Find research datasets worth reusing

Data from: Hydrological niche segregation defines forest structure and drought tolerance strategies in a seasonal Amazon forest

1) Understanding if and how trees coordinate rooting depth and aboveground hydraulic traits to define drought-resistance strategies in seasonal Amazon forests is a major gap to model parametrization aimed at predicting the effects of climate change in these ecosystems. 2) We assessed the rooting depth of 12 dominant tree species (representing ~ 42% of the forest basal area) in a seasonal Amazon forest, using the stable isotope ratios (δ18O and δ²H) of water collected from tree xylem and soils from a range of depths. We took advantage of a major ENSO-related drought in 2015/2016 that caused substantial evaporative isotope enrichment on soil. We measured the minimum dry-season leaf water potential both in a normal year (2014; Ψnon-ENSO) and in an extreme drought year (2015; ΨENSO). Furthermore, we measured xylem hydraulic traits that indicate the range of water potentials that trees tolerate without risking hydraulic failure (P50 and P88). 3) We demonstrate that coexisting trees are largely segregated along a single hydrological niche axis defined by root depth differences, access to light, and tolerance of low water potential. These differences in rooting depth were strongly related to tree size; diameter at breast height (DBH) explained 72% of the variation in the δ18Oxylem. Additionally, δ18Oxylem explained 49% of the variation in P50 and 70% of P88, with higher tolerance of low water potential in shallow-rooted species, while δ18O of xylem water explained 47% and 77% of the variation of minimum Ψnon-ENSO and ΨENSO. 4) We propose a new formulation to estimate an effective functional rooting depth, i.e., the likely soil depth from which roots can sustain water uptake for physiological functions, using DBH as predictor of root depth at this site. Based on these estimates, we conclude that a number of families, genera and species are restricted to drawing water from shallow to deep soil in a large area of the Tapajós forest. 5) Our results support the theory of hydrological niche segregation and its underlying trade-off related to drought resistance, which also affect the dominance structure of trees in this seasonal eastern Amazon forest.

Data from: A gravid fossil turtle from the Early Cretaceous reveals a different egg development strategy to that of extant marine turtles

Extant sea turtles develop and lay pliable (flexible) eggs, however, it is unknown if they inherited this reproductive strategy from their closer fossil relatives or corresponds to an evolutionary novelty. Here we describe the first undisputable gravid marine fossil turtle ever found, from the early Cretaceous of Colombia, belonging to Desmatochelys padillai Cadena and Parham, which constitutes a representative of Protostegidae. Using thin sectioning of one the eggs, as well as scanning electron microscopy coupled with elemental characterization, cathodoluminescence, and computer tomography we established that Desmatochelys padillai produced rigid eggs similar to the ones found in some extant and fossil freshwater and terrestrial turtles, and that at least 48 spherical eggs are preserved inside this gravid turtle. We performed also a phylogenetic analysis of several turtle taxa, including some of the extant marine species, plus the information from the gravid specimen of Desmatochelys padillai, and we found more support to previous ideas that egg and eggshell characters lack of strong phylogenetic signal amongst turtle taxa. We suggest that the development of rigid eggs in the marine extinct turtle Desmatochelys padillai resulted as an adaptation for eggs-embryos requirements dictated by the physical attributes of the nesting site

opencc-zeroDec 2015View details →

Data from: Analyzing movement behavior and dynamic space-use strategies among habitats using multi-event capture-recapture modeling

1.The environment of most species is heterogeneous at different spatial and temporal scales; this heterogeneity can have a direct effect on various components of fitness. As a consequence, individual space-use and movement strategies are central issues in ecology and conservation and receive considerable attention from researchers. 2.In the last 30 years, this issue has led to the development of capture–recapture models that allow movement between sites to be quantified, while handling imperfect detection. For studies involving numerous recapture sites in which the emphasis is on dispersal or migration rather than movement between particular sites, Lagrange et al. recently proposed a parsimonious CR multi-event model that contrasts individuals that move and individuals that stay in place, irrespective of the sites involved. 3.In this study, we developed a generalized version of this model to allow survival probability and movement probability to differ for different types of habitat to which the individual sites may be assigned. We investigated the potential of this new parameterization by studying the movements of an amphibian, the yellow-bellied toad (Bombina variegata), in a set of breeding and resting/foraging ponds. 4.Our capture-recapture multi-event model provides a highly flexible tool allowing users to model movements within and between several habitats. This approach can be potentially used to study movement behavior and space-use strategies of a wide range of taxa.

