Find research datasets worth reusing

Figure 8 from: George KH (2020) Restructuring the Ancorabolidae Sars (Copepoda, Harpacticoida) and Cletodidae T. Scott, with a new phylogenetic hypothesis regarding the relationships of the Laophontoidea T. Scott, Ancorabolidae and Cletodidae. Zoosystematics and Evolution 96(2): 455-498. https://doi.org/10.3897/zse.96.51349

Figure 8 P1 of A.Enhydrosoma curticauda (Boeck, 1872); arrow points to inner apical seta (element 3), B.Cletodes meyerorum George & Müller, 2013, C.Touphapleura schminkei (George, 1998), D.Ceratonotus steiningeri George, 2006. Modified from Gee 1994 (A), George and Müller 2013 (B), George 1998b (C), George 2006c (D). No scales.

Figure 7 from: George KH (2020) Restructuring the Ancorabolidae Sars (Copepoda, Harpacticoida) and Cletodidae T. Scott, with a new phylogenetic hypothesis regarding the relationships of the Laophontoidea T. Scott, Ancorabolidae and Cletodidae. Zoosystematics and Evolution 96(2): 455-498. https://doi.org/10.3897/zse.96.51349

Figure 7 Female P5 of A.Heterolaophonte minuta (Boeck, 1872), B.Cletodes meyerorum George & Müller, 2013, C.Ancorabolus chironi Schulz & George, 2010, D.Calypsophontodes macropodia (Gee & Fleeger, 1986). E.Laophontodes sarsi George, 2018, F.Dorsiceratus wilhelminae George & Plum, 2009. Modified from Willen 1992 (A), George and Müller 2013 (B), Schulz and George 2010 (C), Gheerardyn and Lee 2012 (D), George 2018 (E), George and Plum 2009 (F). No scales.

Figure 5 from: George KH (2020) Restructuring the Ancorabolidae Sars (Copepoda, Harpacticoida) and Cletodidae T. Scott, with a new phylogenetic hypothesis regarding the relationships of the Laophontoidea T. Scott, Ancorabolidae and Cletodidae. Zoosystematics and Evolution 96(2): 455-498. https://doi.org/10.3897/zse.96.51349

Figure 5 A. P3 of Tapholaophontodes rollandi Soyer, 1975, B. P3 of Calypsophontodes macropodia (Gee & Fleeger, 1986); dotted circle indicates approximate position and size of coxa; C. P3 of Laophontodes sarsi George, 2018, D. P4 of Probosciphontodes stellata Fiers, 1988. Modified after Mielke 1985 (A), Gheerardyn and Lee 2012 (B), George 2018 (C), Fiers 1988 (D). No scales.

Figure 2 from: George KH (2020) Restructuring the Ancorabolidae Sars (Copepoda, Harpacticoida) and Cletodidae T. Scott, with a new phylogenetic hypothesis regarding the relationships of the Laophontoidea T. Scott, Ancorabolidae and Cletodidae. Zoosystematics and Evolution 96(2): 455-498. https://doi.org/10.3897/zse.96.51349

Figure 2 Cladogram visualising the result of the current phylogenetic evaluation. Capitals A–BB refer to the corresponding sections in the text; asterisks (*; **; ***) refer to the respective discussion in Chapters I and II.

Figure 6 from: George KH (2020) Restructuring the Ancorabolidae Sars (Copepoda, Harpacticoida) and Cletodidae T. Scott, with a new phylogenetic hypothesis regarding the relationships of the Laophontoidea T. Scott, Ancorabolidae and Cletodidae. Zoosystematics and Evolution 96(2): 455-498. https://doi.org/10.3897/zse.96.51349

Figure 6 A. P2 of Arthropsyllus serratus Sars, 1909, B. P2 of Polyascophorus monoceratus George, Wandeness & Santos, 2013, C. Female P3 of Enhydrosoma curticauda Boeck, 1872, D. Female P3 of Cletodes meyerorum George & Müller, 2013. Dotted circles indicate approximate position and size of coxa. Modified after Conroy-Dalton and Huys 2000 (A), George et al. 2013 (B), Gee 1994 (C), George and Müller 2013 (D). No scales.

