Impact of sublethal doses of Piper guineense (Schum and Thonn) on the biological parameters of Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) reared on different cowpea varieties

Cowpea varieties show a wide range of characteristics in their composition that can determine Callosobruchus maculatus (Fabricius) response and survival. Consequently, this work investigated the influence of sublethal doses of Piper guineense on C. maculatus raised on four cowpea varieties: ART-98–12, Niger White, Oloyin, and Ife Brown. Our results demonstrated that C. maculatus from different varieties, despite being reared under the same conditions, responded differently to sublethal doses of P. guineense. Cowpea beetles from ART-98–12 were the most susceptible while those reared on Ife Brown were the least susceptible. Across varieties, survival and reproductive parameters of C. maculatus differed. Furthermore, the ranking for the percentage reduction in the number of eggs laid by C. maculatus was ART-98–12 > Niger White > Oloyin > Ife Brown. According to the log-rank statistic test, the difference observed in C. maculatus’ survival can be explained by variety (log-rank statistic: χ2 [df = 3, N = 16] = 15, p = 0.004). Conversely, the survivability of the chrysomelid beetles reared on Niger white was significantly lower (p = 0.012) compared to the other varieties. This study highlights the role of cowpea variety in dictating the efficacy of a given botanical against C. maculatus.     

Reproductive traits in the tropical moss Octoblepharum albidum Hedw. differ between rainforest and coastal sites

Abstract

Octoblepharum albidum Hedw. is an autoicous moss commonly occurring in tropical savannas, dry forests, rainforests and coastal habitats. It frequently reproduces by spores and asexual structures (gemmae and protonemata or buds at leaf tips), making it a good model for understanding how reproductive traits change with respect to habitat type. Our aims were to characterize the different life-history traits in O. albidum relative to sexual and asexual cycles and to detect variations in reproductive performance among the different habitats, trade-offs among these traits, and relationships among reproductive traits and plant length. We studied colonies from two Atlantic rainforests and two coastal sites in north-eastern Brazil. Shoots in the coastal sites, compared to those of the forest sites, had higher numbers of sporophytes, male and female branches per shoot, male gametangia per sexual branch, and longer setae. Numbers of female gametangia per sexual branch did not differ between forest and coastal sites. A male-biased sex ratio of branches and gametangia occurred in all sites. Compared to gemmae, sporophytes and protonemata or buds were more likely to be found on longer shoots than on shorter ones, but this relationship was only applicable to forest sites. The abundant production of gemmae and protonemata or buds at leaf tips, and sporophytes (spores) in O. albidum are important components in explaining colonization success and maintenance in this tropical moss. Longer sporophytic setae in addition to a higher reproductive performance (especially for number of male gametangia and sporophytes per shoot) may favour spore dispersal and colonization in plants of coastal sites.     

Comparison of genetic diversity in the two arctic–alpine plants Diapensia lapponica var. obovata (Diapensiaceae) and Empetrum nigrum var. japonicum (Empetraceae) between Sakhalin in Russian Far East and Jeju Island in Korea, the southernmost edge of their distribution range

We compared allozyme variation in the two arctic–alpine plants Diapensia lapponica var. obovata and Empetrum nigrum var. japonicum between Sakhalin Island in Russian Far East, within their range core, and the Korean island of Jeju, their world’s southernmost distribution. For D. lapponica var. obovata, Sakhalin populations harbored moderate levels of within-population genetic variation and low among-population divergence, whereas extremely low levels of within-population genetic diversity and high among-population differentiation were found in Jeju Island populations. In contrast, we found moderate levels of within-population variation and low among-population differentiation in E. nigrum var. japonicum in both northern populations (those of Sakhalin and an additional population from northern Japan) and Jeju Island populations. Under a similar scenario of immigration history of arctic–alpine plants on Jeju Island during the glacial periods of the Pleistocene and local persistence through glacial/interglacial cycles, the contrasting genetic structure between D. lapponica var. obovata and E. nigrum var. japonicum is mainly attributable to their different life-history, ecological, and demographic traits: (1) hermaphroditic versus monoecious, dioecious or polygamous, (2) seeds with no adaptations for long-distance dispersal versus berry-like drupes dispersed by animals and birds, and (3) a very small patch near the peak of Mt. Halla with a few hundred individuals versus a relatively continuous distribution around the peak of Mt. Halla with numerous individuals. From a conservation perspective, in situ and ex situ conservation measures should be strengthened for D. lapponica var. obovata on Jeju Island given their extreme rarity there.     

