Male indifference to female traits in an arctiid moth (Utetheisa ornatrix)

Abstract.  1. Female Utetheisa ornatrix (Lepidoptera: Arctiidae) mate selectively with large males able to transmit sizeable quantities of nutrient and defensive pyrrolizidine alkaloid with the spermatophore. The female gauges male size indirectly by assessment of the male's courtship pheromone.
2. Male Utetheisa invest upward of 10% of body mass in spermatophore production, and could therefore have been expected to be choosy; however, when offered females differing in alkaloid content, body mass, or mating status, males showed disregard of these parameters, both in their choice of partner and in their allocation of resources to the spermatophore.
3. It is concluded that Utetheisa males do not have the option to select females by comparison shopping . Females broadcast their attractant pheromone for less than an hour per day. Given this time constraint and the potentially high cost of mate localisation, males may have no choice but to mate on an opportunistic basis.     

Isolation of five polymorphic microsatellite markers in Utetheisa ornatrix (Lepidoptera: Arctiidae)

We isolated five polymorphic microsatellite markers for the arctiid moth Utetheisa ornatrix as part of an effort to investigate the role of inbreeding in the degree of polyandry seen in natural populations of the moth. We tested the primers on 105 individuals collected from scrub habitat in central Florida. These microsatellite loci provide a new research tool for understanding the population structure and reproductive behaviour of U. ornatrix.     

Female Promiscuity Does Not Lead to Increased Fertility or Fecundity in an Arctiid Moth (<Emphasis Type="Italic">Utetheisa ornatrix</Emphasis>)

Prior work has demonstrated significant phenotypic benefits to female promiscuity in the arctiid moth Utetheisa ornatrix. We were interested in determining whether U. ornatrix females also derive genetic benefits from mating multiply. We specifically tested whether, by mating with several males, females are able to exploit postcopulatory mechanisms that decrease the risk of fertilization by incompatible sperm. We show evidence that U. ornatrix females are not taking multiple mates as fertilization insurance because: (1) females that mate once are as fertile as those that mate three times; and (2) females that take three different mates are no more fertile than those that mate three times with the same male.     

Why do larvae of Utetheisa ornatrix penetrate and feed in pods of Crotalaria species? Larval performance vs. chemical and physical constraints

Larvae of Utetheisa ornatrix (L.)(Lepidoptera: Arctiidae) are found mainly inside unripe pods of several alkaloid‐bearing Crotalaria (Fabaceae) species. Although eggs are laid on the leaves, the larvae are usually found feeding on unripe seeds in the pods. In this work, we investigated the selective pressures that could explain why U. ornatrix larvae feed primarily on unripe pods with seeds and not on leaves. Our results showed that larval survivorship in the laboratory was unaffected by feeding on leaves or unripe seeds, and that larval development up to the pupal stage was better in larvae that fed on unripe seeds, although perforating unripe pods to reach seeds was costly in terms of survivorship. Females were also heavier when fed on unripe seeds, but there was no significant difference in the fecundity of females fed either of the two diets. Feeding on unripe seeds in pods had other benefits for U. ornatrix, including a lower predation rate for larvae that fed inside compared to larvae that fed outside the pods. Similarly, adults derived from larvae that fed on unripe seeds were preyed upon less frequently by the orb‐weaving spider Nephila clavipes than were adults that fed on leaves. The latter benefit may be closely related to the high concentration of pyrrolizidine alkaloids in unripe seeds, which is about five times more than in leaves. These alkaloids are sequestered by the larvae and transferred to adults, which then become chemically protected. However, this chemical defence does not protect the larvae against ants such as Ectatomma quadridens and Camponotus crassus. Pods with unripe seeds that confer physical protection to larvae and pyrrolizidine alkaloids that confer chemical protection to adults limit the use of leaves by U. ornatrix larvae.     

