Flexible life history responses to flower and rosette bud removal in three perennial herbs

Abstract

In a garden experiment we investigated the response to continuous removal of either flower buds or rosette buds in three perennial grassland species (Hypochaeris radicata, Succisa pratensis and Centaurea jacea), which differ in longevity and flowering type. We distinguished two possible responses: compensation for lost buds by making more buds of the same type, and switching towards development of other life history functions. Both responses were demonstrated in our experiment, but bud removal had significantly different effects in each of the three species. The degree of compensation and the expression of trade-offs between life history functions differed markedly between species and seem related to longevity and developmental constraints. With respect to switching, our results suggest costs of reproduction and a trade-off between life history functions, at least for Hypochaeris and Succisa. For these species weight of new rosettes increased when resource allocation to flowering was inhibited. In Hypochaeris, we see that both compensation for lost flower buds and switching from lost rosette buds increased production of flower buds, underscoring the pivotal role of sexual reproduction in this short-lived species. The most prominent response seen in Centaurea is compensation for lost rosette buds, indicating that this long-lived species with monocarpic rosettes relies on rosette formation. Although Succisa does respond to bud removal, time is an important constraint in this species with long-lived rosettes and preformed flowering stalks. Trade-offs in Succisa seem to operate at a larger time scale, requiring long-lasting experiments to reveal them. We conclude that the response of these species to inflicted damage is likely to be linked to their longevity and developmental constraints.

Plant Reproductive Allocation Predicts Herbivore Dynamics across Spatial and Temporal Scales

“…Meristem allocation strategies to cope with these tradeoffs can vary widely among species, among populations within species, among individuals within populations, and within individuals across time; such variation is consistent with theory and may be driven by genetic and/or environmental factors (Geber 1990;Bowers 1996;Duffy et al 1999;Reekie 1999;Hartemink et al 2004;Mendez and Karlsson 2004). These patterns lead to the prediction that variation in the production of vegetative versus reproductive parts should have consequences for herbivores that prefer or specialize on specific plant structures.…”

“…Resource allocation decisions can be quantified in the currency of meristems, the primordial tissues from which vegetative and reproductive organs arise (Geber 1990;Bonser and Aarssen 1996;Geber et al 1997;Olejniczak 2001;Hartemink et al 2004). The total number of active meristems available at a given time is finite, and once committed to a particular function, a meristem cannot be redirected to another function (Watson 1984).…”

“…Allocation of meristems to current reproduction has the potential for immediate fitness benefits, but it constrains growth and, consequently, future reproductive potential. Conversely, the allocation of meristems to production of vegetative structures limits current reproductive output, but long-term gains in size, survival, and future fecundity could outweigh current losses (Geber 1990;Hartemink et al 2004).…”

Asexual and sexual reproductive strategies in clonal plants

“…However, in practice, it's hard to detect because there are many possible allocation patterns and allocations in individual plant are often in a hierarchical manner. The variation in resource allocation to clonal growth versus sexual reproduction may be determined by genetics (Bostock, 1980;Reekie, 1991;Ronsheim and Bever, 2000;Hartemink et al, 2004), plant size (Hartnett, 1990;Mendez and Obeso, 1993;Schmid and Bazzaz, 1995;Sato, 2002), age (Lopez et al, 2001), environmental conditions and population density (Abrahamson, 1975;Holler and Abrahamson, 1977;Nishitami et al, 1999;Ronsheim and Bever, 2000;.…”

“…Westley (1993) found experimentally induced failure of sexual reproduction can increase allocation to asexual reproduction under common garden conditions. Hartemink et al (2004) investigated the response to continuous removal of either flower buds or rosette buds in three perennial grassland species, Hypochaeris radicata, Succisa pratensis and Centaurea jacea. In a garden experiment, they distinguished two possible responses: compensation for lost buds by making more buds of the same type, and switching towards development of other life history functions, but bud removal had significantly different effects in each of the three species.…”