The potential for worker reproduction in the ant <Emphasis Type="Italic">Aphaenogaster cockerelli</Emphasis> and its absence in the field

A reproductive division of labor between subordinates and established reproductives is a hallmark of eusociality. In most groups, however, workers retain some reproductive capabilities. Across insect societies, measures of successful worker reproduction in the presence of a queen, with few exceptions, indicate that worker reproduction is kept at very low levels. There are, however, certain colony-level characteristics that may influence the degree to which worker reproduction is promoted, such as queen number, queen mating frequency, and physical presence of a queen in species with multiple nesting sites (polydomy). In this study, the level of worker reproduction in field colonies of the ant species Aphaenogaster cockerelli was measured. A. cockerelli is a monogynous and polydomous species, so worker reproduction across nesting sites was investigated. None of the 297 males sampled provided any evidence of worker reproduction. Worker reproduction would have been detectable if it was present at or above a level of 1.5 % of the total males per colony. An effective mating frequency for queens of this species was found to be 1.03. Although A. cockerelli colonies have many colony-level factors potentially promoting worker reproduction (workers with active, trophic egg-producing ovaries, a single singly-mated queen, workers who are physically separated from the queen), it is evident that worker reproduction is highly regulated. Synthesizing the extensive amount of policing and fertility signaling data previously reported on this species, A. cockerelli is presented as case study for how worker reproduction is repressed and cooperation is maintained in insect societies.     

Aggressive interactions between the introduced Argentine ant, Linepithema humile and the native odorous house ant, Tapinoma sessile

The Argentine ant (Linepithema humile) is an invasive species that disrupts the balance of natural ecosystems by displacing indigenous ant species throughout its introduced range. The mechanisms by which Argentine ants effectively compete against native ant species have been previously addressed in field studies that centered on interference and exploitation competition at baits and mainly examined the colony-level performance of Argentine ants. Detailed behavioral observations explaining the basis for the strong competitive ability of L. humile are comparatively rare. To gain a better understanding of the mechanisms by which Argentine ants displace native ants we examined the aggressive interactions between the Argentine ants and the odorous house ant, Tapinoma sessile in four different aggression assays: (1) worker dyad interactions, (2) symmetrical group interactions, (3) intruder introductions into an established resident colony, and (4) a resource competition assay which focused on competition for food and nesting space. Our results demonstrate a clear disparity between worker-level and colony-level fighting ability of Argentine ants and provide behavioral evidence to explain the superior interference ability of Argentine ants in group assays. Argentine ants experienced mixed success in fighting against odorous house ants in dyad interactions, but gradually gained a numerical advantage in symmetrical group interactions by active cooperation among nestmates. Results of the resource competition assay indicate that Argentine ants recruit rapidly, numerically dominate food and nesting sites, and aggressively displace T. sessile from baits. Taken together, the results of these assays allow us to pinpoint the behavioral mechanisms responsible for the remarkable competitive ability of Argentine ants.     

三种同域分布喉毛花的繁殖分配

以青藏高原高寒草甸中三种同域分布的喉毛花为研究对象,通过比较三个种的植株性状和繁殖分配,探讨繁殖分配的种间差异及其与植株个体大小的关系。结果表明:(1)三个种的植株高度、顶花大小和单株花数目、繁殖分配均存在种间差异,这可能与其各自的交配系统和具体的生境以及相应的生活史对策有关;(2)在三种喉毛花中,投入到营养器官和繁殖器官的绝对资源量均呈显著正相关,未检测到植株生长和繁殖间的权衡关系;(3)三个种的个体大小与繁殖器官生物量均呈显著正相关,而与繁殖分配均呈显著负相关,这表明个体越大,繁殖投入越高,而繁殖分配越低,与以往研究结果一致,这可能是由于繁殖分配与个体大小之间存在异速关系。     

Reproductive biology of viviparous and oviparous species of the leaf beetle genus Oreina

