Local adaptations of life‐history traits of a Drosophila parasitoid,Leptopilina boulardi: does climate drive evolution?

1. Climate is an important source of selection on life histories, and local adaptations to climate have been described in several cline studies. Temperature is the main climatic factor that has been considered as an agent of selection, whereas other factors may vary with it, such as precipitation. 2. We compared life‐history traits of five populations of Leptopilina boulardi, a Drosophila parasitoid, originating from contrasting climates. Referring to cline studies, we hypothesised shorter lifespan, earlier reproduction, and lower lipid content in populations from the hottest and driest areas if life histories have been selected in response to temperature and/or humidity. 3. Our results are opposite to these predictions. Females from humid and mild climates invested more in early reproduction and lived for fewer days than females from dry and hot areas, which were synovigenic (i.e. they matured additional eggs during adult life) and able to synthesise lipids during adult life. 4. We suggest that life histories are more adapted to host distribution than to climatic factors. Drosophila patches are more abundant in the humid area, allowing the parasitoids to spend less energy and time finding hosts. This may result in selection for early reproduction traded‐off against longevity. In the hot and dry climate, females have to fly large distances to find host patches. Synovigeny, a long lifespan, lipogenesis, and high dispersal ability may be adaptive there. This is the first time that between‐population differences in the ability to synthesise lipids have been described in parasitoids.     

Heat Stress-Induced Life Span Extension in Yeast

The yeastSaccharomyces cerevisiaehas a limited life span that can be measured by the number of times individual cells divide. Several genetic manipulations have been shown to prolong the yeast life span. However, environmental effects that extend longevity have been largely ignored. We have found that mild, nonlethal heat stress extended yeast life span when it was administered transiently early in life. The increased longevity was due to a reduction in the mortality rate that persisted over many cell divisions (generations) but was not permanent. The genesRAS1andRAS2were necessary to observe this effect of heat stress. TheRAS2gene is consistently required for maintenance of life span when heat stress is chronic or in its extension when heat stress is transient or absent altogether.RAS1,on the other hand, appears to have a role in signaling life extension induced by transient, mild heat stress, which is distinct from its life-span-curtailing effect in the absence of stress and its lack of involvement in the response to chronic heat stress. This distinction between theRASgenes may be partially related to their different effects on growth-promoting genes and stress-responsive genes. Theras2mutation clearly hindered resumption of growth and recovery from stress, while theras1mutation did not. TheHSP104gene, which is largely responsible for induced thermotolerance in yeast, was necessary for life extension induced by transient heat stress. An interaction between mitochondrial petite mutations and heat stress was found, suggesting that mitochondria may be necessary for life extension by transient heat stress. The results raise the possibility that theRASgenes and mitochondria may play a role in the epigenetic inheritance of reduced mortality rate afforded by transient, mild heat stress.     

The life history of Callophyllis firma (Kylin) Norris in laboratory culture

Callophyllis firma (Kylin) Norris has been shown to have a life history in laboratory culture in which the tetrasporangial and gametangial phases are morphologically identical. This is the first published report of such a Polysiphonia-type of life history in a member of the Cryptos nemiales.     

Relationship between pace of life and immune responses in wild rodents

Life histories of animals tend to vary along a slow to fast continuum. Those with fast life histories have shorter life spans, faster development, and higher reproductive rates relative to animals with slower life histories. These differences in life histories have been linked to differences in investment in immunological defenses. Animals with faster life histories are predicted to invest relatively more in innate immune responses, which include rapidly‐deployed, non‐specific defenses against a broad spectrum of invaders. On the other hand, animals with slower life histories are predicted to invest relatively more in adaptive immune responses, which are more slowly‐deployed and are highly pathogen‐specific. These predictions have been confirmed in some taxa, but other studies have not found this association. We tested this prediction by measuring innate and adaptive immunity of white‐footed mice Peromyscus leucopus, chipmunks Tamias striatus, and gray squirrels Sciurus carolinensis, three species of rodents that inhabit deciduous forests in the northeastern US. These species exhibit a range of life histories, with mice having a relatively fast life history, squirrels a relatively slow one, and chipmunks an intermediate one. We found mice to have the greatest ‘bacterial killing capacity’, a common measure of innate immunity, and squirrels the lowest, consistent with the pace‐of‐life immune‐defense hypothesis. We also found squirrels to mount the most pronounced antibody response when challenged with lipopolysaccharide (LPS), an immunogenic component of bacteria, while mice had the lowest, again consistent with predictions based on their life histories. These results have implications beyond ecoimmunology because the probability that a host species will transmit an infection – its ‘reservoir competence’ – has been linked to its immune strategy. Understanding the relationship between immunology and reservoir competence is a critical frontier in the ecology of infectious diseases.     

