Homeomorphy in Paleozoic bryozoans: a search for explanations

Paleobiology ◽  
1980 ◽  
Vol 6 (4) ◽  
pp. 451-465 ◽  
Author(s):  
Daniel B. Blake
Keyword(s):  
Life History ◽  
Environmental Conditions ◽  
Convergent Evolution ◽  
Controlling Factors ◽  
Life History Strategies ◽  
Taxonomic Analysis ◽  
Ample Opportunity ◽  
Key Innovation

Many apparent homeomorphs have been recognized among genera assigned to the Paleozoic stenolaemate bryozoan orders Trepostomata and Cryptostomata. Morphologies are evaluated to determine whether such homeomorphy should be expected, or is likely to have resulted from incomplete taxonomic analysis. Historical and constructional constraints prevalent in the phylum appear to provide ample opportunity for adaptive convergence, a conclusion supported by the occurrence of similar morphologies in distantly related post-Paleozoic bryozoans.Cryptostomes are distinguished in part by the presence of restricted budding loci. Loci pattern is hypothesized to be the key innovation in the establishment of the clade and the pattern also is considered critical to the evolution of the relatively slender branches and short zooecia typical of cryptostomes.Loci development does not provide a taxonomic panacea. This is because the hypothesis does not preclude convergent evolution of broadly similar restricted loci in Paleozoic non-cryptostome groups, although presumably the cryptostomes in general would have been best equipped to succeed under conditions favoring restricted loci.Environmental conditions for the cryptostomes in general and changing life history strategies for rhabdomesoids in particular provide possible controlling factors for the evolution of these bryozoans.

scholarly journals Contrasting effects of climate change on seasonal survival of a hibernating mammal

2020 ◽  
Vol 117 (30) ◽  
pp. 18119-18126 ◽  
Author(s):  
Line S. Cordes ◽  
Daniel T. Blumstein ◽  
Kenneth B. Armitage ◽  
Paul J. CaraDonna ◽  
Dylan Z. Childs ◽  
...  
Keyword(s):  
Climate Change ◽  
Population Dynamics ◽  
Life History ◽  
Environmental Conditions ◽  
Temporal Trends ◽  
Life History Strategies ◽  
Environmental Drivers ◽  
Age Classes ◽  
History Of ◽  
Colorado Rocky Mountains

Seasonal environmental conditions shape the behavior and life history of virtually all organisms. Climate change is modifying these seasonal environmental conditions, which threatens to disrupt population dynamics. It is conceivable that climatic changes may be beneficial in one season but result in detrimental conditions in another because life-history strategies vary between these time periods. We analyzed the temporal trends in seasonal survival of yellow-bellied marmots (Marmota flaviventer) and explored the environmental drivers using a 40-y dataset from the Colorado Rocky Mountains (USA). Trends in survival revealed divergent seasonal patterns, which were similar across age-classes. Marmot survival declined during winter but generally increased during summer. Interestingly, different environmental factors appeared to drive survival trends across age-classes. Winter survival was largely driven by conditions during the preceding summer and the effect of continued climate change was likely to be mainly negative, whereas the likely outcome of continued climate change on summer survival was generally positive. This study illustrates that seasonal demographic responses need disentangling to accurately forecast the impacts of climate change on animal population dynamics.

Smelling the future: subtle life-history adjustments in response to environmental conditions and perceived transmission opportunities in a trematode

Parasitology ◽  
2016 ◽  
Vol 144 (4) ◽  
pp. 464-474 ◽  
Author(s):  
C. LAGRUE ◽  
R. RINNEVALLI ◽  
R. POULIN
Keyword(s):  
Life History ◽  
Life Cycle ◽  
Intermediate Host ◽  
Definitive Host ◽  
Environmental Conditions ◽  
Life History Strategy ◽  
Host Density ◽  
Life Cycles ◽  
Life History Strategies ◽  
Priming Effects