Data from: Fighting in rounds: males of a Neotropical cricket switch assessment strategies during contests

How animals decide to withdraw from contests is central to understand the evolution of fighting behavior. Game theory models suggest two major types of decision criteria: 1) self-assessment, where individuals withdraw when they reach a cost-threshold determined by their own fighting ability that may or may not be affected by injuries, or 2) mutual assessment, where the decision is based on information about the relative fighting ability of the opponents. Many empirical studies have assumed that opponents use a single strategy throughout the whole fight. However, they often find partial support for a specific model. This might be due to individuals changing their strategy between phases of a contest. In this work, we addressed this issue by evaluating if males of the cricket Melanotes ornata switch their assessment strategy between phases. We used hind femur length as a proxy for fighting ability, as it was the attribute most strongly associated with contest outcome. Overall fight duration was positively associated with the loser's femur length and negatively associated with the winner's femur length, while the probability of escalation to physical aggression was negatively related to the difference in femur between opponents. However, such relationships held only at the first contest phase. During the escalated phase, fight duration was only correlated (although weakly) with femur length of losers. These results indicate that M. ornata males perform mutual assessment in the initial phase but switch their assessment strategy when fights escalate, suggesting a single strategy does not correctly explain how contests are settled.

opencc-zeroDec 2014View details →

Data from: Trade-offs in female signal apparency to males offer alternative anti-harassment strategies for color polymorphic females

Color polymorphisms are known to influence receiver behavior, but how they affect a receiver's ability to detect and recognize individuals in nature is usually unknown. I hypothesized that polymorphic female damselflies represent an evolutionary stable strategy, maintained by trade-offs between the relative apparency of morphs to male receivers. Using field experiments on Enallagma hageni and focal studies of E. hageni and E. boreale, I tested for the first time the predictions that 1) green heteromorphs and blue andromorphs gain differential protection from sexual harassment via background crypsis and sexual mimicry respectively, and 2) female morphs behaviorally optimize their signal apparency to mate-searching males. First, based on male reactions elicited by females, against a high contrast background the two morphs did not differ in being detected by males and once detected, did not differ in being recognized (eliciting sexual reactions). However, on green ferns, heteromorphs were detected less often (elicited only fly-bys) than andromorphs but once detected, the morphs did not differ in being recognized. In contrast, when perched on a dowel with two male signal distractors, andromorphs were detected less often and once detected, were recognized less often than heteromorphs. Second, in fields where females foraged, andromorphs perched higher on vegetation than heteromorphs, and were more often in the vicinity of males. Neither harassment rates nor evasive behaviors differed between morphs. Males aggregated in high density near shore where solitary females were rare. Equilibrium frequencies of these and other color morphs should reflect the relative ease with which receivers detect and recognize them in the context where they are encountered.

opencc-zeroDec 2011View details →

Data from: Proteomic evidence of a paedomorphic evolutionary process within a marine snail species: a strategy for adapting to extreme ecological conditions?

