Effects of Reproductive Mode on Demography and Life History in Arabis fecunda (Brassicaceae)

Lesica, Peter; Shelly, J. Stephen.

doi:10.2307/2445615

Cited by 28 publications

(35 citation statements)

References 22 publications

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“…However, because the root stock diameter, and thus the stored photosynthate in roots and rosette leaves, is greater for naturally browsed plants, recovery of lost tissue may be easier for those plants. There is a tradeoff between allocating resources to growth or reproduction (Biere 1995;Lesica and Shelly 1995;Reekie 1997) and our results indicate that clipped and naturally browsed plants are allocating resources towards the production of biomass in lieu of seeds. Despite their larger size, fruit and seed production of naturally browsed plants seed did not exceed that of control plants.…”

Section: Discussionmentioning

confidence: 72%

Flowering phenology and compensation for herbivory in Ipomopsis aggregata

2003

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The mechanisms and circumstances that affect a plant's ability to tolerate herbivory are subjects of ongoing interest and investigation. Phenological differences, and the timing of flowering with respect to pollinators and pre-dispersal seed predators, may provide one mechanism underlying variable responses of plants to herbivore damage. The subalpine wildflower, Ipomopsis aggregata, grows across a wide range of elevations and, because phenology varies with elevation, phenological delays associated with elevation may affect the ability of I. aggregata to compensate for or tolerate browsing. Thus, we examined the response of I. aggregata to herbivory across an elevation gradient and addressed the interactions among phenological delays imposed by damage, elevation, pre-dispersal seed predation and pollination, on I. aggregata's compensatory response. Among high and low elevation populations in areas near the Rocky Mountain Biological Laboratory (RMBL) in Gothic, Colorado, we compared the responses of naturally browsed, artificially browsed (clipped), and unbrowsed (control) plants of I. aggregata. We compared responses in the date of initiation of flowering, timing of peak bloom, floral display, nectar production and sugar concentration, oviposition and fruit destruction by the pre-dispersal seed predator Hylemya sp. (Anthomyiidae), fruit production, and aboveground biomass production. Clipping had the greatest effect on reproductive success and clipped plants at high elevation exhibited the lowest tolerance for herbivory. The effects of browsing appear to be mediated by flowering phenology, and both browsing and elevation delayed flowering phenology. Time needed for regrowth delays flowering, and thus affects the overlap with seed predators and pollinators. As a result of delayed flowering, naturally browsed and clipped plants incurred lower rates of seed predation. In the absence of seed predation, plants would exhibit a lower tolerance to herbivory since naturally and artificially browsed plants had fewer fruits destroyed by Hylemya larvae. We provide additional evidence that, for populations near the RMBL, clipping and natural browsing do not have the same effect on I. aggregata plants. This may be due to the selection of larger plants by herbivores. Although under some conditions plants may tolerate browsing, in areas where the growing season is short a phenological delay imposed by damage is likely to significantly reduce plant fitness. Identifying the mechanisms that allow plants to tolerate herbivore damage will help to develop a general framework for understanding the role of tolerance in plant population and community dynamics, as well as plant-herbivore interactions.

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Section: Discussionmentioning

confidence: 72%

Flowering phenology and compensation for herbivory in Ipomopsis aggregata

2003

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“…According to the classification of Grime (1979), Sarcocapnos species should be considered an S type of strategy, adapted to live in habitats of scarce or nil perturbation but highly tolerant to the stresses resulting from developing in cracks where the substrate, water, and nutrients are severely limited. Life-history theory predicts that environments where adult mortality is high and (or) highly variable encourage early maturation and high initial fecundity (Wilbur et al 1974;Young 1981;Stearns 1992), leading to shorter generation times and faster population growth rates (Lesica and Shelly 1995). However, characteristics of S. enneaphylla, such as a short life-span, early sexual maturity, and high seedling production, are found in species with a predominantly r-type strategy (Hutchings 1989), that is, species that are adapted to environments with a certain degree of periodic perturbation.…”

Section: Discussionmentioning

confidence: 99%

“…The matrix projections assume fixed transition probabilities between population stages through time (Menges 1990). In addition, this assumes density-independent population growth and, thus, does not accurately project the long-term population future (Lesica and Shelly 1995). Nevertheless, this approach can be used to summarize short-term population dynamics and to compare the dynamics of different populations (Caswell 1989).…”

Section: Population Dynamicsmentioning

confidence: 99%

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Demographic structure of three species ofSarcocapnos(Fumariaceae) as a basis for their conservation

Salinas¹,

Suárez²,

Blanca³

2002

Can. J. Bot.