SUMMARYA number of parasites with complex life cycles can abbreviate their life cycles to increase the likelihood of reproducing. For example, some trematodes can facultatively skip the definitive host and produce viable eggs while still inside their intermediate host. The resulting shorter life cycle is clearly advantageous when transmission probabilities to the definitive hosts are low. Coitocaecum parvum can mature precociously (progenesis), and produce eggs by selfing inside its amphipod second intermediate host. Environmental factors such as definitive host density and water temperature influence the life-history strategy adopted by C. parvum in their crustacean host. However, it is also possible that information about transmission opportunities gathered earlier in the life cycle (i.e. by cercariae-producing sporocysts in the first intermediate host) could have priming effects on the adoption of one or the other life strategy. Here we document the effects of environmental parameters (host chemical cues and temperature) on cercarial production within snail hosts and parasite life-history strategy in the amphipod host. We found that environmental cues perceived early in life have limited priming effects on life-history strategies later in life and probably account for only a small part of the variation among conspecific parasites. External cues gathered at the metacercarial stage seem to largely override potential effects of the environmental conditions experienced by early stages of the parasite.

scholarly journals Facultative sex and reproductive strategies in response to male availability in the spiny stick insect, Extatosoma tiaratum

2010 ◽  
Vol 58 (4) ◽  
pp. 228 ◽  
Author(s):  
Angela Schneider ◽  
Mark A. Elgar
Keyword(s):  
Life History ◽  
Environmental Conditions ◽  
Reproductive Strategies ◽  
Reproductive Output ◽  
Stick Insect ◽  
Model System ◽  
Life History Strategies ◽  
Evolutionary Significance ◽  
Social Environments ◽  
Reproductive State

Facultative thelytoky, in which females can reproduce both sexually and asexually, offers a promising model system to understand the evolutionary significance of sex, by providing insights into whether the different reproductive modes reflect an adaptive life-history response to varying environmental conditions. Females of the spiny stick insect, Extatosoma tiaratum, can reproduce both sexually or asexually. We show that virgin females signal their reproductive state: males respond to signals produced by virgin females that have not commenced ovipositing, but fail to respond to ovipositing virgin females. Virgin females reared under different social environments varied their reproductive output: virgin females reared in the absence of males laid more eggs over a seven-day period than virgin females reared in the presence of males. The reproductive output of mated females over a seven-day period was higher than that of virgin females. These data suggest that female E. tiaratum adjust several life-history strategies in conjunction with facultative thelytoky.

scholarly journals When the going gets tough, the tough get going: effect of extreme climate on an Antarctic seabird’s life history

2019 ◽  
Author(s):  
Stéphanie Jenouvrier ◽  
Lise Aubry ◽  
Silke van Daalen ◽  
Christophe Barbraud ◽  
Henri Weimerskirch ◽  
...  
Keyword(s):  
Life History ◽  
Individual Differences ◽  
Old Age ◽  
Environmental Conditions ◽  
Life History Strategies ◽  
Demographic Rates ◽  
Individual Traits ◽  
Evolution Of Life ◽  
Favorable Conditions ◽  
Seabird Population

1AbstractIndividuals differ in many ways. Most produce few offspring; a handful produce many. Some die early; others live to old age. It is tempting to attribute these differences in out-comes to differences in individual traits, and thus in the demographic rates experienced. However, there is more to individual variation than meets the eye of the biologist. Even among individuals sharing identical traits, life history outcomes will vary due to individual stochasticity, i.e., to chance. Quantifying the contributions of heterogeneity and chance is essential to understanding natural variability. Inter-individual differences vary across environmental conditions. Heterogeneity and stochasticity depend on environmental conditions. We show that favorable conditions increase the contributions of individual stochasticity, and reduce the contributions of heterogeneity, to variance in demographic outcomes in a seabird population. The opposite is true under poor conditions. This result has important consequence for understanding the ecology and evolution of life history strategies.

