Despite it is widely accepted that intrapopulation variation is fundamental to ecological and evolutionary processes,this level of information has only recently been included into network analysis of species/populatio...Despite it is widely accepted that intrapopulation variation is fundamental to ecological and evolutionary processes,this level of information has only recently been included into network analysis of species/population interactions.When done,it has revealed non-random patterns in the distribution of trophic resources.Nestedness in resource use among individuals is the most recurrent observed pattern,often accompanied by an absence of modularity,but no previous studies examine bipartite modularity.We use network analysis to describe the diet composition of the Balearic endemic lizard Podarcis lilfordi in 2 islets at population and individual levels,based on the occurrence of food items in fecal samples.Our objectives are to 1)compare niche structure at both levels,2)characterize niche partition using nestedness and modularity,and 3)assess how size,sex,season,and spatial location influence niche structure.At population-level niche width was wide,but narrow at the level of the individual.Both islet networks were nested,indicating similar ranking of the food preferences among individuals,but also modular,which was partially explained by seasonality.Sex and body size did not notably affect diet composition.Large niche overlap and therefore possibly relaxed competition were observed among females in one of the islets and during spring on both islets.Likewise,higher modularity in autumn suggests that higher competition could lead to specialization in both populations,because resources are usually scarce in this season.The absence of spatial location influence on niche might respond to fine-grained spatio-temporally distribution of food resources.Behavioral traits,not included in this study,could also influence resource partitioning.展开更多
In many species with continuous growth,body size is an important driver of life-history tactics and its relative importance is thought to reflect the spatio-temporal variability of selective pressures.We developed a d...In many species with continuous growth,body size is an important driver of life-history tactics and its relative importance is thought to reflect the spatio-temporal variability of selective pressures.We developed a deterministic size-dependent integral projection model for 3 insular neighboring lizard populations with contrasting adult body sizes to investigate how size-related selective pressures can influence lizard life-history tactics.For each population,we broke down differences in population growth rates into contributions from size-dependent body growth,survival,and feeundity.A life table response experiment(LTRE)was used to compare the population dynamics of the 3 populations and quantify the contributions of intrinsic demographic coefficients of each population to the population growth rate(z).Perturbation analyses revealed that the largest adults contributed the most to the population growth rate,but this was not true in the population with the smallest adults and size-independent fertility.Although we were not able to identify a single factor responsible for this difference,the combination of the demographic model on a continuous trait coupled with an LTRE analysis revealed how individuals from sister populations of the same species follow different life strategies and showed different compensatory mechanisms among survival,individual body growth,and fertility.Our results indicate that body size can play a contrasting role even in closely-related and closely-spaced populations.展开更多
基金This work is framed within projects CGL2017-88122-P and BFU 2009-09359 financed by the Spanish Government.
文摘Despite it is widely accepted that intrapopulation variation is fundamental to ecological and evolutionary processes,this level of information has only recently been included into network analysis of species/population interactions.When done,it has revealed non-random patterns in the distribution of trophic resources.Nestedness in resource use among individuals is the most recurrent observed pattern,often accompanied by an absence of modularity,but no previous studies examine bipartite modularity.We use network analysis to describe the diet composition of the Balearic endemic lizard Podarcis lilfordi in 2 islets at population and individual levels,based on the occurrence of food items in fecal samples.Our objectives are to 1)compare niche structure at both levels,2)characterize niche partition using nestedness and modularity,and 3)assess how size,sex,season,and spatial location influence niche structure.At population-level niche width was wide,but narrow at the level of the individual.Both islet networks were nested,indicating similar ranking of the food preferences among individuals,but also modular,which was partially explained by seasonality.Sex and body size did not notably affect diet composition.Large niche overlap and therefore possibly relaxed competition were observed among females in one of the islets and during spring on both islets.Likewise,higher modularity in autumn suggests that higher competition could lead to specialization in both populations,because resources are usually scarce in this season.The absence of spatial location influence on niche might respond to fine-grained spatio-temporally distribution of food resources.Behavioral traits,not included in this study,could also influence resource partitioning.
基金A.R.was supported by JAE fellowship(JAEPreO31,Spanish National Research Council(CSIC)-Spanish Minister for Science,Innovation and Universities)The research was partially financed by the Spanish Minister for Science,Innovation and Universities(project number BFU2009-09359).
文摘In many species with continuous growth,body size is an important driver of life-history tactics and its relative importance is thought to reflect the spatio-temporal variability of selective pressures.We developed a deterministic size-dependent integral projection model for 3 insular neighboring lizard populations with contrasting adult body sizes to investigate how size-related selective pressures can influence lizard life-history tactics.For each population,we broke down differences in population growth rates into contributions from size-dependent body growth,survival,and feeundity.A life table response experiment(LTRE)was used to compare the population dynamics of the 3 populations and quantify the contributions of intrinsic demographic coefficients of each population to the population growth rate(z).Perturbation analyses revealed that the largest adults contributed the most to the population growth rate,but this was not true in the population with the smallest adults and size-independent fertility.Although we were not able to identify a single factor responsible for this difference,the combination of the demographic model on a continuous trait coupled with an LTRE analysis revealed how individuals from sister populations of the same species follow different life strategies and showed different compensatory mechanisms among survival,individual body growth,and fertility.Our results indicate that body size can play a contrasting role even in closely-related and closely-spaced populations.