The exposed and sheltered ecotypes of the marine snail Littorina saxatilis from European rocky shores are considered a key model system to study adaptation and ecological speciation. Previous studies showed that two ecotypes (RB and SU) of this species in NW Spain have differently adapted to different shore levels and microhabitats. In order to understand how this divergent adaptive process has been accomplished, we followed a quantitative proteomic approach to investigate the proteome variation in a number of different biological factors, i.e. ecotype, ontogeny and their interactions. This approach allowed testing the hypothesis that one of the ecotypes has evolved by paedomorphosis, and also whether or not the molecular mechanisms related to ecotype differentiation are set up in early developmental stages. Additionally the identification of some candidate proteins by mass spectrometry provides some functional insights about these evolutionary processes. Results from this study provided evidence of higher ontogenetic differentiation at proteome level in the RB (metamorphic) than in SU (paedomorphic) ecotype that point to the possibility of juvenile stage retention in this latter ecotype. The level of protein expression (proteome) differences between ecotypes maintained nearly constant from late embryonic stages to adulthood, although some proteins involved in these changes considerably differed in embryonic compared to other ontogenetic stages. Paedomorphosis may be the evolutionary response of the SU ecotype of solving the trade-off during sexually immaturity that is caused by the evolution of small size arising from adaptation to the wave exposed habitat. Some potential candidate genes of adaptation related to energetic metabolism have been identified, providing a promising baseline for future functional analyses.

Data from: Conquering the inner couch potato: precommitment is an effective strategy to enhance motivation for effortful actions

Letting effort-free gratification derail us from effort-requiring goals is one reason why we fail to realize health-relevant intentions like 'exercise regularly'. We tested the effectiveness of the self-control strategy precommitment in such effort-related conflicts, using a novel laboratory choice paradigm, where participants could precommit to an effort-requiring large reward by pre-eliminating an effort-free small reward from their choice set. Our participants used precommitment frequently and effectively, such that they reached effort-requiring large rewards more often. Using computational modelling and Bayesian model comparisons, we assessed whether participants employed precommitment to avoid anticipated willpower failures (i.e. as a self-regulatory measure) or to maximize their motivation to choose the effort-requiring option (i.e. as a self-motivational measure). Observed choices and precommitment decisions were consistent with the motivation maximization hypothesis, but not the willpower hypothesis. Our findings show that offering precommitment is effective in helping individuals optimize their motivation and choice behaviour and thereby achieve effort-requiring goals, and strongly encourage application of precommitment schemes in exercise and rehabilitation interventions. This article is part of the theme issue 'Risk taking and impulsive behaviour: fundamental discoveries, theoretical perspectives and clinical implications'.

opencc-zeroDec 2013View details →

Data from: Shared decision-making as a cost-containment strategy: US physician reactions from a cross-sectional survey

Objective: To assess US physicians' attitudes towards using shared decision-making (SDM) to achieve cost containment. Design: Cross-sectional mailed survey. Setting: US medical practice. Participants: 3897 physicians were randomly selected from the AMA Physician Masterfile. Of these, 2556 completed the survey. Main outcome measures: Level of enthusiasm for "Promoting better conversations with patients as a means of lowering healthcare costs"; degree of agreement with "Decision support tools that show costs would be helpful in my practice" and agreement with "should promoting SDM be legislated to control overall healthcare costs". Results: Of 2556 respondents (response rate (RR) 65%), two-thirds (67%) were 'very enthusiastic' about promoting SDM as a means of reducing healthcare costs. Most (70%) agreed decision support tools that show costs would be helpful in their practice, but only 24% agreed with legislating SDM to control costs. Compared with physicians with billing-only compensation, respondents with salary compensation were more likely to strongly agree that decision support tools showing costs would be helpful (OR 1.4; 95% CI 1.1 to 1.7). Primary care physicians (vs surgeons, OR 1.4; 95% CI 1.0 to 1.6) expressed more enthusiasm for SDM being legislated as a means to address healthcare costs. Conclusions: Most US physicians express enthusiasm about using SDM to help contain costs. They believe decision support tools that show costs would be useful. Few agree that SDM should be legislated as a means to control healthcare costs.