In five species of the genus Oreina Chevrolat (Coleoptera, Chrysomelidae) we compared the size of offspring, the fecundity of the females, the timing of offspring production and female investment over the season. Two of the species, O. elongata and O. luctuosa, laid eggs, while O. cacaliae, O. gloriosa and O. variabilis gave birth to larvae. Offspring size corrected for female size was similar in the two oviparous species and in the viviparous O. cacaliae. In the two other viviparous species the larvae were two to three times bigger in relation to the female. The greater size of the offspring was not traded off for lower fecundity in these latter two species, yet the production of bigger larvae was associated with a longer laying period and thereby a spreading of reproductive investment over the season. The prediction of life history theory that higher investment in individual offspring should be traded off for lower fecundity could not be confirmed. The investigation of egg and larval development showed that in one of the oviparous species, O. luctuosa, the length of the egg stage was more variable. This corroborates the view that in this species the eggs can be retained for varying times before being laid. Greater size at birth does not necessarily lead to shortened developmental times: the larval periods of O. cacaliae, O. elongata, O. gloriosa and O. variabilis were all comparable although the larvae of the first two species were relatively smaller when laid; only the small larvae of O. luctuosa needed significantly longer for their development. For all growth parameters examined the differences between species were larger than the differences between populations. A comparison of larval growth of the oligophagous species O. cacaliae on three plant genera showed that larval growth rate is influenced by the food plant. However, the plant on which the larvae grew worst is apparently not chosen for oviposition in the field. A comparison with a phylogeny of the species based on allozymes suggests that species with similar reproductive parameters are closely related, yet that viviparity evolved independently in O. cacaliae on one hand and O. variabilis and O. gloriosa on the other.     

Individual resource allocation to vegetative growth and reproduction in subgenus <Emphasis Type="Italic">Cyclobalanopsis</Emphasis> (<Emphasis Type="Italic">Quercus</Emphasis>, Fagaceae) trees

The resource allocation for vegetative growth and female reproduction in three tree species of subgenus Cyclobalanopsis (Quercus, Fagaceae), i.e., Q. salicina, Q. sessilifolia, and Q. acuta, were examined on a per-individual basis in two consecutive reproductive seasons, in order to test whether these trees fit the predictions of the masting hypotheses about resource matching versus resource switching. Since the three Quercus species have a biennial fruiting habit, it takes 3 years for the observation of two reproductive events. Female flower and acorn production per tree were investigated by using a seed-trap method and a numerical analysis of seed dispersal. The net production of each individual was estimated as the sum of the annual increase in the dry mass of vegetative organs and reproductive investment per tree. In the data analyses, the three species were pooled, since all 12 sample trees of the subgenus apparently showed masting in the same year, with no exceptions. Female flower and acorn production per individual tree changed considerably between years. The net production per tree increased with tree size, but did not differ between years. Therefore, the reproductive allocation (proportion of a plant’s annual assimilated resources which are used for reproduction) differed dramatically between years. On the other hand, within a year, the reproductive allocation increased with increasing net production per tree. These results suggest that the switching of resource allocation between years within an individual are occurring in subgenus Cyclobalanopsis species, and the intensity of the switching increases with increasing tree size.     

Consequences of chronic infections with three different avian malaria lineages on reproductive performance of Lesser Kestrels (Falco naumanni)

We studied the consequences of chronic infections by three different lineages of avian malaria, two Plasmodium (RTSR1, LK6) and one Haemoproteus (LK2), on reproductive performance of Lesser Kestrels (Falco naumanni). Malaria infections in male and female parents had no effect on clutch size, hatching success or nesting success. However, when only successful nests were considered, we found that males parasitized by LK6 raised a lower number of fledglings, suggesting that the level of parental effort by males may be limited by this particular lineage of Plasmodium. This effect was not evident in females, probably due to the higher investment of males during the chick rearing period in this species. Overall, we have found that chronic stages of specific malaria lineages have certain negative consequences on host reproductive performance, highlighting the importance of considering genetic differences among malaria parasites to study their consequences on natural bird populations.     

