File Name: rotifer life history strayegies and evolution in freshwater plankton communities .zip
Metrics details. Higher temperatures and increased environmental variability under climate change could jeopardize the persistence of species. Organisms that rely on short windows of rainfall to complete their life-cycles, like desert annual plants or temporary pool animals, may be particularly at risk. Although some could tolerate environmental changes by building-up banks of propagules seeds or eggs that buffer against catastrophes, climate change will threaten this resilience mechanism if higher temperatures reduce propagule survival. Using a crustacean model species from temporary waters, we quantified experimentally the survival and dormancy of propagules under anticipated climate change and used these demographic parameters to simulate long term population dynamics.
Metrics details. Higher temperatures and increased environmental variability under climate change could jeopardize the persistence of species. Organisms that rely on short windows of rainfall to complete their life-cycles, like desert annual plants or temporary pool animals, may be particularly at risk. Although some could tolerate environmental changes by building-up banks of propagules seeds or eggs that buffer against catastrophes, climate change will threaten this resilience mechanism if higher temperatures reduce propagule survival.
Using a crustacean model species from temporary waters, we quantified experimentally the survival and dormancy of propagules under anticipated climate change and used these demographic parameters to simulate long term population dynamics.
Integrating these reduced survival rates into population models demonstrated the inability of the bank to maintain populations; thereby exacerbating extinction risk caused by shortened growing seasons. Overall, our study demonstrates that climate change could threaten the persistence of populations by both reducing habitat suitability and eroding life-history strategies that support demographic resilience.
Climate scenarios predict increased temperatures and environmental variability for many regions across the globe [ 1 , 2 ]. These changes are likely to increase species extinction rates [ 3 , 4 ].
Organisms that depend strongly on short windows of rainfall and suitable temperatures to complete their life cycles may be especially vulnerable to climate change. They will be exposed to shortened growing seasons, which impose more stringent time constraints on maturation and reproduction, reduce population growth rates and increase extinction risks [ 5 , 6 , 7 ].
Many organisms from temporary habitats, such as desert annuals or temporary pool zooplankton, have dormant life stages seeds or eggs , known as propagules, that can withstand harsh conditions including desiccation and survive extended dry periods as part of a propagule bank [ 8 , 9 ]. The propagule bank spreads recruitment over multiple potential growing seasons through long term dormancy and delayed development, thereby buffering populations against unfavorable growing seasons and demographic catastrophes [ 10 , 11 ].
Both empirical and modelling studies demonstrate that propagule banks are crucial for the resilience of populations, especially when growing seasons are often unsuitable for successful reproduction [ 7 , 9 , 12 ]. The propagule bank can only promote population resilience when two crucial assumptions are met. First, a given fraction of propagules must survive desiccation until the next suitable growing season [ 9 ].
Thus, propagules must be able to remain dormant for long periods without dying and their dormancy should be lifted by cues of favorable conditions [ 13 , 14 , 15 ]. Second, all propagules should not hatch or germinate simultaneously during any given reproductive window as this could lead to a demographic catastrophe if the window is too short for successful reproduction. The fractions of propagules that resume development or remain dormant are probably important determinants of long term population fitness [ 7 , 16 , 17 ], but empirical evidence supporting this is sparse [ 11 ].
Combined, propagule survival and development rates buffer populations against environmental stochasticity. Although it has been suggested that propagule banks will be vital for organisms such as freshwater zooplankton to maintain positive long term population growth in the face of climate change [ 12 , 18 , 19 ], little research exists on the possible effects of climate change on propagule banks.
For instance, it is mostly unknown whether propagule survival would be affected by realistic changes in current temperatures under climate change. If this is the case, climate change could threaten the very mechanisms needed for demographic resilience. However, thus far, there are no studies that have investigated the long term effects of changes to current temperature cycles on the survival of dormant propagules of plants or animals, let alone the consequences for population growth rates.
In this context, demographic models that can incorporate experimentally determined responses of life history traits and link this to fitness, may have an important role to play and can contribute to more realistic estimates of the responses of populations to climate change. Here, we used an animal with dormant propagules as a model system and performed a long term experiment to measure the impact of increased temperature on the survival and hatching of propagules.
We then fed these measured life-history parameters into a recently developed matrix population model [ 12 ] and examined how they affect the long term persistence of populations. As model organism, we used fairy shrimps Crustacea, Branchiopoda, Anostraca , which are common inhabitants of temporary aquatic habitats on all continents. They are dominant filter feeders and strong competitors and their biomass is important as a food source for higher trophic levels [ 20 ].
Our model species is Branchipodopsis wolfi Daday , a fairy shrimp from small temporary pool habitats in South Africa [ 21 , 22 ]. Since this species may already be approaching the physiological limits of drought tolerance, it is likely to be more vulnerable to the effects of increased temperatures under climate change than species that experience less extreme conditions.
During an 8-month laboratory experiment, we exposed B. We hypothesize that anticipated increases in temperature will reduce propagule survival and that older eggs will be more sensitive to increased temperatures than younger eggs due to energy depletion.