scholarly journals Unusually Paced Life History Strategies of Marine Megafauna Drive Atypical Sensitivities to Environmental Variability

2020 ◽  
Vol 7 ◽  
Author(s):  
Isabel M. Smallegange ◽  
Marta Flotats Avilés ◽  
Kim Eustache
Keyword(s):  
Life History ◽  
Environmental Conditions ◽  
Life Histories ◽  
Life History Traits ◽  
Environmental Variability ◽  
Life History Strategies ◽  
Marine Biodiversity ◽  
Juvenile Mortality ◽  
Population Responses ◽  
Marine Megafauna

Understanding why different life history strategies respond differently to changes in environmental variability is necessary to be able to predict eco-evolutionary population responses to change. Marine megafauna display unusual combinations of life history traits. For example, rays, sharks and turtles are all long-lived, characteristic of slow life histories. However, turtles also have very high reproduction rates and juvenile mortality, characteristic of fast life histories. Sharks and rays, in contrast, produce a few live-born young, which have low mortality rates, characteristic of slow life histories. This raises the question if marine megafaunal responses to environmental variability follow conventional life history patterns, including the pattern that fast life histories are more sensitive to environmental autocorrelation than slow life histories. To answer this question, we used a functional trait approach to quantify for different species of mobulid rays, cheloniid sea turtles and carcharhinid sharks – all inhabitants or visitors of (human-dominated) coastalscapes – how their life history, average size and log stochastic population growth rate, log(λs), respond to changes in environmental autocorrelation and in the frequency of favorable environmental conditions. The faster life histories were more sensitive to temporal frequency of favourable environmental conditions, but both faster and slower life histories were equally sensitive, although of opposite sign, to environmental autocorrelation. These patterns are atypical, likely following from the unusual life history traits that the megafauna display, as responses were linked to variation in mortality, growth and reproduction rates. Our findings signify the importance of understanding how life history traits and population responses to environmental change are linked. Such understanding is a basis for accurate predictions of marine megafauna population responses to environmental perturbations like (over)fishing, and to shifts in the autocorrelation of environmental variables, ultimately contributing toward bending the curve on marine biodiversity loss.

scholarly journals Capital and income breeding traits differentiate trophic match–mismatch dynamics in large herbivores

2013 ◽  
Vol 368 (1624) ◽  
pp. 20120484 ◽  
Author(s):  
Jeffrey Kerby ◽  
Eric Post
Keyword(s):  
Life History ◽  
Reproductive Performance ◽  
Environmental Conditions ◽  
Life History Strategies ◽  
Breeding Strategies ◽  
Large Herbivores ◽  
Income Breeding ◽  
Resource Variability ◽  
Capital And Income Breeding ◽  
Trophic Mismatch

For some species, climate change has altered environmental conditions away from those in which life-history strategies evolved. In such cases, if adaptation does not keep pace with these changes, existing life-history strategies may become maladaptive and lead to population declines. We use life-history theory, with a specific emphasis on breeding strategies, in the context of the trophic match–mismatch framework to form generalizable hypotheses about population-level consumer responses to climate-driven perturbations in resource availability. We first characterize the income and breeding traits of sympatric caribou and muskoxen populations in western Greenland, and then test trait-based hypotheses about the expected reproductive performance of each population during a period of high resource variability at that site. The immediate reproductive performance of income breeding caribou decreased with trophic mismatch. In contrast, capital breeding muskoxen were relatively unaffected by current breeding season resource variability, but their reproductive performance was sensitive to resource conditions from previous years. These responses matched our expectations about how capital and income breeding strategies should influence population susceptibility to phenological mismatch. We argue for a taxon-independent assessment of trophic mismatch vulnerability based on a life-history strategy perspective in the context of prevailing environmental conditions.

