Morphological traits of stem to indirect selection of resistance to lodging in Avena sativa L

Journal of Crop Science and Biotechnology - The runout of newly cultivated areas in the world without recurring to the deforestation, demand a necessity to improve yield to sustain a growth...     

Population viability and perturbation analyses to support recovery of imperilled Eastern Sand Darter (Ammocrypta pellucida)

Small‐bodied freshwater fishes are often understudied, with the result that data gaps create uncertainties that can complicate and constrain conservation strategies aimed at species recovery. Use of matrix models and perturbation population viability analyses (PVA) are ideally suited for use in studying the consequences of life‐history parameter variation and environmental stochasticity to better understand the fate of threatened small‐bodied fishes. We use data for Eastern Sand Darter (Ammocrypta pellucida) populations from the Thames River, Canada, to explore the consequences of life‐history uncertainties such as age at maturation, multiple clutch sizes and age‐specific fertility for population recovery in this species. Environmental stochasticity acting on all life‐history parameters was found to pose significant risks for the continued viability of lower Thames River populations, with significant chances of local extinction predicted under current conditions. The intrinsic rate of population increase was most sensitive to 0+ survival rates, clutch size and clutch number. As demonstrated here, population models can successfully provide a means of exploring the population dynamics of small‐bodied fishes and can inform managers of risks posed by factors acting on life‐history parameters to affect continued population viability. Management actions for Eastern Sand Darter should focus on strategies designed to ensure successful spawning and improvement of 0+ survival rates, through programmes aimed at the protection, enhancement or recovery of additional spawning and juvenile rearing habitats.     

Quantifying allowable harm in species at risk: application to the Laurentian black redhorse (Moxostoma duquesnei)

• 1. When a species is identified for conservation, often the only way to effect recovery is to reduce the harm imposed by stressors threatening the survival of the species. Ideally all threats would be removed; however, this is often not feasible or practical. Within this context, a demographic approach is presented to assess how much human‐induced harm could be allowed without impairing the persistence of the species. Harm is defined as a negative perturbation that can target one or more vital rates and life stages simultaneously.
• 2. Allowable harm, defined as a level of harm that will not jeopardize survival or recovery, will be a function of the vital rates affected by human actions, the sensitivity of population growth to changes in these vital rates (their elasticities), the population growth rate prevailing before harm occurs, and the set of demographic parameters considered safe for long‐term persistence. This life‐history based approach requires minimal data, can link demography with habitat‐explicit information, is flexible enough to encompass complex life histories, and follows a precautionary approach.
• 3. Quantification of allowable harm could be applied to any species at risk. This approach is introduced by applying it to a Canadian population of a freshwater fish, the black redhorse (Moxostoma duquesnei), demonstrating that in the absence of habitat constraints population dynamics of this species are most sensitive to the survival of young adults, but population fitness is particularly sensitive to the loss of habitat used by young‐of‐the‐year fish under current levels of habitat supply.

Copyright © 2009 John Wiley & Sons, Ltd.