Fire-mediated disruptive selection can explain the reseeder–resprouter dichotomy in Mediterranean-type vegetation

Abstract

life histories, with few intermediate forms, despite the fact that the transition between strategies is evolutionarily labile. How did this strong dichotomy evolve? We address this question by developing a stochastic demographic model to assess determinants of relative fitness of reseeders, resprouters and hypothetical intermediate forms. The model was parameterised using published demographic data from South African protea species and run over various relevant fire regime parameters facets. At intermediate fire return intervals, trade-offs between investment in growth versus fire resilience can cause fitness to peak at either of the extremes of the reseeder-resprouter continuum, especially when assuming realistic non-linear shapes for these trade-offs. Under these circumstances, the fitness landscape exhibits a saddle which could lead to disruptive selection. The fitness gradient between the peaks was shallow, which may explain why this life-history trait is phylogenetically labile. Resprouters had maximum fitness at shorter fire-return intervals than reseeders. The model suggests that a strong dichotomy in fire survival strategy depends on a non-linear trade-off between growth and fire persistence traits.

Future of African terrestrial biodiversity and ecosystems under anthropogenic climate change

“…Increasing temperatures and drought could advance this threshold, as well as leading to larger fires due to greater realized fuel continuity 85 . Niche-based models indicate substantial risk of range losses by largely endemic species in Mediterranean-climate shrublands 86 , but these do not take account of potential increases in fire frequency that would exacerbate climate-driven range losses in slower-maturing species that are killed by fire and regenerate from seed banks 87 . The position of Mediterranean-type ecosystems at the southern tip of Africa strongly limits potential for species migration with a warming and drying climate, exacerbating extinction risk.…”

Fire and life history affect the distribution of plant species in a biodiversity hotspot

“…The importance of fire as a determinant of fynbos distributions was more apparent among seeder species than resprouters, confirming the variation in sensitivity of resprouters and seeders to fire regimes cited by other studies (Bond & Midgley, ; Enright et al, ; Keith et al, ; Wilson et al, ). Seeder species are highly dependent on the timing and frequency of fire (Altwegg et al, ; Pausas & Keeley, ). Most seeders require fires to release seed and/or germinate and depend on fire‐free intervals long enough for individuals to establish and mature, but not so long that they begin to senesce (Pratt et al, ).…”

“…Although our study only focuses on fire return interval, we do acknowledge the ecological importance of other components of the fire regime in driving plant species distributions in fire‐prone ecosystems. For example, Altwegg et al () highlight the differential effects of fire seasonality and fire intensity on resprouters and seeders that result in the dominance of one life history over the other in a given space. In their study, Altwegg et al () predict resprouters to have greater resilience against out of season fires, or fires followed by unfavourable conditions for establishment (e.g., unpredictable rainfall), while high‐intensity fires are predicted to favour seeder species.…”

“…Fire destroys above ground biomass, exterminating species that cannot resprout or do not have a strategy for regenerating from seed (Altwegg et al, ; Bond & Midgley, )…”

Production and Nutrient Content of Two Shrub Species Related to Fire in Central Idaho

“…Sprouting species in this region commonly include Physocarpus malvaceus (Greene) Kuntze and Symphoricarpos albus (L.) Blake, which likely originated in regions of higher disturbance where adaptation was influenced by more frequent fires (Pausas 2001, Altwegg et al 2015. Physocarpus spp.…”