Transient Habitats Research Articles

Biofilms in drinking water and their role as reservoir for pathogens

Most microorganisms on Earth live in various aggregates which are generally termed "biofilms". They are ubiquitous and represent the most successful form of life. They are the active agent in biofiltration and the carriers of the self-cleaning potential in soils, sediments and water. They are also common on surfaces in technical systems where they sometimes cause biofouling. In recent years it has become evident that biofilms in drinking water distribution networks can become transient or long-term habitats for hygienically relevant microorganisms. Important categories of these organisms include faecal indicator bacteria (e.g., Escherichia coli), obligate bacterial pathogens of faecal origin (e.g., Campylobacter spp.) opportunistic bacteria of environmental origin (e.g., Legionella spp., Pseudomonas aeruginosa), enteric viruses (e.g., adenoviruses, rotaviruses, noroviruses) and parasitic protozoa (e.g., Cryptosporidium parvum). These organisms can attach to preexisting biofilms, where they become integrated and survive for days to weeks or even longer, depending on the biology and ecology of the organism and the environmental conditions. There are indications that at least a part of the biofilm populations of pathogenic bacteria persists in a viable but non-culturable (VBNC) state and remains unnoticed by the methods appointed to their detection. Thus, biofilms in drinking water systems can serve as an environmental reservoir for pathogenic microorganisms and represent a potential source of water contamination, resulting in a potential health risk for humans if left unnoticed.

Ciliados (Protozoa) de sedimentos secos de una charca temporaria de la Argentina

Temporary ponds represent special environments that are inhabited by organisms adapted to changingenvironmental conditions. Ciliates are able to survive complete loss of water in these transient habitats through cyst formation. However, ciliates from the Neotropical region in general have been poorly studied with modern techniques. The main goal of this study is to describe the ciliates in dried sediments of a temporary pond from Buenos Aires Province, Argentina, through sampling efforts that were performed 2003-2005. Soil samples were obtained during drought phases and rewetted in laboratory to establish raw and enriched cultures. Ciliates were then studied both in vivo and after impregnation with protargol. In this study, we present 4 new records for Argentina (Gonostomum affine (Stein, 1859) Sterki, 1878, Stylonychia bifaria (Stokes, 1887) Berger, 1999, Pleurotricha lanceolata (Ehrenberg, 1835) Stein, 1859, Meseres corlissi Petz and Foissner, 1992), 1 for South America (Blepharisma americanum (Suzuki, 1954) Hirshfi eld, Isquith and Bhandary, 1965), and 2 for the Neotropical Realm (Gonostomum strenuum (Engelmann, 1862) Sterki, 1878, Stylonychia lemnae Ammermann and Schlegel, 1983).

Mating system, reproduction mode and diaspore size affect metacommunity diversity

1 Metapopulation persistence and metacommunity diversity in patchy dynamic landscapes critically depend on efficient dispersal. Dispersal strategies could involve trade-offs that result in different species responses to habitat fragmentation, alteration in habitat quality and changes in landscape dynamics. 2 We studied spatial structuring in species richness of obligate epiphytic bryophytes in 135 deciduous forest patches in a largely coniferous landscape in Sweden. We tested the effects of forest patch size (0.01–15 ha), patch quality and present and historic connectivity (as revealed by air photographs) on species richness of species groups with different mating systems, reproduction modes and diaspore sizes. 3 Present connectivity to other deciduous forest patches had positive effects on richness of dioecious species with predominant asexual reproduction, whereas richness of monoecious species with predominant sexual reproduction was affected by historic connectivity only. The scale of spatial structuring in species richness increased with decreasing diaspore sizes. Forest patch quality affected richness of monoecious species reproducing sexually but not of dioecious species reproducing asexually. 4 Our results suggest shorter dispersal distances, but higher establishment rates, of large asexual diaspores than of small sexual ones. In monoecious species with sexual reproduction, it may take several decades from establishment to first spore production, and this may explain the strong effect of historic, but not present, forest patch connectivity on species richness of this group. This suggests a trade-off between dispersal distance and age at first reproduction, which may explain the parallel evolution of asexual reproduction and monoecism in species inhabiting patchy, transient habitats. 5 Synthesis. We conclude that dispersal success of metacommunity members is influenced both by species traits and habitat characteristics. In patch-tracking metacommunities, trade-offs in species traits may have evolved as a consequence of conflicting selection pressures imposed by habitat patchiness and dynamics. Syndromes of interrelated species traits imply that fairly small changes in habitat conditions may lead to distinct changes in metacommunity diversity: Species reproducing asexually may drastically decline with increasing distances among patches, whereas sexually reproducing species may decline with increasing patch dynamics.

