Clutch Production Research Articles

The female red jungle fowl (Gallus gallus gallus) reproductive investment stimulated by male attractiveness

Abstract. Lelono A, Riedstra B, Groothuis T. 2024. The female red jungle fowl (Gallus gallus gallus) reproductive investment stimulated by male attractiveness. Biodiversitas 25: 2931-2936. To maximize their capacity for reproduction, mothers are expected to modify their investment in offspring based on the quality of their mates. A recent study showed that females in female-care only species do so by investing more in egg mass when mated with attractive males rather than in other reproductive traits. In our study, we investigated how red jungle fowl (Gallus gallus gallus) mothers invest in clutch production based on the size of the male's comb, a trait signaling attractiveness. We randomly paired 14 females with 14 males of either large or small combs and monitored their egg laying, clutch completion, and brood rearing. Following the initial clutch, we exchanged male partners and permitted females to establish up second generation. We found that females who were partnered with males who had bigger combs laid down their eggs earlier after pairing compared to those paired with males with smaller combs. However, there were no variations in egg mass or clutch size that we could find. Furthermore, the size of the male's comb influenced the growth and body condition of female chicks, with those sired by males with larger combs being heavier and in better condition at twenty-four weeks old. These data support the premise of the positive Differential Allocation (DA) hypothesis, where maternal investment varies with mate quality, rather than the negative DA, where females more investment in offspring from lower quality mates.

The influence of pair duration on reproductive success in the monogamous ‘Alalā (Hawaiian crow, Corvus hawaiiensis)

Conservation breeding program practitioners select potential mates in an attempt to maximize pair compatibility and maintain genetic diversity. Therefore, pair duration, or the number of breeding seasons that individuals retain the same mate, is practitioner-determined in these settings. There is a critical need to evaluate whether pair duration influences reproductive success in ex situ assurance populations, particularly for socially monogamous species. The ‘Alalā (Hawaiian crow, Corvus hawaiiensis) is a monogamous forest bird that is currently extinct in the wild. Today, ‘Alalā exist only in human care for intensive conservation breeding. We analyzed breeding program data from 2018-2021 to determine the effects of ‘Alalā pair duration and age on reproduction (nest building, egg laying, hatching, and fledging). We found that pair duration does not influence reproductive outcomes, and thus practitioners can be more proactive when re-pairing birds. Female and male age, on the other hand, influenced the probability of nest building, clutch production, and overall reproductive success. Nest building and clutch production probabilities were high (near 1) and stable as females aged from 2 to ~ 12 years old, declining sharply thereafter. In males, overall reproductive success (from building robust nests to rearing at least one nestling to fledge) increased with age from 2 to ~ 9 years old, peaked and reached an asymptote with males ≳ 9 to ~ 13 years old, and decreased in males ≳ 13 years old. Thus, integrating age into the pair selection process will increase the likelihood of achieving conservation goals. To our knowledge, we are the first to utilize empirical pair duration results to provide specific management recommendations for mate selection in an avian conservation breeding program. Our findings have critical utility for guiding ‘Alalā pairing decisions, and more broadly underscore the importance of evaluating mate retention and selection protocols in other conservation breeding programs.

Copepod egg production estimates are biased by female mortality

AbstractEgg production rate (EPR, eggs ♀−1d−1) is a key measure of the nutritional state of metazoans such as copepods. Chlorophyll concentration is most often used to index responses of copepod vital rates to ambient food, but the fits to EPR are often poor. A known but unexplored bias in EPR estimates is the interaction between lifetime reproductive schedules of adult females and their mortality. We examined this interaction for Pseudodiaptomus forbesi, an abundant sac‐spawning calanoid copepod, in the San Francisco Estuary (SFE), USA. The reproductive schedule of P. forbesi comprises a latent period followed by a generally steady rate of clutch production. We used a Bayesian approach to analyze data from two studies which included 141 individual estimates of proportion ovigerous, eggs per clutch, and mortality from 28 sampling events. Proportion ovigerous contributed 95% of the variation in EPR. Mortality was 0.01–0.73 d−1 by one method and ~ 20% higher by another. When mortality was high, most females were young, few were past the latent stage, and ~ 25% were ovigerous. Proportion ovigerous up to 75% occurred only with mortality > ~0.1 d−1. Adjusting for mortality increased estimates of proportion ovigerous by 3%–88% (median 36%) and allowed for a relationship with chlorophyll, which could not be fitted to the raw data. However, the adjustments increased uncertainty. Given the large effort required, we recommend that others investigate this phenomenon for other species and environments before this adjustment should be recommended for estimating copepod egg production.