竹亚科单枝竹属芸香竹花枝和花特征补充描述

繁殖器官在竹类植物的分类学研究中具有重要意义,研究组在广西马山县观察到竹亚科单枝竹属芸香竹正在开花,该文根据观察到的开花状况和采集到的标本解剖观察结果,对其花枝和繁殖器官特征做了详细的中文及拉丁文补充描述。经对比芸香竹与属内已知繁殖器官结构的单枝竹和小花单枝竹的繁殖器官,3个竹种有相同的繁殖器官结构特征,但在小花数目和大小等方面具有差异。繁殖器官比较表明该属竹种的繁殖器官对喀斯特地貌环境有特殊的适应性,也支持依据营养器官差异划分为3个独立竹种。     

Variation in reproductive investment among and within populations of the scorpion Centruroides vittatus

Although information concerning variation among and within populations is essential to understanding an organism's life history, little is known of such variation in any species of scorpion. We show that reproductive investment by the scorpion Centruroides vittatus varied among three Texas populations during one reproductive season. Females from the Kickapoo population produced smaller offspring and larger litters than females from the Independence Creek or Decatur populations; this pattern remained when adjusting for among population variation in either female mass or total litter mass. Relative clutch mass (RCM) and within-litter variability in offspring mass (V*) did not differ among populations. Among-population variation may result from genetic differences or from phenotypically plastic responses to differing environments. Within populations, the interrelationships among reproductive variables were similar for Decatur and Independence Creek: females investing more in reproduction (measured by total litter mass, TLM) produced larger litters and larger offspring, and V* decreased with increased mean offspring mass (and with decreased litter size at Decatur). At Kickapoo, larger females produced larger litters and had larger TLM; females investing more in reproduction produced larger litters but not larger offspring. Within litter variability in offspring mass was not correlated with any reproductive variables in this latter population. These patterns may be explained by the fractional clutch hypothesis, the inability of females precisely to control investment among offspring or morphological constraints on reproduction.     

Offspring size-number trade-off in a lizard with small clutch sizes: tests of invariants and potential implications

Models of small clutch sizes predict a number of invariant relationships between means and variances of measures of reproductive investment. However, empirical tests of the models have been lagging behind theoretical work. We tested the predictions using data on the mallee dragon, Ctenophorus fordi, a species where the basic assumptions of the models are likely to be fulfilled. Some, but not all, qualitative predictions of the models were shown to hold true, but the data fitted poorly to quantitative predictions. The patterns of deviation from theory may suggest the presence of a lower, and potentially an upper, limit on egg mass. We also argue that multiple and non-independent allocation decisions between total reproductive effort, growth and maintenance, and offspring size-number allocation could be important factors in the evolution of size-number strategies in lizards and thus need to be taken into account in theoretical models. The present study shows the potential to use small clutch size models to gain further insights into reproductive investment and allocation decisions in squamates.     

Variation of pollen and ovule parameters among different ploidy levels ofCorydalis (Fumariaceae)

The size and number of pollen grains and ovules are compared between 20 populations of different ploidy levels in two self-incompatible species ofCorydalis (Fumariaceae), to test the presence of ploidy-related variation in these reproductive characters. In both species, higher ploidy levels are associated with larger pollen grains, ovules and corolla, but the number of pollen grains and ovules are not different between ploidy levels. The investment per flower is consequently larger at higher ploidy levels, but the flower number per individual is lower, suggesting that the mode of partition of the investment for sexual reproduction varies between different ploidy levels. InC. orthoceras, sex allocation estimated by pollen:ovule ratios in number and volume is more female-biased in polyploids than in diploids. In spite of these variations, the characters studied can not be used as indicators of ploidy level due to the large overlaps between the ploidy levels.     

Family planning inDaphnia: resistance to starvation in offspring born to mothers grown at different food levels

Summary We observed a shift in maternal investment per offspring in clonal cultures of twoDaphnia species. Mothers grown at high food levels produced large clutches of smaller eggs but their offspring could not survive long under starvation conditions. Genetically identical mothers grown at low food levels produced small cultches of larger eggs, and their offspring, albeit low in numbers, were able to survive long periods of starvation. Our data show thatDaphnia mothers are capable of assessing food level and use this information in adjusting their fractional peroffspring allocation of reproductive resources.     

