Climatic limitation of the southern distribution of the common blossom bat Syconycteris australis in New South Wales

Abstract This study investigates the importance of climate as a factor influencing the southern distributional limit of the common blossom bat (Syconycteris australis). Using the climatic predictive model BIOCLIM and 73 locality records, 5. australis was predicted to have a coastal distribution in eastern Australia, where winter temperatures are relatively warm and moist conditions prevail throughout the year. The actual southern limit of S. australis, determined by mist-netting suitable habitats, was found to be at Booti-Booti (32°19'S 152°3l'E) on the mid-north coast of New South Wales. BIOCLIM predicted the southerly limit of 5. australis to be 150–200km further south of their actual limit. Booti-Booti was occupied at relatively low levels of abundance year round, while the abundance of S. australis at a site 50 km to the north was much greater, fluctuating with changes in Banksia flower numbers. Seasonal range extensions beyond Booti-Booti were not detected, despite the availability of apparently suitable habitat at Myall Lakes only 20–35 km further south. Metabolic costs of S. australis at Booti-Booti were estimated to exceed basal metabolic rate (BMR) by 4.5 times, well above the physiologically predicted limit of 2.5 times BMR. These results, together with the lack of range extensions and the close correspondence of BIOCLIM'S predicted southern limit of S. australis with their actual limit, suggest that the bat's southern distribution is limited by cold, wet winters and dry summers.     

Farming with native bees (<Emphasis Type="Italic">Apis mellifera</Emphasis> subsp. <Emphasis Type="Italic">capensis</Emphasis> Esch.) has varied effects on nectar-feeding bird communities in South African fynbos vegetation

Outside their natural range, honeybees (Apis mellifera) are known to have detrimental effects on indigenous pollinators through exploitative or interference competition, but little is known about the effect of honeybee farming in areas where honeybees occur naturally. In the Cape Floristic Region of South Africa, where honeybees are indigenous, managed hives potentially elevate the abundance of honeybees far above natural levels, but impacts on other floral resource-dependent species have not been studied. Here we use experimental manipulation of honeybee density to test whether honeybee farming affects nectar-feeding birds. We selected the common sugarbush (Protea repens), utilized by both birds and bees, and analysed the time (before/after) by treatment (control/experiment) interaction to explore changes in bee abundance, nectar availability and bird abundance at three sites. Hive addition increased honeybee abundance in inflorescences of P. repens above expected levels. Despite experimental increase in honeybee numbers, there is no reduction in nectar sugar availability relative to the control areas. Where honeybee density was highest, sugarbird (Promerops cafer) numbers declined relative to expected, but sunbirds (Nectarinidae) were not affected at any of the sites. We conclude that stocking rates of more than one honey bee per P. repens inflorescence have detrimental effects on bird abundance due to interference, rather than resource competition.     

Factors affecting the occupation of a colony site in Sydney,New South Wales by the Grey‐headed Flying‐fox Pteropus poliocephalus (Pteropodidae)

Previous authors have reported that Pteropus poliocephalus colony sites are occupied in response to blossom availability. However, in the present study it is reported that at the Gordon site in suburban Sydney, colony numbers were negatively correlated with the occurrence of pollen in the droppings. In addition, in contrast to reported occupational patterns at other colony sites, where flying‐foxes are not present at the site during winter and early spring, the Gordon site was occupied by substantial numbers of flying‐foxes throughout the entire period of 62 months from 1985 to 1990. As a result of the introduction of plants native to other parts of Australia and exotics from other continents, there is a variety of foods available throughout the year in the Sydney region, in comparison with less urbanized areas. This food supply permits the occupation of the Gordon colony site during winter and spring and reduces the migratory behaviour of flying‐foxes throughout the year. It is concluded that in the absence of a restrictive food supply, the occupational pattern of the Gordon colony of P. poliocephalus is the result of the reproductive requirements of the species modified by the vagaries of blossom production in the native forests outside the foraging range of the colony.     

