Floral trait variation across individual plants within a population enhances defense capability to nectar robbing

Floral trait variation may help pollinators and nectar robbers identify their target plants and,thus,lead to differential selection pressure for defense capability against floral antagonists.However,the effect of floral trait variation among individuals within a population on multi-dimensional plant-animal interactions has been little explored.We investigated floral trait variation,pollination,and nectar robbing among individual plants in a population of the bumble bee-pollinated plant,Caryopteris divaricata,from which flowers are also robbed by bumble bees with varying intensity across individuals.We measured the variation in corolla tube length,nectar volume and sugar concentration among individual plants,and evaluated whether the variation were recognized by pollinators and robbers.We investigated the in-fluence of nectar robbing on legitimate visitation and seed production per fruit.We found that the primary nectar robber(Bombus nobilis)preferred to forage on plants with long-tubed flowers,which produced less nectar and had lower sugar concentration compared to those with shorter corolla tubes.Individuals with shorter corolla tubes had comparatively lower nectar robbing intensity but higher visitation by legitimate visitors(mainly B.picipes)and higher seed production.Nectar robbing signifi-cantly reduced seed production because it decreased pollinator visits.However,neither pollination nor seed production differed between plants with long and short corolla tubes when nectar robbers were excluded.This finding suggests that floral trait variation might not be driven by pollinators.Such variation among individual plants thus allows legitimate visitors and nectar robbers to segregate niches and enhances population defense against nectar robbing in unpredictable conditions.

Pollen analysis reveals the effects of uncovered interactions,pollen-carrying structures,and pollinator sex on the structure of wild bee-plant networks

Pollination networks are increasingly used to model the complexity of interactions between pollinators and flowering plants in communities.Different methods exist to sample these interactions,with direct observations of plant-pollinator contacts in the field being by far the most common.Although the identification of pollen carried by pollinators allows uncovering interactions and increasing sample sizes,the methods used to build pollen-transport networks are variable and their effect on network structure remains unclear.To understand how interaction sampling influences the structure of networks,we analyzed the pollen found on wild bees from eight communities across Mallorca Island and investigated the differences in pollen loads between bee body parts(scopa vs.body)and sexes.We then assessed how these differences,as well as the uncovered interactions not detected in the field,influenced the structure of wild bee-plant networks.We identified a higher quantity and diversity of pollen in the scopa than in the rest of the female body,but these differences did not lead to differences in structure between plant-pollination(excluding scopa pollen)and bee-feeding interaction(including scopa pollen)networks.However,networks built with pollen data were richer in plant species and interactions and showed lower modularity and specialization(H2'),and higher nestedness than visitation networks based on field observations.Female interactions with plants were stronger compared to those of males,although not richer.Accordingly,females were more generalist(low d')and tended to be more central in interaction networks,indicating their more key role structuring pollination networks in comparison to males.Our study highlights the importance of palynological data to increase the resolution of networks,as well as to understand important ecological questions such as the differences between plant-pollination and bee-feeding interaction networks,and the role of sexes in pollination.

Nestling sex ratio is unaffected by individual and population traits in the griffon vulture

Variation in offspring sex ratios is a central topic in animal demography and population dynamics.Most studies have focused on bird species with marked sexual dimorphism and multiple-nestling broods,where the offspring sex ratio is often biased due to different individual or environmental variables.However,biases in offspring sex ratios have been far less investigated in monomorphic and single-egg laying species,and few studies have evaluated long-term and large-scale variations in the sex ratio of nestling vultures.Here,we explore individual and environmental factors potentially affecting the secondary sex ratio of the monomorphic griffon vulture Gyps fulvus.We used information collected at three breeding nuclei from central Spain over a 30-year period(1990–2020)to analyse the effects of nestling age,parental age,breeding phenology,conspecific density,population reproductive parameters,and spatial and temporal variability on nestling sex.Sex ratio did not differ from parity either at the population or the nuclei level.No significant between-year differences were detected,even under highly changing conditions of food availability associated with the mad-cow crisis.We found that tree nesting breeders tend to have more sons than daughters,but as this nesting behavior is rare and we consequently have a small sample size,this issue would require additional examination.Whereas further research is needed to assess the potential effect of breeder identity on nestling sex ratio,this study contributes to understanding the basic ecology and population dynamics of Griffon Vultures,a long-lived species with deferred maturity and low fecundity,whose minor deviations in the offspring sex ratio might imply major changes at the population level.

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.

Contrasting size-dependent life history strategies of an insular lizard

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.

Altitudinal variation in the reproductive performance of the Mediterranean shrub Rhamnus lycioides L.