Influences of Parental Care and Food Deprivation on Regulation of Body Mass in a Burying Beetle

Changes in adult body mass during breeding can reveal how parents prepare energetically for care, the stress of care, and the need to terminate care in a state conducive for future reproduction. Interpreting changes in parent mass can be difficult, however, because temporal variation in body mass may reflect a constraint imposed by the stress of care, revealing conflict within the family, or a shift to a new body mass optimum adaptive for a different stage of the breeding cycle. Here, we examined the effect of food deprivation and parenting on variation in female body mass of Nicrophorus orbicollis, an insect in which parents and offspring share a common food resource (a prepared carrion ball). Female parents demonstrated a remarkable degree of regulation of body mass: Despite varied periods of food deprivation (0–8 d) prior to discovery of a carcass, females attained a similar body mass (108.3–109.2% of pre‐deprivation mass) at the time of larval hatching. Females attained a greater body mass in anticipation of rearing a greater number of young. Mothers lost mass during active parental care, and mass at the end of caregiving was less in mothers that reared more and heavier young. Body mass at the end of care was less than the preferred mass for females searching for a carcass, indicating that the mothers sacrificed self‐maintenance and future reproductive potential for their current brood. Contrary to prediction, pre‐breeding food deprivation had no effect on offspring size or on female condition at the end of care. We conclude that there is a limited degree of conflict over the sharing of food among N. orbicollis parents and offspring, but that this conflict is not exacerbated by food deprivation prior to breeding.     

Body size as an estimator of production costs in a solitary bee

Abstract 1. Body weight is often used as an estimator of production costs in aculeate Hymenoptera; however, due to differences between sexes in metabolic rates and water content, conversion of provision weight to body weight may differ between males and females. As a result, the cost of producing female progeny may often have been overestimated.
2. Provision weight and body weight loss throughout development were measured in a solitary bee, Osmia cornuta (Latreille), to detect potential differences between sexes in food weight/body weight conversion.
3. Male O. cornuta invest a larger proportion of larval weight in cocoon spinning, and presumably have higher metabolic rates than females during the larval period; however, this is compensated by a slightly longer larval period in females.
4. Overall, body weight loss throughout the life cycle does not differ significantly between sexes. As a result, cost production ratios calculated from provision weights and from adult body weights are almost identical.
5. The validity of other weight (cocoon, faeces) and linear (head width, intertegular span, wing length, cocoon length, and cell length) measures as estimators of production costs is also discussed.
6. Valid estimators of production costs vary across species due to differences in sex weight ratio, cocoon shape, provision size in reference to cell size, and adult body size.     

产卵次序对山麻雀卵色、卵大小和重量的影响

产卵次序可对鸟类卵黄中的营养成分、卵壳色素以及卵壳厚度等产生影响。一些鸟类可通过产卵次序对不同卵的资源进行分配,从而实现繁殖成效的最大化。本研究对不同产卵次序下山麻雀(Passer cinnamomeus)的卵色、卵大小和卵重量进行分析,结果表明,山麻雀的卵重和卵大小随着产卵次序并无显著变化,卵色与卵的大小和重量均无显著相关性,但卵背景的色度随产卵次序有明显下降趋势,而卵斑点密度则呈相反的变化。卵背景的色度随产卵次序下降可能是山麻雀有限的色素在卵中不均匀分配的结果,而卵斑点密度的增加则可能是对后期卵壳厚度变薄的一种补偿。     

Size delays female senescence in a medium sized marsupial: The effects of maternal traits on annual fecundity in the northern brown bandicoot (Isoodon macrourus)

