Reproduction and annual gametogenic cycle in Nephtys hombergii and N. caeca (Polychaeta: Nephtyidae)

The gametogenic cycles of Nephtys hombergii Audouin et M. Edw. and N. caeca Fabricius are described. Both species are polytelic (=discrete, iteroparous) and breed in their second and subsequent years. They spawn in May in the Tyne estuary. After spawning, N. hombergii retains a large number of gametocytes, which are ultimately resorbed. A new generation of gametocytes is proliferated by September and mature gametes accumulate during the winter months. Gametic development is not well synchronised.     

Reproductive success,relative abundance and population structure of two species of Nephtys in an estuarine beach

During 1978 and 1979 specimens of Nephtys hombergii in the River Tyne estuary (North East England) became gravid during the winter but did not spawn in the spring breeding season; instead their gametes were resorbed. The drastic effects of these spawning failures were apparent in the population structure in 1980, when the 1978 and 1979 year-classes were shown to be virtually absent, by the size of the individuals in the population and the numbers of growth lines in their jaws. The population structure in 1975, by contrast, indicated that recruitment during the preceding 4 to 5 yr had been good. Spawning was also effective in 1980, and an 0 group was detected in August 1980. Comparable data has been obtained for N. caeca, which occurs in the same beach. It shows that recruitment of this species during 1976–1980 was consistently good, whereas analysis of the age-class frequencies suggests that recruitment of N. caeca was poor in 1973 and 1975. The dominance relationship of the two species in the beach has been reversed during the period 1975–1980. It is suggested that the sympatric distribution of the two species is maintained in part by periodic reproductive failure. The causes of this are not yet known; possible reasons, including the extremely cold conditions experienced in 1978–1979 are discussed. The difference in frequency of the 1978, 1979 and 1980 year classes will now permit a rigorous evaluation of the relationship between the number of growth lines in the jaws and age in N. hombergii.     

Comparison of spatial overlap between the polychaetes Nereis virens and Nephtys caeca in two intertidal estuarine environments

An intensive study of spatial overlap between the polychaetes Nereis virens (Sars) and Nephtys caeca (Fabricius) was conducted in 1992 on two tidal sand flats, which differ by their exposure to dominant winds and residual currents in the Lower St. Lawrence Estuary (Québec, Canada). Results showed that spatial overlap (Lloyd's index and spatial distribution) was higher among adults of both species at the lower tidal elevation of l'Anse-à-l'Orignal (north-east oriented). Results also suggest weaker interspecific interactions among juveniles of both species because of limited spatial overlap. In Baie-du-Ha!Ha! (south-west oriented), spatial overlap was greater than that observed in l'Anse-à-l'Orignal and appeared important in adults as well as in juveniles. Levins' directional measure of competition indicated an asymmetric spatial overlap between N. virens and N. caeca in Baie-du-Ha!Ha! and a symmetric overlap in l'Anse-à-l'Orignal. The intraspecific encounter values, estimated from Lloyd's mathematical expression, were significantly higher than values of interspecific interactions only in l'Anse-à-l'Orignal. Moreover, no vertical stratification was found inside the sediment, with no effect of the densities and individual body weights of the polychaetes. Juveniles of both species mainly inhabited the organic-rich upper portion of the sediments (0 to 12 cm), while adults colonised greater depths (>25 cm) where organic matter content was lower. A complementary field experiment was conducted in 1993 to investigate interspecific interactions (predation and competition) existing between N. virens and N. caeca. Results from this experiment depend on which species was first-introduced and showed an important variation in mortality rates between allopatric and sympatric conditions. The influence of competition and predation on the structure of these populations is also discussed in relation to their spatial overlap.     

Population dynamics and secondary production in an estuarine population of Nephtys hombergii (Polychaeta: Nephtyidae)

From July 1978 to March 1980, a study was made on the distribution, population dynamics and secondary production of Nephtys hombergii Audouin et Edw. occurring in the sublittoral industrialised region of Southampton Water in south England. The distribution of the worm was related to the silt content and copper level of the sediment, the greatest densities of N. hombergii being found in sediment containing 60 to 100% silt. Breeding occurred at a low level throughout the year, with a maximum in July to September and November to January in the second year of growth. Spawning occurred when the oocytes measured 200m in diameter, and unshed gametes were resorbed. Annual production varied between 0.092 and 4.32 g C m^-2 yr^-1 (ash-free dry weight) and amounted to 1.9–39.4% of the total macrofaunal production at the sampling stations. The production:biomass (P:B) ratio of the species varied between 1.6 and 2.9.     

