The seasonality of arboreal arthropods foraging within an Australian rainforest tree

Abstract.

• 1 The seasonality of arboreal arthropods foraging within the crown of the canopy tree Argyrodendron actinophyllum. Edlin (Sterculiaceae) was studied in a subtropical rain forest near Brisbane, Australia, during 2 years with interception traps and restricted canopy fogging.
• 2 Minimal air temperatures explained most of the seasonal variance in arthropod‘density activity'. However, the host phenology was important for several phytophagous groups. Rainfall, relative humidity and lunar phase influenced arthropod activity slightly.
• 3 Seasonal ranges were significantly different among arboreal guilds and were related to food resource availability in time, associated with both the host and the rainforest environment. Seasonal peaks of herbivores were more marked than in tropical rain forests, but less sharp than in temperate woodlands.'
• 4 Quantitative changes in arthropod density activity and abundance were important for most groups, with a marked trough during cool and dry months. The numerical contribution of most arthropod guilds to the arboreal community was not constant throughout the year.
• 5 Seasonal changes in the species composition of the arboreal community appeared not as a succession of well-defined subcommunities throughout the year, but as a continuum of species of extended seasonal ranges.
• 6 This subtropical insect-plant system presented several phenological features which were classified under tropical and temperate characteristics. This partition is open to discussion.

     

Seasonal changes in the canopy arthropod fauna in Rinorea beniensis in Budongo Forest,Uganda

Arthropods were collected by insecticidal tree fogging on the understorey tree species Rinorea beniensis Engler (Violaceae) in Budongo Forest, a seasonal rain forest in Uganda. Eight trees were fogged in adjacent plots of primary, selectively logged and swamp forest during the wet season and again in the dry season. In all forest types, Psocoptera, parasitoid Hymenoptera, and especially Formicidae and Auchenorrhyncha were more abundant during the dry season, while Ensifera, Heteroptera, Lepidoptera, Diptera, and Coleoptera were more abundant during the wet season. Seasonal change in arthropod composition was very low in the swamp forest located near a stream, where permanent water supply is crucial for the development of the distinct swamp vegetation, with comparatively constant microclimatic conditions all over the year. Seasonal change increased in the primary forest, and shows most significant changes of athropod abundance between dry and wet season in the selectively logged forest which also had the highest heterogeneity in forest structures. Especially small and soft bodied arthropods probably accumulate along a humidity gradient in the dense canopies of Rinorea during the dry season, when the forest floor outside the swamp forest is dry. This effect, which is also strongest in the selectively logged forest, leads to a much higher density of canopy dwelling arthropods during the dry season.     

Long-term ecology of euglossine orchid-bees (Apidae: Euglossini) in Panama

Summary Abundance patterns during 6–7 years and orchid visitation were determined for 51 species of the 57 local euglossine bees. Male bees were counted at 3 chemical attractants presented in the same manner each month. Sites were separated by 75 km but included wet Atlantic forest at 500 m elevation, moist forest at 180 m near Barro Colorado Island, and cloud forest at 900 m near the Pacific ocean. 1. From 15 to 30 euglossine species of 4 genera were active in each month and site; monthly species number and general bee abundance were positively correlated. Many species had 3 annual abundance peaks (range 1–4) and were active throughout the year, but peak annual abundances rarely occurred during late wet or early dry seasons. In contrast, Eufriesea generally were present as adults only 1–2 months in a year. 2. Euglossine populations were exceptionally stable. Species at each site were more stable than any known insect population, and stability and abundance were positively associated. However, year-to-year population stability and the degree of seasonality were not correlated. Among the three sites, the more diverse (species rich) bee assemblages displayed lower stability; these were the wetter and upland sites. 3. The most abundant bees visited more orchid species. Eg. and El. each visited and average of 4 orchid species (range 0–13); Ex. and Ef. visited 0–3. Stable populations did not visit more or fewer orchid species than did unstable populations. 4. Less than 68% of species at each site visited orchid flowers; less than a few dozen of the 100–800 bees counted in a day carried orchid pollinaria. Over 20% of the euglossine species never were seen with pollinaria at any site and probably seldom visit orchids in central Panama. 5. Most bee species visited 1 or no fragrance orchids in a given habitat. Orchids tended to utilize common pollinators that seldom included more than 1 species, and they utilized stable or unstable, seasonal or aseasonal bees. However, the most stable and abundant bee, Eg. imperialis, rarely pollinated orchids; fewer than 10 of ca. 20000 bees carried pollinaria. 6. Orchids may interact primarily with discrete seasonal bee population peaks-probably the emerging adults. Although specialized orchid preferences are implicated for species that visit few or no local orchids but pollinate other species and carry pollinaria in other areas, euglossine bees do not need orchids to survive or reproduce.     