Impacts of Cyclone Larry on arboreal folivorous marsupials endemic to upland rainforests of the Atherton Tableland,Australia

Abstract Intense cyclones might be expected to adversely affect populations of arboreal mammals, either directly or as a consequence of the destruction of food resources and other key habitat elements. However, such impacts have rarely been quantified. The present study examined the response of five species of arboreal folivorous marsupials to Severe Cyclone Larry at nine sites in upland rainforests of the Atherton Tableland, north‐east Australia. Sites were originally surveyed for folivores in 1995–1997, and then resurveyed in 2006, 6–8 months after Cyclone Larry had traversed the region. All sites showed evidence of structural damage to vegetation, but overall damage levels (assessed in terms of canopy cover, damage to trees, basal area of dead trees and volume of woody debris) decreased from east to west across the study region. The detectability of rainforest possums increased after the cyclone. For the most commonly observed species, the proportion of individuals observed >5 m from survey transects was correlated with the amount of structural damage to vegetation. To avoid confounding changes in detectability with changes in abundance, only observations close (<5 m) to transects were used to estimate folivore abundance before and after the cyclone. On this basis, there were no significant differences between pre‐ and post‐cyclone abundance estimates for any folivore species. Further, changes in folivore abundance after the cyclone were not correlated with damage to vegetation across sites. Cyclone Larry does not appear to have caused a catastrophic loss of key habitat resources for marsupial folivores at the sites surveyed. The high degree of folivory practiced by marsupial folivores may help make them resilient to cyclone impacts. These conclusions are more robust for three commonly observed folivore species (Hemibelideus lemuroides, Pseudochirulus herbertensis and Trichosurus vulpecula johnstonii) than for two less frequently encountered species (Pseudochirops archeri and Dendrolagus lumholtzi).     

Honeyeater population changes in relation to food availability in the Jarrah forest of Western Australia

The numbers of honeyeaters present at particular sites in the Jarrah forest varied significantly from month to month, with peak abundance occurring between May and September. Numbers also varied from site to site, depending upon the major plant species present. Honeyeater abundance was not limited by arthropod availability, but in many instances was closely correlated with the availability of nectar, particularly that produced by Dryandra sessilis. Large honeyeaters, such as Anthochaera chrysoptera and Phylidonyris novaehollandiae, were generally most abundant at times and sites of greatest nectar production. Small honeyeaters, such as Acanthorhynchus superciliosis, were never abundant but were present for most of the year. The production of nectar between October and December was such that more honeyeaters could have been supported than were actually present. Low numbers at these times can be explained in terms of reduced foraging efficiency that would have resulted from more widely dispersed flowers, and the possible availability of more rewarding nectar resources at other sites.     

Food limitation of population density in the orb-wed spider,Nephila clavata

Field studies were conducted to clarify whether variation in food availability among habitats influences population density, and whether population density has a negative effect on foraging success in the orb-web spider, Nephila clavata. Lifetime food consumption per individual (i.e., foraging success) strongly correlated with mean body size of adult females and mean fecundity in populations. Also, there was a positive correlation between foraging success and population density. Since foraging success reflected potential prey availability in the habitat, food resource appeared to be a limiting factor for populations in this spider. Mean fecundity per individual correlated with population density of the following year, suggesting that decreased reproduction is a major component of food limitation on population density. Consistent defferences in mean body size between particular sites were observed over years, while such difference was less obvious in density. Thus, ranking of food abundance among habitats seems to be predictable between years. A field experiment revealed that an artificial increase in population density had no negative effect on the feeding rate of individuals, suggesting that intraspecific competition for food is not important in this species.     

Ecology and conservation of insectivorous bats in fragmented areas of macadamia production in eastern Australia

Microbats perform important ecological services in agro‐ecosystems, but several species are globally threatened by loss of roosting and breeding habitats. The successful conservation of bats in agricultural land requires adequate knowledge of their ecology. Using ultrasonic recorders, we studied the activity of insectivorous bats in areas of macadamia production in eastern Australia at two spatial scales: across woodland‐orchard transects at the local scale and across three levels of fragmentation at the landscape scale. At the local scale, activity patterns of ‘clutter’ and ‘edge’ specialists were consistently higher in woodland patches, gradually decreasing towards isolated orchards, where only a few ‘open’ specialists were active. At the landscape scale, bat community activity was affected by the level of fragmentation, partly because three of the most recorded taxa (Austronomus australis, Saccolaimus flaviventris and Miniopterus australis) had their highest activity in less‐fragmented areas. A distance‐based model explained 24% of the bat community activity based on a combination of six environmental variables. Canonical correspondence analysis showed that a number of bat taxa were associated with open areas of macadamia, whereas other taxa were associated with increasing values of landscape composition, and arthropod and water availability. In addition, total bat activity was highly correlated with foraging rate. These results suggest that most bat taxa were influenced by proximity to woodland and the degree of fragmentation, and only few taxa were able to exploit isolated orchards. Environmental factors that promote bat activity could be exploited to strengthen conservation efforts. Preserving remnant woodland and promoting habitat heterogeneity will benefit several bat species. In particular, the foraging activity of ‘edge’ specialists could be fostered by increasing landscape connectivity and maintaining unobstructed water bodies near macadamia orchards. Considering that bats forage as they navigate these areas, conservation efforts could also bring benefits to farmers through pest‐reduction services.     