Data from: Genetic structure of introduced American mink (Neovison vison) in Patagonia: colonisation insights and implications for control and management strategies

Context: Biological invasions have caused dramatic changes in native biodiversity and ecosystem function. Studies of genetic variation and evolutionary changes are useful for understanding population dynamics during biological invasions, and shed light on management, prevention and restoration strategies. Aims: This study aimed to investigate the structure and genetic variability of American mink (Neovison vison), an invasive species in southern South America, introduced for fur farming in the 1930s. Methods: Samples from 153 mink were obtained from 12 locations in southern Chile to sequence the mitochondrial DNA (mtDNA) control region and to genotype 11 polymorphic microsatellite loci. Key results: The highest mtDNA diversity was detected in Puerto Cisnes, suggesting multiple introductions and/or the most probable area where mink was first introduced. The latter is also supported by microsatellite data, because a high percentage of individuals from different locations were assigned to this location. All other locations showed low or no mtDNA diversity, possibly due to founder effect. The results also indicate marked population structure, with three genetic clusters coincident with the main historical introduction points, with low dispersal among them. Conclusions: The results suggest that control strategies for American mink in southern Chile should be concentrated on these three genetically differentiated management units, and particularly on source populations and locations with low effective population size and restricted connectivity. Implications: Genetic approaches have been used for the management of numerous alien species worldwide. Recommendations delivered here for American mink control could also be implemented in other regions and for other invasive species with similar genetic diversity distribution and connectivity.

Data from: Amphotericin B-conjugated polypeptide hydrogels as a novel innovative strategy for fungal infections

The present work is focused on design and development of novel Amphotericin B-conjugated biocompatible and biodegradable poly-peptide hydrogels to improve the antifungal activity. Using three kinds of promoting self-assembly groups (2-naphthalene acetic acid, Naproxen and Dexamethasone) and poly-peptide sequence (Phe-Phe-Asp-Lys-Tyr, FFDKY), we successfully synthesized the Nap-FFDK (AmB) Y gels, Npx-FFDK (AmB) Y gels and Dex-FFDK (AmB) Y gels. The Amphotericin B-conjugated hydrogelators are highly soluble in different aqueous solutions. The Cryo-transmission electron microscopy (TEM) and scanning electron microscopy (SEM) micrographs of hydrogels afford nanofibers with width of 20~50 nm. Powder X-ray diffraction (PXRD) analyses demonstrate that the crystalline structure of the AmB and Dex are changed into amorphous structure after formation of hydrogels. Circular dichroism (CD) spectra of the solution of blank carriers and the corresponding drug deliveries further help elucidate the molecular arrangement in gel phase, indicating the existence of turn features. The in vitro drug releases suggest that the Amphotericin B-conjugated hydrogels are suitable as drug-controlled release vehicles for hydrophobic drug. The antifungal effect of AmB-conjugated hydrogels significantly exhibits the antifungal activity against Candida albicans. The results of present study indicated that the Amphotericin B-conjugated hydrogels are suitable carriers for poorly water soluble drugs and for enhancement of therapeutic efficacy of antifungal drugs.

opencc-zeroDec 2014View details →

Data from: Random versus game trail-based camera trap placement strategy for monitoring terrestrial mammal communities

Camera trap surveys exclusively targeting features of the landscape that increase the probability of photographing one or several focal species are commonly used to draw inferences on the richness, composition and structure of entire mammal communities. However, these studies ignore expected biases in species detection arising from sampling only a limited set of potential habitat features. In this study, we test the influence of camera trap placement strategy on community-level inferences by carrying out two spatially and temporally concurrent surveys of medium to large terrestrial mammal species within Tanzania's Ruaha National Park, employing either strictly game trail-based or strictly random camera placements. We compared the richness, composition and structure of the two observed communities, and evaluated what makes a species significantly more likely to be caught at trail placements. Observed communities differed marginally in their richness and composition, although differences were more noticeable during the wet season and for low levels of sampling effort. Lognormal models provided the best fit to rank abundance distributions describing the structure of all observed communities, regardless of survey type or season. Despite this, carnivore species were more likely to be detected at trail placements relative to random ones during the dry season, as were larger bodied species during the wet season. Our findings suggest that, given adequate sampling effort (> 1400 camera trap nights), placement strategy is unlikely to affect inferences made at the community level. However, surveys should consider more carefully their choice of placement strategy when targeting specific taxonomic or trophic groups.