Evaluation of Black Soldier Fly Hermetia illucens as Food for Pink-Spotted Lady Beetle Coleomegilla maculata.

The discovery of new and improved factitious and artificial diets is necessary for cost-effective rearing of predatory arthropods. This study evaluated Hermetia illucens black soldier fly (BSF) as a suitable alternative food source for rearing the predatory coccinellid Coleomegilla maculata (Cmac). The hypothesis that BSF larval powder was suitable food to support the growth, development, and reproduction of Cmac was tested in the laboratory. When compared to a standard in-house diet containing brine shrimp egg powder plus Chlorella vulgaris green algae and myristic acid (BSE+CM), the BSF and BSF+CM diets reduced immature growth and development. Immatures successfully reared to teneral adults were smaller when fed BSF or BSF+CM rather than BSE+CM. Combining BSF with a powdered artificial diet (AD), i.e., BSF+AD, did not improve predator growth or development, compared to Cmac reared on BSE+CM. Cmac oviposition responses, i.e., egg clutch production, to BSF vs. BSE+CM or BSF+AD vs. BSE+CM did not differ significantly. In conclusion, BSF has the potential to be food that supports Cmac oviposition behavior. Future research is necessary to discover an ideal mixture of BSF, BSE+CM, or AD that supports Cmac growth, development, and reproduction over multiple generations.

Chronic and transgenerational effects of silver nanoparticles in freshwater gastropod Lymnaea stagnalis

Traditional ecotoxicological studies prove to be focused mainly on single-generation, multigenerational research in ecotoxicological testing is needed to improve the predictive approaches in ecological risk assessment. Silver nanoparticles (AgNPs) have been increasingly detected in aquatic environments due to their extensive use in consumer products. We investigated the transgenerational effects of AgNPs on the life traits of freshwater model gastropods Lymnaea stagnalis for two generations. The reversibility of the effects of using recovery experiments was also performed. Results showed that AgNPs induced high Ag bioaccumulation in the whole soft tissues of parental L. stagnalis after 21 days of exposure. The increased ROS production and reduced condition index and fecundity were found after exposure to AgNPs at 500 μg/L. These results highlight that under AgNPs exposure, adult gastropods might allocate more resources to resist oxidative stress rather than to growth or reproduction. Furthermore, the Ag accumulation and ROS production of egg clutches were significantly related to parental exposure duration and concentrations. On the other hand, isolated eggs exposure demonstrated biological effects were persistent in terms of the next generation. For example, after transfer to a clean medium, similar Ag bioaccumulation and ROS production were observed from eggs which parents were pre-exposed to 50 and 500 μg/L AgNPs. Current explicit consideration of offspring performance adds value to existing toxicity testing protocols. Parental exposure duration has important implications for offspring effects, and parental exposure can cause transgenerational changes in resistance that have significant implications for toxicity testing and adaptive responses. These effects across generations point out the need for multigenerational tests to assess the environmental risk of MNPs in aquatic organisms.

Investigating the potential impacts of coal ash runoff on the freshwater Seminole ramshorn snail (Planorbella duryi) under laboratory conditions

Coal fly ash is an industrial waste product generated by coal fired powerplants which has been shown to contain elevated concentrations of several toxic trace metals. When stored in landfills or other repositories, these trace metals can enter nearby surface waters via a number of routes including leaching or runoff. Our study examined 1) the presence and concentration of eleven trace elements in a range of lab-created coal ash leachate solutions at neutral pH using ICP-OES, 2) the physiological effects of these leachate solutions on a freshwater gastropod (Planorbella duryi), and 3) the ability of these trace metals to bioaccumulate in the tissues of exposed individuals. As, Cd, Cu, Mg, Mn, and Pb were detected in solutions at increasing concentrations concurrent with ash concentration. Exposure to leachates caused significant delays in embryonic development, reduced juvenile shell growth, decreases in egg and clutch production, and the display of avoidance behaviors. Tissues of exposed snails contained elevated concentrations of As, Cd, Cu, and Cr, with bioconcentration factors 177,550 times higher in cadmium and 85,468 times higher in arsenic in the highest treatment compared to control organisms. Our results highlight the potential harmful effects of coal ash leachates on a novel freshwater invertebrate species using several unique methodologies, providing key information regarding their potential impacts on surrounding aquatic ecosystems.

