领燕■繁殖群体的集群觅食(英文)

集合点假说(Assembly-point hypothesis)认为动物局部地区聚群数量的增加有助于不同的繁殖地的个体聚集成群体,然后一起寻找食物斑块觅食,这种聚群有助于个体从集群觅食中获得利益。本文通过领燕■(Glareola pratincola)离开和回到繁殖地的先后顺序来验证以上假说。我们在29天的观察中,发现有4天该群中个体离开繁殖地的先后顺序不是随机分布的,尽管这种策略会随着环境条件而改变,但仍然表明领燕■的觅食群体在繁殖地就已经聚集形成了。食物资源(飞虫)的短暂性和波动性以及由繁殖地到觅食地的距离均与所验证的假说的假设相一致。

Invasive cichlids(Teleostei:Cichliformes)in the Amacuzac River,Mexico:Implications for the behavioral ecology of the native Mexican mojarra Amphilophus istlanus

The introduction of species is a leading cause of biodiversity loss and habitat alteration.Several species have invaded Mexican freshwater ecosystems,adversely affecting native fishes.Specifically,in the Amacuzac River of the Balsas Basin(Central Mexico),at least four non-native cichlids have been recorded:tilapia Oreochromis sp.,convict cichlid Amatitlania nigrofasciata,spotcheek cichlid Thorichthys maculipinnis,and green terror Andinoacara rivulatus.These species co-occur with the Mexican mojarra Amphilophus istlanus,the only native cichlid in the Basin.Invasive cichlids compete for resources such as shelter and food,and prey on offspring of the Mexican mojarra.In the presence of invasive cichlids,the costs and risks of foraging and finding available shelter increase for the native cichlid.Predation pressure from invasive cichlid fishes on the Mexican mojarra increases the time invested by parents in caring for offspring and their stress levels,potentially contributing to Mexican mojarra population declines.Here,we gathered the best evidence available to discuss some mechanisms and consequences of such co-occurrences in relation to reproductive behaviors,parental care,competition for resources,and dominance hierarchy,and how the four invasive cichlids have negatively affected the Mexican mojarra.

Coping with drought?Effects of extended drought conditions on soil invertebrate prey and diet selection by a fossorial amphisbaenian reptile

Arid climates are characterized by a summer drought period to which animals seem adapted.However,in some years,the drought can extend for unusually longer periods.Examining the effects of these current extreme weather events on biodiversity can help to understand the effects of climate change,as models predict an increase in drought severity.Here,we examined the effects of“unusual”extended drought on soil invertebrate prey availability and on diet composition(based on fecal contents)and diet selection of a fossorial amphisbaenian,the checkerboard worm lizard Trogonophis wiegmanni.Weather data show interannual variations in summer drought duration.The abundance and diversity of soil invertebrates in spring were high,and similar to those found in a“normal”early autumn,after some rain had ended with the summer drought.In contrast,in years with“unusual”extended drought,abundance,and diversity of soil invertebrates in early autumn were very low.Also,there were seasonal changes in amphisbaenians’diet;in autumn with drought,prey diversity,and niche breadth decreased with respect to spring and autumns after some rain had fallen.Amphisbaenians did not eat prey at random in any season,but made some changes in prey selection that may result from drought-related restrictions in prey availability.Finally,in spite that amphisbaenians showed some feeding flexibility,their body condition was lower in autumn than in spring,and much lower in autumn with drought.If extended drought became the norm in the future,amphisbaenians might suffer important negative effects for their health state.

Comparative analysis of two nonlethal methods for the study of the gut bacterial communities in wild lizards

Fecal samples or cloacal swabs are preferred over lethal dissections to study vertebrate gut microbiota for ethical reasons,but it remains unclear which nonlethal methods provide more accurate information about gut microbiota.We compared the bacterial communities of three gastrointestinal tract(GIT)segments,that is,stomach,small intestine(midgut),and rectum(hindgut)with the bacterial communities of the cloaca and feces in the mesquite lizard Sceloporus grammicus.The hindgut had the highest taxonomic and functional alpha diversity,followed by midgut and feces,whereas the stomach and cloaca showed the lowest diversities.The taxonomic assemblages of the GIT segments at the phylum level were strongly correlated with those retrieved from feces and cloacal swabs(rs>0.84 in all cases).The turnover ratio of Amplicon Sequence Variants(ASVs)between midgut and hindgut and the feces was lower than the ratio between these segments and the cloaca.More than half of the core-ASVs in the midgut(24 of 32)and hindgut(58 of 97)were also found in feces,while less than 5 were found in the cloaca.At the ASVs level,however,the structure of the bacterial communities of the midgut and hindgut were similar to those detected in feces and cloaca.Our findings suggest that fecal samples and cloacal swabs of spiny lizards provide a good approximation of the taxonomic assemblages and beta diversity of midgut and hindgut microbiota,while feces better represent the bacterial communities of the intestinal segments at a single nucleotide variation level than cloacal swabs.

Endophytes versus biotrophic and necrotrophic pathogens—are fungal lifestyles evolutionarily stable traits?

