Diet composition of the lizard P odarcis lilfordi (Lacertidae) on 2 small islands: an individualresource network approach

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.

Early dynamics in plant community trait responses to a novel, more extreme hydrological gradient

Aims For temperate regions such as Northern Europe,predicted climate change patterns include an increase in winter precipitation causing increased risk of flooding,whereas periods of droughts will become more frequent in summer.The aim of this study is to explore vari-ations in plant functional trait distributions along a hydrological gradient spanning from recurrent drought events to recurrent flood-ing-mimicking future precipitation patterns.Methods The experiment was conducted in a controlled grassland experi-ment over a period of 3 years.A novel and more extreme hydro-logical regime was achieved by manipulating the flow of a nearby stream thereby creating a continuous hydrological gradient from flooding during winter to drought during summer.Plant commu-nity responses were recorded along this hydrological gradient.Community-weighted trait distribution changes along the gradient were described using null models.Six functional traits were con-sidered:seed mass,leaf dry matter content(LDMC),leaf area,leaf thickness,specific leaf area(SLA)and height.Important findings Over time,responses in plant functional traits changed at the community level.Over the study period consistent changes occurred in the mean trait value of several traits.Communities in relatively dry plots became dominated by species with water-conserving life strategies,represented by high seed mass and thick leaves.In contrast,disturbance-resistant species(high leaf dry matter content)became dominant in flooded plots,indicating that persistence to flooding was the most important factor control-ling the functional structure in those communities.Furthermore,a high abundance of small-seeded species in flooded plots likely indicates higher frequency of species with higher dispersal ability through hydrochory.In conclusion,plant traits are useful for predicting responses to climate change,but abrupt and extreme climate event may cause unexpected responses because they have no analog to previously more stable conditions.We suggest that traits related to dispersal and resistance to disturbance are useful in describing responses to flooding and that these traits should be included in future inves-tigations of plant community responses to extreme hydrological events.