The degree to which females allocate resources between current reproduction, future fecundity and survival is a central theme in life history theory. We investigated two hypotheses proposed to explain patterns of reproductive investment, terminal investment and senescence, by examining the effects of maternal traits (age and maternal mass) on annual fecundity in female northern brown bandicoots, Isoodon macrourus (Marsupialia: Peramelidae). We found that annual fecundity in females declined in their final year of reproduction, indicating reproductive senescence. Maternal mass significantly influenced the rate of senescence and, in turn, a female's lifetime reproductive output. Mass had little effect on fecundity in 1st and 2nd year females, but a positive relationship with fecundity in 3rd year females. This meant that heavy, 3rd year females did not suffer the decline in fecundity shown in light 3rd year females. For 1st year females, mass and leg length increased between their first and second reproductive seasons, indicating a temporary shift, from the allocation of resources to reproduction, to increasing condition or structural size post their first breeding event. There were no net changes to body mass in subsequent years. We suggest that this year of post‐reproductive growth has important consequences for senescent effects on reproduction. Overall, results provided support for the effects of senescence on annual fecundity. Our findings were not consistent with the terminal investment hypothesis; reproductive output did not increase in females' final reproductive season despite a rapid decline in survival. However, this notion cannot be entirely dismissed; other measures of reproductive performance not examined here (e.g. offspring mass) may have provided an indication that females did increase their effort at the end of their lifespan. This study highlights the difficulty of measuring reproductive costs and the importance of understanding the combined effects of specific characteristics of an individual when interpreting reproductive strategies in iteroparous organisms.     

Evolutionary trends in the male pheromone systems of arctiid moths: evidence from studies of courtship in Phragmatobia fuliginosa and Pyrrharctia isabella (Lepidoptera: Arctiidae)

Male Phragmatobia fuliginosa and Pyrrharctia Isabella evert tubular abdominal scent-organs (coremata: during courtship. The coremata secrete a pheromone that is derived from pyrrolizidine alkaloids (PAs) obtained during larval feeding. Field-collected males vary widely in the amount of pheromone they possess. The courtship behaviour of these species was studied to determine whether this variation among males serves as a basis for mate choice by females, in a wind-tunnel a male approaches a pheromone-releasing female from downwind with his coremata everted in flight. A female perceiving the pheromone responds by fluttering her wings and emitting a clicking sound. This response did not occur in all courtships, and successful copulation was not dependent on its occurrence. Males denied access as larvae to the PA-precursors of the corematal pheromone (PA-denicd males' mated as rapidly as males allowed access to pheromone precursor (PA-supplied males). Moreover, antennectomized females mated as rapidly as normal females. Comparative analyses of transitional probabilities indicated no differences among courtships involving ! I': PA-denicd males and normal females, (II) PA-supplied males and normal females, or antennectomized females and normal males of unspecified feeding history. Field observations of courtship interactions between laboratory-reared females and wild males indicated that males having little or no pheromone succeed in mating in a natural setting as do males having a relativelv large amount of pheromone. It is hypothesized that the failure of female Ph. fuliginosa and Py, Isabella to enforce the display of PA-derived pheromone is related to an cvolutionarv trend away from an ancestral larval host-range restricted to PA-containing plants toward the polyphagv shown by manv temperate and arctic arctiids in the lineage (subfamily Arctiinae: tribe Arctiini) to which Ph. fuliginosa and Py. Isabella belong. Parallels in other moth groups are cited to support the notion that a plesiomorphic courtship pheromone system could persist in a vestigial state, despite the loss of its adaptive raison dêtre.     

Extrafloral nectaries as a deterrent mechanism against seed predators in the chemically protected weed Crotalaria pallida (Leguminosae)