The handaxe reloaded: a morphometric reassessment of Acheulian and Middle Paleolithic handaxes

This paper examines shape and size variability in Mousterian of Acheulian Tradition (MTA) handaxes and compares the observed patterns to those in the Lower Paleolithic Acheulian, both to better understand variability in MTA handaxes and to test whether or not this variability, particularly as it relates to resharpening and reduction, is structured similarly to that in the Acheulian. The Acheulian data set is based on previously published data with the addition here of a study of the handaxes from the site of Boxgrove, England. The MTA data set is based on four classic sites from southwest France with large handaxe collections. Both standard caliper-based morphometrics and Elliptical Fourier Analysis applied to coordinate data taken from digitized images of handaxes are used to assess shape. The result is that, contrary to expectations based on assumptions of evolving technological skill, handaxes in the MTA are as or more variable in shape than Acheulian ones. This variation is allometric in Acheulian handaxes, and is linked to resharpening from the tip down to the base, but is not related to size in the MTA samples. These results suggest that the goals and constraints of handaxe manufacture, but particularly handaxe reduction as a result of reworking during use, were quite different in the MTA and Acheulian, implying that conclusions about hominin cognition drawn from patterns in shape variability in handaxes must be understood in the context of artifact life histories.     

Ontogeny of osmoregulatory patterns in the South American shrimp Macrobrachium amazonicum: Loss of hypo-regulation in a land-locked population indicates phylogenetic separation from estuarine ancestors

Ontogenetic changes in osmoregulation were compared between two geographically separate populations of a South American shrimp, Macrobrachium amazonicum, originating from the Amazon delta (A) and the Pantanal (P), respectively. Population A lives in coastal rivers and estuaries in northern Brazil, whereas population P may be considered as land-locked, spending its entire life cycle in inland freshwater (FW) habitats in southwestern Brazil. All life-history stages of population A tolerated brackish and seawater (SW) conditions, being hyper-osmoregulators at salinities < 17, iso-osmotic at ca. 17, and hypo-regulators at higher concentrations. The capabilities to survive and osmoregulate in FW were in this population expressed already at hatching (zoea I), but not any longer in the subsequent larval stages (II-IX), which showed complete mortality during an experimental 24 h exposure to fully limnic conditions. FW tolerance re-appeared only in the juvenile and adult life-history stages. Similarly, the ability to hyper-regulate at salinities 1-5 was strong in the zoea I, weaker in the subsequent larval stages, and increasing again after metamorphosis. The function of hypo-regulation in concentrated media including SW was present throughout ontogeny, particularly in late larval and early juvenile stages. These ontogenetic patterns of osmoregulation and FW tolerance are congruent with a diadromous life cycle, which includes larval release in FW and a subsequent downstream transport of the salt-dependent early larvae towards estuarine or coastal marine waters, where development to metamorphosis is possible. The FW-tolerant juveniles can later migrate upstream, recruiting to riverine populations. In the land-locked population P, all life-history stages tolerated FW and brackish conditions up to salinity 25, but mortality was high in SW (100% in adults). All postembryonic stages of this population were hyper-osmoregulators at salinities < 17, with a strong osmoregulatory capacity in FW. Unlike in population A, all stages were osmoconformers at higher salinities, lacking the function of hypo-regulation. In summary, our results show in two hydrologically and genetically isolated shrimp populations close relationships between differential patterns of ontogenetic change in osmoregulatory functions, salinity tolerance, and the ecology of successive life-history stages. In all postembryonic stages of the hololimnetic Pantanal population, the acquisition of an increased ability to hyper-osmoregulate in FW and, in particular, the complete loss of the ability to hypo-osmoregulate at high salt concentrations represent striking differences to the diadromous population from the Amazon estuary. These differences reflect different life styles and reproductive strategies, suggesting an at least incipient phylogenetic separation.     

An experimental test of the role of environmental temperature variability on ectotherm molecular, physiological and life-history traits: implications for global warming

Global climate change is one of the greatest threats to biodiversity; one of the most important effects is the increase in the mean earth surface temperature. However, another but poorly studied main characteristic of global change appears to be an increase in temperature variability. Most of the current analyses of global change have focused on mean values, paying less attention to the role of the fluctuations of environmental variables. We experimentally tested the effects of environmental temperature variability on characteristics associated to the fitness (body mass balance, growth rate, and survival), metabolic rate (VCO(2)) and molecular traits (heat shock protein expression, Hsp70), in an ectotherm, the terrestrial woodlouse Porcellio laevis. Our general hypotheses are that higher values of thermal amplitude may directly affect life-history traits, increasing metabolic cost and stress responses. At first, results supported our hypotheses showing a diversity of responses among characters to the experimental thermal treatments. We emphasize that knowledge about the cellular and physiological mechanisms by which animals cope with environmental changes is essential to understand the impact of mean climatic change and variability. Also, we consider that the studies that only incorporate only mean temperatures to predict the life-history, ecological and evolutionary impact of global temperature changes present important problems to predict the diversity of responses of the organism. This is because the analysis ignores the complexity and details of the molecular and physiological processes by which animals cope with environmental variability, as well as the life-history and demographic consequences of such variability.     