opencc-zeroDec 2009View details →

Data from: The evolution of alternative adaptive strategies for effective communication in noisy environments

Animals communicating socially are expected to produce signals that are conspicuous within the habitats in which they live. The particular way in which a species adapts to its environment will depend on its ancestral condition and evolutionary history. At this point, it is unclear how properties of the environment and historical factors interact to shape communication. Tropical Anolis lizards advertise territorial ownership using visual displays in habitats where visual motion or 'noise' from windblown vegetation poses an acute problem for the detection of display movements. We studied eight Anolis species that live in similar noise environments, but belong to separate island radiations with divergent evolutionary histories. We found that species on Puerto Rico displayed at times when their signals were more likely to be detected by neighboring males and females (during periods of low noise). In contrast, species on Jamaica displayed irrespective of the level of environmental motion, apparently because these species have a display that is effective in a range of viewing conditions. Our findings appear to reflect a case of species originating from different evolutionary starting points evolving different signal strategies for effective communication in noisy environments.

Data from: Climate-woodland effects on population genetics for two congeneric lichens with contrasting reproductive strategies

Genetic variation is expected to be influenced by the interaction between reproductive mode and dispersal traits on the one hand, and environmental and habitat setting affecting establishment success on the other. We evaluated how environmental/habitat setting affect population genetic variation (i.e. variation in genetic diversity and structure) when regulated by contrasting dispersal traits. We used fungus-specific microsatellite markers to examine genetic diversity and structure of two closely related epiphytic lichen fungi that differ in their primary reproductive mode: Nephroma laevigatum (sexually reproducing, N = 191, ten microsatellites) and N. parile (asexually, N = 182, twelve microsatellites), along a steep climatic gradient in Scotland. Despite their reproductive differences, we found a high proportion of clones in both species and a background pattern of genetic structure related to climatic gradients. We also demonstrated that woodland connectivity, rather than geographic distance, explained genetic diversity in both species. Environmental/habitat setting, modulated by the reproductive mode of the species, affects genetic diversity and structure, but the putative dissimilarity in their reproductive mode is less important than has been previously assumed. We reinforce the importance of protecting highly connected populations, positioned along a gradient capturing the segregation of gene pool differences in response to climatic variation.

opencc-zeroDec 2015View details →

Data from: Migration strategies and annual space-use in an Afro-Palaearctic aerial insectivore – the European nightjar Caprimulgus europaeus

Obligate insectivorous birds breeding in high latitudes travel thousands of kilometres during annual movements to track the local seasonal peaks of food abundance in a continuously fluctuating resource landscape. Avian migrants use an array of strategies when conducting these movements depending on e.g. morphology, life history traits and environmental factors encountered en route. Here we used geolocators to derive data on the annual space-use, temporal pattern and migratory strategies in an Afro-Palaearctic aerial insectivorous bird species – the European nightjar Caprimulgus europaeus. More specifically, we aimed to test a set of hypothesises pertaining to the migration of a population of nightjars breeding in south-eastern Sweden. We found that the birds wintered across the central and western parts of the southern tropical Africa almost entirely outside the currently described wintering range of the species. The nightjars performed a narrow loop migration across Sahara, with spring Sahel stopovers significantly to the west of autumn stops indicative to an adaptive response to winds during migration. To our surprise, the migration speed was faster in the autumn (119 km d− 1) than in the spring (99 km d− 1), possibly due to the prevailing wind regimes over the Sahara. The estimated flight fraction in both autumn (14%) and spring (12%) was almost exactly as the theoretically predicted 1:7 time relationship between flights and stopovers for small birds. The temporal patterns within the annual cycle indicate that individuals follow alternative spatiotemporal schedules that converge towards the breeding season. The positive relationship between the spatially and temporally distant winter departure and breeding arrival suggests that individuals´ temporal fine-tuning to breeding may be constrained, leading to potential negative fitness consequences.

