scholarly journals Variation in life history traits of the Sahara frog (Pelophylax saharicus) with elevation and predation in northeast Algeria

2021 ◽  
pp. 8-14
Author(s):  
Soufyane Bensouilah ◽  
Amel Lazli ◽  
Zinette Bensakhri ◽  
Rabah Zebsa ◽  
Hichem Amari ◽  
...  
Keyword(s):  
Body Weight ◽  
Life History ◽  
Life History Theory ◽  
High Elevation ◽  
North African ◽  
Stressful Environment ◽  
The North ◽  
Adaptive Mechanisms ◽  
Dry Conditions ◽  
Different Populations

Ectotherms respond quickly to environmental change and thus are prone to show adaptive mechanisms across a gradient of environmental conditions. Frogs in particular have been widely used in experimental ecology to test life history theory and plasticity across gradients. However, little has been carried out on the North African Sahara frog (Pelophylax saharicus) which experiences a particularly stressful environment characterized by warm and dry conditions. In this study, we documented the adaptation of P. saharicus life history across elevation in northeast Algeria using six different populations spanning across a range of 5–1000 m. Based on snout-vent length (SVL) and body weight, we estimated the growth rate of tadpoles of each population in two predation treatments (presence and absence of Anax sp. dragonfly chemical cue). We found that the fastest-growing population was that at low elevation, followed by intermediate elevations and high elevation. Predation affected only low-elevation populations, increasing the rate of growth in body weight but not in SVL. Our results indicate that P. saharicus has adapted its life history to different conditions across elevation, suggesting low gene flow between low- and high-elevation populations.

Estimation of natural mortality in two demersal squat lobster species off Chile

2019 ◽  
Vol 99 (7) ◽  
pp. 1639-1650
Author(s):  
T. Mariella Canales ◽  
Rodrigo Wiff ◽  
Juan Carlos Quiroz ◽  
Dante Queirolo
Keyword(s):  
Life History ◽  
Indirect Method ◽  
Life History Theory ◽  
Stock Assessment ◽  
Total Mortality ◽  
Theoretical Background ◽  
High Variability ◽  
Natural Mortality ◽  
Squat Lobster ◽  
The North

AbstractNatural mortality (M) is a key parameter for understanding population dynamics, especially in relation to harvested populations. Direct observations of M in crustaceans are scarce, due to the moulting process. Indirect methods to estimate M with easier-to-obtain life history attributes are therefore used routinely. Given their theoretical background, we reviewed the applicability of these methods for crustaceans. We applied the selected methods to two crustacean species harvested in Chilean waters: the yellow squat lobster (Cervimunida johni) and red squat lobster (Pleuroncodes monodon). Uncertainty of each M estimate was incorporated in the life history parameters that input into the indirect method (trait-error) and parameters defining the indirect method (coefficient-trait-error). Methods based on the relationship between total mortality and maximum age, or with different ages and based on life history theory were the most appropriate for crustaceans since they apply across taxa. M estimates showed high variability between species, sexes and areas. Estimations of M for C. johni varied from 0.13 to 0.28 (year−1) for males and 0.17 to 0.51 (year−1) for females. For P. monodon values for the north varied from 0.26 to 0.37 (year−1) for males and 0.24 to 0.45 (year−1) for females. In the south, values of M were higher for both males (0.43–0.68 year−1) and females (0.41–1.06 year−1). High variability in the M estimates was associated with the method and number of parameters, their uncertainty, theoretical background and probability distribution. M estimates are not comparable, raising the need to propagate the uncertainty of M into the stock assessment of Chilean squat lobsters.

The influence of food resources on life history in Columbian ground squirrels

1985 ◽  
Vol 63 (9) ◽  
pp. 2105-2109 ◽  
Author(s):  
F. Stephen Dobson ◽  
Julia D. Kjelgaard
Keyword(s):  
Body Weight ◽  
Life History ◽  
Litter Size ◽  
Life History Theory ◽  
Experimental Manipulation ◽  
Food Resources ◽  
Ground Squirrels ◽  
Life History Characteristics ◽  
Columbian Ground Squirrels ◽  
Two Populations

Life history characteristics were studied experimentally in Columbian ground squirrels (Spermophilus columbianus) at two elevations in the Rocky Mountains of southwestern Alberta, Canada, from 1981 to 1984. In two populations with supplemented food resources, survival of young increased, age at maturity of females decreased, litter size increased, and spring body weight increased in comparison with an initial unmanipulated period and with two populations monitored for reference. For individual ground squirrels, litter size and spring body weight increased under supplementation. Thus, life history characteristics exhibited phenotypically plastic responses to experimental manipulation of food resources. Life history patterns changed among natural ground squirrel populations at different elevations and these changes were likely due to changes in food resources. A general prediction of life history theory that reproductive effort should be highest in years favorable for juvenile survivorship was supported by the experimental results. The results did not support predictions from interspecific studies of changes in life history characteristics that scale to body weight.