Aims Rhamnus lycioides L.subsp.Oleoides(Rhamnaceae)is a perennial shrub native to the Mediterranean Basin distributed along an altitudinal gradient,from sea level up to 1000 m a.s.l.The specific goals of our study were(i)to compare plant morphology between two contrasting populations,(ii)to determine the reproductive system of R.lycioides,quantifying the relative importance of insects and wind as pollen vectors,(iii)to test if pollen limitation differs between populations,(iv)to study the main factors influencing fruit set and(v)to compare plant reproductive performance(mass allocation to flowers,fruits and seeds)between the two habitats.Methods In the present study,we examined plant morphology and the reproductive performance of R.lycioides L.in contrasting environments in two populations located at the extremes of its altitudinal range in the island of Mallorca(Balearic Islands,Western Mediterranean Basin)along a 3-year period.Plant morphology,the relative importance of insects and wind as pollen vectors,the pollen limitation to seed production and the plant reproductive performance(mass allocation to flowers,fruits and seeds)were determined.Important Findings Rhamnus lycioides individuals showed a higher plant surface/plant height ratio at the mountain than at the coast.This species appeared to be ambophilous despite its inconspicuous flowers,although the relative importance of wind as a pollination vector was higher at the mountain than at the coastal site.Fruit set was much higher at the mountain,where pollen appeared to be a limiting factor.By contrast,fruit set was not limited by pollen availability at the coastal population,where resource(water and nutrients)limitation seemed to be more determining.Flower size was greater at the coast,in contrast to fresh fruit weight that was higher at the mountain.Despite the relatively few differences between sites in precipitation patterns along the study period,water availability appeared to be the key factor explaining not only fruit set but also the reproductive performance of this species in the study populations.

Functional responses of cougars(Puma concolor)in a multiple prey-species system

The study of predator-prey interactions is commonly analyzed using functional responses to gain an understanding of predation patterns and the impact they have on prey populations.Despite this,little is known about predator-prey systems with multiple prey species in sites near the equator.Here we studied the functional response of cougars(Puma concolor)in relation to their main prey,armadillo(Dasypus novemcinctus),coati(Nasua narica)and white-tailed deer(Odocoileus virginianus).Between 2004 and 2010,cougar scats were collected along 5 transects to estimate the consumption of different prey species.A relative abundance index(RAI)was calculated for each prey species and cougar using 18 camera traps.We compared Holling type I,II and III functional response models to determine patterns in prey consumption based on the relative abundance and biomass of each prey species consumed.The 3 main prey species comprised 55%(armadillo),17%(coati)and 8%(white-tailed deer)of the diet.Type I and II functional responses described consumption of the 2 most common prey species armadillos and coati similarly well,while a type I response best characterized consumption of white-tailed deer.A negative correlation between the proportions of armadillo versus coati and white-tailed deer biomass in cougar scats suggests switching to consume alternative prey,confirming high foraging plasticity of this carnivore.This work represents one of the few studies to compare functional responses across multiple prey species,combined with evidence for prey-switching at low densities of preferred prey.

Climate warming induced a stretch of the breeding season and an increase of second clutches in a passerine breeding at its altitudinal limits

The increase in the average air temperature due to global warming has produced an early onset of the reproduction in many migratory birds of the Paleartic region.According to the“mismatch hypothesis”this response can lead to a decrease in the breeding output when the conditions that trigger the departure from the wintering areas do not match the availability of food resources in the breeding ground.We used 653 brooding events registered during the period 1991–2013 to investigate the link between climatic variables and individual breeding performance of a partially migratory passerine,the Rock Sparrow Petronia petronia,breeding at the altitude limit of its distribution.The laying date(LD)of the earliest first clutch was associated with local spring(minimum)temperatures but did not show a significant trend during the period considered.The LD of the latest first clutch had a positive and statistically significant trend,unrelated to local covariates and resulting in a longer breeding season(1.5 days/year).A longer breeding season allowed birds to produce more second clutches,which proportion increased from 0.14 to 0.25.The average breeding success was also positively correlated with the average temperature in July and with the duration of the breeding season.Contrary to expectations,the most important climate-dependent effect was a stretch of the breeding season due to a significant increase of the LD of the latest first-clutches rather than an earlier breeding onset.We show how climate changes act on bird populations through multiple paths and stress the need to assess the link between climatic variables and several aspects of the breeding cycle.

Does a giant tortoise taxon substitute enhance seed germination of exotic fleshy-fruited plants?