Predispersal seed predation by a coleophorid on the threatened Gulf of St. Lawrence aster

AbstractThe Gulf of St. Lawrence aster,Symphyotrichum laurentianum(Fernald) G.L. Nesom (Asteraceae), a small annual halophyte endemic to disturbed and highly transient habitats in the Gulf of St. Lawrence, is classified as “threatened” by the Committee on the Status of Endangered Wildlife in Canada. Lepidopteran larvae that are predispersal seed predators of the Gulf of St. Lawrence aster are reported for the first time from populations in Prince Edward Island National Park. DNA barcoding was used to identify the seed predators tentatively as larvae of the casebearing mothColeophora triplicisMcDunnough (Lepidoptera: Coleophoridae), which is typically associated with a related halophyte,Solidago sempervirensL. (Asteraceae). These larvae were found to consume a large proportion of seeds from one of two aster populations in Prince Edward Island National Park and may be yet another risk to the survival of this threatened species.

Ontogenetic Factors Affecting Diffusion Dispersal in the Introduced Mediterranean Gecko, Hemidactylus turcicus

Abstract Dispersal occurs when an individual leaves its natal area or home range, travels through adjacent areas, and then establishes a new home range where it will attempt to reproduce. Previous studies have suggested that subadults (i.e., hatchlings and juveniles) are the main agents of dispersal among introduced populations of Mediterranean Geckos, Hemidactylus turcicus. We derived a testable hypothesis for subadult dispersal in Mediterranean Geckos. In September 2006, we conducted tethering experiments to test the prediction that adults act aggressively toward subadults. From June to October 2006, we conducted 18 mark-recapture samples to test predictions of perch height occupancy and relative presence of adults and subadults at buildings and areas between buildings (i.e., transient habitats). As predicted, subadults occupied lower regions of buildings than adults, and subadults were disproportionately abundant in transient habitats. Apparently because of small sample size, there was no difference in...

Amassing diversity in an ancient lake: evolution of a morphologically diverse parthenogenetic gastropod assemblage in Lake Malawi

Exceptional ecological niche diversity, clear waters and unique divergent selection pressures have often been invoked to explain high morphological and genetic diversity of taxa within ancient lakes. However, it is possible that in some ancient lake taxa high diversity has arisen because these historically stable environments have allowed accumulation of lineages over evolutionary timescales, a process impossible in neighbouring aquatic habitats undergoing desiccation and reflooding. Here we examined the evolution of a unique morphologically diverse assemblage of thiarid gastropods belonging to the Melanoides polymorpha'complex' in Lake Malawi. Using mitochondrial DNA sequences, we found this Lake Malawi complex was not monophyletic, instead sharing common ancestry with Melanoides anomala and Melanoides mweruensis from the Congo Basin. Fossil calibrations of molecular divergence placed the origins of this complex to within the last 4 million years. Nuclear amplified fragment length polymorphism markers revealed sympatric M. polymorpha morphs to be strongly genetically differentiated lineages, and males were absent from our samples indicating that reproduction is predominantly parthenogenetic. These results imply the presence of Lake Malawi as a standing water body over the last million years or more has facilitated accumulation of clonal morphological diversity, a process that has not taken place in more transient freshwater habitats. As such, the historical stability of aquatic environments may have been critical in determining present spatial distributions of biodiversity.

Source–sink dynamics of virulence evolution

To understand the evolution of genetic diversity within species--bacterial and others--we must dissect the first steps of genetic adaptation to novel habitats, particularly habitats that are suboptimal for sustained growth where there is strong selection for adaptive changes. Here, we present the view that bacterial human pathogens represent an excellent model for understanding the molecular mechanisms of the adaptation of a species to alternative habitats. In particular, bacterial pathogens allow us to develop analytical methods to detect genetic adaptation using an evolutionary 'source-sink' model, with which the evolution of bacterial pathogens can be seen from the angle of continuous switching between permanent (source) and transient (sink) habitats. The source-sink model provides a conceptual framework for understanding the population dynamics and molecular mechanisms of virulence evolution.