opencc-zeroJul 2020View details →

Fossil microbodies are melanosomes: evaluating and rejecting the 'fossilised decay-associated microbes' hypothesis

Melanosomes are membrane-bound organelles of varying geometry, commonly found within a range of vertebrate tissues, that contain the pigment melanin. Melanosomes have been identified in the fossil record in many exceptionally preserved fossils allowing reconstructions of the coloration of many extinct animals. However, these microstructures have also been interpreted as "microbial cells" or melanin producing bacteria based on their geometric similarities to melanosomes. Here we test these two conflicting hypotheses experimentally. Our results demonstrate multiple lines of evidence that these fossil microbodies are indeed melanosomes: the geometry of decay-associated microbes differs significantly from fossil microbodies; fossil microbodies are very strongly localized to in vivo melanized tissues and are absent in tissues typically unmelanized in vivo, in all fossils examined regardless of lithology or age. On the basis of these results, as well as a thorough review of existing literature on melanin like pigments, we are able to rule out a bacterial origin for fossil microbodies and demonstrate that fossil microbodies associated with exceptional vertebrate fossils are in fact preserved melanosomes.

opencc-by-4.0Aug 2020View details →

Fig. 22. Phylogenetic hypothesis for the Plumulariidae McCrady, 1859 in Plumularioid hydroids (Cnidaria: Hydrozoa) from off New Caledonia collected during KANACONO and KANADEEP expeditions of the French Tropical Deep-Sea Benthos Program

Fig. 22. Phylogenetic hypothesis for the Plumulariidae McCrady, 1859. Species discussed in this study are highlighted in yellow. Newly produced sequences are in bold. Numbers at nodes represent BPP and BS, respectively, and are shown only when both BPP Ż 0.9 and BS Ż 75.

opencc-zeroSep 2020View details →

Data from: A test of the niche variation hypothesis in a ruminant herbivore

1. Despite the shared prediction that the width of a population's dietary niche expands as food becomes limiting, the Niche Variation Hypothesis (NVH) and Optimal Foraging Theory (OFT) offer contrasting views about how individuals alter diet selection when food is limited. 2. Classical OFT predicts that dietary preferences do not change as food becomes limiting, so individuals expand their diets as they compensate for a lack of preferred foods. In contrast, the NVH predicts that among-individual variation in cognition, physiology, or morphology create functional trade-offs in foraging efficiency, thereby causing individuals to specialize on different subsets of food. 3. To evaluate (a) the predictions of the NVH and OFT and (b) evidence for physiological and cognitive-based functional trade-offs, we used DNA microsatellites and metabarcoding to quantify the diet, microbiome, and genetic relatedness (a proxy for social learning) of 218 moose (Alces alces) across six populations that varied in their degree of food limitation. 4. Consistent with both the NVH and OFT, dietary niche breadth increased with food limitation. Increased diet breadth of individuals—rather than increased diet specialization—was strongly correlated with both food limitation and dietary niche breadth of populations, indicating that moose foraged in accordance with OFT. Diets were not constrained by inheritance of the microbiome or inheritance of diet selection, offering support for the little-tested hypothesis that functional trade-offs in food use (or lack thereof) determine whether populations adhere to the predictions of the NVH or OFT. 5. Our results indicate that both the absence of strong functional trade-offs and the digestive physiology of ruminants provide contexts under which populations should forage in accordance with OFT rather than the NVH. Also, because dietary niche width increased with increased food limitation, OFT and the NVH provide theoretical support for the notion that plant-herbivore interaction networks are plastic rather than static, which has important implications for understanding interspecific niche partitioning. Lastly, because population-level dietary niche breadth and calf recruitment are correlated, and because calf recruitment is a proxy for food limitation, our work demonstrates how diet data can be employed to understand a populations' proximity to carrying capacity.

opencc-zeroOct 2020View details →

A comparative analysis of the photoprotection hypothesis for the evolution of autumn colors