Aims The use of exotic species as taxon substitutes to restore lost ecological interactions is currently hotly debated.Aldabrachelys gigantea giant tortoises have recently been introduced to three islands in the Mascarene archipelago(Ile aux Aigrettes,Round Island and Rodrigues)to resurrect herbivory and seed dispersal functions once performed by extinct giant tortoises.However,potential unintended impacts by frugivore substitutes on native ecosystems,e.g.whether they will facilitate the germination of exotic plant species,are largely unknown.We investigated whether A.gigantea introduced to Rodrigues in 2006 could enhance the germination percentage of four widespread fleshy-fruited exotic species on the island.Using germination trials to forecast unintended impacts that could arise from the introduction of a frugivorous taxon substitute enables conservation managers to limit potential adverse negative interactions before they occur.Methods In germination trials that ran over 4 months,we investigated the effects of ingestion(gut passage and deposition in faeces)by subadult and adult A.gigantea on the germination percentage of four exotic fleshy-fruited plant species introduced to Rodrigues.We fed fruits of these plant species to sub-adult and adult A.gigantea to test how variation in age and size of the frugivore would affect seed germination.Feeding of distinctly coloured plastic pellets together with the fruits allowed us to test for individual tortoise effects on seed germination.Important Findings Ingestion by A.gigantea increased the percentage of seeds germinating of Mimusops coriacea and Lantana camara,but not percentage of germination of Veitchia merrillii or Wikstroemia indica.Seeds were more likely to germinate following ingestion by sub-adult rather than adult tortoises,which may be a consequence of the shorter gut passage time observed for sub-adults.Our results demonstrate that introduced frugivorous taxon substitutes could facilitate germination of exotic and invasive plants and highlight the need for conservation managers to weigh the risk of taxon substitutes potentially facilitating the germination and recruitment of exotic fleshy-fruited plants against the benefit of restoring lost seed dispersal functions of threatened indigenous plants.Our findings also highlight the importance of considering age and size variation in frugivores,in particular in long-lived taxa such as giant tortoises,when studying ingestion effects on the germination performance of plants.

Galápagos land iguana(Conolophus subcristatus)as a seed disperser

The role of the most common land iguana(Conolophus subcristatus)in the Galápagos Islands as an effective seed disperser is explored in this study.A total of 5705 seeds of 32 plant species were identified from 160 scats,4545 of which(80%)appeared visually undamaged.Germination trials of 849 seeds from 29 species revealed that at least 10 species remained viable after passing through the iguana’s gut,although only a small propor­tion of those seeds(4%)germinated.In any case,we argue that C.subcristatus exerts an important role on the 7 Galapagos islands where it occurs because of its abundance and capacity to ingest and disperse seeds at long distances.Our results strongly suggest that the Galápagos C.subcristatus plays an important role as a seed dis­perser of not only of native species but also some introduced plants in the Galápagos Islands.

Subpicosecond pulses in a self-starting mode-locked semiconductor-based figure-of-eight fiber laser

We have experimentally studied the mode-locking dynamics of a polarization-maintaining figure-of-eight laser which has a semiconductor optical amplifier as gain medium. Self-starting mode-locking at the fundamental repetition rate of 18 MHz is obtained at the lasing threshold, and further increasing the bias current leads to the progressive emission of additional optical pulses in each round trip and eventually to mode-locked emission at increasingly high harmonics of the fundamental repetition rate, up to 2.45 GHz. The intensity autocorrelation of the amplified mode-locked pulses has a full width at half-maximum duration of 382 fs, which corresponds to a pulse duration of 247 fs.

Sex steroids of black scabbardfish,Aphanopus carbo,in relation to reproductive and migratory dynamics

Black scabbardfish,Aphanopus carbo,is a commercially important species that takes distant migrations throughout its life cycle.Sex steroids were measured by radioimmunoassay in the blood plasma of specimens caught off the Madeira Archipelago and mainland Portugal to link this species migratory path with its reproductive cycle.Furthermore,a pilot study using Mozambique tilapia(Oreochromis mossambicus)was designed to evaluate the effect of sample freshness on steroid levels because black scabbardfish blood was collected at separate times after specimens were caught.The changes in T and 11-KT concentrations between the time of blood extraction and the time after preservation did not statistically differ among the different methods applied.Therefore,measured black scabbardfish steroid concentrations were directly used in the subsequent data analyses.In females,E2 and in T concentrations peaked at a late stage of vitellogenesis.E2 concentration was significantly different between females caught off each area.Clustering E2 and T concentrations from all developing females resulted in the separation of two distinct groups,independently of their geographical area.In males,T and 11-KT were not significantly different between maturity stages.The hepatosomatic index of males caught off mainland Portugal was relatively high.This may reflect a mechanism for storing energy that will later be consumed during migration to the spawning grounds.The trend of sex steroids concentrations throughout the sexual maturation of the species is consistent with the morphological indicators and shows evidence of the reproductive and migratory pattern hypothesised for the black scabbardfish in NE Atlantic.