Holococcolithophore‐heterococcolithophore (Haptophyta) life cycles: Flow cytometric analysis of relative ploidy levels

Several coccolithophore species are known to exhibit heteromorphic life cycles. In certain species, notably Emiliania huxleyi, the heterococcolith‐bearing phase alternates with a non‐calcifying stage, whereas in others the heterococcolith‐bearing phase alternates with a holococcolith‐bearing phase. Heterococcolithophore‐holococcolithophore life cycles have previously been observed for only one species in culture, but have also been inferred from an increasing number of observations of combination coccospheres. 18S rDNA sequences from pure cultures of both the heterococcolith‐bearing and holococcolith‐bearing phases of Coccolithus pelagicus were identical, providing an additional indication of their identity as different life cycle stages of the same species. Flow cytometric analyses have been undertaken on SybrGreen‐stained nuclei isolated from pure cultures of the two phases of four coccolithophore species (Coccolithus pelagicus, Calcidiscus leptoporus, Coronosphaera mediterranea and Emiliania huxleyi) in order to determine relative DNA content. Results confirm the hypothesis that holococcolithophore‐heterococcolithophore life cycles are haplo‐diploid in nature. Light microscope observations of the processes of sexual fusion and meiosis are reported for two of the experimental species. The results are discussed in the context of the evolution of bio‐mineralization in the coccolithophores and the possible ubiquity of haplo‐diploidy in the haptophytes.     

Inter-population genetic variation in the freshwater leech Nephelopsis obscura in relation to environmental heterogeneity

The temporal distribution of populations of aquatic macroinvertebrates have been extensively investigated in temperate arctic regions, but little information is available for alpine regions in North America. This paper describes phenology patterns of the aquatic macroinvertebrates of a high elevation wetland (3593 m) in the Green Lakes Valley, Colorado Front Range.Abundant taxa were Chironomidae (primarily Orthocladius and the limnephilid trichopteran Asynarchus curtus (Banks). Temperature patterns were related to the seasonal timing of life stages of most species. Phenology of most alpine aquatic macroinvertebrates appears to be controlled by seasonal climatic patterns, particularly temperature patterns. All chironomid species and Asynarchus curtus (Banks) had univoltine life cycles. Multi-year life cycles were not observed at this alpine site, although they have been observed at some arctic sites with colder temperature regimes than observed in this study.     

Life history shifts and alterations in the early development of parasitic wasps

Summary

In insects, the regulation of embryonic development has been intensively studied in model species like Drosophila melanogaster. Previous comparative studies have suggested that the developmental processes documented in Drosophila well describe embryogenesis of holometabolous insects generally. However, there have been few attempts to take into account how life history has influenced insect embryogenesis or to characterize early development of species with life histories fundamentally different from flies. Our studies of advanced insects in the order Hymenoptera suggest that punctuated shifts in life history can profoundly influence these events. In particular, alterations associated with the evolution of endoparasitism argue that departures from the fly paradigm may occur commonly among insects that develop under conditions different from typical terrestrial species.     

Spatially varying selection shapes life history clines among populations of Drosophila melanogaster from sub‐Saharan Africa

Clines in life history traits, presumably driven by spatially varying selection, are widespread. Major latitudinal clines have been observed, for example, in Drosophila melanogaster, an ancestrally tropical insect from Africa that has colonized temperate habitats on multiple continents. Yet, how geographic factors other than latitude, such as altitude or longitude, affect life history in this species remains poorly understood. Moreover, most previous work has been performed on derived European, American and Australian populations, but whether life history also varies predictably with geography in the ancestral Afro‐tropical range has not been investigated systematically. Here, we have examined life history variation among populations of D. melanogaster from sub‐Saharan Africa. Viability and reproductive diapause did not vary with geography, but body size increased with altitude, latitude and longitude. Early fecundity covaried positively with altitude and latitude, whereas lifespan showed the opposite trend. Examination of genetic variance–covariance matrices revealed geographic differentiation also in trade‐off structure, and Q_ST‐F_ST analysis showed that life history differentiation among populations is likely shaped by selection. Together, our results suggest that geographic and/or climatic factors drive adaptive phenotypic differentiation among ancestral African populations and confirm the widely held notion that latitude and altitude represent parallel gradients.     