Seasonal variation in abundance and diversity of eavesdropping frog‐biting midges (Diptera,Corethrellidae) in a neotropical rainforest

1. In the tropics, precipitation patterns result in seasonal fluctuations in the abundance and distribution of plant and animal species. Tropical predators and parasites are therefore faced with seasonal changes in prey and host availability. 2. This study investigates the seasonal interaction among a specialised ectoparasite, eavesdropping frog‐biting midges (Corethrella spp.), and their anuran hosts, examining how the abundance and diversity of the frog‐biting midge community fluctuate between the rainy (host abundant) and dry (host sparse) seasons. 3. Midges were captured in both the rainy and dry seasons using acoustic playbacks of calls from a common frog species that breeds during the rainy season, the túngara frog (Engystomops, Physalaemus, pustulosus). During the dry season túngara frog choruses are absent. To explore seasonal shifts in host preference or changes in the midge community due to host specificity, midges were also captured using playbacks of calls from a frog that breeds during the dry season, the pug‐nosed tree frog (Smilisca sila). 4. While the overall abundance of midges decreased in the dry season, only slight differences in the relative abundance between midge species were found. These results suggest that midge populations can shift between hosts as they become available across seasons, allowing adult populations of frog‐biting midges to persist year‐round. To overcome the challenge of detecting and localising different host species, it is proposed that frog‐biting midges have evolved a generalised acoustic template, allowing them to respond to a broad range of available hosts, regardless of seasonal host composition.     

Life histories, production dynamics and resource utilisation of mayflies (Ephemeroptera) in two tropical Asian forest streams

SUMMARY 1. A 2‐year study of the life histories, production dynamics and resource utilisation of five mayfly species was undertaken in two forest streams in Hong Kong [Tai Po Kau Forest Stream (TPKFS) and Shing Mun River (SMR)]. Afronurus sp. and Cinygmina sp. (Heptageniidae), Procloeon sp. and Baetiella pseudofrequenta (Baetidae), and Choroterpes sp. (Leptophlebiidae) were abundant in both streams and contributed more than 50% of the total mayfly populations. 2. All species had asynchronous larval development with recruitment occurring throughout the year. Mean annual production (all mayflies combined) was 3.1 and 2.0 g dry weight m^?2 year^?1 in SMR and TPKFS, respectively – the higher value at SMR reflecting greater mayfly densities – with more than 70% of production occurring during the wet season. Mayfly production varied between years, decreasing by 5% in TPKFS and 43% in SMR during 1996–97, reflecting lower densities of heptageniids relative to 1995–96. Annual biomass turnover rates (P/B) were high in both sites ranging from 27.2 to 94.6 in TPKFS (Cinygmina sp. and Procloeon sp.) and from 31.8 to 109.8 in SMR (Cinygmina sp. and B. pseudofrequenta). 3. Patterns of daily production in both streams showed that Afronurus sp., Cinygmina sp. and Choroterpes sp. were most productive during the wet season, while Procloeon sp. maintained high production levels throughout the year. The highest daily production of B. pseudofrequenta occurred during the wet season in TPKFS, but in the dry season at SMR. Temporal overlap in production and hence resource utilisation in both streams, calculated using the proportional similarity index (PS), ranged from 0.39 to 0.81. It was highest (0.63–0.81) between pairs of species of Heptageniidae and Baetidae, and lowest between Choroterpes sp. and other mayflies (0.39–0.61). No clear temporal segregation was observed among any species. However, when using the fraction of production attributable to each food, lower PS values were obtained for all species in both sites. In SMR, trophic segregation may have occurred between the two species pairs Procloeon sp.–Cinygmina sp. and Procloeon sp.–Choroterpes sp. (PS=0.17 and 0.03, respectively). 4. A combination of production data and information on the stable isotope signature of mayflies revealed that, during both the wet and dry seasons, more than 50% of total mayfly production in TPKFS was derived from autochthonous foods. In SMR, 68% of production was supported by allochthonous foods during the wet season, and 72% by autochthonous sources in the dry season. Considering that more than 70% of the total production occurred in the wet season, the trophic basis of mayfly production in SMR is mostly allochthonous (58%) while in TPKFS it is mainly of autochthonous origin (66%). The year‐round importance of autochthonous foods in shaded streams such as TPKFS is surprising, but the wet season contribution of allochthonous foods (especially in SMR) may have resulted from depletion of algal biomass during spates.     