Relationships between temperature and Pacific hake distribution vary across latitude and life-history stage

2020 ◽  
Vol 639 ◽  
pp. 185-197 ◽  
Author(s):  
MJ Malick ◽  
ME Hunsicker ◽  
MA Haltuch ◽  
SL Parker-Stetter ◽  
AM Berger ◽  
...  
Keyword(s):  
Life History ◽  
Environmental Effects ◽  
Environmental Conditions ◽  
Vancouver Island ◽  
Additive Models ◽  
Life History Stage ◽  
Fish Stocks ◽  
Merluccius Productus ◽  
Multiple Dimensions ◽  
Effects Of Temperature

Environmental conditions can have spatially complex effects on the dynamics of marine fish stocks that change across life-history stages. Yet the potential for non-stationary environmental effects across multiple dimensions, e.g. space and ontogeny, are rarely considered. In this study, we examined the evidence for spatial and ontogenetic non-stationary temperature effects on Pacific hake Merluccius productus biomass along the west coast of North America. Specifically, we used Bayesian additive models to estimate the effects of temperature on Pacific hake biomass distribution and whether the effects change across space or life-history stage. We found latitudinal differences in the effects of temperature on mature Pacific hake distribution (i.e. age 3 and older); warmer than average subsurface temperatures were associated with higher biomass north of Vancouver Island, but lower biomass offshore of Washington and southern Vancouver Island. In contrast, immature Pacific hake distribution (i.e. age 2) was better explained by a nonlinear temperature effect; cooler than average temperatures were associated with higher biomass coastwide. Together, our results suggest that Pacific hake distribution is driven by interactions between age composition and environmental conditions and highlight the importance of accounting for varying environmental effects across multiple dimensions.

scholarly journals Metabolic traits in brown trout (Salmo trutta) vary in response to food restriction and intrinsic factors

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Louise C Archer ◽  
Stephen A Hutton ◽  
Luke Harman ◽  
W Russell Poole ◽  
Patrick Gargan ◽  
...  
Keyword(s):  
Life History ◽  
Metabolic Rate ◽  
Intraspecific Variation ◽  
Brown Trout ◽  
Environmental Conditions ◽  
Food Restriction ◽  
Metabolic Rates ◽  
Intrinsic Factors ◽  
Metabolic Traits ◽  
Food Conditions

Abstract Metabolic rates vary hugely within and between populations, yet we know relatively little about factors causing intraspecific variation. Since metabolic rate determines the energetic cost of life, uncovering these sources of variation is important to understand and forecast responses to environmental change. Moreover, few studies have examined factors causing intraspecific variation in metabolic flexibility. We explore how extrinsic environmental conditions and intrinsic factors contribute to variation in metabolic traits in brown trout, an iconic and polymorphic species that is threatened across much of its native range. We measured metabolic traits in offspring from two wild populations that naturally show life-history variation in migratory tactics (one anadromous, i.e. sea-migratory, one non-anadromous) that we reared under either optimal food or experimental conditions of long-term food restriction (lasting between 7 and 17 months). Both populations showed decreased standard metabolic rates (SMR—baseline energy requirements) under low food conditions. The anadromous population had higher maximum metabolic rate (MMR) than the non-anadromous population, and marginally higher SMR. The MMR difference was greater than SMR and consequently aerobic scope (AS) was higher in the anadromous population. MMR and AS were both higher in males than females. The anadromous population also had higher AS under low food compared to optimal food conditions, consistent with population-specific effects of food restriction on AS. Our results suggest different components of metabolic rate can vary in their response to environmental conditions, and according to intrinsic (population-background/sex) effects. Populations might further differ in their flexibility of metabolic traits, potentially due to intrinsic factors related to life history (e.g. migratory tactics). More comparisons of populations/individuals with divergent life histories will help to reveal this. Overall, our study suggests that incorporating an understanding of metabolic trait variation and flexibility and linking this to life history and demography will improve our ability to conserve populations experiencing global change.

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