Desertification Drives the Shift in Egg Size-Number Trade-Off in an Agamid Lizard

Desertification is a serious ecological problem leading to significant biodiversity loss,but how desertification drives shifts in life history and fitness of animals remains understudied.To clarify whether habitat desertification causes shifts in life history strategies,we compared ecological factors and reproductive traits of Phrynocephalus przewalskii from three different desertification habitats-fixed dune,semi-fixed dune and mobile dune of a semi-arid region of Inner Mongolia,at the eastern edge of Hobq Desert,China.Our results showed a significant shift in the egg size-number trade-off of P.przewalskii in response to desertification,with lizards from the mobile dune habitat producing smaller clutches of larger eggs than lizards from the fixed and semi-fixed dune habitats.This life history shift is likely adaptive and driven by abiotic factors(temperature and precipitation)rather than biotic factors(food availability and lizard population density).Our study demonstrates that habitat desertification drives the shift in egg size-number trade-off in a lizard and highlights the importance of exploring the life history responses of animals to habitat desertification as well as to other traditionally well-studied factors like temperature,especially in the context of future global clima te change.

Benefits of heterospecific aggregation on necromass: in fluence of temperature, group density, and compositi on on fitness-related traits

Necrophagous blowflies(Diptera:Calliphoridae)such as Calliphora vicina,a cold-tolerant species,and L ucilia serie ata,a warm-adapted species,are pioneer carrion・breeder.Although these two species have different temperature preferences,larvae aggregate actively and often feed simultaneously on carrion.The hypothesis to be tested was that L.sericata benefits from the association with C.vicina at lower temperatures(i.e.,15℃)and that C.vicina derives greater benefits from this association at higher temperatures(i.e.,28℃).Therefore,both species were raised at these two constant temperatures from first instars to adults under three different conditions:monospecific low-density,monospecific high-density,and heterospecific high-density.The time until larval migration,surface area of puparia,and survival rates were determined for each condition.Differences between these fitness-related traits were found between species,temperatures,group densities,and species compositions.At 28°C,C.vicina larvae bred in heterospecific groups migrated significantly earlier and in higher numbers than that under same density conspecific con・ditions,with a lower mortality rate.At 15°C,both species benefited from high-density heterospecific associations,expressed by faster development and larger puparia.In conclusion,necrophagous larvae benefited from heterospecific aggregations at suboptima 1 temperatures by adapting their migration time to that of the faster species.Since temperature changes throughout the day and over the year,the beneficiary of such a collective association also changes.The costs involved and deviations to the temperature-size rule highlight the complexity of the carrion ecosystem.