Mesophyll cell‐sucking herbivores (Cicadellidae: Typhlocybinae) on rainforest trees in Papua New Guinea: local and regional diversity of a taxonomically unexplored guild

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Variations in bird abundance in tropical arid and semi-arid habitats

Temporal variation in bird abundance was studied during a complete annual cycle in a thorn scrub, a thorn woodland and a deciduous forest in northeastern Venezuela. Abundance of site-attached and transient birds from different feeding guilds was determined by mist-netting at 2-week intervals. Diets were investigated by regurgitated samples. The overall avifauna was characterized by a low number of species but they were present all year despite showing strong seasonal fluctuations in abundance. The number of bird species and individuals peaked before and after the reproductive period. These high values probably were associated with movement of species feeding on plant food during the late dry season and the post-breeding dispersion of juveniles. Bird richness and abundance were lowest during the breeding season and in the early dry season when food abundance was low. Birds from different feeding guilds showed distinct patterns of seasonal abundance which tended to be similar at all three sites. Transient birds represented a large portion of the avifauna, particularly in nectarivores, frugivores and granivores during the dry season. We used a canonical correspondence analysis to demonstrate that bird abundance was correlated with breeding activity, rainfall seasonality and food abundance, with the influence of each parameter varying according to feeding guilds, spatial behaviour of individuals and habitats. Despite a great turnover in the occurrence of the diverse food types available, species composition remained strikingly constant during the year, with birds responding to seasonal changes primarily through a generalist feeding habit and a highly variable rate of transience.     

Insect herbivores foraging on seedlings in an unlogged rain forest in Guyana: spatial and temporal considerations

About 9,000 individuals of sap-sucking and leaf-chewing insects, representing 345 species, were collected from 10,000 seedlings belonging to 5 rainforest tree species in an unlogged forest in Guyana. For the 40 most common species, it was possible to estimate their host specificity, diurnal activity, seasonal distribution, spatial aggregation, abundance and body weight. Most species were generalists but more specialised species tended to show a higher spatial aggregation, a more restricted diurnal activity and a higher seasonality. Although insect abundance was highest at the onset of the long wet season in May, seasonal amplitude was not pronounced. The combined effects of host and rainfall explained 14.5% of the total variance in insect seasonality, which was poorly explained by the leaf production of seedlings. The spatial distribution of insects was often aggregated and, overall, explained by host effect, production of young foliage, number of conspecific trees within a radius of 50m, and number of dead seedlings at each collecting station. However, these variables explained only 7% of the variance in spatial distribution. The lack of notable influence of leaf production and other important variables recorded at the collecting stations suggests that the seedlings represent a marginal food resource for most of the insect species collected.     

Diet selection in the green ringtail possum (Pseudochirops archeri): A specialist folivore in a diverse forest

Abstract This study investigated the feeding ecology of the green ringtail possum, Pseudochirops archeri (Pseudocheiridae) in a tropical rainforest with 94 plant species in the canopy. Over 50% of tree use was from only four tree species, Aleurites rockinghamensis, Ficus fraseri, Arytera divaricata and Ficus copiosa. These species were used significantly more frequently than would be expected if tree species were selected randomly in proportion to their relative abundance in the forest. Conversely, 88 other tree species present were used less frequently than expected. Possums also favoured particular individual trees within some of the preferred tree species. In 91% of feeding observations, possums consumed mature leaves only. The availability of young leaves, flowers and fruit varied throughout the year, with a peak in availability of these resources during the early wet season. By primarily selecting mature leaves, green ringtail possums reduce their dependence on seasonally variable resources. We suggest that green ringtail possums should be considered as specialist folivores, focusing on only a few of the tree species available, possibly due to advantages associated with limiting the number of plant secondary metabolites in their diet. Furthermore, they favour certain individual trees within species, perhaps due to intraspecific variation in plant secondary metabolites or nutrient content, behaviour that has been well established in eucalypt folivores. We conclude that green ringtail possums are highly specialized in their feeding ecology, limiting their diet to a small number of continuously available food items.     