The adaptive value of autumn colors – the seasonal production of red anthocyanins observed in many species of trees and shrubs – is still debated. According to the photoprotection hypothesis, anthocyanins protect leaves from photoinhibition and photooxidation at low temperatures, enabling the tree to reabsorb nutrients more efficiently before leaf fall. Hence, the hypothesis predicts that autumn colors are more likely to evolve in species growing in colder environments. We tested this prediction by comparing the climatic parameters of 237 North American tree species. We found that, while species with yellow autumn leaves grow under lower minimum temperatures than species with green leaves, there is no significant difference in temperaturebetween species with red autumn leaves and species with green or yellow autumn leaves. We conclude that, while reabsorbing chlorophyll in autumn, and the consequent unmasking of yellow carotenoids, may be an adaptation to cold temperatures, the production of red anthocyanins is not. Hence, our inter-specific comparative analysis does not support the photoprotection hypothesis as an explanation for the evolution of autumn colors.

opencc-zeroNov 2020View details →

Variation in community structure of gall-inducing insects associated with a tropical plant supports the hypothesis of competition in stressful habitats

Environmental factors act as drivers of species coexistence or competition. Mesic environments favor the action of parasites and predators on gall communities, while the factors that determine the structure of gall communities in xeric environments remain unknown. We evaluated the structure of gall communities along an environmental gradient defined by intrinsic plant characteristics, soil fertility and aridity, and investigated the role of competition as a structuring force of gall communities in xeric environments. We created null models to compare observed and simulated patterns of co-occurrence of galls and used the C-score index to assess community aggregation or segregation. We used the NES C-score (standardized C-score) to compare patterns of co-occurrence with parameters of environmental quality. Xeric environments had poorer and more arid soils and more-sclerophyllous plants than mesic environments, which was reflected in the distribution patterns of gall communities. Values of the C-score index revealed a segregated distribution of gall morphospecies in xeric environments, but a random distribution in mesic environments. The low availability of resources for oviposition and the high density of gallers in xeric environments reinforce interspecific competition as an important structuring force for gall communities in these environments.

opencc-zeroNov 2020View details →

Data from: The value of the species interaction-abiotic stress hypothesis (SIASH) for invasion biology: using native latitude to explain non-native latitudinal range sizes

Establishment and spread of introduced species are difficult to predict because they are subject to a myriad of factors. A hypothesis which integrates multiple ecological processes, such as the species interaction-abiotic stress hypothesis (SIASH), may improve our ability to predict introduction success (i.e. establishment and spread). SIASH postulates that, along an environmental gradient, species' range limits are set by abiotic stress at the environmentally harsh end of that gradient and by species interactions at the environmentally benign end of the gradient. Given that species richness increases nearer the equator and that climate becomes harsher (colder) nearer the poles, latitude represents a useful gradient with which to test simple predictions of SIASH. In order to test whether non-native ranges conform to the predictions of SIASH, we evaluated non-native latitudinal range size data for 195 cross-continental, naturalized introductions of 140 animal and plant species. Median latitude of native range was positively related to range size in the introduced zone, such that species native to high latitudes occupied larger introduced ranges than species native to low latitudes. Furthermore, temperate native species occupied larger latitudinal ranges when introduced to tropical and subtropical zones than did tropical native species introduced to temperate zones. Our results suggest that where a species originates is as important as where it is introduced for predicting introduction success. Abiotic stress from cold more strongly constrains the range extents of introduced species than species interactions, which is particularly pronounced for species originating from tropical regions. Future work should determine how species interactions and abiotic stress jointly explain other components of non-native species' success across different spatial gradients to better integrate SIASH into invasion biology.

opencc-by-4.0Nov 2020View details →

Figure 3 from: Wildish DJ, Radulovici AE (2020) Amphipods in estuaries: the sibling species low salinity switch hypothesis. Zoosystematics and Evolution 96(2): 797-805. https://doi.org/10.3897/zse.96.55896

Figure 3 Distribution of O. aestuarensis (closed circles) and O. mediterranea (open circles) in the Medway Estuary, from Wildish (1969).

opencc-zeroDec 2010View details →

Data from: The coupling hypothesis: why genome scans may fail to map local adaptation genes