Seasonal variation in food availability and relative importance of dietary items in the Gambian epauletted fruit bat (Epomophorus gambianus)

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Using dynamic N‐mixture models to test cavity limitation on northern flying squirrel demographic parameters using experimental nest box supplementation

Dynamic N‐mixture models have been recently developed to estimate demographic parameters of unmarked individuals while accounting for imperfect detection. We propose an application of the Dail and Madsen ( 2011 : Biometrics, 67 , 577–587) dynamic N‐mixture model in a manipulative experiment using a before‐after control‐impact design (BACI). Specifically, we tested the hypothesis of cavity limitation of a cavity specialist species, the northern flying squirrel, using nest box supplementation on half of 56 trapping sites. Our main purpose was to evaluate the impact of an increase in cavity availability on flying squirrel population dynamics in deciduous stands in northwestern Québec with the dynamic N‐mixture model. We compared abundance estimates from this recent approach with those from classic capture–mark–recapture models and generalized linear models. We compared apparent survival estimates with those from Cormack–Jolly–Seber (CJS) models. Average recruitment rate was 6 individuals per site after 4 years. Nevertheless, we found no effect of cavity supplementation on apparent survival and recruitment rates of flying squirrels. Contrary to our expectations, initial abundance was not affected by conifer basal area (food availability) and was negatively affected by snag basal area (cavity availability). Northern flying squirrel population dynamics are not influenced by cavity availability at our deciduous sites. Consequently, we suggest that this species should not be considered an indicator of old forest attributes in our study area, especially in view of apparent wide population fluctuations across years. Abundance estimates from N‐mixture models were similar to those from capture–mark–recapture models, although the latter had greater precision. Generalized linear mixed models produced lower abundance estimates, but revealed the same relationship between abundance and snag basal area. Apparent survival estimates from N‐mixture models were higher and less precise than those from CJS models. However, N‐mixture models can be particularly useful to evaluate management effects on animal populations, especially for species that are difficult to detect in situations where individuals cannot be uniquely identified. They also allow investigating the effects of covariates at the site level, when low recapture rates would require restricting classic CMR analyses to a subset of sites with the most captures.     

Feeding chronology,daily ration,and the effects of temperature upon gastric evacuation in the pipefish,Syngnathus fuscus

Synopsis Feeding chronology, daily ration, and the effects of temperature upon gastric evacuation were examined in the pipefish,Syngnathus fuscus, from field and laboratory data.S. fuscus displayed a pattern of diurnal feeding, characteristic of syngnathids. Daily ration calculations yielded estimates of 4.0 and 4.4% body weight per day, which are comparable to estimates for other teleosts. Evacuation rate was found to be temperature dependent. with more rapid evacuation with increasing temperature. In addition, evacuation rate was found to be positively correlated with gut content. Slowing of evacuation rate with decreasing gut content may allow for increased assimilation efficiency during periods of low food availability. Daily ration, although controlled by the temperature dependence of evacuation rate, may also be controlled by prey abundance; fish maximize food intake during periods of high prey availability, and maximize upon assimilation during periods of low prey availability.Contribution number 1035 of the Virginia Institute of Marine Science of the College of William and Mary.     

Mobile epifauna onZostera marina,and infauna of its inflorescences

The faunal colonization of the leaves and inflorescences of intertidalZostera marina L. and of the ambient water has been studied at the Island of Sylt (North Sea). The abundance of the snailLittorina littorea L. and the isopodJaera albifrons Leach correlates significantly with leaf surface area. This is not the case with the abundance of meiofaunal Plathelminthes, Nematoda, Copepoda, and Polychaeta. However, they increase significantly with the numbers of generative shoots in the sampled seagrass bunches. Members of these taxa inhabit theZostera inflorescences, and average abundance increases with the degree of decay of inflorescences. This temporary microhabitat presumably offers food and shelter. Copepods and ostracods dominate in the ambient water. Planktonic calanoid copepods correlate with the amount of sampled seawater, while Ostracoda correlate with the amount of resuspended detritus suggesting that they were resuspended themselves. The study shows that some meiofaunal taxa can rapidly exploit a short-lived habitat such as theZostera inflorescences. Juvenile polychaetes use inflorescences as a nursery.     