Population interactions between Culex vishnui mosquitoes and their natural enemies in Pondicherry, India

Population interactions among mosquitoes in the Culex vishnui subgroup, which are vectors of Japanese Encephalitis, and their natural enemies were studied in Pondicherry, India. We tested the hypothesis that the breakdown of interactions between the larvae and their natural enemies due to drought followed by rain was responsible for the sudden increase in the vector population above the threshold for disease transmission during the heavy rainy period. We randomly sampled mosquito larvae and their predators in different breeding habitats and subjected the mean densities of prey, predator, and mosquito larvae infected with parasites/pathogens to covariate analysis to understand the interaction between prey and their natural enemies in relation to environmental factors. In rice fields, neither prey nor predator showed any positive correlation with temperature, RH, or the number of rainy days. However, the pathogen/parasite of mosquito immatures showed a positive correlation with RH. Among the mosquito predators, notonectids exhibited a significant positive correlation with Cx. vishnui larvae. The parasitic Romanomermis iyengari and pathogenic Coelomomyces anopheliscus also showed positive correlations with immatures. No parasites and pathogens of mosquito larvae were recorded in shallow water pools (SWP) or cement tanks (CT) during the study period. Important predators recorded in SWP were notonectids, damselfly nymphs, Diplonychus indicus, and hydrophilids. Dragonfly nymphs, gerrids, and tadpole shrimps were recorded in CT. In CT, prey and their predators were positively correlated with RH and rainy days. In SWP, there was a highly significant correlation between prey, predators and environmental factors. We conclude that rice fields are a stable ecosystem where regular interaction occurs between larvae and their natural enemies and a sudden increase in mosquito populations is uncommon. In transient habitats, no such stability is present and they become more important as breeding habitats in terms of seasonality and number. Shallow water pools should be seriously considered for the control of these vectors.

Conservation of Species in Dynamic Landscapes: Divergent Fates ofSilene tataricaPopulations in Riparian Habitats

In transient environments, where local extinctions occur as a result of destruction or deterioration of the local habitat, the long-term persistence of a species requires successful colonizations at new, suitable sites. This kind of habitat tracking should be associated with the asynchronous dynamics of local populations, and it can be especially important for the conservation of rare plant species in riparian habitats. We determined spatiotemporal variation in the demography of the perennial Silene tatarica (L.) Pers. in 15 populations (1998-2003) located in periodically disturbed riparian habitats. The habitats differed according to their morphology (flat shores, slopes) and the amount of bare ground (open, intermediate, closed) along a successional gradient. We used elasticity and life-table response analyses and stochastic simulations to study the variation in population demography. Finite population growth rate was higher in intermediate habitats than in open and closed habitats. In stochastic simulations population size increased in most cases, but four populations were projected to become extinct within 12-70 years. The viability of local populations depended most on the survival and growth of juvenile individuals and on the fecundity of large fertile individuals. On a regional scale, the persistence of this species will require a viable network of local populations as protection against local extinctions caused by natural disturbances and succession. Accordingly, the long-term persistence of riparian species may depend on habitat changes; thus, their conservation requires maintenance of natural disturbance dynamics. Along regulated rivers, management activities such as the creation of open habitats for new colonization should be implemented. Similarly, these activities can be rather general requirements for the conservation of endangered species dependent on transient habitats along successional gradients.

Metapopulation persistence in dynamic landscapes: the role of dispersal distance

Species associated with transient habitats need efficient dispersal strategies to ensure their regional survival. Using a spatially explicit metapopulation model, we studied the effect of the dispersal range on the persistence of a metapopulation as a function of the local population and landscape dynamics (including habitat patch destruction and subsequent regeneration). Our results show that the impact of the dispersal range depends on both the local population and patch growth. This is due to interactions between dispersal and the dynamics of patches and populations via the number of potential dispersers. In general, long‐range dispersal had a positive effect on persistence in a dynamic landscape compared to short‐range dispersal. Long‐range dispersal increases the number of couplings between the patches and thus the colonisation of regenerated patches. However, long‐range dispersal lost its advantage for long‐term persistence when the number of potential dispersers was low due to small population growth rates and/or small patch growth rates. Its advantage also disappeared with complex local population dynamics and in a landscape with clumped patch distribution.