Endophytes infect living plant tissues without causing symptoms of disease.Indeed,many of them contribute to the resistance phenotype of their host.However,fungal endophytes are generally closely related to plant pathogens,fungi that either develop within living host tissue(biotrophic fungi)or that kill the host cells and then live in the dead tissue(necrotrophic fungi).We adopted a phylogenetic approach to investigate whether these strategies represent evolutionarily stable lifestyles and to elucidate their general phylogenetic relationships.We analysed 163 fungal strains for which we found information on the sequence of the 5.8S rRNA gene and the flanking internal transcribed spacer regions,the identity of the host plant and the concrete phenotypic outcome of the infection.A Maximum-Likelihood analysis combined with ancestral character mapping by maximum parsimony revealed that some fungal lineages had switched multiple times between a necrotrophic and an endophytic lifestyle.Ancestral character mapping indicated a minimum of four changes from an endophytic to a necrotrophic lifestyle,four changes in the opposite direction and eight changes among these lifestyles for which the direction could not be determined unambiguously.By contrast,biotrophs formed five clusters that did not contain necrotrophs or endophytes.Once biotrophy evolves there is apparently no regression to one of the other two lifestyles.We conclude that biotrophy usually represents a derived and evolutionarily stable trait,whereas fungi easily can switch between an endophytic and necrotrophic lifestyle at the evolutionary and even the ecological timescale.Future experimental studies should focus on the environmental or genetic changes that cause the rapid switches between these two phenotypically different lifestyles.

Extensive pollen immigration and no evidence of disrupted mating patterns or reproduction in a highly fragmented holm oak stand

Aims Forest fragmentation and reduced tree population densities can poten-tially have negative impacts on mating patterns,offspring genetic diversity and reproductive performance.the aim of the present study is to test these hypotheses comparing an extremely fragmented,low tree density(~0.02 trees/ha)holm oak(Quercus ilex l.)stand from Central spain with a nearby high tree density stand(~50 trees/ha).Methods We genotyped adult trees and seeds from the low-density stand(436 seeds from 15 families)and the high-density stand(404 seeds from 11 families)using nine microsatellite markers.With these data,we performed paternity analyses,determined pollen flow,mating patterns and pollen pool structure,and estimated progeny genetic diversity in both stands.We also studied seed set and production and performed a pollen supplementation experiment to determine whether reduced tree density has limited foreign pollen availability.Important Findings We have found extensive pollen immigration(>75%)into the low tree density stand and monte Carlo simulations revealed that pollen moves larger distances than expected from null models of random dispersal.mating patterns and differentiation of pollen pools were similar in the high-density stand and the low-density stand but we found higher inter-annual differentiation of pollen pools in the for-mer.Progeny genetic diversity and self-fertilization rates did not dif-fer between the low-density stand and the high-density stand.seed set rates were significantly lower in the low-density stand than in the high-density stand and experimental cross-pollen supplementation evidenced that foreign pollen availability is indeed a limiting factor in the former.However,seed crops did not differ between the low-density stand and the high-density stand,indicating that limitation of foreign pollen is not likely to be of great concern in terms of reduced seed production and potential recruitment.Poor forest regeneration due to other ecological and human factors is probably a more important threat for the persistence of fragmented and low tree density stands than reduced pollen flow and only extremely small and isolated tree populations would be expected to suffer severe loss of genetic diversity in the long term.

Relationships between soil pollution by heavy metals and melanin-dependent coloration of a fossorial amphisbaenian reptile

Melanin is the basis of coloration in many animals,and although it is often used in communication,thermoregulation,or camouflage,melanin has many other physiological functions.For example,in polluted habitats,melanin can have a detoxifying function.Melanic coloration would help to sequester in the skin the heavy metal contaminants from inside the body,which will be expelled to the exterior when the skin is sloughed.Moreover,animals should have evolved more melanic colorations in more polluted habitats(“industrial melanism”hypothesis).We examined whether the fossorial amphisbaenian reptile,Trogonophis wiegmanni,is able to eliminate heavy metals,derived from soil pollution by seagull depositions,through sloughing its skin.Our results suggest a covariation between levels of soil pollution by heavy metals and the concentration of heavy metals in the sloughed skins of amphisbaenians.This suggests that amphisbaenians may expel heavy metals from their bodies when they slough the skins.We also tested whether amphisbaenians inhabiting soils with higher levels of heavy metal pollution had darker(melanin-dependent)body colorations.However,contrary to predictions from the“industrial melanization”hypothesis,we found a negative relationship between soil pollution and proportions of melanic coloration.This contradictory result could,however,be explained because heavy metals have endocrine disruption effects that increase physiological stress,and higher stress levels could result in decreased melanogenesis.We suggest that although amphisbaenians might have some detoxifying mechanism linked to melanin in the skin,this process might be negatively affected by stress and result ineffective under conditions of high soil pollution.

Gourds and Tendrils of Cucurbitaceae: How Their Shape Diversity, Molecular and Morphological Novelties Evolved via Whole-Genome Duplications

Whole-genome duplications(WGDs)are regarded as important drivers of macroevolution in plants(Clark and Donoghue,2018).However,there are few studies that test a connection between WGDs and evolutionary novelty.The proper study of evolutionary patterns related to WGDs needs a well-resolved phylogeny,accurate dates of the WGD events,and historical reconstructions of the evolutionary novelties(Clark and Donoghue,2018).The advent of exhaustive phylogenomic studies is becoming a promising way to solve these issues,as wholegenome data can help clarify obscure phylogenetic relationships,evaluate patterns associated with WGDs,and track down the evolution of life-history traits that shaped plant lineages(Bellot et al.,2020).