Reproductive allocation strategies in desert and Mediterranean populations of annual plants grown with and without water stress

Abstract

Reproductive effort (relative allocation of biomass to diaspore production) was compared in matched pairs of Mediterranean and desert populations of three unrelated annual species, Erucaria hispanica (L.) Druce, Bromus fasciculatus C. Presl. and Brachypodium distachyon (L.) Beauv., grown under high and low levels of water availability in a common-environment experiment. Desert populations in all three species showed higher reproductive effort than corresponding Mediterranean populations, as expressed by both a reproductive index (RI= reproductive biomass/vegetative biomass), and a reproductive efficiency index (REI=number of diaspores/total plant biomass). Moreover, in E. hispanica and Brachypodium distachyon, inter-populational differences in reproductive effort were greater under water stress, the main limiting factor for plant growth in the desert. These results indicate that variability in reproductive effort in response to drought is a critical and dynamic component of life history strategies in annual species in heterogeneous, unpredictable xeric environments. When subjected to water stress the Mediterranean populations of E. hispanica and B. distachyon showed greater plasticity (e.g. had a greater reduction) in reproductive effort than the desert populations, while in Bromus fasciculatus both populations showed similar amounts of plasticity.

Reconstructing the Origin of Helianthus deserticola: Survival and Selection on the Desert Floor

“…Small leaves and early flowering are both characteristic of desert annuals and are thought to be of adaptive significance. In general, small leaves can reduce water loss and prevent heat stress while early flowering enables seed production before the onset of strong summer drought (Givnish 1979;Fox 1989;Aronson et al 1992Aronson et al , 1993Smith et al 1997;Gibson 1998). Both of these traits were negatively transgressive in a previous greenhouse study, implying strong genetic control (Rosenthal et al 2002).…”

A demographic approach to study effects of climate change in desert plants

“…However, for this prediction to hold true, changes in l must be strongly and positively coupled with variation in the abiotic factor. A few examples exist in the literature where this is not the case [30,31]. These studies highlight the importance of demographic buffering [32,33], that is, a population's ability to retain a more or less constant a despite varying climate by virtue of re-adjusting its vital rates.…”

Architectural plasticity in a Mediterranean winter annual

“…59 The risks associated with biological activity outside the boundaries of the growing season have selected for various risk-averse developmental schemes 29,33,60 and responsiveness to various environmental cues, enabling plants to both take advantage of growth opportunities and to avoid stresses and catastrophes. 56,[61][62][63][64] The current findings suggest that in addition to size variability, architectural plasticity may also play an important role in mitigating environmental risks and help Analysis of variance for the effects of origin (MED and SAR), Water level (high and low), and Season (FS, EC and LG) on size and architectural variables in T. purpureum. Population is included as a random factor nested within origin, and replicate-block is included as a covariate.…”

“…[51][52][53] Therefore, plants from arid populations are expected to display risk-averse development, 33,54,55 including reduced numbers of basal branches. In contrast, plants from more mesic populations 30,34,56 are expected to demonstrate more "optimistic" growth schemes and to develop more basal branches.…”