Maintenance of andromonoecy in an autogamous species:Superior male function in male flowers of the endangered Sagittaria guayanensis

Andromonoecy is a rare sexual system in plants.The function of additional male flowers in andromonoecious species has been widely discussed;however,few studies have taken offspring fitness into account.In addition,little is known about the mechanisms that maintain andromonoecy in autogamous species.In this study,we compared morphology,pollinator preference,pollen production and export,siring ability,natural siring success,hundred seed dry weight,and seed germination rates between male and hermaphroditic flowers in an endangered autogamous andromonoecious species,Sagittaria guayanensis.Male flowers,which are larger than hermaphroditic flowers,required fewer resources to produce.Pollinators visited male flowers more frequently than they visited hermaphroditic flowers.In addition,pollen production and export were higher in male flowers.Hand pollination demonstrated that siring ability did not differ between flower type.However,the natural siring success of male flowers was triple that of hermaphroditic flowers.The seeds sired by male flowers performed better than those sired by hermaphroditic flowers,with greater dry weight and higher germination rate.In conclusion,male flowers may be superior pollen donors for outcrossing.The maintenance of andromonoecy in S.guayanensis may result from the better performance of male flowers in male function compared to that of hermaphroditic flowers.

Maternal egg care enhances hatching success and offspring quality in an oviparous skink

Maternal egg-caring behavior can often be observed in oviparous scincid lizards.The expression of such behavior is predictably affected by the trade-off between its resultant costs and benefits for mothers and/or offspring,which has been investigated in only a few scincid species.Here,post-ovipositional Plestiodon chinensis females were treated to care for their egg clutches without interference,under simulated predation pressure,or to be caredeprived.Potential maternal costs and offspring benefits associated with egg-caring behavior were then evaluated by measuring changes in maternal body condition,egg mortality,and hatchling performance.Egg-caring behavior caused post-ovipositional females to participate less in outside-nest activity,eat less food,and show relatively poorer body conditions at egg hatching.By contrast,compared with care-deprived females,egg-caring females gained mass slightly faster,and achieved a similar body condition within a few months of hatching.Eggs that were cared for by their mothers were more likely to hatch and produced larger,faster-running and better-growing hatchlings with higher survival than uncared-for eggs.Simulated exposure to a potential predator had no distinct impact on maternal egg-caring behavior expression and offspring performance.These results indicated that marked benefits of offspring viability but minor maternal energy costs might play a decisive role in the occurrence of maternal egg-caring behavior in P.chinensis.

Evaluation of Darwin＇s fecundity advantage hypothesis in Parthenium beetle, Zygogramma bicolorata

In the Parthenium beetle, Zygogramma bicolorata Pallister （Coleoptera： Chrysomelidae）, variation in body size exists between and within the sexes. The females are larger than the males. Darwin （1874） proposed the fecundity advantage hypothesis, that is, large-sized females produce more progeny, with subsequent studies supporting, as well as, refuting the hypothesis. Thus, in order to evaluate whether this hypothesis stands in Z. bicolorata we performed experiments to investigate the role of body size in influencing： （i） assortative mating; （ii） reproductive attributes; and （iii） growth, development and survival of offspring. It is the first attempt in this beetle. We found that size influenced assortative mating, reproductive output and offspring fitness. Larger males and females were preferred as mates over smaller ones. The pairs, having larger adults as mates, had higher fecundity, while the egg viability was influenced by the male size only. The offspring of larger parents had fast development and higher survival, indicating thereby possible better nutrient allotment by the female and supply of accessory gland proteins by the male in addition to better quality of genes.

Effect of carcass contamination on necrophagous invertebrate performance

Background:The breakdown of dead organic matter is driven by a diverse array of organisms and is an important process increasingly impacted by a range of contaminants.While many studies have documented how contaminants affect food webs that are fueled by decaying plant litters,much less is known about how contaminants affect organisms that rely on dead animal material.Here,we begin to explore the effects of food contamination—using silver nanoparticles(AgNPs)as a model contaminant—on the carrion beetle Nicrophorus vespilloides that buries carcasses of small vertebrates in soils as food source and larval nursing grounds.Results:Our data show that a single ingestion of a non-lethal dose of 1μg mL^(−1) AgNPs by adult female beetles does not affect overall gut microbial activity but results in shifts in the gut microbial community composition towards pathogens including Alcaligenes,Morganella,and Pseudomonas.While no effects were observed in offspring clutch size,some reductions were visible in clutch weight,number of larvae,and number of eclosing pupae in exposed N.vespilloides in comparison with controls.Repeated ingestion of AgNPs over several weeks led to a decrease in survival of adult beetles,suggesting that more environmentally realistic exposure scenarios can directly affect the success of carcass-feeding animals.Conclusions:Sub-lethal carcass contamination with a model pollutant can affect the gut microbial composition in female beetles and reduce offspring fitness.This encourages consideration of currently overlooked propagation routes of contaminants through necrophagous food webs and inherent consequences for ecological and evolutionary processes.