Dormancy, dispersal and the survival of cyclopoid copepods (Cyclopoida, Copepoda) in a lowland floodplain

1. The survival of cyclopoid copepods was investigated in a floodplain for 2 years where flooding occurred during the cold season. The cyclopoid community was studied in three waterbodies with distinct hydroperiods: a permanent pond connected to the flooded area during inundation, a temporary pool that is part of the flooded area and an isolated temporary pool.2. Field studies, including data obtained from samples of water, sediment and soil, showed the overall predominance of species with a summer diapause over those with a winter diapause or without diapause. Emergence of cyclopoid copepods at the onset of flooding, examined using emergence traps and data from recently filled or still isolated temporary pools, showed that some species can survive several months of drying.3. The ability of the diapausing fourth copepodid stages of Cyclops strenuus and C. insignis, the two cyclopoids most abundant during winter and spring flooding, to survive terrestrial conditions was tested in laboratory experiments. Both species survived for several months, but rates differed among the species. A higher percentage of C. strenuus survived for a longer period, possibly explaining why this species was relatively more abundant in more temporary habitats.4. Both dormancy and dispersal facilitated survival of cyclopoid copepods in transient habitats connected to each other during flood periods. Dormancy was the most important survival strategy, whereas dispersal could be more important following prolonged periods without flooding.

Dispersal by Benthic Invertebrates: The in Situ Swimming Behaviour of the Amphipod Corophium Volutator

Studies of the dispersal behaviour of marine and estuarine benthic invertebrates have concentrated on the majority of species where the individuals disperse as a planktonic larva. The view that seems to be prevalent, summarised by Crisp (1974, 1976), is that larvae are an adaptation to allow species to colonise transient habitats and for species with adults of limited mobility to colonise distant habitats. The spreading of the species over wide areas has the advantages of reducing competition and facilitating greater genetic diversity, leaving the species more adaptable to subsequent environmental changes. These advantages are greater with longer distances travelled, and are an explanation for larvae spending up to several weeks drifting in the plankton, despite the acknowledged high mortality rates associated with the pelagic existence.

Do invading species have definable genedc characteristics?

The search for general answers to this question dates at least from the seminal conference at Asilomar in 1964. It has included comparative surveys of a wide range of taxa, investigations within congeneric groups of why some species are successful invaders and others are not, and, at the intraspecific level, comparisons of genetic variability in colonist versus source populations. The relevant data are reviewed. They suggest that successful invading species have genetic characteristics (defined here as the set of attributes that collectively determine the form in which, and frequency with which, genetic information is passed from one generation to the next), which need only be sufficiently protean to ensure rapid expansion in the new environment. Generalizations attempting to relate colonizing ability to polyploidy, to levels of genetic variability, heterozygosity, or phenotypic plasticity, or to mating system types, ignore the interaction in individuals of these components of the genetic system, and rarely consider chromosomal and genic controls of recombination. The poor predictive power of such generalizations is emphasized by considering invaders into the British flora, which are drawn from a wide spectrum of families and life forms. They include only a few ‘colonizing species’, those that habitually invade and occupy transient habitats and from which most models of invaders have been derived. Analysis of the origin and spread of Spartina anglica emphasizes that serendipity is often an important element in successful invasions. Studies of the genetic consequences of invading, especially those that take an experimental approach, are more likely to throw light on current problems in evolutionary theory than those that analyse the shared attributes of past invaders.

Post-metamorphic change in activity metabolism of anurans in relation to life history.

Newly-metamorphosed individuals of some species of frogs and toads differ from adults in behavior, ecology, and physiology. These differences may be related to broader patterns of the life histories of different species of frogs. In particular, the length of larval life and the size of a frog at metamorphosis appear to be significant factors in post-metamorphic ontogenetic change. These changes in performance are associated with rapid post-metamorphic increases in oxygen transport capacity. Bufo americanus (American toads) and Rana sylvatica (wood frogs) spend only 2-3 months as tadpoles and metamorphose at body masses of 0.25 g or less. Individuals of these species improve endurance and aerobic capacity rapidly during the predispersal period immediately following metamorphosis. Increases in hematocrit, hemoglobin concentration, and heart mass relative to body mass are associated with this improvement in organismal performance. Rana clamitans (green frogs) spend from 3 to 10 months as larvae and weigh 3 g at metamorphosis. Green frogs did not show immediate post-metamorphic increases in performance. Rana palustris (pickerel frogs) are intermediate to wood frogs and green frogs in length of larval life and in size at metamorphosis, and they are intermediate also in their post-metamorphic physiological changes.American toads and wood frogs appear to delay dispersal from their natal ponds while they undergo rapid post-metamorphic growth and development, whereas green frogs disperse as soon as they leave the water, even before they have fully absorbed their tails. The very small body sizes of newly metamorphosed toads and wood frogs appear to limit the scope of their behaviors. The brief larval periods of these species permit them to exploit transient aquatic habitats, but impose costs in the form of a period of post-metamorphic life in which their activities are restricted in time and space compared to those of adults.