Phylogenetic Diversity of New Zealand Gelidiales as Revealed by rbcL Sequence Data

Diversity and phylogenetic relationships of New Zealand representatives of the red algal order Gelidiales have been examined using rbcL sequence data. Extensive field collections have been made from throughout the New Zealand region. Six genera have been reported previously from New Zealand (Capreolia, Gelidium, Pterocladia, Pterocladiella, Pterocladiastrum, Ptilophora). This research has revealed species with very restricted local distributions, as well as the discovery of several undescribed, cryptic taxa. The common and widespread Gelidium caulacantheum is confirmed to be more closely related to Capreolia than to other species of Gelidium. The generic concept of Capreolia, based on life history characters, will need to be modified to accommodate additional species possessing “Gelidium” life histories. A species endemic to New Zealand, Gelidium ceramoides, has been found to differ significantly from all other members of the Gelidiales and requires reclassification in another genus and order. Examination of field collections and herbarium specimens in addition to molecular sequence data have led us to conclude that specimens previously placed in the genera Ptilophora and Pterocladiastrum belong within Pterocladia lucida.     

Ultraviolet Inactivation and Photoreactivation in Synchronized Chlorella

Synchronous cultures of Chlorella pyrenoidosa have been used in studies of the action of UV-irradiation during different stages in the life cycle on cell division capacity. These experiments show that there is a considerably higher sensitivity to UV-irradiation during the first hours of the life cycle. The variations in photoreactivating capacity of UV-damaged cells during a life cycle have been investigated. The results from these investigations show that the photoreactivating capacity varies and that it is higher in young daughter cells (autospores) and 12–15 hour cells. These variations can be due to variations in the activity of the photoreactivating enzyme during the life cycle.     

Phenotypic Variations in the Life History of Two Clones of Macrobiotus richtersi (Eutardigrada, Macrobiotidae)

A comparative study of life history traits of two clones (CDMr01 and CDMr02) of a triploid thelytokous apomictic population of the eutardigrade Macrobiotus richtersi has been carried out. Both clones were reared under the same lab conditions: temperature of 14 °C, photoperiod of 12 h/12 h (L/D), and nematodes ad libitum as food. Statistical analysis of the life history traits considered has indicated interclonal variability. The two clones were significantly different in the number of eggs per clutch (fertility), number of eggs laid per female per life span (fecundity), hatching percentage of eggs and hatching time. Similarities between clones have been observed with regard to life span, total number of ovipositions per life span, and age at first oviposition. In addition, significant differences in hatching time, with eggs hatched over a long period, were found within each clone. Interclonal variability in life history traits indicated the effects of genetic factors, whereas intraclonal variability reflected the effects of environmental factors. The evolutionary and adaptive significance of the life history phenotypic variations is discussed.     

Leucosporidium gen. n., the heterobasidiomycetous stage of several yeasts of the genusCandida

Investigation of yeasts from Antarctic regions revealed that certain species ofCandida have heterobasidiomycetous life cycles. Two distinct but overlapping groups of species were found: heterothallic and self-sporulating species.Candida scottii is a heterothallic species with the following life cycle: opposite mating types will conjugate and develop a dikaryotic mycelium with clamp connections. Karyogamy occurs in the teliospore which germinates and produces a promycelium. Meiosis takes place in the promycelium, followed by development of haploid sporidia to complete the life cycle. In addition,C. scottii has a self-sporulating phase. From a single cell, in the apparent absence of mating, a uninucleate mycelium is produced that lacks clamp connections. Teliospores, promycelia and sporidia develop that appear similar to those produced from dikaryotic mycelium.The self-sporulating species have life histories similar to the self-sporulating phase ofC. scottii; except that heterothallism has not been observed.Based on these life histories the new genusLeucosporidium is proposed with two heterothallic species (Leu. scottii andLeu. capsuligenum) and five self-sporulating species (Leu. antarcticum, Leu. frigidum, Leu. gelidum, Leu. nivalis andLeu. stokesii. Leu. antarcticum) andLeu. stokesii have not been described under the genusCandida.Contribution No. 1138 from the Institute of Marine Sciences, University of Miami, Fla.This study was supported by the National Science Foundation through the Office of Antarctic Programs, Grant GA-3957. The authors are grateful to Dr. E. Marelli for editing the Latin diagnosis.     

