uplifts and climatic shifts (Hughes and Atchison, 2015), and by the evolution of key trait innovations allowing the colonization of new adaptive zones (sensu Simpson, 1944). Some of the best examples of key innovations for high‐elevation habitats in plants are specialized growth‐forms such as cushions (Boucher et al, 2016a) and caulescent rosettes (Monasterio and Sarmiento, 1991; Pouchon et al, 2018), as well as stem woodiness (Nürk et al, 2019) and several freezing‐avoidance mechanisms (Rada, 2016), which clearly improved adaptation to life in these relatively cold, dry, and irradiated environments. However, the precise mechanisms of increased speciation rate within this adaptive zone remain uncertain.…”

“…1C). Many species in Espeletia , particularly among caulescent rosettes, exhibit a series of morphological and physiological traits with presumably high adaptive value in the relatively harsh environments of páramos, such as covering of stems by the remains of dead leaves, large pith volumes, dense leaf pubescence, and super‐cooling capacity (Luteyn, 1999; Rada, 2016). In addition, Espeletia shows large ecological variation for habitat preferences, i.e., from wetlands to open landscapes and dry rocky slopes, and from the upper limit of the Andean forests to the edge of glaciers in super‐páramo habitats (ca.…”