Reproductive cycle,larval development,juvenile growth and population dynamics of Patiriella pseudoexigua (Echinodermata: Asteroidea) in Taiwan

A field study was conducted at Wanlitung, southern Taiwan, in 1986–1089, to determine the reproductive cycle, development mode, growth rate and population dynamics of the small seastar Patiriella pseudoexigua (Dartnall), which occurs in highly stressful and disturbed intertidal pools in this area. An inverse relationship between gonad index and pyloric-caccum index was only recorded immediately prior to spawning. A short, well-synchronized seasonal spawning occurs in October. When reared at 25 °C, lecithotrophic larvae develop directly, lack a bipinnaria stage, and metamorphose completely on the seventh day after fertilization. The growth curves of field juveniles are linear, those of laboratory-reared juveniles are sigmoid. Juveniles appear in tide pools in spring-early summer of each year. Adults spawn mainly in late fall, enabling spawning to occur in time for the larvae to benefit from the environmentally favorable winter season. Populations in high-tidal pools decrease in later summer, but remain more stable in lowtidal pools and lagoons.     

Reproductive energetics of two species of dorid nudibranchs with planktotrophic and lecithotrophic larval strategies

Onchidoris muricata (Müller) and Adalaria proxima (Alder and Hancock) are sympatric, potentially competing species of dorid nudibranchs, which preferentially graze the cheilostome polyzoan Electra pilosa (L.). O. muricata is small and lays small eggs which hatch as poorly-developed planktotrophic veliger larvae. A. proxima is larger and reproduces by means of larger eggs which hatch, as well-developed lecithotrophic larvae, that can metamorphose within approximately 24 h of release. A. proxima larvae can feed in the plankton, but do not require extrinsic nutrition to undergo complete development. Both species spawn in February–april, and have a strictly annual life-cycle. Comparisons of the calorific content of spawn have shown that A. proxima apportions a greater number of calories to reproduction, but that O. muricata makes a greater relative effort. A. proxima shown considerable individual variability in reproductive effort, which fails to correlate with, body size or rate of spawning. A more deterministic situation applies to O. muricata, because body size and fecundity follow an allometric relationship. It appears that there is a threshold of absolute energy required to support the lecithotrophic larval strategy in nudibranchs, and that this is not attained by the smaller species, O. muricata. A. proxima thus appears to have both reproductive strategies open to it, and to have adopted lecithotrophy in order to offset the unpredictability of energy available for reproduction.Communicated by J. M. Mauchline, Oban     

Spatial scaling of avian population dynamics: population abundance, growth rate, and variability

Synchrony in population fluctuations has been identified as an important component of population dynamics. In a previous study, we determined that local-scale (<15-km) spatial synchrony of bird populations in New England was correlated with synchronous fluctuations in lepidopteran larvae abundance and with the North Atlantic Oscillation. Here we address five questions that extend the scope of our earlier study using North American Breeding Bird Survey data. First, do bird populations in eastern North America exhibit spatial synchrony in abundances at scales beyond those we have documented previously? Second, does spatial synchrony depend on what population metric is analyzed (e.g., abundance, growth rate, or variability)? Third, is there geographic concordance in where species exhibit synchrony? Fourth, for those species that exhibit significant geographic concordance, are there landscape and habitat variables that contribute to the observed patterns? Fifth, is spatial synchrony affected by a species' life history traits? Significant spatial synchrony was common and its magnitude was dependent on the population metric analyzed. Twenty-four of 29 species examined exhibited significant synchrony in population abundance: mean local autocorrelation (rho)= 0.15; mean spatial extent (mean distance where rho=0) = 420.7 km. Five of the 29 species exhibited significant synchrony in annual population growth rate (mean local autocorrelation = 0.06, mean distance = 457.8 km). Ten of the 29 species exhibited significant synchrony in population abundance variability (mean local autocorrelation = 0.49, mean distance = 413.8 km). Analyses of landscape structure indicated that habitat variables were infrequent contributors to spatial synchrony. Likewise, we detected no effects of life history traits on synchrony in population abundance or growth rate. However, short-distance migrants exhibited more spatially extensive synchrony in population variability than either year-round residents or long-distance migrants. The dissimilarity of the spatial extent of synchrony across species suggests that most populations are not regulated at similar spatial scales. The spatial scale of the population synchrony patterns we describe is likely larger than the actual scale of population regulation, and in turn, the scale of population regulation is undoubtedly larger than the scale of individual ecological requirements.     