Abstract In several plants, extrafloral nectaries (EFN) are located close to the reproductive structures, suggesting that ants may act as a defence against specialized seed predators that overcome chemical defences. Alternatively, ants may also deter herbivores in a generalized manner, thereby protecting the whole plant. In this work, we examined the relationship between the chemically protected weed Crotalaria pallida Ait. (Leguminosae) that bears EFN, its specialized seed predator, the larvae of the arctiid moth Utetheisa ornatrix L. (Arctiidae) and ants. We tested two hypotheses related to the type of deterrence caused by ants. The Seed Predator Deterrence Hypothesis predicts that ant deterrence is directed primarily towards herbivores that destroy seeds and other reproductive structures, without attacking herbivores on vegetative structures. The General Deterrence Hypothesis states that ants are general in their effects, equally deterring herbivores in vegetative and reproductive structures. Our results supported the predictions of the Seed Predator Deterrence Hypothesis, namely, that (i) ant activity on EFN was related to the vulnerability of reproductive structures to attack by U. ornatrix; (ii) ant patrolling was restricted almost entirely to racemes; (iii) ants removed termites used as baits more frequently on racemes than on leaves; and (iv) U. ornatrix larvae were often expulsed from the racemes. These results indicate that EFN can act as another deterrent mechanism in chemically protected plants by promoting the expulsion of specialist seed predators.     

胎仔数与父本缺失对棕色田鼠幼仔体重发育的影响

室内饲养条件下,测量了出生后不同发育阶段棕色田鼠Microtus mandarinus的体重,并探讨了胎仔数(分别为1只、2只、3只和4只)及父本缺失(母鼠单独抚育)对幼仔体重发育的影响.结果表明,棕色田鼠出生后第一周体重的瞬时生长率最高,此后逐步下降;出生后28～35 d,体重增益最大(P<0.05).出生后7 d,不同胎仔数的体重没有明显差异,但至断乳时(出生后21 d),胎仔数为2只的幼仔平均体重明显高于其它胎仔数的平均体重(P<0.05).与双亲抚育相比,母鼠单独抚育的幼仔在断乳时的体重明显下降(P<0.05).这些结果说明,哺乳期内棕色田鼠幼仔的体重发育与胎仔数有关.由于棕色田鼠是单配制,双亲育幼,父本雄鼠的缺失减少了亲本投资,影响了幼仔的身体发育.     

Pyrrolizidine alkaloids in arctiid moths (Lep.) with a discussion on host plant relationships and the role of these secondary plant substances in the Arctiidae

Pyrrolizidine alkaloids (PA) have been identified in six species of Arctiidae reared on Senecio and Crotalaria. These include senecionine, seneciphylline, integerrimine, jacobine, jacozine, jacoline, jaconine and a metabolite (C₁₅H₂₅NO₅) from Senecio , and monocrotaline, trichodesmine and crispatine from Crotalaria.
The all-red aberration of Tyria jacobaeae (var. conyi) contained much less of the metabolite than normal examples of this species. Female Spilosoma lutea reared on the same plants of S. jacobaea contained markedly more jacobine and jacoline than die males.
Host plant relationships and secondary plant substances are discussed. It is suggested that the Arctiid moths' own deterrent secretions, directed against vertebrate predators, pre-adapts them for feeding on foliage likewise protected against large herbivores by toxic secondary plant substances such as cardenolides and pyrrolizidine alkaloids. These latter substances are more toxic to vertebrate than to insect herbivores, and their dual function of deterrent and insect aphrodisiac puts a premium on their sequestration and storage once a species has achieved the initial steps, and occupied the plant niche concerned. It is further suggested that the polyphagous habits of the Arctiidae result in a more equitable distribution of die secondary plant substances within the Mullerian complex concerned, thus providing a generalized warning message for the potential vertebrate predator.     

Parental investment and quality of insurance offspring in an obligate brood-reducing species, the American white pelican

The last-hatched chick, or B-offspring, of American white pelicanstypically survives only as "insurance" when its elder siblingfails. Life-history theory suggests that parents should investrelatively less in these disadvantaged insurance offspring.For an insurance strategy to be effective, however, reducedinvestment may be constrained by the need to maintain potentialinsurance offspring in a viable condition until at least 3–6days of age, after which they are rarely needed. In agreementwith the life-history prediction, egg size, resultant hatchingmass, and growth rates at two-chick nests were significantlylower for B-offspring. When hatched in the laboratory, B-eggswere also slightly but significantly less efficient at convertingegg size into hatching mass. Despite these differences, B-chicksthat were reared as singles, free from sibling competition fromhatching onward, showed no decrement in survival or growth rate.When A-chicks were removed from nests with underweight 3- or6-day-old B-chicks, a minority (21%) of B-chicks failed to recover,but mean growth rates of survivors increased rapidly to controllevels. Results suggest that although parental investment inB-offspring is reduced, it is usually adequate to produce andmaintain potential insurance offspring in viable condition duringthe time that they are most likely to be needed as replacementsfor failed elder siblings.     