Seasonal and Spatial Patterns in Ground Foraging Ants in a Rain Forest in the Western Ghats,India1

Seasonal variation and spatial distribution in ground foraging rain forest ants were studied in South Kannada–Kodagu District in Karnataka (India) between 1990 and 1991 by pit-fall trap sampling. All ant species showed marked seasonality. A total of 31 species were recorded from the primary forest over a period of two years. More species were recorded from the closed canopy forest than from tree fall gaps in primary forest. All ant species showed marked seasonality with fewer species and individuals sampled/plot during the wetter seasons. The numerically dominant species, Pheidole sp., was markedly lower in abundance during the wet seasons. Spatial patterns were also studied during a dry season both in the primary forest and an adjacent logged forest. More species were recorded from the logged forest than the primary forest. Community composition in primary forest was different from that in logged forest. Common species were more ubiquitous than rarer species. Species were distributed bimodally across sampling plots. Probable underlying processes behind these seasonal and spatial patterns have been discussed.     

Abundance of arbuscular mycorrhizal fungi spores in different environments in a tropical rain forest, Veracruz, Mexico

 The aim of this study was to compare mycorrhizal abundance and diversity in sites with different regimes of disturbance in a tropical rain forest at Los Tuxtlas, Veracruz, Mexico. Arbuscular mycorrhizal spores were quantified at two sites: closed canopy and gaps in the forest. Data were recorded during dry, rainy, and windy ("nortes") seasons. Spores of eight Glomus species, sporocarps of three Sclerocystis species, three species of Acaulospora and two of Gigaspora were found. Significant differences in the number of species and spores were found among seasons. The highest numbers of species and spores were observed during the dry season, with a marked decrease during the rainy season. Our results show that disturbance does not but seasonality does affect abundance and richness of mycorrhizal spores in this tropical wet forest. Accepted: 11 October 1998     

Temporal variation in diets and trophic partitioning by coexisting lizards (Ctenotus: Scincidae) in central Australia

Summary The diets of five syntopic species of Ctenotus were examined over a two-year period on a 60 ha spinifex grassland site in central Australia. The aims of the study were to test predictions that termites were an important part of the food web for syntopic Ctenotus in spinifex grasslands, and to examine seasonal changes in prey use and dietary overlap between the species. Environmental conditions during the first season of the study were dry resulting in generally low invertebrate abundance. In contrast the second season was relatively moist and overall invertebrate abundance was higher than in the first season. Diets of five species of Ctenotus contained a range of terrestrial prey although one species (C. pantherinus) was relatively termite-specialized at all times. Dietary overlap at the ordinal level between the species was generally higher during dry periods when prey abundance was low, and higher for species-pairs that were similar in body size. During the driest period of the study most species of Ctenotus ate a high proportion of termite prey which accounted for the high dietary overlap. However, each species of Ctenotus consumed different genera or foraging guilds of termites. The results suggest that most of these lizards were opportunistic in their selection of prey but that during dry periods when prey are scarce, termites may play a significant role in supporting a high -diversity of Ctenotus.     

Parasitoid assemblages reared from geometrid defoliators (lepidoptera: geometridae) of larch and fir in the alps

1 Geometrid larvae were collected from larch and fir in the Swiss Alps in 1991–94. Eight geometrid species were found in sufficient numbers to rear out parasitoids: Agriopis aurantiaria, Bupalus piniarius, Epirrita autumnata, Eupithecia lariciata, Odontopera bidentata, Lycia isabellae and Semiothisa liturata were collected from larch, and Puengeleria capreolaria was obtained from fir. 2 Parasitoid species belonging to five different guilds and four families were obtained; however, the taxonomic status of some of these is not completely resolved. 3 The parasitoid complex of the larch‐feeding species was totally different from that of Tortricidae and Tenthredinidae, which feed on the same host tree. In general, there was little overlap in the parasitoid complexes of the larch geometrids, with the most dominant parasitoid of each species reared from only one host. By contrast, many parasitoid species found during our study are also known to attack the same hosts or closely related hosts on different host tree species in different environments, suggesting that host specificity in geometrid parasitoids is more related to host taxonomy than to host plant or habitat.     