Optimization of salinity levels for the culture of cyclopoid copepod Dioithona oculata (Farran, 1913) with respect to total population, reproduction, development and adult longevity

Cyclopoid copepod, Dioithona oculata, is a common free-living euryhaline species in tropical and temperate waters having potential as live feed in marine fish larval rearing. Here, the effect of salinity on adult and naupliar survival, total population, population composition, clutch production, clutch size, development rate and adult longevity was investigated. Adult copepods survived the abrupt changes in salinities from 15 to 50 ppt (parts per thousand). The highest naupliar survival was at 30 ppt (86.33 ± 2.84%) and the lowest at 15 ppt (12.6 ± 2.34%). The highest production was at 30 ppt (883.0 ± 5.5 individuals/L) and the lowest at 15 ppt (49.0 ± 6.56 individuals/L). The proportion of nauplii was higher at salinities from 20 to 40 ppt, whereas the total population of copepodites and adults was significantly less at 15 and 45 ppt. The highest clutch production was observed at 30 ppt (8.6 ± 0.54 clutches) and the lowest at 45 ppt (2.6 ± 0.54 clutches). Maximum clutch size of D. oculata was recorded at 30 ppt (19.2 ± 2.94 eggs/clutch) and minimum at 45 ppt (7 ± 1 eggs/clutch) respectively. Development time from nauplius to adult was significantly (p < 0.05) longer at 45 ppt (12.72 ± 0.03 days) and shorter at 20 ppt (9.06 ± 0.02). Adult longevity was significantly higher at 30 ppt (27 ± 1.0 days) and lower at 45 ppt (11.3 ± 1.15). Salinity changes significantly affected the production performance of D. oculata. The optimum salinity for mass culture of D. oculata was found to be 30 ppt.

Green turtle population recovery at Aldabra Atoll continues after 50 yr of protection

Green turtles Chelonia mydas have been subject to high levels of anthropogenic exploitation, with harvesting at their nesting sites especially pronounced throughout the late 19th and early 20th centuries, leading to worldwide declines. Due to their delayed sexual maturity, long-term protection and monitoring is crucial to allow and accurately demonstrate population recovery. Subsequent to their exploitation, Aldabra Atoll (Republic of Seychelles) has offered the longest continuous protection for nesting green turtles anywhere in the Western Indian Ocean, beginning in 1968. Here, we document the continuing recovery of that population by estimating clutch production within 12 mo nesting seasons over 50 yr of monitoring. An estimated mean of 15297 clutches were laid annually between December 2014 and November 2019. This represents an increase of 173% since Aldabra’s intensive monitoring programme was initiated in 1980, and 410-�665% since 1968. Clutch number increases were recorded at all but 1 of 6 monitored beach groups around the atoll but were most pronounced at Settlement Beach, where exploitation of nesting females was historically most intense. Seasonality data since 2000 showed a year-round nesting season, with elevated activity in April-June peaking on average in May, and a potential shift to later in the year over time. This study highlights the considerable contribution of Aldabra Atoll to regional green turtle numbers and the benefit of long-term protection and monitoring at what can be considered a global reference site for this species.

