DNA metabarcoding reveals seasonal changes in diet composition across four arthropod-eating lizard species(Phrynosomatidae:Sceloporus)

Diet composition and its ecological drivers are rarely investigated in coexisting closely related species.We used a molecular approach to characterize the seasonal variation in diet composition in four spiny lizard species inhabiting a mountainous ecosystem.DNA metabarcoding revealed that the lizards Sceloporus aeneus,S.bicanthalis,S.grammicus,and S.spinosus mostly consumed arthropods of the orders Hemiptera,Araneae,Hymenoptera,and Coleoptera.The terrestrial lizards S.aeneus and S.bicanthalis mostly predated ants and spiders,whereas the arboreal–saxicolous S.grammicus and saxicolous S.spinosus largely consumed grasshoppers and leafhoppers.The taxonomic and phylogenetic diversity of the prey was higher during the dry season than the rainy season,likely because reduced prey availability in the dry season forced lizards to diversify their diets to meet their nutritional demands.Dietary and phylogenetic composition varied seasonally depending on the species,but only dietary composition varied with altitude.Seasonal dietary turnover was greater in S.spinosus than in S.bicanthalis,suggesting site-specific seasonal variability in prey availability;no other differences among species were observed.S.bicanthalis,which lives at the highest altitude in our study site,displayed interseasonal variation in diet breadth.Dietary differences were correlated with the species’feeding strategies and elevational distribution,which likely contributed to the coexistence of these lizard species in the studied geographic area and beyond.

Bacterial and archaeal communities in saline soils from a Los Negritos geothermal area in Mexico

In recent years,there has been a growing need to understand how salinity affects microbial communities in agricultural soils.Archaeal and bacterial community diversities and structures were investigated by high-throughput sequencing analysis of their 16S rRNA in two arable soils with low electrical conductivity(EC)(2.3 and 2.6 dS m^(-1))and a saline soil(EC=17.6 dS m^(-1)).The dominant bacterial phyla in the soils were Proteobacteria(relative abundance(RA)=46.2%),followed by Acidobacteria(RA=13.1%)and Actinobacteria(RA=10.0%),whereas Serratia(RA=6.0%)and Bacillus(RA=4.0%)were the dominant bacterial genera.Candidatus Nitrososphaera(53.5%)was the dominant archaeal phylotype in the arable soils,whereas Nitrosopumilus(RA=0.4%)dominated in the saline soil.The archaeal and bacterial community structures were different between the soils and significantly correlated with soil sand,arsenic,barium,and antimony contents,but not with soil salinity.

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.

Resting metabolic rates increase with elevation in a mountain-dwelling lizard

ndividuals that inhabit broad elevational ranges may experience unique environmental challenges.Because temperature decreases with increased elevation,the ectotherms living at high elevations have to manage limited activity time and high thermoregulatory effort.The resting metabolic rate(RMR)of a postabsorptive animal is related to its total energy requirements as well as many other fitness traits.Mesquite lizards(Sceloporus grammicus)living on La Malinche Volcano,Mexico,inhabit a wide elevational range with some populations apparently thriving above the tree line.We measured the RMR of lizards from different elevations(i.e.,2,600,3,200,and 4,100 m)at four ecologically relevant temperatures(i.e.,15,25,30,and 35°C)and found that RMR of mesquite lizards increased with temperature and body mass.More importantly,lizards from the high-elevation population had mass specific RMR that was higher at all temperatures.While the higher RMRs of high-elevation populations imply higher metabolic costs at a given temperature these lizards were also smaller.Both of these traits may allow these high elevation populations to thrive in the face of the thermal challenges imposed by their environment.