Data from: Habitat-mediated effects of diurnal and seasonal migration strategies on juvenile salmon survival

Behavioral decisions during periods of vulnerability to predation risk, such as migrations during the juvenile life-history stage, may strongly affect the probability of survival. Habitats through which animals migrate are heterogeneous, and risk-reducing behaviors may be more important in some habitats than others. Using biotelemetry data, diurnal and seasonal riverine migration patterns of >3800 juvenile salmon across four species, 12 watersheds, and five years were quantified to evaluate possible effects of migration timing on survival from lower river reaches to coastal waters. In small, clear rivers most salmon avoided migrating during daylight hours, and average survival of fish migrating at night (55%; 95% confidence limits 50–61%) was twice that of fish migrating in daylight (24%; CL 17-31%). Conversely, in the large, heavily silted Fraser River neither preference for nocturnal travel nor effects of diurnal timing on survival were observed. Early ocean survival was also influenced by the timing of ocean entry, but in opposite directions for fish from the Fraser River and smaller rivers. In the Fraser River, average survival for later migrants (69%; CL 60–77%) was nearly twice that of earlier migrants (38%; CL 33–44%), likely related to seasonal increases in river flow. In contrast, in smaller rivers, average survival for earlier migrants (70%; CL 65–74%) was 3-fold greater than survival for later migrants (19%; 95% CL 14–25%). Together these results demonstrate that timing decisions affecting survival of juvenile salmon during their migration are likely mediated by landscape characteristics that plausibly influence the risk of predation.

opencc-zeroDec 2016View details →

Data from: Caching for where and what: evidence for a mnemonic strategy in a scatter-hoarder

Scatter-hoarding animals face the task of maximizing retrieval of their scattered food caches while minimizing loss to pilferers. This demand should select for mnemonics, such as chunking, i.e. a hierarchical cognitive representation that is known to improve recall. Spatial chunking, where caches with the same type of content are related to each other in physical location and memory, would be one such mechanism. Here we tested the hypothesis that scatter-hoarding eastern fox squirrels (Sciurus niger) are organizing their caches in spatial patterns consistent with a chunking strategy. We presented 45 individual wild fox squirrels with a series of 16 nuts of four different species, either in runs of four of the same species or 16 nuts offered in a pseudorandom order. Squirrels either collected each nut from a different location or collected all nuts from a single location; we then mapped their subsequent cache distributions using GPS. The chunking hypothesis predicted that squirrels would spatially organize caches by nut species, regardless of presentation order. Our results instead demonstrated that squirrels spatially chunked their caches by nut species but only when caching food that was foraged from a single location. This first demonstration of spatial chunking in a scatter hoarder underscores the cognitive demand of scatter hoarding.

opencc-zeroDec 2014View details →

Data from: Can impacts of climate change and agricultural adaptation strategies be accurately quantified if crop models are annually re-initialized?

Estimates of climate change impacts on global food production are generally based on statistical or process-based models. Process-based models can provide robust predictions of agricultural yield responses to changing climate and management. However, applications of these models often suffer from bias due to the common practice of re-initializing soil conditions to the same state for each year of the forecast period. If simulations neglect to include year-to-year changes in initial soil conditions and water content related to agronomic management, adaptation and mitigation strategies designed to maintain stable yields under climate change cannot be properly evaluated. We apply a process-based crop system model that avoids re-initialization bias to demonstrate the importance of simulating both year-to-year and cumulative changes in pre-season soil carbon, nutrient, and water availability. Results are contrasted with simulations using annual re-initialization, and differences are striking. We then demonstrate the potential for the most likely adaptation strategy to offset climate change impacts on yields using continuous simulations through the end of the 21st century. Simulations that annually re-initialize pre-season soil carbon and water contents introduce an inappropriate yield bias that obscures the potential for agricultural management to ameliorate the deleterious effects of rising temperatures and greater rainfall variability.

opencc-zeroDec 2015View details →

Data from: From resource to female defence: the impact of roosting ecology on a bat's mating strategy