Abundance responses of frugivorous bats (Stenodermatinae) to coffee cultivation and selective logging practices in mountainous central Veracruz,Mexico

Shifting and permanent cultivation, selective logging, cattle production and coffee plantations are among the most important factors in montane cloud forest conversion and disturbance. Although shaded-coffee plantations can contribute to the preservation of local species richness, abundance of organisms could be determined by habitat resource availability in agricultural landscapes. We compared abundance of Sturnira and Artibeus bats (Phyllostomidae, Stenodermatinae), in shade coffee plantations and disturbed cloud forest fragments, which represent habitats with different chiropterochorous plant density. We also investigated the relationship between bat species abundance and food plant richness, abundance and diversity. We captured 956 bats, 76% in cloud forest fragments and 24% in shaded coffee plantations. Abundance of Sturnira spp. (small bats) was greater in cloud forest than in coffee plantations, but Artibeus spp. (large bats) abundance was similar in both habitats. Chiropterochorous plant abundance was positively related with bat abundance for Sturnira spp., while chiropterochorous plant richness and diversity were negatively related for Artibeus spp. This suggests that frugivorous bats with different morphological and ecological characteristics respond differentially to anthropogenic activities. For landscape management purposes, the maintenance and augmentation of diverse food resources, for frugivorous bats with different foraging requirements in coffee plantations, will benefit the resilience of bats to modification of their natural habitat.     

Caterpillar abundance in the territory affects the breeding performance of great tit Parus major minor

The effects of caterpillar food supply on the breeding performance of a population of the Japanese great tit Parus major minor were investigated. Since more than 90% of the food items in our study site were caterpillars living on trees, we estimated the food availability using 20 frass traps per hectare. The sampling error of this method was about 10% on average, which was accurate enough to detect differences between territories. Food abundance at laying in each territory affected the timing of egg laying. However, food amount after hatching was correlated with clutch size. No relationship was found between fledgling quality and food availability, probably because the effects of local variation in food abundance could be canceled out by parental effort such as extending the foraging area. There was a significant negative correlation between the length of the nestling period and food availability. We suggest that parent tits decide the timing of fledging at the point where two factors, predation risk before fledging and additional improvement of nestling quality, are balanced. Food availability just after fledging affected the length of post-fledging parental care; it seems that fledglings in “poor” territories would have had difficulty in finding food and hence needed to depend on their parents longer than those in “rich” territories. Received: 10 June 1997 / Accepted: 29 December 1997     

Evaluation of conservation status, distribution, and reproductive characteristics of an endemic Gulf Coast freshwater mussel, Lampsilis australis (Bivalvia: Unionidae)

The southern sandshell, Lampsilis australisSimpson, 1900, is a rare freshwater mussel endemic to the Escambia, Yellow, andChoctawhatchee river drainages in Alabama and Florida. Laboratory observationsconfirmed L. australis as a superconglutinate producer.Superconglutinate and glochidial morphology are similar to those of othersuperconglutinate producers. The current distribution of L.australis, as determined from recent surveys (1995–2000) andfield notes (1990–2000), is compared with its historical distribution asdefined by museum collections and field notes made between 1900 and 1989. Thecurrent distribution of L. australis is reduced by76% compared to its historical distribution, although L. australis waslocated at new sites in the recent surveys. Relative abundance of L.australis was low at all but two sites. Based on reproductivestrategy, range reductions, low relative abundance, and potential threats withinthe Escambia, Yellow, and Choctawhatchee river drainages, we believeL. australis should be considered for protection under theEndangered Species Act.     