Life History Variations of Anadromous Cisco (Coregonus artedii), Lake Whitefish (C. clupeaformis), and Round Whitefish (Prosopium cylindraceum) Populations of Eastern James–Hudson Bay

1982 ◽  
Vol 39 (7) ◽  
pp. 958-967 ◽  
Author(s):  
Roderick Morin ◽  
Julian J. Dodson ◽  
Geoffrey Power
Keyword(s):  
Life History ◽  
North American ◽  
Life History Theory ◽  
Life History Traits ◽  
Reproductive Effort ◽  
Hudson Bay ◽  
Lake Whitefish ◽  
The North ◽  
Interspecific Differences ◽  
Coregonus Artedii

Differences in life history among three species of anadromous coregonines from La Grande River, James Bay, were significant with lake whitefish (Coregonus clupeaformis) and round whitefish (Prosopium cylindraceum) displaying reproductive patterns more typical of harsh northern environments and characteristic of "K-selection," relative to cisco (Coregonus artedii). Interspecific differences at La Grande River were more apparent than intraspecific differences in life history traits of cisco and lake whitefish over the James–Hudson Bay range. Although cisco exhibit decreasing reproductive effort independent of growth over the North American range, thus conforming to life history theory, both growth and reproductive effort are reduced northwards over their James–Hudson Bay range. The observations suggest that physiological constraints related to the shorter growing season at the northern limit of cisco's coastal Hudson Bay range may overwhelm expected coadapted life history traits. Lake whitefish exhibit reduced reproductive effort independent of variations in growth northwards over their North American and James–Hudson Bay coastal range; this suggests coadaptation of life history traits that permit survival at northern sites.Key words: reproduction, growth, life history theory, anadromous coregonines, James–Hudson Bay

Interrelationships of factors of social development are more complex than Life History Theory predicts

2019 ◽  
Vol 42 ◽  
Author(s):  
Boris Kotchoubey
Keyword(s):  
Life History ◽  
Social Development ◽  
Life History Theory ◽  
Strong Correlations ◽  
Behavioral Features

Abstract Life History Theory (LHT) predicts a monotonous relationship between affluence and the rate of innovations and strong correlations within a cluster of behavioral features. Although both predictions can be true in specific cases, they are incorrect in general. Therefore, the author's explanations may be right, but they do not prove LHT and cannot be generalized to other apparently similar processes.

Skeletochronology and mark–recapture assessments of growth in the North African agamid lizard (Agama impalearis)

1999 ◽  
Vol 249 (4) ◽  
pp. 455-461
Author(s):  
El Hassan El Mouden ◽  
Mohammed Znari ◽  
Richard P. Brown
Keyword(s):  
North African ◽  
Mark Recapture ◽  
Agamid Lizard ◽  
The North

scholarly journals Five reasons COVID-19 is less severe in younger age groups

2020 ◽  
Author(s):  
Paul W Turke
Keyword(s):  
Life History ◽  
Life History Theory ◽  
Age Of Onset ◽  
Age Groups ◽  
Medical Community ◽  
System Function ◽  
The Third ◽  
Immune System Function ◽  
Age Related ◽  
Younger Age

Abstract The severity of COVID-19 is age-related, with the advantage going to younger age groups. Five reasons are presented. The first two are well-known, are being actively researched by the broader medical community, and therefore are discussed only briefly here. The third, fourth, and fifth reasons derive from evolutionary life history theory, and potentially fill gaps in current understanding of why and how young and old age groups respond differently to infection with SARS-CoV-2. Age of onset of generalized somatic aging, and the timing of its progression, are identified as important causes of these disparities, as are specific antagonistic pleiotropic tradeoffs in immune system function.

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