Aspidoscelis costatus costatus (Squamata, Teiidae): high elevation clutch production for a population of whiptail lizards

Clutch size and number of clutches per reproductive cycle are important life history traits that can be influenced by anatomical, physiological, evolutionary, and ecological factors. This report on the clutch size and number of clutches of an endemic Mexican whiptail lizard, Aspidoscelis costatus costatus (Cope, 1878), is based on a study of population at an unusually high elevation for a member of this genus. The study site is located in Ixtapan de la Sal, southeastern Estado de México, Central Mexico, at 2090 m a.s.l. Lizards were sampled in June 2006, and from May to July 2007, where females of Aspidoscelis costatus costatus were collected by hand along a drift fence. Female reproductive condition was evaluated based on abdominal palpation for presence of developing eggs; clutch size was determined by actual counts of either vitellogenic follicles or oviductal eggs. The smallest reproductive female was 77 mm snout-vent length; females produced a minimum of two clutches during the breeding season, the mean clutch size of 6.5 eggs (n = 33) was one of the largest reported for the genus. However, both length and width of its eggs, and the relative clutch mass have not been diminished by development of a large clutch. Additionally, comparisons of clutch size were undertaken within the polytypic A. costatus complex, within the genus Aspidoscelis, and between certain genera of whiptail lizards. This apparently represents the first study of whiptail lizards (genus Aspidoscelis), assessing the aforementioned reproductive characteristics, in a population above 2000 m.

Estimates of marine turtle nesting populations in the south-west Indian Ocean indicate the importance of the Chagos Archipelago

AbstractGlobal marine turtle population assessments highlight the importance of the south-west Indian Ocean region, despite data gaps for the Chagos Archipelago. The archipelago hosts nesting hawksbill Eretmochelys imbricata and green turtles Chelonia mydas, both heavily exploited for 2 centuries until protection in 1968–1970. We assessed available nesting habitat and spatial distribution of nesting activity during rapid surveys of 90% of the archipelago's coastline in 1996, 1999, 2006 and 2016. We quantified seasonality and mean annual egg clutch production from monthly track counts during 2006–2018 along a 2.8 km index beach on Diego Garcia island. An estimated 56% (132 km) of coastline provided suitable nesting habitat. Diego Garcia and Peros Banhos atolls accounted for 90.4% of hawksbill and 70.4% of green turtle nesting. Hawksbill turtles showed distinct nesting peaks during October–February, and green turtles nested year-round with elevated activity during June–October. Estimates of 6,300 hawksbill and 20,500 green turtle clutches laid annually during 2011–2018 indicate that nesting on the Chagos Archipelago has increased 2–5 times for hawksbill turtles and 4–9 times for green turtles since 1996. Regional estimates indicate green turtles produce 10 times more egg clutches than hawksbill turtles, and the Chagos Archipelago accounts for 39–51% of an estimated 12,500–16,000 hawksbill and 14–20% of an estimated 104,000–143,500 green turtle clutches laid in the south-west Indian Ocean. The improved status may reflect &gt; 40 years without significant exploitation. Long-term monitoring is needed to captureinterannual variation in nesting numbers and minimize uncertainty in population estimates.

Improving Productivity by Reducing Cycle Time Through New Fixture Design and Inspection Method

In this aggressive global the manufactures need to deliver their product in a shorter term. To fulfill the customers, the manufacture must reduce the unnecessary process time and the errors. In this paper, the clutch operating lever production line in an automobile industry was analysed. The bottleneck operation was found in a fixture design and during the inspection process. A new fixture and an inspection gauge are designed to reduce the setup and inspection time the clutch production. The overall loading and set up change over time is reduced by the newly designed fixture which reduces the end-line defects and saves time and effort. The productivity is highly increased by 55% by the newly designed fixture and the inspection rate is boosted by 80% and the rejection rate is reduced by 83% which is proven by the comparison to older methods.

Distribution pattern and competition of insects breeding on Camellia japonica flower

AbstractThe distribution pattern and competition of insects exploiting Camellia japonica flowers were studied in Tokyo, central Japan, to understand how their distributions are determined. Dasiops sp. of Lonchaeidae (Diptera) exploited flower buds and showed random distribution, whereas Drosophila unipectinata, D. oshimai and D. lutescens of Drosophilidae (Diptera) and Epuraea commutata of Nitidulidae (Coleoptera) exploited fully opened, late and fallen flowers and showed aggregated distribution. From the distribution pattern, it is assumed that Dasiops sp. has clutches of single egg whereas drosophilid and nitidulid species have clutches of more than one egg. In resource supplementary experiments, body size of drosophilid flies increased if resources were supplemented, although their survival is assumed to be unaffected. However, their body size did not decrease with increase of larval density in resource patches. It is therefore unclear whether resource competition occurs among drosophilid flies in Camellia flowers in nature. From the present and previous studies, it is assumed that aggregation (or production of clutches of more than one egg) is related to the use of fermenting or decayed resources; aggregation might increase larval survival and/or performance under the presence of molds or microorganisms.