Furthermore, we propose that hatching fractions will increase with higher temperatures because increased energy consumption and subsequent energy depletion may release propagules from dormancy prematurely.
Finally, we expect that combining the measured temperature responses with other life history parameters in a matrix population model will demonstrate that long term population growth rates will decline if temperatures increase, thereby exacerbating the risk of extinction.
The fairy shrimp B. Adapted to short-lived temporary waters, B. Subsequently, they reproduce sexually to produce between 20 and 30 dormant eggs per day [ 25 , 26 ]. Like the propagules of many zooplankton species, the eggs are highly resistant to adverse conditions, including extreme temperatures and drought, and can remain viable in a dormant state for many years [ 25 ].
Dry sediment with B. Care was taken to select different types of pools including small, large, deep and shallow pool basins. Before reaching maturity, all B. Subsequently, the populations were bred for two generations under these common garden conditions to minimize long lasting maternal effects resulting from differences in the environmental conditions in the pools of origin. Both batches of old and young eggs were composed of a random mixture selected in equal proportions from all nine laboratory populations.
Based on these measurements, we calculated the average temperature for each hour of the day, with separate values calculated for each month of the year. We converted these ambient air temperatures to the temperatures actually experienced in the sun-exposed sediment of a rock pool at a depth of 0.
The hourly conversion factors were determined by calculating the ratio between the temperature that was measured at 0. Based on this prediction and the ambient-sediment conversion factor, we reconstructed daily temperature cycles that are anticipated under climate change in Additional file 2.
Since the laboratory experiment was initiated in the month of October, we opted to use the October temperature conditions as a starting-point Additional file 2. Intact dry eggs i. Each egg was assigned to a separate well to avoid any potential interference among eggs and to ensure statistical independence.
To minimize any confounding effects of the different incubators, temperature regimes were re-divided across incubators and plates were randomly repositioned within incubators three times during the experiment. Furthermore, plates were randomly repositioned within each incubator on a weekly basis to exclude position effects. Hatching fractions were established during common garden experiments under optimal hatching conditions cf. During each hatching experiment, seven well plates i.
At the end of each hatching experiment, the viability of every individual egg was checked according to the protocol of Pinceel and colleagues [ 24 ] by removing the egg shell with a fine pair of tweezers and evaluating the embryo under a light microscope. Based on this, the number of dead eggs was subtracted from the original number of eggs before calculating hatching fractions.
All analyses were performed in R v. We tested for effects of temperature regime on egg survival and hatching fraction using generalized linear mixed models GLMM with a binomial error distribution and corresponding logit link function since both egg survival dead or alive and hatching no hatch or hatch were measured as the binary response of individual eggs.
The models were built using the glmer function in the lme4 package for linear mixed effects models. We used likelihood ratio tests LRT to test the significance of the main effects.
Since different plates of eggs were removed from the incubators at each time step to test viability and hatching, there was no need for a repeated measures design with incubation period as a random factor. We estimated the impact of measured changes in survival of B.
The model comprises two life stages, one corresponding to two age classes to account for age-specific trait values: 1 eggs produced during the previous inundation, N 0 , 2 older eggs in the egg bank, N 1 , and 3 individuals from the active population in the water column, N 2. Detailed information on the modelling procedure is included in Additional file 3 and in Pinceel et al.
The selection of egg survival parameter values is motivated further in Additional file 4. Combined, these findings support the assumption that prolonged exposure to hot conditions will increase egg mortality.
Both cycles represent daily temperature fluctuations that were calculated based on the average temperature for each hour of the day, with separate values calculated for each month of the year.
Survival of a young and b old B. Hatching fractions of c young eggs were not significantly impacted by temperature or incubation time while d hatching of old eggs increased significantly in the future climate treatment.
Error bars represent standard errors. After incorporating average egg survival, as measured in the current temperature treatment, in the matrix population model, simulations indicated that B. When survival parameters of old and young eggs are set to the average values measured over the four time points under the expected future temperature treatment, matrix population models indicate that a the median hydroperiod required for positive population growth increases and that also b the extinction risk of populations in pools with a certain median hydroperiod increases.
The grey bands represent standard errors of population growth rate estimates. Our simulations show that under current temperature conditions extinction risk increases from 0. In contrast, a similar decline in median inundation length under climate change temperatures will inflate the extinction risk from These changes are expected to alter the hydrological regimes of temporary aquatic ecosystems considerably [ 29 , 30 ], which compromises their suitability as habitats for aquatic species.
In this study, we demonstrated how rising temperatures will not only threaten the persistence of aquatic species by reducing habitat suitability, but by also compromising a common life-history strategy that supports demographic resilience.
Once fed into a matrix population model, our findings showed that higher temperatures reduce the survival rates of dormant propagules in a way that jeopardizes the long term persistence of these populations and may lead to the extinction of vulnerable populations. The susceptibility of zooplankton populations to drying in temporary aquatic ecosystems is well known [ 5 , 6 , 12 ]. Rather than decreasing gradually with decreasing inundation length, our simulations suggest that the probability of B.