SEX ALLOCATION AND OUTCROSSING RATE: A TEST OF THEORETICAL PREDICTIONS USING BROMEGRASSES (BROMUS)

Predictions of sex-allocation theory were tested by comparisons among hermaphroditic bromegrass (Bromus) species that differed in outcrossing rate. Relative maternal and paternal investment were calculated using both the ratio of pollen to seed production, and absolute allocations in units of energy, nitrogen, phosphorus, potassium, magnesium, and calcium. Outcrossing rate had a large effect on sex allocation; species having greater outcrossing rates had relatively more paternal reproductive effort. Bromus inermis was obligately outcrossing, and nearly half of its reproductive effort was devoted to pollen production. Three partially outcrossed species, B. kalmii, B. ciliatus, and B. latiglumis, invested between 5% and 11% of reproductive effort in pollen production. Paternal investment was less than 2% in the selling species B. tectorum. Estimates of sex allocation were relatively unaffected by the resource currency used in calculation. The differences among species in sex allocation were mostly due to differences in anther size and seed set.>     

A comparison of reproductive allocation and reproductive effort between semelparous and iteroparous fucoids (Fucales,Phaeophyta)

Reproductive allocation, the proportion of total dry weight allocated to receptacle tissue and reproductive effort, the proportion of reproductive carbon requirement contributed by receptacle photosynthesis, were measured in two fucoid algal species Fucus serratus and Himanthalia elongata at sites in NE Scotland. Reproductive development takes over ten months in H. elongata, a semelparous (single reproductive event) species, and reproductive allocation at receptacle maturity is over 98%. Following gamete release, the whole thallus dies. In contrast, reproductive development in F. serratus takes four months. Fucus serratus is iteroparous (capable of multiple reproductive events), reproductive allocation is 38.6% for the first reproductive event and 50.5% for the following year's event. In Fucus serratus, the receptacles appear to make a major contribution to their own carbon requirements after the first month of reproductive development. The receptacles of Himanthalia elongata contribute only a small proportion of the receptacle carbon requirements in the first four months of reproductive development, after which the contribution made through receptacle photosynthesis increases.     

Reproductive energy investment in corals: scaling with module size

In colonial modular organisms, differences in module size and colony growth patterns among species have the potential to impose varying constraints on reproductive investment. Here, we compare reproductive output among seven morphologically different species of spawning reef corals, and analyse the relationship between reproductive output and module (polyp) size. Reproductive output ranged between 132 and 384 J cm^–2, with lipid constituting the key indicator of energy investment. Lipid decreased by 85–100%, whereas protein and carbohydrate were relatively invariant between pre- and post-spawning tissues in all species, representing 1–15% and <1%, respectively, of the energy investment to reproductive output. The ratio of energy content in reproductive to somatic tissues (gonadosomatic index, GSI) varied among species from 0.20 (Symphyllia recta) to 1.31 (Acropora tenuis), the latter being the highest value reported for any iteroparous marine invertebrate. Surprisingly, small-polyped species (Acropora, Montipora) had 2- to 6-fold higher GSIs than large-polyped ones (Lobophyllia, Symphyllia). Energy equivalents of tissues increased with the 1.50–1.76 power of polyp diameter for somatic tissues and with the 1.42–1.80 power of polyp diameter for reproductive output. In both cases, increases in energy equivalents with polyp diameter were less than the scaling exponent of 3 predicted for an isometric relationship between tissue volume (or mass) and polyp diameter, indicating significant constraints of space, design or physiological energetics with increasing polyp size. We hypothesise that such constraints have played a key role in the evolution of modularity in cnidarians.     

Reproductive investment and somatic growth rates in longear sunfish

Synopsis Allocation of energy to current reproduction at the expense of other functions, such as growth, can limit future reproductive potential. This cost of reproduction is a central concept of life history theory but has been difficult to verify in comparative field studies. Three levels of comparison of growth rates and reproductive investments were evaluated within and among populations of longear sunfish,Lepomis megalotis. All three demonstrated high levels of reproductive investment associated with reduced somatic growth. Within populations of central longear sunfish there are precociously mature sneaker makes and later maturing parental makes; sneakers have greater gonadosomatic index (GSI) values and slower somatic growth rates than parental makes. Between subspecies of longear sunfish grown under common conditions, there are differences in age at maturity and in the level of physiological reproductive investment that are associated with distinct differences in growth rates. Between populations of central longear sunfish inhabiting different sites, there are differences in the level of reproductive investment that are also associated with differences in somatic growth. Each comparison produced evidence that trade-offs occur between these life history traits, supporting the hypothesis that there is a cost of reproduction among male sunfish and suggesting that differences in strategies of reproductive investment contribute to variation in somatic growth.     