Tropical Secondary Forest Management Influences Frugivorous Bat Composition,Abundance and Fruit Consumption in Chiapas,Mexico

Most studies on frugivorous bat assemblages in secondary forests have concentrated on differences among successional stages, and have disregarded the effect of forest management. Secondary forest management practices alter the vegetation structure and fruit availability, important factors associated with differences in frugivorous bat assemblage structure, and fruit consumption and can therefore modify forest succession. Our objective was to elucidate factors (forest structural variables and fruit availability) determining bat diversity, abundance, composition and species-specific abundance of bats in (i) secondary forests managed by Lacandon farmers dominated by Ochroma pyramidale, in (ii) secondary forests without management, and in (iii) mature rain forests in Chiapas, Southern Mexico. Frugivorous bat species diversity (Shannon H’) was similar between forest types. However, bat abundance was highest in rain forest and O. pyramidale forests. Bat species composition was different among forest types with more Carollia sowelli and Sturnira lilium captures in O. pyramidale forests. Overall, bat fruit consumption was dominated by early-successional shrubs, highest late-successional fruit consumption was found in rain forests and more bats consumed early-successional shrub fruits in O. pyramidale forests. Ochroma pyramidale forests presented a higher canopy openness, tree height, lower tree density and diversity of fruit than secondary forests. Tree density and canopy openness were negatively correlated with bat species diversity and bat abundance, but bat abundance increased with fruit abundance and tree height. Hence, secondary forest management alters forests’ structural characteristics and resource availability, and shapes the frugivorous bat community structure, and thereby the fruit consumption by bats.     

Seasonal changes in energetics and torpor patterns in the subtropical blossom-bat Syconycteris australis (Megachiroptera)

Little is known about how animals from tropical and subtropical climates adjust their energy expenditure to cope with seasonal changes of climate and food availability. To provide such information, we studied the thermal physiology, torpor patterns and energetics of the nocturnal blossom-bat (Syconycteris australis 18 g) from a subtropical habitat in both summer and winter. In both seasons, S. australis frequently entered daily torpor at ambient temperatures between 12 and 25°C when food and water were withheld. Unlike patterns observed in temperate animals, mean minimum metabolic rates during torpor were lower in summer (0.47 ± 0.07 ml O₂ g⁻¹ h⁻¹) than in winter (0.75 ± 0.11 ml O₂ g⁻¹ h⁻¹). Body temperatures during torpor were regulated at 19.3 ± 1.0°C in summer and at 23.4 ± 2.0°C in winter. Torpor bout duration was significantly longer in summer (7.3 ± 0.6 h) than in winter (5.5 ± 0.3 h), but in both seasons, bout duration was not affected by ambient temperature. Consequently, average daily metabolic rates were also significantly lower in summer than in winter. Body temperatures and metabolic rates in normothermic bats did not change with season. Our findings on seasonal changes of torpor in this bat from the subtropics are opposite to those made for many species from cold climates which generally show deeper and longer torpor in winter and are often entirely homeothermic in summer. More pronounced torpor in subtropical S. australis in summer may be due to low or unpredictable nectar availability, short nights which limit the time available for foraging, and long days without access to food. Thus, the reversed seasonal response of this subtropical bat in comparison to temperate species may be an appropriate response to ecological constraints. Received: 6 May 1997 / Accepted: 19 October 1997     

A comparison of floral resource exploitation by native and invasive Argentine ants

Ants are often considered antagonists when they visit flowers because they typically steal nectar without providing pollination services. Previous research on ant–flower interactions on two species of South African Proteaceae in the Cape Floral Kingdom revealed that the invasive Argentine ant (Linepithema humile), but not native ants, displace other floral arthropod visitors. To determine how common Argentine ant use of inflorescences is, how Argentine and native ant visits differ in the numbers they recruit to inflorescences, and what factors may affect Argentine and native ant foraging in inflorescences, I surveyed 723 inflorescences in 10 species in the genera Protea and Leucospermum across 16 sites and compared ant presence and abundance in inflorescences with abundance at nearby cat food and jam baits. Argentine ants were the most commonly encountered ant of the 22 observed. Argentine ants, as well as six species of native ants were present in all inflorescences for which they were present at nearby baits. Mean Argentine ant abundance per inflorescence was 4.4 ± 0.84 (SE) ants and similar to that of Anoplolepis custodiens and Crematogaster peringueyi, but higher than observed for the other most commonly encountered native ants, Camponotus niveosetosus and Lepisiota capensis. Both Argentine ants and A. custodiens were more likely to be found foraging in spring and under humid conditions, and in inflorescences closer to the ground, with lower sucrose concentrations, and with a greater proportion of open flowers. Argentine ants were more likely to be found in Protea inflorescences, whereas A. custodiens and L. capensis more often visited Leucospermum inflorescences. Considering its displacement of floral arthropods and widespread use of Proteaceae inflorescences, the Argentine ant could be posing a serious threat to plant and pollinator conservation in this biodiversity hotspot.     