Diversity of Breadfruit (<Emphasis Type="Italic">Artocarpus altilis</Emphasis>, Moraceae) Seasonality: A Resource for Year-Round Nutrition<Superscript>1</Superscript>

Diversity of Breadfruit ( Artocarpus altilis , Moraceae) Seasonality: A Resource for Year-Round Nutrition. Breadfruit, Artocarpus altilis (Parkinson) Fosberg, is an important but underutilized staple crop cultivated throughout Oceania and much of the wet tropics. Indigenous peoples have selected and cultivated cultivars with different fruiting seasons to effectively extend fruit production for most of the year. In the present study, the seasonality of 219 breadfruit accessions originating from 17 Pacific island groups, the Seychelles, the Philippines, and Indonesia, and now growing in the National Tropical Botanical Garden’s (NTBG) Kahanu Garden, Hana, Hawaii, were evaluated. The predominant season of male flower production for most cultivars was from May to September, and fruit was produced most frequently between August and January. However, there were differences in the duration of the fruiting season from year to year and among cultivars. Over the 10-year period, 14 cultivars did not reliably produce fruit; most of this group were ‘ulu afa’ trees collected from Tokelau. About 24 cultivars exhibited very little seasonality and produced fruit throughout the year. The rest of the cultivars could be clustered into seasonality groups with characteristic fruiting patterns. Comparison of literature values indicates that unlike Hawaii, the breadfruit season in most locations begins around the date the sun reaches zenith prior to the summer months and extends throughout the summer months. Five cultivars asexually propagated from the NTBG collection growing in Kiribati (1°28′ N) exhibit similar fruiting patterns as in Hawaii, except that they begin 2–3 months earlier. These data predict that cultivars with complementary fruiting seasons in Hawaii may experience a temporal shift in their seasonality but will maintain their compatibility when cultivated in different locations and could enable year-round fruit production in many regions.     

Population persistence of the parasitoid fly Zaira cinerea (Fallén) (Diptera: Tachinidae) utilizing multiple host carabid beetles with different seasonality and quality

Zaira cinerea (Fallén) is a parasitoid fly (Diptera: Tachinidae) that attacks adult carabid beetles. To better understand mechanisms of population persistence in this species, we examined seasonality of host beetle abundance, the frequency of parasitism, and the timing of fly eclosion. In addition, we evaluated host quality using numbers of larvae or puparia per individual beetle as a measure of quality. The fly parasitized only large carabids (≥15 mm body length); the lengths of fly puparia reached 7.4–10.8 mm during development in beetle abdomens, and larger hosts are likely essential. Of the 18 large carabid species collected in this study, we chose two, Carabus maiyasanus Bates and Leptocarabus procerulus (Bates), because they were large and abundant (87% of total catch). The two carabids had different phonologies; C. maiyasanus was abundant from spring to summer, and its abundance dropped sharply in autumn, while L. procerulus was abundant in autumn and rare from spring to summer except July. Parasitism was observed in all the months from May to November except June, and adult flies eclosed more than once a year (in early summer, late summer, and mid‐autumn), indicating that the species is multivoltine. Host quality of L. procerulus was higher than that of C. maiyasanus. Carabus maiyasanus was mainly used as a host from spring to summer, and L. procerulus was used in autumn. Thus, adult beetles of one or both species are available over most of spring, summer, and autumn, allowing population persistence of this fly species over time.     

Temporal coexistence of dung-dweller and soil-digger dung beetles (Coleoptera, Scarabaeoidea) in contrasting Mediterranean habitats

The western part of the Mediterranean basin is a transitional biogeographical region for the distribution of the representatives of the main guilds of dung beetles; towards the south, Aphodiinae (dung-dwellers) become scarce, whereas northwards Scarabaeinae (soil-diggers) progressively disappear. The number of species in local dung beetle assemblages is enhanced by this double faunistic contribution. Annual dung beetle assemblages were sampled in two sub-Mediterranean sites, which differed by 600 m in elevation, in order to determine the phenological dynamics related to the way of using dung (dung-dwellers/Aphodiinae vs. soil-diggers/Scarabaeinae and Geotrupinae). Aphodiids were active all year round, although they were affected by summer drought and, at high elevation, by the length of the cold season. This reduced activity was related to an impoverishment of Aphodiinae and to reduced temporal segregation between species. In contrast, soil-diggers were not active all year round and showed different species assemblages in the two sites. An extension of the activity period of these beetles was observed due to the occurrence of cold resistant species at high elevation. Our results suggested that the occurrence of soil-diggers seemingly did not affect the seasonality of dung-dwellers; their local abundance showed no negative correlation and, most importantly, phenological differences between dung-dwellers were always significantly higher than the seasonal differences between dwellers and diggers.     