Irruptive population dynamics in Yellowstone pronghorn.

Irruptive population dynamics appear to be widespread in large herbivore populations, but there are few empirical examples from long time series with small measurement error and minimal harvests. We analyzed an 89-year time series of counts and known removals for pronghorn (Antilocapra americana) in Yellowstone National Park of the western United States during 1918-2006 using a suite of density-dependent, density-independent, and irruptive models to determine if the population exhibited irruptive dynamics. Information-theoretic model comparison techniques strongly supported irruptive population dynamics (Leopold model) and density dependence during 1918-1946, with the growth rate slowing after counts exceeded 600 animals. Concerns about sagebrush (Artemisia spp.) degradation led to removals of >1100 pronghorn during 1947-1966, and counts decreased from approximately 700 to 150. The best models for this period (Gompertz, Ricker) suggested that culls replaced intrinsic density-dependent mechanisms. Contrary to expectations, the population did not exhibit enhanced demographic vigor soon after the termination of the harvest program, with counts remaining between 100 and 190 animals during 1967 1981. However, the population irrupted (Caughley model with a one-year lag) to a peak abundance of approximately 600 pronghorn during 1982-1991, with a slowing in growth rate as counts exceeded 500. Numbers crashed to 235 pronghorn during 1992-1995, perhaps because important food resources (e.g., sagebrush) on the winter range were severely diminished by high densities of browsing elk, mule deer, and pronghorn. Pronghorn numbers remained relatively constant during 1996-2006, at a level (196-235) lower than peak abundance, but higher than numbers following the release from culling. The dynamics of this population supported the paradigm that irruption is a fundamental pattern of growth in many populations of large herbivores with high fecundity and delayed density-dependent effects on recruitment when forage and weather conditions become favorable after range expansion or release from harvesting. Incorporating known removals into population models that can describe a wide range of dynamics can greatly improve our interpretation of observed dynamics in intensively managed populations.     

Interactive effects of prey and p,p'-DDE on burrowing owl population dynamics.

We used population models to explore the effects of the organochlorine contaminant p,p'-DDE and fluctuations in vole availability on the population dynamics of Burrowing Owls (Athene cunicularia). Previous work indicated an interaction between low biomass of voles in the diet and moderate levels of p,p'-DDE in Burrowing Owl eggs that led to reproductive impairment. We constructed periodic and stochastic matrix models that incorporated three vole population states observed in the field: average, peak, and crash years. We modeled varying frequencies of vole crash years and a range of impairment of owl demographic rates in vole crash years. Vole availability had a greater impact on owl population growth rate than did reproductive impairment if vole populations peaked and crashed frequently. However, this difference disappeared as the frequency of vole crash years declined to once per decade. Fecundity, the demographic rate most affected by p,p'-DDE, had less impact on population growth rate than adult or juvenile survival. A life table response experiment of time-invariant matrices for average, peak, and crash vole conditions showed that low population growth under vole crash conditions was due to low adult and juvenile survival rates, whereas the extremely high population growth under vole peak conditions was due to increased fecundity. Our results suggest that even simple models can provide useful insights into complex ecological interactions. This is particularly valuable when temporal or spatial scales preclude manipulative experimental work in the field or laboratory.     

Reproductive dynamics of endeavour prawns, Metapenaeus endeavouri and M. ensis, in Albatross Bay, Gulf of Carpentaria, Australia

