Population biology of bryozoans: correlates of sessile, colonial life histories in freshwater habitats

1995 ◽  
Vol 51 (5) ◽  
pp. 510-525 ◽  
Author(s):  
B. Okamura ◽  
T. Hatton-Ellis
Keyword(s):  
Population Biology ◽  
Life Histories ◽  
Freshwater Habitats

scholarly journals Parasites—the new frontier: celebrating Darwin 200

2009 ◽  
Vol 5 (5) ◽  
pp. 625-627 ◽  
Author(s):  
Paul Schmid-Hempel
Keyword(s):  
Population Biology ◽  
Life Histories ◽  
Evolutionary Ecology ◽  
Adaptive Value ◽  
Wide Range ◽  
New Frontier ◽  
Underlying Mechanisms ◽  
The One ◽  
Immune Defences ◽  
Recurrent Theme

To Darwin, parasites were fascinating examples of adaptation but their significance as selective factors for a wide range of phenomena has only been studied in depth over the last few decades. This work has had its roots in behavioural/evolutionary ecology on the one hand, and in population biology/ecology on the other, thus shaping a new comprehensive field of ‘evolutionary parasitology’. Taking parasites into account has been a success story and has shed new light on several old questions such as sexual selection, the evolution of sex and recombination, changes in behaviour, adaptive life histories, and so forth. In the process, the topic of ecological immunology has emerged, which analyses immune defences in a framework of costs and benefits. Throughout, a recurrent theme is how to appropriately integrate the underlying mechanisms as evolved boundary conditions into a framework of studying the adaptive value of traits. On the conceptual side, major questions remain and await further study.

Laboulbeniomycetes: Intimate Fungal Associates of Arthropods

2021 ◽  
Vol 66 (1) ◽  
pp. 257-276 ◽  
Author(s):  
Danny Haelewaters ◽  
Meredith Blackwell ◽  
Donald H. Pfister
Keyword(s):  
Population Biology ◽  
Life Histories ◽  
Invasion Biology ◽  
Species Discovery ◽  
Phylogenetic Studies ◽  
Intimate Association ◽  
Red Algal ◽  
Molecular Phylogenetic ◽  
Parasitic Worms ◽  
Host Parasite

Arthropod–fungus interactions involving the Laboulbeniomycetes have been pondered for several hundred years. Early studies of Laboulbeniomycetes faced several uncertainties. Were they parasitic worms, red algal relatives, or fungi? If they were fungi, to which group did they belong? What was the nature of their interactions with their arthropod hosts? The historical misperceptions resulted from the extraordinary morphological features of these oddly constructed ectoparasitic fungi. More recently, molecular phylogenetic studies, in combination with a better understanding of life histories, have clearly placed these fungi among filamentous Ascomycota (subphylum Pezizomycotina). Species discovery and research on the classification of the group continue today as arthropods, and especially insects, are routinely collected and examined for the presence of Laboulbeniomycetes. Newly armed with molecular methods, mycologists are poisedto use Laboulbeniomycetes–insect associations as models for the study of a variety of basic evolutionary and ecological questions involving host–parasite relationships, modes of nutrient intake, population biology, host specificity, biological control, and invasion biology. Collaboration between mycologists and entomologists is essential to successfully advance knowledge of Laboulbeniomycetes and their intimate association with their hosts.

scholarly journals Local conspecific density does not influence reproductive output in a secondary cavity-nesting songbird

The Auk ◽  
2020 ◽  
Vol 137 (2) ◽  
Author(s):  
Jeffrey P Hoover ◽  
Nicole M Davros ◽  
Wendy M Schelsky ◽  
Jeffrey D Brawn
Keyword(s):  
Body Condition ◽  
Population Biology ◽  
Life Histories ◽  
Reproductive Output ◽  
Local Density ◽  
Food Limitation ◽  
Primary Objective ◽  
Cavity Nesting ◽  
Nestling Provisioning ◽  
Local Densities