Fuel for the pace of life: Baseline blood glucose concentration co‐evolves with life‐history traits in songbirds

Abstract It has been proposed that life histories have co‐evolved with a suite of physiological and behavioural adaptations, termed pace‐of‐life syndromes. Here, we hypothesise that basal concentration of blood glucose (G0), a major source of energy circulating in blood, may constitute a key component of pace‐of‐life syndromes. To test this hypothesis, we measured G0 in 30 passerine species and tested its covariation with body mass and other life‐history traits. Importantly, body mass is a major life‐history determinant and, when its effect is controlled for, there may be no single fast–slow life‐history continuum in birds comprising both fecundity and life span. Hence, we used individual life‐history traits, rather than principal component analysis, to characterise life‐history variation in our analysis. In support of G0‐life‐history co‐evolution, we found G0 to be negatively correlated with body mass and positively with reproductive investment in a single clutch across 30 passerine species. Higher G0 in females suggests that the energy demands of clutch production and incubation may be an important selection force driving co‐evolution of G0 with reproductive output. In contrast, G0 was not associated with maximum life span, suggesting that high G0 may not constrain evolution of longevity. This implies that long‐lived species can evolve physiological adaptations preventing harmful effects of high glucose concentrations, known to cause pathologies and accelerate ageing. In addition, G0, but not basal metabolic rate (BMR), was negatively correlated with migration distance, attesting to evolutionary changes in energy metabolism in long‐distance migrants. Our results further suggest that the links between body mass, reproduction and G0 are not mediated by BMR and that G0 is associated with fast–slow life‐history variation more closely than available BMR data. A species life history is determined to a great extent by body mass. When this effect is controlled for, only those traits related to reproduction (but not life span) constitute the principal axis of life‐history variation in birds. Hence, the co‐evolution of G0 with body mass and reproductive output evidenced in our study indicates that G0 constitutes an important physiological component of pace‐of‐life syndromes. A plain language summary is available for this article.

Evolution of steroid hormones in reproductive females of the threespine stickleback fish

Hormones play a prominent role in animal development, mediating the expression of traits and coordinating phenotypic responses to the environment. Their role as physiological integrators has implications for how populations respond to natural selection and can impact the speed and direction of evolutionary change. However, many emerging and established fish models with the potential to be ecologically or evolutionarily informative are small-bodied, making hormone sampling through traditional methods (whole-body or plasma) lethal or highly disruptive. Sampling methodology has thus restricted study design, often limiting sample sizes, and has prevented the study of at-risk/endangered populations. We utilize water-borne hormone sampling, a minimally invasive method of measuring the rate of steroid hormone release across the gills and further validate this method in a novel, evolutionary context. First, we compare water-borne hormone measures of cortisol with those quantified from plasma and whole-body samples collected from the same individuals to establish the relationship between concentrations quantified via the three methods. We then compare the release of steroid hormones in three populations of threespine stickleback to establish the sensitivity of this tool in measuring within-individual and between-individual variation in biologically relevant contexts (reproductive stages), and in assessing differences among populations with distinct evolutionary histories. We demonstrate a strong positive relationship between cortisol concentrations measured with water-borne, plasma, and whole-body collection techniques. Tracking estradiol and testosterone throughout clutch production in females produced anticipated patterns associated with growing and maturing eggs, with divergence in estradiol production in one population. Additionally, differences among populations in cortisol levels at ovulation paralleled the relative presence of a social stressor, and thus expected energetic needs within each population. We confirm that water-borne hormone sampling is sufficiently sensitive to capture biologically relevant fluctuations in steroid hormones between environmental contexts and demonstrate that among-population differences are detectable. This technique can be applied broadly to small fish to answer important ecological and evolutionary questions. By linking population variation in hormones and the multivariate phenotype, this technique will help elucidate both proximate mechanisms underlying phenotypic development and variation, and the way hormone networks alter evolutionary responses to selection.