With their extraordinary species richness and diversity in ecological traits and social systems, bats are a promising taxon for testing socio-ecological hypotheses in order to get new insights into the evolution of animal social systems. Regarding its roosting habits, proboscis bats form an extreme by occupying sites which are usually completely exposed to daylight (e.g. tree trunks, vines or rocks). This is accompanied by morphological and behavioural adaptations to remain cryptic in exposed day roosts. With long-term behavioural observations and genetic parentage analyses of individually marked proboscis bats, we assessed its social dispersion and male mating strategy during day and night. Our results reveal nocturnal male territoriality—a strategy which most closely resembles a resource-defence polygyny that is frequent also in other tropical bats. Its contrasting clumped social dispersion during the day is likely to be the result of strong selection for crypsis in exposed roosts and is accompanied by direct female defence in addition to male territoriality. To the best of our knowledge, such contrasting male mating strategies within a single day–night cycle have not been described in a vertebrate species so far and illustrate a possible evolutionary trajectory from resource-defence to female-defence strategy by small ecologically driven evolutionary steps.

Data from: Life-history strategies indicate live-bearing in Nothosaurus (Sauropterygia)

In Sauropterygia, a diverse group of Mesozoic marine reptiles, fossil evidence of viviparity (live‐bearing) only exists for Pachypleurosauria and Plesiosauria, and was assumed to also be the case for nothosaurs. Previous studies have successfully applied an extant squamate model to sauropterygian life‐history traits. In extant squamates, oviparity and viviparity are associated with differences in life‐history trait combinations. We establish growth curves for Nothosaurus specimens based on their humeral histology. We then analyse life‐history traits derived from these curves and compare inferred traits to those of modern squamates and pachypleurosaurs to assess their reproduction mode. We show that birth to adult size ratios (i.e. birth size divided by the mother's size) provide good estimates of clutch sizes in extant squamates and in viviparous extinct marine reptiles, but these ratios cannot discriminate viviparous and oviparous squamates. Thus, large ratios do not indicate viviparity in fossil taxa to which the extant squamate model is applicable. Applying differences in birth size, age at maturation, and maximum longevity that are observed between extant viviparous and oviparous squamates to our Nothosaurus sample, we identified 7 out of 24 specimens as being potentially viviparous. Conversely, they suggested oviparity for many nothosaurs but also for many pachypleurosaur samples. Under the assumption that the entire clade Pachypleurosauria was viviparous, the majority of nothosaurs would also have been viviparous as they comprised trait combinations similar to those seen in pachypleurosaurs. Overall, this suggests that within nothosaurs and pachypleurosaurs both reproduction modes existed in different taxa.

Data from: Behavioral diversity is maintained by a conditional strategy in a freshwater zooplankton

Many populations have intraspecific diversity in phenotype and ecological strategy, but the mechanisms maintaining such diversity are not fully understood. Multiple behaviors can be maintained either as a conditional strategy, where fitness depends on an individual's phenotype, or as a mixed strategy where alternative behaviors have similar fitness independent of phenotype. Using high-resolution depth and time sampling, we characterize two distinct diel vertical migration behaviors in a population of freshwater zooplankton (Daphnia pulicaria). Individuals in this population differ in their color phenotype and migratory behavior with red morphs upregulating hemoglobin and undergoing a deep migration, and pale morphs not producing hemoglobin and undergoing a shallow migration. We experimentally manipulated the behavior of each phenotype in the field, and measured population growth in their natural migration behavior as well as population growth in their alternative behaviors. Experimental populations of pale and red morphs under their natural migrations had roughly equal fitness, despite vast differences in environmental conditions. When forced to switch behaviors, pale morphs suffered reduced fitness, whereas red morphs had similar fitness compared to their natural migration. Our results suggest that while behavioral diversity may be promoted by the opportunity for alternative behaviors of equal fitness, the distinct physiological conditions required for survival in alternative behaviors limit the capacity for individual behavioral switching and likely maintain behavioral diversity as a conditional strategy.