Abstract Density dependence is a conceptual cornerstone of avian population biology and, in territorial songbirds, past research has emphasized interactions among food limitation, density, and reproduction. Documenting the importance of density effects is central to understanding how selective forces shape life histories and population dynamics. During the 2008–2011 breeding seasons, we nearly doubled overall conspecific breeding densities on study sites, and manipulated nest box spacing to increase local breeding densities (defined as the number of pairs breeding within 200 m of a pair’s nest) of a secondary cavity-nesting songbird, the Prothonotary Warbler (Protonotaria citrea). Our primary objective was to test for effects of food limitation, as mediated by conspecific local densities, on measures of productivity. We monitored breeding pairs and recorded the total number of fledglings produced along with several components of reproductive output (clutch size, hatching success, nestling survival, and probability of attempting a second brood), rates of nestling provisioning, and nestling body condition prior to fledging. We predicted that if the availability of food were affected by local densities, then one or more of these parameters measuring reproduction would be affected negatively. We did not detect an effect of local density on total reproductive output or its components despite our vast range of local densities (1–27 pairs; i.e. 0.16–2.23 pairs ha–1). Further, we also did not detect differences in nestling provisioning rates and nestling body condition relative to local density. By breeding in a productive ecosystem rich in food resources, these warblers appear to avoid reduced reproductive output when breeding in high densities. Whereas density-dependent food limitation may commonly reduce reproductive output in many species, the ecological circumstances underlying when it does not occur merit further investigation and may provide new insights into what is driving territoriality and what are the primary factors affecting individual fitness.

scholarly journals Marine trophic diversity in an anadromous fish is linked to its life-history variation in fresh water

2013 ◽  
Vol 9 (1) ◽  
pp. 20120824 ◽  
Author(s):  
Susan P. Johnson ◽  
Daniel E. Schindler
Keyword(s):  
Life History ◽  
Life Histories ◽  
Sockeye Salmon ◽  
Freshwater Ecosystems ◽  
Life History Variation ◽  
Trophic Diversity ◽  
Trade Offs ◽  
Salmon Population ◽  
Freshwater Habitats ◽  
Foraging Tactics

We used carbon and nitrogen stable isotopes from muscle tissues accrued in the ocean to examine whether marine foraging tactics in anadromous sockeye salmon ( Oncorhynchus nerka ) are linked to their ultimate freshwater life history as adults. Adults from large-bodied populations spawning in deep freshwater habitats had more enriched δ 15 N than individuals from small-bodied populations from shallow streams. Within populations, earlier maturing individuals had higher δ 15 N than older fish. These differences in δ 15 N suggest that the fish with different life histories or spawning habitats in freshwater either fed at different trophic positions or in different habitats in the ocean. We propose that, nested within interspecific diversity in the ecological attributes of salmon, population and life-history diversity in spawning adults is associated with variation in marine foraging tactics. These results further indicate that the trophic diversity of sockeye salmon in the ocean may be linked to trade-offs in ecological and evolutionary constraints they eventually experience as adults in freshwater ecosystems.

Does proximity to freshwater refuge affect the size structure of an estuarine predator (Carcharhinus leucas) in the north-western Gulf of Mexico?

2020 ◽  
Vol 71 (11) ◽  
pp. 1501 ◽  
Author(s):  
Philip Matich ◽  
Robert J. Nowicki ◽  
Jonathan Davis ◽  
John A. Mohan ◽  
Jeffrey D. Plumlee ◽  
...  
Keyword(s):  
Life Histories ◽  
Environmental Variability ◽  
Size Structure ◽  
Distribution Patterns ◽  
Freshwater Inflow ◽  
The North ◽  
Carcharhinus Leucas ◽  
Freshwater Habitats ◽  
Bull Shark ◽  
River Mouths