Seasonal changes in plasma concentrations of the thyroid, glucocorticoid and reproductive hormones in the tegu lizard Salvator merianae

The tegu lizard Salvator merianae is a large, widely distributed teiid lizard endemic to South America that exhibits annual cycles of high activity during the spring and summer, and hibernation during winter. This pattern of activity and hibernation is accompanied by profound seasonal changes in physiology and behavior, including endothermy during the austral spring. The unusual combination of seasonal endothermy, hibernation and oviparity, in a non-avian, non-mammalian species, makes S. merianae an interesting subject for study of comparative aspects of endocrine regulation of seasonal changes in physiology. In the present study, we first validated commercially available immunoassay kits for quantification of hormone concentrations of the reproductive (testosterone, estradiol and progesterone), adrenal (corticosterone), and thyroid [thyroxine (T4) and triiodothyronine (T3)] axes in plasma of an outdoor, captive adult male and female S. merianae in southeastern Brazil. All assays exhibited parallelism and accuracy with S. merianae plasma. We next assessed patterns of concentration of these hormones across the annual cycle of S. merianae. Testosterone in males and estradiol in females peaked in spring coincident with the peak in reproductive behavior. Progesterone in females was significantly elevated in October coincident with putative ovulation when gravid females build nests. Thyroid hormones, known for regulating energy metabolism, varied seasonally with some sex-dependent differences. T4 gradually increased from an annual nadir during pre-hibernation and hibernation to high concentrations during spring in both sexes. In contrast, T3 did not vary seasonally in males, but females showed a two-fold increase in T3 during the spring reproductive season. T3 may be involved in energy investment during the seasonal production of large clutches of eggs. Corticosterone was significantly elevated during the active season in both sexes, suggesting its involvement in mobilization of energy stores and modulation of behavior (territoriality) and physiology. Ours is the first investigation of concurrent changes in reproductive, thyroid and adrenal hormone concentrations in this endemic and physiologically unique South American lizard. Our findings set the stage for future investigations to determine the extent to which these hormones influence activity and thermoregulation in S. merianae.

Facultative production of multiple-egg clutches in a quasi-gregarious parasitoid: fitness gains for offspring at low developmental temperature

In the quasi-gregarious parasitoid wasp Anastatus disparis, a mother may lay more than one egg in a host during a single host encounter. This is conventionally known as self-superparasitism and, since only one adult offspring can complete development on the host, it may represent a waste of eggs and time. However, this behavior may be better described as “multiple-egg clutches,” which differs fundamentally from self-superparasitism and has seldom been addressed. The potential benefits of laying multiple-egg clutches are currently unclear, and we therefore aimed to investigate them in A. disparis. First, our results showed that production of multiple-egg clutches by A. disparis is not due to a lack of discrimination between unparasitized and parasitized hosts, as females preferred to lay eggs in unparasitized hosts. It was also unrelated to the age of the female or her mating status, or to the presence of conspecific females. However, compared to the temperatures of 26 and 32 °C, we observed that the frequency of multiple-egg clutches increased at the temperature of 20 °C. In addition, low developmental temperatures significantly decreased the rate of successful wasp eclosion from hosts in which a single egg was deposited, and this rate was increased by laying multiple-egg clutches. These results suggest that female A. disparis adults produce multiple-egg clutches to increase the probability of obtaining offspring from the host, and may have the ability to regulate oviposition and reproduction strategy based on environmental temperature. Anastatus disparis exhibited an oviposition behavior of facultative production of multiple-egg clutches, which is not due to a lack of host discrimination, or due to the age of the female or her mating status nor the presence of conspecific females. However, our results suggest that A. disparis adults produce multiple-egg clutches when it increased the probability of obtaining offspring from the host, and may have the ability to regulate their oviposition strategy based on environmental temperature.

Breeding decisions and output are correlated with both temperature and rainfall in an arid-region passerine, the sociable weaver.