Improving population estimates by quantifying diving and surfacing patterns: A dugong example

Diving animals are available for detection from above the water when environmental conditions are favorable and the animals are near the surface. The number of animals that are unavailable for detection needs to be estimated to obtain unbiased population estimates. The current availability correction factors used in aerial surveys for the dugong (Dugong dugon) allow for variation in environmental conditions but use the average time dugongs spend near the surface (i.e., constant availability corrections). To improve availability estimates, we examined location and dive data from nine dugongs fitted with satellite telemetry units and time‐depth recorders (TDRs) in eastern Australia. The effects of water depth, tidal conditions, and habitat types on dugong surfacing time were examined using generalized linear mixed models (GLMMs). We found that availability for detection differed with water depth, and depth‐specific availability estimates were often lower than the constant estimates. The habitat effect was less influential, and there was no tidal effect. The number of dugongs estimated using depth‐specific availabilities were higher than those obtained using constant availabilities across water depth. Hence, information on water depth can refine availability estimates and subsequent abundance estimates from dugong aerial surveys. The methodology may be applicable to other aquatic wildlife.     

Climate constrains the establishment and proliferation of Anthonomus santacruzi,a flower-feeding biological control agent of the invasive weed Solanum mauritianum in South Africa

The flowerbud-feeding weevil Anthonomus santacruzi Hustache (Coleoptera: Curculionidae) was released in South Africa in 2008 for the biological control of the invasive tree Solanum mauritianum Scopoli (Solanaceae). The weevil was widely deployed throughout KwaZulu-Natal province, which supports large S. mauritianum infestations, and has become well established in its warmer coastal regions. The aim of this study was to provide field evidence that climate is constraining the weevil’s distribution in South Africa. Solanum mauritianum populations were sampled at 23 sites across an altitudinal gradient in KwaZulu-Natal to determine A. santacruzi densities in relation to food availability and climatic variables. Despite significantly higher amounts of floral material on S. mauritianum at the higher altitude inland sites, A. santacruzi numbers were significantly higher at the lower altitude coastal sites. There was thus a significant negative relationship between A. santacruzi numbers and altitude and significant positive relationships between A. santacruzi numbers and both temperature and humidity. Neither rainfall nor food availability influenced A. santacruzi numbers, although lower amounts of floral material at the coastal sites may well have been caused by higher weevil densities at these sites. Anthonomus santacruzi was absent at only three sites, all at higher altitudes, further demonstrating that conditions in coastal or low-altitude regions are favourable for establishment and population proliferation. Future release efforts in KwaZulu-Natal, but also in other South African provinces, should thus be focused on coastal regions and inland regions that are below 1000 m above sea level.     

Oviposition preferences and larval performance of a flower-feeding weevil,Coelocephalapion aculeatum, in relation to host development

The oviposition behaviour ofCoelocephalapion aculeatum Fall (Coleoptera: Apionidae), a host specific florivore exploiting an ephemeral resource, was studied in relation to host development. Immature inflorescences of its host, the weedMimosa pigra L. (Mimosaceae), were categorised into 5 developmental stages ranging from first appearance to one day before opening. The duration, weight, percent abortion, and nitrogen content of each stage were measured. Oviposition preferences ofC. aculeatum for all inflorescence stages were determined in multiple choice trials. Newly hatched, larvae were transferred into inflorescences of each stage to determine larval survival as a function of stage. Numbers of eggs laid into inflorescences generally correlated with larval survival except that oviposition was greater in stage 4 inflorescences than expected from the larval survival. Numbers of eggs laid into inflorescences generally correlated with their carrying capacity except that adults avoided stage 5 inflorescences in which larval survival was low. The evolution of oviposition preferences ofC. aculeatum appears to have been influenced by two opposing selective forces. The need to complete development before the inflorescence deteriorated would have selected for oviposition in young inflorescences. The greater availability of food and lower probability of abortion offered by older inflorescences would have selected for oviposition in these. The net outcome of these pressures has resulted in the observed oviposition strategy.