The life histories of estuarine species are often adapted to the environmental variability they experience. However, estuaries are increasingly vulnerable to natural and anthropogenic changes, necessitating an understanding of how shifting conditions affect the survival, behaviour and population structure of estuarine-dependent animals. In this study we used data from fisheries-independent surveys collected across six estuaries with variable salinity regimes in Texas, USA, from 1975 to 2016 to investigate the role sources of freshwater inflow play in shaping juvenile bull shark Carcharhinus leucas size structure. High frequencies of co-occurrence with similarly sized conspecifics (59% of capture events) suggest bull sharks segregated within Texan estuaries based on body size. Bull shark sizes increased with distance to the nearest source of freshwater inflow, although effect sizes were small and access to freshwater habitats may be more important in shaping size-dependent distribution patterns. River mouths were disproportionately used by smaller juveniles (<90-cm total length, TL) and avoided by larger juveniles (>135cm TL). However, the use of river mouths decreased in estuaries characterised by limited freshwater inflow and greater variability in salinities at river mouths, highlighting geographic differences in the functions these habitats provide as potential environmental and predator refugia. Young-of-the-year (i.e. age-0) sharks also increased their use of river mouths throughout the 40-year study period, revealing the growing importance of river mouths as potential nursery habitats.

Life-history concepts and the population biology of clonal organisms

1987 ◽  
Vol 232 (1266) ◽  
pp. 35-57 ◽  
Keyword(s):  
Life History ◽  
Clonal Growth ◽  
Population Biology ◽  
Life Histories ◽  
Cost Of Reproduction ◽  
Reproductive Value ◽  
Structured Population ◽  
Clonal Organisms ◽  
Age Structured ◽  
Different Levels

Existing life-history concepts deal inadequately with clonal organisms. To make them more generally applicable, several assumptions must be widened: (i) life histories may be expressed at different levels of individual organization. e. g. genets and modules; (ii) parts of a life cycle may be executed more than once by a single genetic individual; (iii) genetic individuals do not necessarily senesce; (iv) size and reproductive value of genetic individuals may increase indefinitely with age; and (v) dor­mancy, dispersal of progeny, and production of genetically different progeny are not necessarily linked to the same process, as they are in reproduction of unitary organisms. A model is presented of a size-structured population of genets, in which each genet comprises an age-structured metapopulation of modules. The model predicts that the extent to which clonal growth evolves depends on: constraints in genet architecture (high or low within-genet ‘disper­sal’); cost of reproduction relative to that of clonal growth; the presence or absence of density-dependent regulation of population size; the pres­ence of lethal events that kill entire genets, as opposed to genet mortality occurring only as a consequence of the mortality of all its modules; the ability of genets to predict such lethal events; and the temporal heterogeneity of the environment. The predicted responses to r - and K -selection differ markedly from those predicted for unitary organisms, especially for genets with high within-genet dispersal. For example, r -selection may favour clonal growth with no reproduction, whereas K -selection favours greater reproduction.

scholarly journals conservation of freshwater and euryhaline elasmobranchs: a review

2005 ◽  
Vol 85 (5) ◽  
pp. 1049-1073 ◽  
Author(s):  
r. aidan martin
Keyword(s):  
South America ◽  
Conservation Biology ◽  
Life Histories ◽  
Significant Risk ◽  
Trophic Levels ◽  
Published Data ◽  
Human Populations ◽  
Geographic Ranges ◽  
Freshwater Habitats ◽  
Anthropogenic Threats