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The genus Sarcocapnos DC., endemic to the western Mediterranean basin, contains seven species, all of which are rare. Monthly monitoring of the number and flowering status of individuals as well as the appearance of new seedlings in five populations of three species, Sarcocapnos baetica (Boiss. & Reuter) Nyman, Sarcocapnos enneaphylla (L.) DC., and Sarcocapnos pulcherrima Morales & Romero-García, was conducted between July 1997 and June 1998. This monitoring was repeated in May 1999 and 2000. Given the difficulty in establishing the age of individuals, those that did not produce flowers in the study period were considered juveniles, and reproductive individuals that wilted for no apparent external cause were deemed senescent. Sarcocapnos enneaphylla has a short life-span, early sexual maturity, and high seedling production. This combination appears to be highly effective, because the species is widely distributed geographically with many populations. In contrast, S. pulcherrima and S. baetica have longer lifespans, delayed sexual maturity, and lower production of seedlings. The low recruitment rate in these two species is offset by a long life expectancy among reproductive individuals, although this strategy apparently limits their capacity for geographical expansion. The equilibrium growth rate (λ) varied markedly in S. enneaphylla populations (SE-1: λ = three species, an elasticity analysis of matrix projection models revealed that the elements with the greatest effect on population growth were those of reproductive plants remaining within the same reproductive class. In addition, in S. enneaphylla, seedlings had important weight for population growth. The fact that the reproductive stages are the most critical to population growth should be taken into account where protective or conservation action is required. exercent un poids important sur la croissance de la population. Le fait que les stades reproductifs sont les plus critiques pour la croissance de la population devrait être pris en compte là où des mesures de protection et de conservation sont nécessaires.

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“…Though few studies have gathered data over more than three years (for exceptions see Meagher 1982, Pinero et al 1984, Enright and Watson 1991, 1992, Waite and Hutchings 1991, Bengtsson 1993, Svensson et al 1993, Horvitz and Schemske 1995, Lesica and Shelly 1995, Oostermeijer et al 1996, those that did have typically revealed more temporal variation in vital rates than have studies of shorter duration (Enright and Watson 1991). Though few studies have gathered data over more than three years (for exceptions see Meagher 1982, Pinero et al 1984, Enright and Watson 1991, 1992, Waite and Hutchings 1991, Bengtsson 1993, Svensson et al 1993, Horvitz and Schemske 1995, Lesica and Shelly 1995, Oostermeijer et al 1996, those that did have typically revealed more temporal variation in vital rates than have studies of shorter duration (Enright and Watson 1991).…”

Section: Discussionmentioning

confidence: 99%

Looking Backwards: Assessing the Projections of a Transition Matrix Model

Bierzychudek

1999

Ecological Applications

109

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Analyses of population projection models are increasingly being used by conservation biologists and land managers to assess the health of sensitive species and to evaluate the likely effects of management strategies, harvesting, grazing, or other manipulations. Here I describe some of the limitations of this approach and illustrate how these limitations may affect its usefulness. I do this by comparing the results of such an analysis, performed in 1979 on two populations of a perennial plant, Arisaema triphyllum, with new information about the size and structure of these same populations gathered in 1994, 15 years later. While one population changed as the model projected it would, the other behaved quite differently from the projection. Instead of increasing in size, this population decreased between 1979 and 1994.Possible shortcomings in the data and in the model include: too few plants to provide accurate transition probabilities; too few years to capture accurately the complete range of year-to-year environmental variability; and the failure of the most commonly used form of the model to account for density-dependent vital rates. In addition, the asymptotic growth rates () these models yield may sometimes be irrelevant and even misleading if one's primary interest is in a population's short-term prospects for survival, as is often the case in studies of sensitive species. These shortcomings may apply to many studies involving the use of projection models, and they have important implications for the value of this approach in conservation biology and species management decisions.

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Effects of Reproductive Mode on Demography and Life History in Arabis fecunda (Brassicaceae)

Cited by 28 publications

References 22 publications

Flowering phenology and compensation for herbivory in Ipomopsis aggregata

Flowering phenology and compensation for herbivory in Ipomopsis aggregata

Demographic structure of three species ofSarcocapnos(Fumariaceae) as a basis for their conservation

Looking Backwards: Assessing the Projections of a Transition Matrix Model

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