Reproduction and ontogeny of Mastacomys fuscus (Rodentia: Muridae) in the Australian Alps and comparisons with other small mammals living in alpine communities

Two species of small rodents, Mastacomys fuscus and Rattus fuscipes, and one small dasyurid marsupial Antechinus swainsonii live sympatrically in the subalpine habitat of SE Australia. This paper describes the reproductive characteristics and ontogeny of M. fuscus, and shows that the three species have different reproductive strategies that, in part, are a reflection of their different phylogenies. Cold and snow in winter, and a short summer season, limit the length of time available for reproduction and development. The rodent species exhibit similar reproductive characteristics to those in alpine regions of Europe, North America and South Africa.     

The use of ultrasonography to assess reproductive investment and output in pythons

Reproductive investment and output are integral fitness components, often incorporated into life‐history trade‐off models and important to population dynamics. The trade‐offs associated with reproduction can be dramatic in species such as snakes that make especially large investments into reproduction. Unfortunately, traditional methods used to determine reproductive investment and output are effective in many (but not all) situations. Thus, we used portable ultrasonography to serially estimate reproductive investment and reproductive output in three python species that exhibit significant variation in phylogeny, geographic range, body size, egg size, and clutch size: ball pythons (Python regius), Children's pythons (Antaresia childreni), and water pythons (Liasis fuscus). At each time point of measurement (range: 1–49 days pre‐oviposition), ultrasound estimates of viable clutch size were highly accurate in all three species. However, ultrasound estimates of mean viable egg mass, and thus viable clutch mass, significantly differed from the actual values (range: 23–73% error). Interestingly, this error was considerably smaller as females approached oviposition, suggesting that female pythons transfer a significant amount of water into their eggs during the week before oviposition. Thus, water balance during late‐stage egg development may be an integral part of reproductive success. The results obtained in the present study form the foundation for future assessments of reproductive investment, and also provide insight into the use of ultrasound technology to assist such efforts. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 772–778.     

Chronology of reproductive investment determines predation risk aversion in a felid‐ungulate system

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Spawning behavior and reproductive isolation of two species ofPseudolabrus

The reproductive behavior of two wrasses,Pseudolabrus eoethinus (Richardson, 1846) andP. sieboldi Mabuchi & Nakabo, 1997, was studied on a rocky coast in Shikoku, Japan, where the two species occur sympatrically. In the study area, individual males of each species established mating territories within which pair spawnings occurred. Pair spawnings were observed only between conspecifics, indicating that the two coexisting species were reproductively isolated. Both species usually spawned during the afternoon in early winter and had similar reproductive behavior. Although habitat, temporal and behavioral isolation mechanisms were not apparent, reproductive isolation seemed to occur via premating isolation through visual recognition of conspecific mates because the two species differed in body size and coloration. On one occasion a maleP. sieboldi was observed to perform streaking behavior to join a spawning pair ofP. eoethinus. Thus, postmating isolation between the two species is also discussed.     

Cost of reproduction as reduced growth in genotypes of two congeneric species with contrasting life histories

Summary We examined the effect of reproduction on growth in 33 genotypes of Plantago major and 14 genotypes of P. rugelii. These two herbaceous perennials have contrasting life histories; P. major reproduces at a smaller size, and allocates a larger proportion of its biomass to reproduction, than P. rugelii. The effect of reproduction on frowth was determined experimentally using photoperiod manipulations to control level of reproduction. The difference in growth between reproductive treatments was divided by the difference in capsule weight to produce a measure of reproductive cost per g of capsule for genotypes of the two species. In both species there was substantial variation among genotypes in the effect of reproduction on growth. Much of this variation could be correlated with differences among genotypes in the extent of reproductive investment and plant size. Cost in terms of reduction in growth per g of capsule increased with reproductive investment in P. rugelii, and with plant size in P. major. We suggest the differences between species in timing and extent of reproduction are related to the differences between species in effect of reproduction on growth. Plantago rugelii may reproduce to a lesser extent than P. major because cost per g of capsule in terms of reduced vegetative biomass, increases with reproductive output in the former species, but not in the latter. Similarly, P. major may reproduce earlier than P. rugelii because cost per g of capsule increases with plant size in P. major, but not in P. rugelii.