published data on the diversity, life history, ecology, and status of freshwater and euryhaline elasmobranchs was reviewed in the context of anthropogenic threats and principles of conservation biology. at least 171 species of elasmobranch, representing 68 genera and 34 families, are recorded from fresh or estuarine waters. of these, over half are marginal in estuaries, less than one-tenth are euryhaline, and one-fifth are obligate in fresh water. obligate freshwater elasmobranchs are dominated by myliobatoid stingrays, of which two-thirds are potamotrygonids endemic to atlantic drainages of south america. freshwater and euryhaline elasmobranchs adhere to strongly k-selected life histories and feed at high trophic levels, similar to those of their marine relatives. however, freshwater and euryhaline elasmobranchs are also subject to habitat constraints, notably more limited volume and physicochemical variability than the ocean, that may render them more vulnerable than marine elasmobranchs to the effects of human activities. the greatest diversity and abundance of freshwater and euryhaline elasmobranchs occur in tropical countries with enormous and rapidly increasing human populations, notably south america, west africa, and south-east asia. knowledge of the biology, distribution, ecology, and status of freshwater and euryhaline elasmobranchs is frustrated by unresolved taxonomic problems, which are briefly summarized. to clarify selected issues in the conservation of freshwater and euryhaline elasmobranchs, special attention is given to sharks of the genus glyphis, pristids, and potamotrygonids. to foster live release when possible as well as prevent discard of specimens and loss of data, an illustrated key to differentiate carcharhinus from glyphis sharks is provided. obligate freshwater elasmobranchs with limited geographic ranges are deemed most vulnerable to extinction, but euryhaline elasmobranchs that require access to the sea to breed are also at significant risk. based on the foregoing data and principles of conservation biology, suggested action plans for the conservation of freshwater and euryhaline elasmobranchs and the conservation of freshwater habitats are provided.

scholarly journals Variation in the population biology of protogynous coral reef fishes over tens of kilometres

2004 ◽  
Vol 61 (2) ◽  
pp. 205-218 ◽  
Author(s):  
Nick Gust
Keyword(s):  
Population Biology ◽  
Life Histories ◽  
Spatial Scales ◽  
Reef Fishes ◽  
Sex Reversal ◽  
Outer Shelf ◽  
Terminal Phase ◽  
Local Populations ◽  
Sexual Composition ◽  
And Shifts

This study describes changes in the timing of maturation and sex reversal and shifts in the sexual composition of unfished local populations of protogynous reef fishes across the continental shelf of the Great Barrier Reef. On outer shelf reef crests, both Chlorurus sordidus and Scarus frenatus matured as females and underwent protogynous sex reversal at reduced sizes and ages relative to fish from equivalent midshelf habitats 20 km away. Earlier maturation at smaller body sizes on the outer shelf is likely to be an adaptive response to the higher mortality rates in these habitats compared with the middle shelf. Furthermore, reduced size and age at sex reversal on the outer shelf is consistent with the reduced growth and increased mortality regimes in these locations. The sexual composition of local populations changed markedly across the shelf for C. sordidus but not for S. frenatus. High densities of C. sordidus on the outer shelf were characterized by threefold higher proportions of both terminal-phase and primary males than on midshelf reefs. Differences between local populations separated by tens of kilometres highlight the danger of assuming homogeneous sexual compositions and life histories when managing exploited reef fishes over larger spatial scales.

scholarly journals Demographic causes of adult sex ratio variation and their consequences for parental cooperation

2017 ◽  
Author(s):  
Luke J. Eberhart-Phillips ◽  
Clemens Küpper ◽  
María Cristina Carmona-Isunza ◽  
Orsolya Vincze ◽  
Sama Zefania ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Social Behaviour ◽  
Population Biology ◽  
Life Histories ◽  
Social Evolution ◽  
Apparent Survival ◽  
Adult Sex Ratio ◽  
Demographic Processes ◽  
Parental Strategies ◽  
Sex Biases

AbstractThe adult sex ratio (ASR) is a fundamental concept in population biology, sexual selection, and social evolution. However, it remains unclear which demographic processes generate ASR variation and how biases in ASR in turn affect social behaviour. Here, we evaluate the demographic mechanisms shaping ASR and their consequences for parental cooperation using detailed survival, fecundity, and behavioural data on 6,119 individuals from six wild shorebird populations exhibiting flexible parental strategies. We show that these closely related populations express strikingly different ASRs, despite having similar ecologies and life histories, and that ASR variation is largely driven by sex differences in the apparent survival of juveniles. Furthermore, families in populations with biased ASRs were predominantly tended by a single parent, suggesting that parental cooperation breaks down with unbalanced sex ratios. Taken together, our results indicate that sex biases emerging during early life have profound consequences for social behaviour.

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