 The spawning patterns of two penaeid prawns, Metapenaeus endeavouri (Schmitt) and M. ensis (De Haan), were examined from data collected at 45 stations between March 1986 and March 1992. An index of population fecundity based on the abundance, proportion and fecundity of sexually mature females was used as a measure of spawning output of the prawn stock. The population fecundity index for M. ensis was higher than that for M. endeavouri. The monthly population fecundity index for M. endeavouri varied markedly among years, while that for M. ensis was consistent among years. Spawning of M. endeavouri occurred year-round, while that of M. ensis was concentrated mainly in spring (September to November). For M. endeavouri, a minor spawning, derived from a relatively small number of summer spawners, occurred in the 20 to 30 m offshore waters in summer. In early summer (after May), the major spawning group consisted of large females from the winter-spawning cohort, and the spawning area shifted to depths of 30 to 60 m. In winter (July), the major spawning, derived from the winter-spawning cohort, occurred at depths of 20 to 40 m. For M. ensis, the major spawning, derived from the spring-spawning cohort, was observed in depths <50 m and was concentrated particularly in inshore waters (<20 m) in spring. In autumn, the spawning output was mainly from the autumn-spawning cohort, which comprised but a small number of individuals. In winter, the major spawning group again consisted of the large females from the spring-spawning cohort, and spawning increased in the oceanic waters (>50 m). These results suggest that mature female M. endeavouri and M. ensis move offshore (>40 m) by May and July, respectively, and return to shallow waters (<35 m) in July and November, respectively. The monthly reproduction patterns of both species in the “effective spawning” area showed that the major spawning season for M. endeavouri is August to October and that for M. ensis is September to December. Received: 19 February 1999 / Accepted: 18 June 2000     

Density dependence vs. independence, and irregular population dynamics of a swallow-wort fruit fly

Although most long-term studies of consumer-resource (e.g., predator-prey) interactions select species showing cyclic population dynamics, strong consumer-resource interactions can also produce irregular, noncyclic dynamics. Here, we present a case in which a seed predator, the tephritid fruit fly Euphranta connexa, shows fluctuations in density of more than two orders of magnitude over a 22-year period. To explain these fluctuations, we analyzed a stage-specific data set to quantify the density-dependent and density-independent components of larval survivorship and realized fecundity. Both larval survivorship and realized fecundity were strongly density dependent. Larval survivorship dropped from 0.62 at low larval density to 0.081 at high larval density, whereas fecundity dropped from 84.3 to 0.32 eggs per individual, more than a 100-fold decrease. We divided density-independent variation in E. connexa population dynamics into components for variability in (1) larval survivorship, (2) realized fecundity, and (3) annual fruit abundance. Of these components, 96% of the density-independent variance in per capita population growth rates was caused by fluctuations in fruit abundance. This highlights the importance of the strong consumer-resource interactions in driving fluctuations in E. connexa abundance. It also demonstrates that E. connexa dynamics are remarkably simple, and aside from the 4% of unexplained variance in per capita population growth rates, our understanding of E. connexa dynamics is remarkably complete.     

Hidden process models for animal population dynamics.

Hidden process models are a conceptually useful and practical way to simultaneously account for process variation in animal population dynamics and measurement errors in observations and estimates made on the population. Process variation, which can be both demographic and environmental, is modeled by linking a series of stochastic and deterministic subprocesses that characterize processes such as birth, survival, maturation, and movement. Observations of the population can be modeled as functions of true abundance with realistic probability distributions to describe observation or estimation error. Computer-intensive procedures, such as sequential Monte Carlo methods or Markov chain Monte Carlo, condition on the observed data to yield estimates of both the underlying true population abundances and the unknown population dynamics parameters. Formulation and fitting of a hidden process model are demonstrated for Sacramento River winter-run chinook salmon (Oncorhynchus tshawytsha).     

Ungulate population dynamics and optimization models

Optimal harvesting strategies for an ungulate population are estimated using stochastic dynamic programming. Data on the Llano Basin white-tailed deer (Odocoileus virginianus) population were used to construct a 2-variable population dynamics model. The model provided the basis for estimating optimal harvesting strategies as a feedback function of the current values of the state variables (prefawning older deer and juveniles). Optimal harvest strategies were insensitive to assumptions about the probability distributions of the stochastic variable (rainfall). The response of the population components to harvesting and the returns obtained from applying optimal strategies were explored through simulation. Mean annual harvest is about 15% of the population. Simplified harvesting strategies based on age-ratios as well as a simplified version based on optimal strategies—but assuming persisting equilibrium juvenile deer density—were compared to optimal strategies through examining values of information. Simplified harvesting strategies lead to a lower harvest over a 50-year simulation period.     