Tissue distribution and biosynthesis of 1,2-saturated pyrrolizidine alkaloids in Phalaenopsis hybrids (Orchidaceae)

Phalaenopsis hybrids contain two 1,2-saturated pyrrolizidine monoesters, T-phalaenopsine (necine base trachelanthamidine) and its stereoisomer Is-phalaenopsine (necine base isoretronecanol). T-Phalaenopsine is the major alkaloid accounting for more than 90% of total alkaloid. About equal amounts of alkaloid were genuinely present as free base and its N-oxide. The structures were confirmed by GC-MS. The quantitative distribution of phalaenopsine in various organs and tissues of vegetative rosette plants and flowering plants revealed alkaloid in all tissues. The highest concentrations were found in young and developing tissues (e.g., root tips and young leaves), peripheral tissues (e.g., of flower stalks) and reproductive organs (flower buds and flowers). Within flowers, parts that usually attract insect visitors (e.g., labellum with colorful crests as well as column and pollinia) show the highest alkaloid levels. Tracer feeding experiments with (14)C-labeled putrecine revealed that in rosette plants the aerial roots were the sites of phalaenopsine biosynthesis. However active biosynthesis was only observed in roots still attached to the plant but not in excised roots. There is a slow but substantial translocation of newly synthesized alkaloid from the roots to other plant organs. A long-term tracer experiment revealed that phalaenopsine shows neither turnover nor degradation. The results are discussed in the context of a polyphyletic molecular origin of the biosynthetic pathways of pyrrolizidine alkaloids in various scattered angiosperm taxa. The ecological role of the so called non-toxic 1,2-saturated pyrrolizidine alkaloids is discussed in comparison to the pro-toxic 1,2-unsaturated pyrrolizidine alkaloids. Evidence from the plant-insect interphase is presented indicating a substantial role of the 1,2-saturated alkaloids in plant and insect defense.     

Maternal body size as an evolutionary constraint on egg size in a butterfly

Genetic and developmental constraints have often been invoked to explain patterns of existing morphologies. Yet, empirical tests addressing this issue directly are still scarce. We here set out to investigate the importance of maternal body size as an evolutionary constraint on egg size in the tropical butterfly Bicyclus anynana, employing an artificial two-trait selection experiment on simultaneous changes in body and egg size (synergistic and antagonistic selection). Selection on maternal body size and egg size was successful in both the synergistic and the antagonistic selection direction. Yet, responses to selection and realized heritabilities varied across selection regimes: the most extreme values for pupal mass were found in the synergistic selection directions, whereas in the antagonistic selection direction realized heritabilities were low and nonsignificant in three of four cases. In contrast, for egg size the highest values were obtained in the lines selected for low pupal mass. Thus, selection on body size yielded a stronger correlated response in egg size than vice versa, which is likely to bias (i.e., constrain), if weakly, evolutionary change in body size. However, it seems questionable whether this will prevent evolution toward novel phenotypes, given enough time and that natural selection is strong. Correlated responses to selection were overall weak. Egg and larval development times tended to be associated with changes in maternal size, whereas variation in pupal development times weakly tended to follow variation in egg size. Lifetime fecundity was similar across selection regimes, except for females simultaneously selected for large body mass and small egg size, exhibiting increased fecundity. Multiple regressions showed that lifetime fecundity and concomitantly reproductive investment were primarily determined by longevity, as expected for an income breeder, whereas egg size was primarily determined by pupal mass. Evidence for a phenotypic trade-off between egg size and number was weak.     

