Browsing by Subject "SEED SIZE"

Sort by: Order: Results:

Now showing items 1-3 of 3
  • Weigang, Helene C.; Kisdi, Eva (2015)
    Resources invested in dispersal structures as well as time and energy spent during transfer may often decrease fecundity. Here we analyse an extended version of the Hamilton-May model of dispersal evolution, where we include a fecundity-dispersal trade-off and also mortality between competition and reproduction. With adaptive dynamics and critical function analysis we investigate the evolution of dispersal strategies and ask whether adaptive diversification is possible. We exclude evolutionary branching for concave trade-offs and show that for convex trade-offs diversification is promoted in a narrow parameter range. We provide theoretical evidence that dispersal strategies can monotonically decrease with increasing survival during dispersal. Moreover, we illustrate the existence of two alternative attracting dispersal strategies. The model exhibits fold bifurcation points where slight changes in survival can lead to evolutionary catastrophes. (C) 2015 Elsevier Ltd. All rights reserved.
  • Cai, Yuhua (2022)
    We study the adaptive dynamics of the colonization rate of species living in a patchy habitat when there is a trade-off with the competitive strength for individual patches. To that end, we formulate a continuous-time competition-colonization model that also includes ownership effects as well as random disturbance affecting the mortality rate. We find that intermediate disturbance (as measured by the fluctuation intensity of the mortality rate), a strong competition-colonization trade-off, and a weak ownership effect are necessary conditions for evolutionary branching and hence for the emergence of polymorphisms (i.e., coexistence) by small evolutionary steps. Specifically, concerning ownership we find that with low-intermediate disturbance, a weak ownership advantage favours evolutionary branching while ownership disadvantage does not. This asymmetry disappears at the higher-intermediate disturbance. Moreover, at a low-intermediate disturbance, the effect of the strength of the competition-colonization trade-off on evolutionary branching is non-monotonic disappears because the possibility of branching disappears again when the trade-off is too strong. We also find that there can be multiple evolutionary attractors for polymorphic populations, each with its own basin of attraction. With small but non-zero random evolutionary steps and depending on the initial polymorphic condition just after branching, a coevolutionary trajectory may come arbitrarily close to the shared boundary of two such basins and may even jump from one side to the other, which can lead to various kinds of long-term evolutionary dynamics, including evolutionary branching-extinction cycles. (C) 2021 The Author(s). Published by Elsevier Ltd.
  • Ramírez-Valiente, José-Alberto; Aranda, Ismael; Sanchez-Gomez, David; Rodriguez-Calcerrada, Jesus; Valladares, Fernando; Robson, Thomas Matthew (2019)
    In Mediterranean-type ecosystems, drought is considered the main ecological filter for seedling establishment. The evergreen oaks Quercus ilex L. and Quercus suber L. are two of the most abundant tree species in the Mediterranean Basin. Despite their shared evergreen leaf habit and ability to resist low soil water potentials, traditionally it has been suggested that Q. ilex is better suited to resist dry conditions than Q. suber. In this study, we examined how seedlings of Q. ilex and Q. suber grown in sandy soils responded to different levels of water availability using natural dry conditions and supplemental watering. Specifically, we estimated survival and water status of seedlings and explored the role of acorn mass and belowground biomass in seedling performance. To our surprise, Q. suber was better able to survive the summer drought in our experiment than Q. ilex. Nearly 55% of the Q. suber seedlings remained alive after a 2-month period without rain or supplemental water, which represents almost 20% higher survival than Q. ilex over the same period. At the end of the dry period, the surviving seedlings of Q. suber had strikingly higher water potential, potential maximum quantum yield of photosystem II (F-v/F-m) and stomatal conductance (g(s)) than those of Q. ilex. Acorn mass was associated with the probability of survival under dry conditions; however, it did not explain the differences in survival or water status between the species. In contrast, Q. suber had a higher root ratio and root: shoot ratio than Q. ilex and these traits were positively associated with predawn leaf water potential, F-v/F-m, g(s) and survival. Taken together, our results suggest that the higher relative investment in roots by Q. suber when growing in a sandy acidic substrate allowed this species to maintain better physiological status and overall condition than Q. ilex, increasing its probability of survival in dry conditions.