Field-scale roles of density, temperature, nitrogen, and predation on aphid population dynamics

Robust analyses of noisy, stage-structured, irregularly spaced, field-scale data incorporating multiple sources of variability and nonlinear dynamics remain very limited, hindering understanding of how small-scale studies relate to large-scale population dynamics. We used a novel, complementary Bayesian and frequentist state-space model analysis to ask how density, temperature, plant nitrogen, and predators affect cotton aphid (Aphis gossypii) population dynamics in weekly data from 18 field-years and whether estimated effects are consistent with small-scale studies. We found clear roles of density and temperature but not of plant nitrogen or predators, for which Bayesian and frequentist evidence differed. However, overall predictability of field-scale dynamics remained low. This study demonstrates stage-structured state-space model analysis incorporating bottom-up, top-down, and density-dependent effects for within-season (nearly continuous time), nonlinear population dynamics. The analysis combines Bayesian posterior evidence with maximum-likelihood estimation and frequentist hypothesis testing using average one-step-ahead residuals.     

Reproductive dynamics of the sea urchin Paracentrotus lividus on the Galicia coast (NW Spain): effects of habitat and population density

We studied the spatial variability in the size at first maturity and the reproductive cycle of Paracentrotus lividus in Galicia, contributing key information for the exploitation and management of this resource. The size at maturity varied between 20.4 (±1.2 SE) mm and 27.9 ± 1.2 mm and was smaller in areas of low population density where sea urchins do not form patches. Using a nonlinear model, we analysed the effect of depth, body size, sex and population density on the temporal pattern of the gonad index. The maximum and minimum indices were obtained at 4 m depth in the months before and after the spring spawning, respectively. The depth also affected the cycle phase, and the sea urchins at 4 m depth spawned 9.4 ± 3.0 days later than the sea urchins at 8 m depth and 20.5 ± 3.0 days later than those at 12 m depth. Moreover, the sea urchins living in patches showed a slight increase in gonad size as a consequence of the better-quality habitat. This shows that there is no intraspecific competition in this area despite the high population densities reached (18.5 kg m^?2).     

Uncertainty analysis of transient population dynamics

Two types of demographic analyses, perturbation analysis and uncertainty analysis, can be conducted to gain insights about matrix population models and guide population management. Perturbation analysis studies how the perturbation of demographic parameters (survival, growth, and reproduction parameters) may affect the population projection, while uncertainty analysis evaluates how much uncertainty there is in population dynamic predictions and where the uncertainty comes from. Previously, both perturbation analysis and uncertainty analysis were conducted on the long-term population growth rate. However, the population may not reach its equilibrium state, especially when there is management by harvesting or hunting. Recently, there has been an increased interest in short-term transient dynamics, which can differ from asymptotic long-term dynamics. There are currently techniques to conduct perturbation analyses of short-term transient dynamics, but no techniques have been proposed for uncertainty analysis of such dynamics. In this study, we introduced an uncertainty analysis technique, the general Fourier Amplitude Sensitivity Test (FAST), to study uncertainties in transient population dynamics. The general FAST is able to identify the amount of uncertainty in transient dynamics and contributions by different demographic parameters. We applied the general FAST to a mountain goat (Oreamnos americanus) matrix population model to give a clear illustration of how uncertainty analysis can be conducted for transient dynamics arising from matrix population models.     

Dispersal, density dependence, and population dynamics of a fungal microbe on leaf surfaces

Despite the ubiquity and importance of microbes in nature, little is known about their natural population dynamics, especially for those that occupy terrestrial habitats. Here we investigate the dynamics of the yeast-like fungus Aureobasidium pullulans (Ap) on apple leaves in an orchard. We asked three questions. (1) Is variation in fungal population density among leaves caused by variation in leaf carrying capacities and strong density-dependent population growth that maintains densities near carrying capacity? (2) Do resident populations have competitive advantages over immigrant cells? (3) Do Ap dynamics differ at different times during the growing season? To address these questions, we performed two experiments at different times in the growing season. Both experiments used a 2 x 2 factorial design: treatment 1 removed fungal cells from leaves to reveal density-dependent population growth, and treatment 2 inoculated leaves with an Ap strain engineered to express green fluorescent protein (GFP), which made it possible to track the fate of immigrant cells. The experiments showed that natural populations of Ap vary greatly in density due to sustained differences in carrying capacities among leaves. The maintenance of populations close to carrying capacities indicates strong density-dependent processes. Furthermore, resident populations are strongly competitive against immigrants, while immigrants have little impact on residents. Finally, statistical models showed high population growth rates of resident cells in one experiment but not in the other, suggesting that Ap experiences relatively "good" and "bad" periods for population growth. This picture of Ap dynamics conforms to commonly held, but rarely demonstrated, expectations of microbe dynamics in nature. It also highlights the importance of local processes, as opposed to immigration, in determining the abundance and dynamics of microbes on surfaces in terrestrial systems.     