Associated community with the zoanthid <Emphasis Type="Italic">Palythoa caribaeorum</Emphasis> (Duchassaing &; Michelotti, 1860) (Cnidaria,Anthozoa) from littoral of Pernambuco,Brazil

The community associated with the zoanthid Palythoa caribaeorum on shores (Porto de Galinhas and Guadalupe) in northeastern Brazil were analysed. Seasonal samples (dry and wet) were made in both beaches throughout one year. This preliminary study identified 28 taxa and recognized two modes of existence, endobionts (three taxa) and hypobionts (25 taxa). Among hypobionts two patterns of ecological relationships were found: those fixed to the rocky substrata or on the base of the zoanthid colony (11 taxa) and the free-living (14 taxa). In some of these relationships, the organisms observed (Carijoa riisei and barnacles), were under the mat as victims of the zoanthid overgrowth (spatial competition). The more abundant taxa were: Mollusca (28%), Crustacea (25%), Nematoda (24%) and Polychaeta (16%). Among all samples species richness, abundance, similarity and diversity were different, especially the dry season of Porto de Galinhas. Porto de Galinhas in the dry season showed the lowest diversity with only one record. After evaluating the different ecological parameters of the P. caribaeorum-associated community, we conclude that the Guadalupe shore maintains annual homogeneity, while Porto de Galinhas shore is notably different during the year. The only environmental difference between them seems to be the effect of human activity from tourism (reef walkers, fishery and diving), that could be directly and indirectly affecting some ecological parameters of this zoanthid-associated community, such as abundance, richness and diversity of species.     

Habitat and host associations of the fish‐burrowing parasite Artystone minima (Cymothoidae: Isopoda) in eastern Amazonia

Cymothoid fish parasites settle on hosts in ways that may impact fish health and energetics. High abundances of Artystone minima observed in Nannostomus beckfordi from the Jeju River in eastern Amazonia were investigated to answer the following questions: (a) What factors are associated with the high prevalence at this locality?; (b) Is high abundance associated with co‐infestation of alternative hosts?; and (c) Is parasite presence associated with host species growth and/or reproduction? Fish assemblages were sampled quarterly (August 2017–May 2018) from five habitats along with environmental data. Parasitic indices were calculated, and parasite presence used to evaluate differences in growth of hosts using analysis of covariance considering host sex and sampling season (wet vs. dry). Parasites were only abundant in one of the habitats, a large, shallow backwater bay with macrophytes. Abiotic environmental factors (flow and depth) likely impact parasite transmission and are, therefore, particularly important in producing these local patterns. Two secondary hosts, Hyphessobrycon cf. rosaceus and Moenkhausia collettii, were found in the wet season. Based on host biology compared to other fish in the habitat, parasite infestation is inferred to be depth associated and long‐term infestation is apparently limited in alternative hosts. Parasite presence was significantly associated with reduced weight (standardized for length) of female Nannostomus beckfordi in the wet season. Furthermore, ovaries of non‐parasitized females from the wet season presented a range of maturation stages, while parasitized females were all immature, indicating a significant association of parasites with host reproductive capacity. Abstract in Portuguese is available with online material     

Population Dynamics of Crustacean Zooplankton in a Mesotrophic Lake,with Emphasis on Boeckella hamata BREHM (Copepoda: Calanoida)

The crustacean zooplankton in Lake Mahinerangi, a polymictic, mesotrophic reservoir, were studied for 19 months. The cladocerans, Bosmina meridionalis and Ceriodaphnia dubia, had unimodal patterns of abundance with peak densities in summer; cyclopoids had a single peak of maximum abundance in autumn and Daphnia carinata showed a bimodal pattern with peak densities in early summer and early winter. The strong seasonality in abundance of zooplankton in Lake Mahinerangi distinguishes this lake from other temperate lakes in New Zealand and may reflect its cool winter temperatures (< 5 °C for 2 months). A calanoid, Boeckella hamata, bred throughout the year and was the dominant species numerically. Instar analysis indicated that there were at least three, and possibly four, generations per year. Instantaneous birth and death rates were low with annual mean values (0.036 and 0.057, respectively) that were 2-3.5 times less than those recorded in a population of the same species in Lake Pounui, but within the range of those recorded in calanoid populations elsewhere in New Zealand. The Boeckella population in Lake Mahinerangi appears to be controlled largely by temperature, parasitism and food, with predation having no, or a negligible, effect.