The life cycle of mitochondria in the true slime mould,Physarum polycephalum

The cytoplasmic aspects of mitochondrial biogenesis have been the focus of much recent attention and a review is presented here of studies on the life cycle of mitochom dria inPhysarum polycephalum. Such studies have focused predominantly on behavior of the mitochondrial genome throughout the mitochondrial life cycle and have been designed to reveal details about (1) the role of the DNA-membrane complex in the segregation of the mitoehondrial genome; (2) the regulation of mitochondrial activity associated with changes in ptoidy of the mitoehondrial nucleus; (3) the hierarchical pattern of transmission of the mitochondrial genome as it relates to the mating-type locus (matA) during the sexual development; and (4) the fusion of mitoehondria that is promoted by a mitochondrial plasmid. The results of such studies contribute significantly to efforts towards a better understanding not only of the mitochondrial life cycle inP. potycephalum but also of the biogenesis of mitoehondria and plastids in many other organisms. Recipient of the Botanical Society Award for Young Scientists, 1988.     

The distribution of benthic marine algae

Hitherto only gametangial and carposporangial phases of Thuretellopsis peggiana Kylin have been reported. A study of this rare member of the Dumontiaceae (Cryptonemiales) in culture has disclosed the existence of an encrusting tetrasporangial phase, previously unknown, whilst the life history has been shown to be of the ‘Bonnemaisonia’ type.     

Life habits and functional morphology of the sediment infaunal spongesOceanapia oleracea andOceanapia peltata (Porifera,Haplosclerida)

Summary In the Santa Marta area of the northern coast of Colombia two species of sponges have been found living within the sediment. The only connection these sponges have with the open water consists of a number of protruding, tubule-like siphons. Through field observations and aquarium experiments, the life habits and the function of the water current system ofOceanapia oleracea andO. peltata have been studied. As an adaptation to life embedded in sediment, both species possess inhalant siphons which draw water from above the sediment surface and duct it to the central body. The inhalant system shows a most unusual separation and concentration of inhalant pores at the tips of the inhalant ducts. The exhalant water leaves the sponge through separate ducts at the opposite side of the central body. Based on the observations onOceanapia, the water flow model forDisyringa proposed by Fry and Fry (1979) is reconsidered.     

Effects of assay conditions in life history experiments with Drosophila melanogaster

Selection experiments with Drosophila have revealed constraints on the simultaneous evolution of life history traits. However, the responses to selection reported by different research groups have not been consistent. Two possible reasons for these inconsistencies are (i) that different groups used different environments for their experiments and (ii) that the selection environments were not identical to the assay environments in which the life history traits were measured. We tested for the effect of the assay environment in life history experiments by measuring a set of Drosophila selection lines in laboratories working on life history evolution with Drosophila in Basel, Groningen, Irvine and London. The lines measured came from selection experiments from each of these laboratories. In each assay environment, we measured fecundity, longevity, development time and body size. The results show that fecundity measurements were particularly sensitive to the assay environment. Differences between assay and selection environment in the same laboratory or differences between assay environments between laboratories could have contributed to the differences in the published results. The other traits measured were less sensitive to the assay environment. However, for all traits there were cases where the measurements in one laboratory suggested that selection had an effect on the trait, whereas in other laboratories no such conclusion would have been drawn. Moreover, we provide good evidence for local adaptation in early fecundity for lines from two laboratories.     

CHLOROPHYCEAN ALGAE FROM LIMESTONE SPRINGS

Two new chlorococcalean algae have been isolated from limestone springs and studied in axenic cultures. Their life histories have been elucidated and supplementary physiological attributes reported. The relationships of these species to previously described species of the genus are discussed, and a key to known species of Spongiococcum is presented.     

Lotharella amoeboformis sp. nov.: A new species of chlorarachniophytes from Japan

The ultrastructure, morphology and life cycle of a new chlorarachniophyte alga collected from Okinawa in Japan have been studied. The life cycle of this alga consists of amoeboid, wall‐less round, coccoid and flagellated cells in culture condition; however, the coccoid and flagellate cells are very rare. The pyrenoid ultra‐structure of this alga is the same as that of a previously described species, Lotharella globosa. Since pyrenoid ultrastructure has been adopted as the main criterion for the generic classification of the chlorarachniophytes, the present alga is placed in Lotharella. However, the present alga has a dominant amoeboid cell stage and a reduced walled‐cell stage in the life cycle, while in L. globosa, the walled‐cell stage is dominant and there is no amoeboid cell stage. Therefore the present alga is described as a new species of Lotharella: Lotharella amoeboformis Ishida et Y. Hara sp. nov.     

The ship-fouling algaEctocarpus

Summary The unilocular reproductive stages of the brown algaEctocarpus have been examined with the electron microscope. One observation in particular, which is believed to have been made for the first time in Phaeophycean studies, is that the zoospore derived from unilocular sporangia possesses a microanatomy considerably different from that of spores formed by plurilocular sporangia. It is suggested that this difference may have an evolutionary significance and may lead to a better understanding of the life cycle ofEctocarpus.