Variation between field and laboratory populations of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

Abstract Rates of development and pupal weights were compared between seven field populations and two laboratory strains of Tribolium castaneum. Rates of development did not differ significantly between field populations, but pupal weights did vary. Laboratory strains were both slower to develop and heavier than the field populations. The data support the hypothesis that field populations undergo selection for fast development in transient habitats. The findings are discussed in the context of r and K selection in field populations and laboratory cultures.

LARVAL ECOLOGY OF MARINE BENTHIC INVERTEBRATES: PALEOBIOLOGICAL IMPLICATIONS

Summary1. Modes of larval development play important roles in the ecology, biogeography, and evolution of marine benthic organisms. Studies of the larval ecology of fossil organisms can contribute greatly to our understanding of such roles by allowing us to race effects on evolutionary time scales.2. Modes of development can be inferred for well preserved molluscan fossils because the size of the initial larval shell (Protoconch I in gastropods, Prodissoconch I in bivalves) reflects egg size. Other morphological criteria are also available, and a comparative approach based on related taxa with known development may be the most reliable method. By combining larval and adult traits, it is possible to recognize modes of larval development in at least some fossil bryozoans, brachiopods, and echinoderms as well. (a) Planktotrophic larvae arise from small eggs, are released in enormous numbers with little parental investment per offspring, and suffer tremendous mortality during and shortly after a planktic existence. These larvae feed on the plankton during development, and are commonly capable of a prolonged free‐swimming existence, and thus wide dispersal. (b) Nonplanktotrophic larvae (which include both planktic lecithotrophic forms and ‘direct developers’) generally arise from large eggs, with relatively few young produced per parent. Relative to planktotrophic larvae, nonplanktotrophic larvae generally receive greater parental investment per larva, and larval mortality is generally lower. These larvae rely on yolk for nutrition during development, and planktic durations are generally much briefer than for species with planktotrophic larvae, so that dispersal capability is considerably less. Energetic investment per egg is generally higher than in planktotrophs, but as there are lower fecundities as well it is difficult to generalize about the total energetic cost of one mode of reproduction against the other.3. Owing to the high dispersal capability of planktotrophic larvae, it has been suggested that species with such larvae will be geographically widespread, geologically long‐ranging, and exhibit low speciation and extinction rates. Species with nonplanktotrophic larvae will tend to be geographically more restricted, geologically short‐ranging, and exhibit high speciation and extinction rates (again, as a consequence of their characteristically low larval dispersal capabilities).4. Recognition of differential dispersal capabilities can play a role in paleobiogeo‐graphic analyses. Concurrent study of the distribution of groups with contrasting modes of development will permit testing of hypotheses concerning timing, magnitudes and frequencies of migration and vicariance events.5. Larval types are not randomly distributed in the oceans, but relationships with other aspects of the organisms' biology and habitats are very complex. Mode of development varies with: (a) Ecology. A simple r–––K model of adaptive strategies is clearly insufficient to explain the observed relationships: while many ‘equilibrium’ species have nonplanktotrophic larvae, and organisms living in less prdictable environments often have planktotrophic larvae, some of the most opportunistic marine species have nonplanktotrophic larvae. Nonetheless, planktotrophic development seems most suited for exploitation of patchy but widespread habitats. (b) Latitude. At shelf depths, planktotrophy is predominant in the tropics, and decreases sharply at high latitudes. (c) Depth. Incidence of planktotrophy decreases with depth across the continental shelf, at least in some taxa. Beyond the shelf, many deep‐sea organisms are nonplanktotrophic (e.g. most bivalves, peracarid crustaceans), but planktotrophic development appears to be present in other groups (prosobranch gastropods, ophiuroids, and bivalves inhabiting transient habitats such as sunken wood and hydrothermal vents).These trends in developmental types will be accompanied by trends in evolutionary rates and patterns as outlined above. The study of larval ecology by paleobiologists will yield insights into the processes that gave rise to ancient evolutionary and biogeographic patterns, and will permit the development and testing of hypotheses on the origins of the patterns observed in modern seas.