中华蟾蜍体重及脏器大小对禁食和重喂食处理的响应

两栖动物的体重和内脏器官大小可随环境条件而变化,具有表型可塑性,但实验例证较少,尤其缺乏与可变的食物可利用性有关的研究。本研究以捕自安徽省定远县县郊的雌、雄中华蟾蜍(Bufo gargarizans)为研究对象,测定了自由取食组、禁食1周组、禁食2周组、重喂食1周组和重喂食2周组其体重、内脏器官湿重和干重的变化情况。1)中华蟾蜍的体重、胴体湿重和干重均无明显的性别(P0.05)和组间(P0.05)差异。2)雌蟾胃的湿重、干重和大肠湿重高于雄蟾(P0.05),其他内脏器官(小肠、胸腺、心、肝、肺、脂肪体、脾和肾)的湿重和干重均无性别差异(P0.05);雄蟾上述指标均无组间差异(P0.05);雌蟾的胃湿重和大肠湿重均无组间差异(P0.05),但胃干重自由取食组高于重喂食1周组(P0.05)。禁食2周组的小肠湿重下降,低于自由取食组、重喂食1周和2周组(P0.05)。3)禁食1周组的心湿重高于重喂食2周组(P0.05)。结果表明,中华蟾蜍在整体水平不受短期禁食和重喂食处理的影响,器官水平可能主要依赖适度饥饿而导致的心肌功能的提升和消化道的可塑性来应对变化的食物条件。     

Reproductive senescence and terminal investment in female Barbary macaques (Macaca sylvanus) at Salem

The reproductive history of 207 female Barbary macaques, living in a large outdoor enclosure in Southwest Germany, was studied during an 11-year period. The results yielded a significant relationship between female age and fecundity, with fertility rates lower than expected among young and old females. Analysis of the reproductive history of individual females revealed a significant decline in fertility from prime age (7–12 years) to mid age (13–19 years), and from mid age to old age (20–25 years). The proportion of long interbirth intervals increased steadily among aging females. Infant survival was not significantly related to maternal age, but offspring of old females showed the highest survivorship. Behavioral observations revealed that old mothers weaned their offspring significantly later than younger mothers, suggesting that prolongation of interbirth intervals is due not only to deteriorating physical condition but also to increased maternal investment, as life history theory predicts. Reproduction ceased during the middle of the third decade of life. Final cessation of estrous cycling invariably occurred 3 or 4 years after the birth of the last offspring, but a postreproductive life span of 5 years appears to be common in this population. Available data suggest that reproductive senescence and menopause are more common among nonhuman primates than widely believed and that both traits are part of an adaptive life history strategy.     

Egg production across a 40-week period in the phasmid Sipyloidea sp. (Diapheromeridae) from a tropical rain forest, north Queensland, Australia

Abstract  In this study we report the results from the first long-term (40 weeks) study of stick-insect fecundity and distribution under natural conditions of which we are aware. We used the number of eggs falling into 72 × 0.5 m² traps to ask: 'Was egg production in Sipyloidea sp. uniform across the sample period'? and 'Was there evidence of host plant species preference or avoidance'? We collected a total of 213 Sipyloidea sp. eggs. The number of eggs caught per week was not uniform and an exponential decay model was the best-fit relationship between egg production and time, indicative of a steep decline from high to low (but continuous) egg production across the study period. Continuous egg production differs from other insect species in tropical areas that often show distinct seasonal differences between wet and dry seasons, timed to leaf production in host plants. The distribution of eggs within traps was aggregated, and more traps than expected from Poisson probabilities received no eggs, or six or more eggs. The concentration of eggs within particular traps was not related to the identity of canopy plant species, however. We suggest that continuous egg production in Sipyloidea sp. may be related to the wider range of plant species available as food resources for the polyphagous Sipyloidea , compared with other tropical insect species.