Temperature-dependent rate of clutch production in a tropical lizard (Paroedura picta: Gekkonidae): Intraspecific test of the metabolic theory of ecology

Recently, a general model based on scaling of metabolic rate and reaction kinetics that predicts dependence of various biological rates on temperature and body size has been proposed as a core of the “Metabolic Theory of Ecology” (MTE). However, its thermal component has been rarely explicitly tested and its usefulness for prediction of thermal effect on key life-history traits such as reproductive rate and hence fitness is still questionable. Here, we tested its applicability to temperature-dependent rate of clutch production in a tropical gecko. The thermal effects on reproductive rates in reptiles are only poorly known and difficult to estimate, because most species lay clutches largely infrequently. Females of the Madagascar ground gecko (Paroedura picta) lay clutches in unusually short intervals, which allowed us to use this species as a model for estimation of dependence of rate of clutch production on temperature. We kept adult females at three constant temperatures (24, 27, 30 °C) and recorded their reproductive characteristics. Increasing temperature positively influences rate of clutch production, but in a manner not predicted by a simple model of reaction kinetics. The results in P. picta suggest that predictions of fitness consequences of shifts in thermal environment can be more complicated than expected under the general relationship of the MTE.     

异鳔鳅年龄结构、生长特性与生活史类型

2010年10月至2011年7月在长江上游宜宾至江津江段采集405尾异鳔鳅鮀(Xenophysogobio boulengeri)样本。以耳石作为主要年龄鉴定材料,研究了异鳔鳅鮀的年龄结构和生长特征,采用模糊聚类分析法推断了异鳔鳅鮀的生活史类型。结果表明:长江上游异鳔鳅鮀由4个年龄组组成,其中优势年龄组为1～2龄(占83.70%);体长(L)与体重(W)关系为W=5×10-6L3.294 3(r2=0.941 3,n=405,F=6 040.22,P0.01),体长与耳石半径(R)的关系为L=0.000 8R2-0.168 4R+42.504(r2=0.836 5,n=399,F=399.20,P0.01);von Bertalanffy方程描述的生长方程为Lt=179.49(1-e-0.249 8(t+0.289 8))、Wt=133.18(1-e-0.249 8(t+0.289 8))3.294 3,体重生长拐点年龄为4.48龄;异鳔鳅鮀属于r-选择类型鱼类。当前长江上游异鳔鳅鮀群体生长特征较2001～2002年已发生变化,因此有必要采取保护措施。     

Life-history strategies of a freshwater snail in response to stream permanence and predation: balancing conflicting demands

Summary Life-history parameters for the freshwater snail Physella virgata virgata were estimated in temporary and permanent streams with and without crayfish (known snail predators). Snails from the permanent stream with crayfish exhibited higher age and size at first reproduction, as well as higher size and age at death, compared to snail populations from both temporary streams and the permanent stream without crayfish. Life-history patterns of snails from the permanent and temporary streams without crayfish were indistinguishable, with small sizes at first reproduction and at death, as well as lower age at first reproduction and at death. The snail population from the temporary stream with crayfish showed an intermediate life-history pattern. The results suggest that snail life-history patterns vary with both predation pressure and habitat stability, exhibiting phenotypically plastic responses to the variables.     

Trade-offs between developmental parameters of two endoparasitoids developing in different instars of the same host species

Trade-offs amongst life history traits is a major theme in evolutionary biology. Parasitoid wasps are important biological control agents and make excellent organisms to examine trade-offs in fitness related traits such as size, development rate and survival. Here, we examined trait-related trade-offs in 2 solitary endoparasitoids developing in different stages (or instars) of the same caterpillar host, the cabbage moth Mamestra brassicae. Microplitis mediator is a small specialist parasitoid that attacks first (L1) to third (L3) instars of M. brassicae; Meteorus pulchricornis is a larger highly generalized parasitoid that attacks L1–L4 instars of the same host species. When developing in early host instars (e.g. L1–L2), both parasitoids differently traded-off size against development time. In M. mediator, adult body mass was smaller in wasps developing in L1 than in L2 and L3 hosts, whereas development time was unaffected by instar. By contrast, adult body mass in M. pulchricornis was smaller and development time longer when developing in L1 and L2 than in L3 and L4 instars. Periodic starvation of M. brassicae caterpillars parasitized by M. pulchricornis further reduced adult mass and extended development time of wasps in L2 (but not L4) hosts. Maximum egg load in M. pulchricornis (but not M. mediator) was correlated with adult female body size. Our results imply that rapid development time is more important than body size for fitness in both species, although in M. pulchricornis both development time and adult size are traded off in determining the optimal phenotype. Developing a better understanding of association-specific patterns of development in parasitoids can assist in the optimization of mass rearing of these insects for biological control.