Chihuahuan Desert kangaroo rats: nonlinear effects of population dynamics, competition, and rainfall

Using long-term data on two kangaroo rats in the Chihuahuan Desert of North America, we fitted logistic models including the exogenous effects of seasonal rainfall patterns. Our aim was to test the effects of intraspecific interactions and seasonal rainfall in explaining and predicting the numerical fluctuations of these two kangaroo rats. We found that logistic models fit both data sets quite well; Dipodomys merriami showed lower maximum per capita growth rates than Dipodomys ordii, and in both cases logistic models were nonlinear. Summer rainfall appears to be the most important exogenous effect for both rodent populations; models including this variable were able to predict independent data better than models including winter rainfall. D. merriami was also negatively affected by another kangaroo rat (Dipodomys spectabilis), consistent with previous experimental evidence. We hypothesized that summer rainfall influences the carrying capacity of the environment by affecting seed availability and the intensity of intraspecific competition.     

Recolonizing wolves and mesopredator suppression of coyotes: impacts on pronghorn population dynamics.

Food web theory predicts that the loss of large carnivores may contribute to elevated predation rates and, hence, declining prey populations, through the process of mesopredator release. However, opportunities to test predictions of the mesopredator release hypothesis are rare, and the extent to which changes in predation rates influence prey population dynamics may not be clear due to a lack of demographic information on the prey population of interest. We utilized spatial and seasonal heterogeneity in wolf distribution and abundance to evaluate whether mesopredator release of coyotes (Canis latrans), resulting from the extirpation of wolves (Canis lupus) throughout much of the United States, contributes to high rates of neonatal mortality in ungulates. To test this hypothesis, we contrasted causes of mortality and survival rates of pronghorn (Antilocapra americana) neonates captured at wolf-free and wolf-abundant sites in western Wyoming, USA, between 2002 and 2004. We then used these data to parameterize stochastic population models to heuristically assess the impact of wolves on pronghorn population dynamics due to changes in neonatal survival. Coyote predation was the primary cause of mortality at all sites, but mortality due to coyotes was 34% lower in areas utilized by wolves (P < 0.001). Based on simulation modeling, the realized population growth rate was 0.92 based on fawn survival in the absence of wolves, and 1.06 at sites utilized by wolves. Thus, wolf restoration is predicted to shift the trajectory of the pronghorn population from a declining to an increasing trend. Our results suggest that reintroductions of large carnivores may influence biodiversity through effects on prey populations mediated by mesopredator suppression. In addition, our approach, which combines empirical data on the population of interest with information from other data sources, demonstrates the utility of using simulation modeling to more fully evaluate ecological theories by moving beyond estimating changes in vital rates to analyses of population-level impacts.     

Feeding ecology and energetics of the Antarctic chaetognaths Eukrohnia hamata, E. bathypelagica and E. bathyantarctica

Ecological and physiological studies focused on dietary preferences, lipid biochemistry and energetics within the three Antarctic chaetognaths Eukrohnia hamata, E. bathypelagica and E. bathyantarctica from meso- and bathypelagic depths. Eukrohnia hamata and E. bathypelagica respired 0.15 μL O₂ mg dry mass (DM)⁻¹ h⁻¹, which translates to an average metabolic loss of only <1.1% of body carbon per day. Lipid storage was not substantial in E. bathypelagica (mean 11.5 ± 6.5% DM) and E. bathyantarctica (mean 15.4 ± 4.1% DM) during summer and winter, suggesting year-round feeding of these predators mainly on copepods. In E. bathypelagica, total fatty acids were dominated by the fatty acids 16:0, 20:5(n-3) and 22:6(n-3) and in E. bathyantarctica also by 18:1(n-9), a fatty acid usually found in storage lipids. Only the latter species was characterized by significant amounts of wax esters, consisting largely of the common fatty alcohols 16:0, 20:1(n-9) and the unusual fatty alcohol isomer 22:1(n-9).