While this change might seem trivially small, it could have considerable consequences for long term persistence. In reality, however, it is unlikely that climate change will reduce egg survival without also altering inundation patterns, although it is unclear how exactly these will change. Some precipitation forecasts—but not all of them—suggest that early summer rains might increase as late summer rains decrease [ 31 ].
So, even if annual precipitation stays constant, it is likely that higher evaporation rates during late summer will accelerate the drying of pools and shorten the median length of inundations.
The long term growth rates of B. As an explosive breeder the species benefits from such rare events by increasing the number of eggs in the propagule bank by several orders of magnitude. Considering that inundation lengths of any one pool are approximately log-normally distributed [ 29 ], such periods of rapid population expansion can help to compensate for the more frequent short inundations with low reproductive success.
However, this compensatory mechanism is reliant on long term survival and staggered hatching of dormant eggs over multiple inundations. In our experiment, B. Partial hatching, with fixed hatching fractions proportionate to the probability of reproductive success, presumably evolved as part of a bet hedging strategy that buffers against unpredictable demographic catastrophes [ 11 , 24 , 32 ].
Our experiment showed that hatching fractions were unaffected by the long term exposure to increased temperatures. Delayed hatching is most successful as a bet hedging strategy when hatching fractions under suitable hatching conditions are consistent over time [ 7 , 9 ]. Our results suggest that this is the case for B. Although other studies have shown that the hatching success of dormant propagules can be affected by the storage temperature of eggs see [ 18 ] for an overview , these did generally not distinguish whether such changes were due to an actual decrease in hatching fraction of viable eggs or reduced egg survival see also [ 19 ].
We do, however, caution against generalizing the finding that hatching fraction is indifferent to higher temperatures. For instance, in their study of annual plants, Ooi and colleagues [ 15 ] found that higher temperatures affected the germination fractions of some species while the seeds of other species remained unaffected.
Thus, a fruitful avenue for future research would be to examine how climate change affects the bet-hedging strategies of various species and how this might influence community interactions [ 33 ].
Our results showed that older B.
Co-occurrence of cryptic species raises theoretically relevant questions regarding their coexistence and ecological similarity. Given their great morphological similitude and close phylogenetic relationship i. This raises the problem of finding the mechanisms that may explain the coexistence of cryptic species and challenges the conventional view of coexistence based on niche differentiation. The cryptic species complex of the rotifer Brachionus plicatilis is an excellent model to study these questions and to test hypotheses regarding ecological differentiation. Rotifer species within this complex are filtering zooplankters commonly found inhabiting the same ponds across the Iberian Peninsula and exhibit an extremely similar morphology—some of them being even virtually identical. Here, we explore whether subtle differences in body size and morphology translate into ecological differentiation by comparing two extremely morphologically similar species belonging to this complex: B.
Progress in Ecological Stoichiometry View all 34 Articles. The theories developed in ecological stoichiometry ES are fundamentally based on traits. Despite their physiological and ecological relevance, traits are rarely explicitly integrated in the framework of ES and, currently, the major challenge is to more closely inter-connect ES with trait-based ecology TBE. Here, we highlight four interconnected nutrient trait groups, i. We also identify key differences between producer-consumer interactions in aquatic and terrestrial ecosystems. For instance, our synthesis shows that, in contrast to aquatic ecosystems, traits directly influencing herbivore stoichiometry in forested ecosystems should play only a minor role in the cycling of nutrients.
Evolutionary Ecology of Freshwater Animals pp Cite as. Rotifers play an important role in many freshwater plankton communities. This regulation, however, is also depending on characteristics of rotifer life histories. Mechanical interference by Daphnia is considered here as a special case of predation as the rotifers are mostly killed by this action. Different defense mechanisms are discussed.
Rotifers play an important role in many freshwater plankton communities. The populations are Rotifer life history strategies and evolution in freshwater plankton communities. Authors; Authors to display preview. Download preview PDF.
Rotifer life history strategies and evolution in freshwater plankton communities. Basel ; Evolutionary ecology of freshwater animals: Concepts and case studies: , Rotifer and crustacean plankton communities of lakes in insular Newfoundland. Internationale Vereinigung fuer Theoretische und Angewandte Limnologie Verhandlungen , The life histories of plankton animals and seasonal cycles of plankton communities in the oceans.
Table 1. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Brachionus leydigii are found here. With large population sizes and high turnover rates, rotifers are significant contributors to lake food webs Herzig , Starkweather , Walz
Plankton are the diverse collection of organisms found in water or air that are unable to propel themselves against a current or wind. Marine plankton includes bacteria , archaea , algae , protozoa and drifting or floating animals that inhabit the saltwater of oceans and the brackish waters of estuaries. Freshwater plankton are similar to marine plankton, but are found in the freshwaters of lakes and rivers. Plankton are usually thought of as inhabiting water, but there are also airbourne versions, the aeroplankton , that live part of their lives drifting in the atmosphere.
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