Animal reproductive cycles are commonly triggered by environmental cues of favourable breeding conditions. In arid environments, rainfall may be the most conspicuous cue, but the effects on reproduction of the high inter- and intra-annual variation in temperature remain poorly understood, despite being relevant to the current context of global warming. Here, we conducted a multiyear examination of the relationships between a suite of measures of temperature and rainfall, and the onset and length of the breeding season, the probability of breeding and reproductive output in an arid-region passerine, the sociable weaver (Philetairus socius). As expected, reproductive output increased with rainfall, yet specific relationships were conditional on the timing of rainfall: clutch production was correlated with rainfall throughout the season, whereas fledgling production was correlated with early summer rainfall. Moreover, we reveal novel correlations between aspects of breeding and temperature, indicative of earlier laying dates after warmer springs, and longer breeding seasons during cooler summers. These results have implications for understanding population trends under current climate change scenarios and call for more studies on the role of temperature in reproduction beyond those conducted on temperate-region species.

Habitat specialization and climate affect arthropod fitness: a comparison of generalist vs. specialist spider species in Arctic and temperate biomes

Life history trade-offs are a key notion in evolutionary biology, notably for understanding how selection shapes the diversity of traits among species. Despite the frequent study of such trade-offs, few studies synchronously investigate the effects of multiple factors, such as niche specialization and adaptation to harsh environments. We compared reproduction (fecundity and egg quality) in two sympatric couples (one habitat generalist and one specialist) of congeneric wolf spider species, in both Arctic and temperate habitats. We found that specialist species at both latitudes invested more in clutch size than did generalist species. We interpret this result as an optimization of clutch production. In the Arctic, the specialist was able to invest in fecundity with increasing body size at a much higher rate than the generalist species. In the temperate habitat, both species showed similar strategies: they increased quantity and quality of offspring relative to body size at the same rate. These results are consistent with the hypothesis that Arctic species must develop distinct strategies in order not to overlap each other's ecological niches as a consequence of limited food resources or niche space. We emphasize the need to test the role of plasticity and environmentally mediated effects of competition on arthropod fitness.

Fecundity of Wild Northern Bobwhite Hens Under Hatchery Conditions

We describe egg production by 88 pairs of randomly selected, mature, wild-caught northern bobwhite (Colinus virginianus) hens housed under optimal conditions of food, water, climate, and a 17-hr photoperiod in a hatchery. We collected eggs daily using an 18-day period to differentiate between clutches. Hens continuously laid eggs until ceasing production. We evaluated number of eggs laid by each hen individually and hens collectively including total number, number/clutch, number/day, hatching success, and egg mass. Eighty-six hens produced 5,888 eggs. Number of eggs produced by individual hens ranged from 0 to 172 over ~ 200 days. Mean number of eggs laid/hen/day was 0.86. Clutch size ranged from 0 (n 1⁄4 2) to 12 (n 1⁄4 1). Mean number of eggs/clutch was 8.57. There was a strong correlation between clutch size and number of clutches. Some hens demonstrated continuous production of several large clutches. Hatching success of 5,793 eggs included for analysis was 61.6% (3,571 hatched, 2,222 failed to hatch). Hatched eggs had a greater mean mass compared to those that did not hatch.

Not what it looks like: mate-searching behaviour, mate preferences and clutch production in wandering and territory-holding female fiddler crabs.

Risks inherent in mate-searching have led to the assumption that females moving sequentially through populations of courting males are sexually receptive, but this may not be true. We examined two types of fiddler crab females: wanderers moving through the population of courting males and residents that were occupying and defending their own territories. Sometimes residents leave territories to look for new burrows and we simulated this by displacing wanderers and residents and observing their behaviour while wandering. We predicted that the displaced wanderers would exhibit more mate-searching behaviours than resident females. However, wandering and resident females behaved nearly identically, displaying mate-searching behaviours and demonstrating matching mate preferences. Also, males behaved the same way towards both female types and similar proportions of wanderers and residents stayed in a male's burrow to mate. But more wanderers than residents produced egg clutches when choosing a burrow containing a male, suggesting females should be categorized as receptive and non-receptive. Visiting and rejecting several males is not the defining feature of female mate choice. Moving across the mudflat by approaching and leaving a succession of burrows (mostly occupied by males) is an adaptive anti-predator behaviour that is useful in the contexts of mate-searching and territory-searching.