Genomic scans of multiple populations often reveal marker loci with greatly increased differentiation between populations. Often this differentiation coincides in space with contrasts in ecological factors, forming a genetic–environment association (GEA). GEAs imply a role for local adaptation, and so it is tempting to conclude that the strongly differentiated markers are themselves under ecologically based divergent selection, or are closely linked to loci under such selection. Here, we highlight an alternative and neglected explanation: intrinsic (i.e. environment-independent) pre- or post-zygotic genetic incompatibilities rather than local adaptation can be responsible for increased differentiation. Intrinsic genetic incompatibilities create endogenous barriers to gene flow, also known as tension zones, whose location can shift over time. However, tension zones have a tendency to become trapped by, and therefore to coincide with, exogenous barriers due to ecological selection. This coupling of endogenous and exogenous barriers can occur easily in spatially subdivided populations, even if the loci involved are unlinked. The result is that local adaptation explains where genetic breaks are positioned, but not necessarily their existence, which can be best explained by endogenous incompatibilities. More precisely, we show that (i) the coupling of endogenous and exogenous barriers can easily occur even when ecological selection is weak; (ii) when environmental heterogeneity is fine-grained, GEAs can emerge at incompatibility loci, but only locally, in places where habitats and gene pools are sufficiently intermingled to maintain linkage disequilibria between genetic incompatibilities, local-adaptation genes and neutral loci. Furthermore, the association between the locally adapted and intrinsically incompatible alleles (i.e. the sign of linkage disequilibrium between endogenous and exogenous loci) is arbitrary and can form in either direction. Reviewing results from the literature, we find that many predictions of our model are supported, including endogenous genetic barriers that coincide with environmental boundaries, local GEA in mosaic hybrid zones, and inverted or modified GEAs at distant locations. We argue that endogenous genetic barriers are often more likely than local adaptation to explain the majority of Fst-outlying loci observed in genome scan approaches – even when these are correlated to environmental variables.

opencc-zeroDec 2015View details →

Data from: Size evolution in microorganisms masks trade-offs predicted by the growth rate hypothesis

Adaptation to local resource availability depends on responses in growth rate and nutrient acquisition. The growth rate hypothesis (GRH) suggests that growing fast should impair competitive abilities for phosphorus and nitrogen due to high demand for biosynthesis. However, in microorganisms, size influences both growth and uptake rates, which may mask trade-offs and instead generate a positive relationship between these traits (size hypothesis, SH). Here, we evolved a gradient of maximum growth rate (μmax) from a single bacterium ancestor to test the relationship among μmax, competitive ability for nutrients and cell size, while controlling for evolutionary history. We found a strong positive correlation between μmax and competitive ability for phosphorus, associated with a trade-off between μmax and cell size: strains selected for high μmax were smaller and better competitors for phosphorus. Our results strongly support the SH, while the trade-offs expected under GRH were not apparent. Beyond plasticity, unicellular populations can respond rapidly to selection pressure through joint evolution of their size and maximum growth rate. Our study stresses that physiological links between these traits tightly shape the evolution of competitive strategies.

opencc-zeroDec 2013View details →

Data from: Evolution of female multiple mating: a quantitative model of the "sexually-selected sperm" hypothesis

Explaining the evolution and maintenance of polyandry remains a key challenge in evolutionary ecology. One appealing explanation is the sexually-selected sperm (SSS) hypothesis, which proposes that polyandry evolves due to indirect selection stemming from positive genetic covariance with male fertilization efficiency, and hence with a male's success in post-copulatory competition for paternity. However, the SSS hypothesis relies on verbal analogy with 'sexy-son' models explaining co-evolution of female preferences for male displays, and explicit models that validate the basic SSS principle are surprisingly lacking. We developed analogous genetically-explicit individual-based models describing the SSS and 'sexy-son' processes. We show that the analogy between the two is only partly valid, such that the genetic correlation arising between polyandry and fertilization efficiency is generally smaller than that arising between preference and display, resulting in less reliable co-evolution. Importantly, indirect selection was too weak to cause polyandry to evolve in the presence of negative direct selection. Negatively-biased mutations on fertilization efficiency did not generally rescue runaway evolution of polyandry unless realized fertilization was highly skewed towards a single male, and co-evolution was even weaker given random mating-order effects on fertilization. Our models suggest that the SSS process is, on its own, unlikely to generally explain the evolution of polyandry.

opencc-zeroDec 2016View details →

Data from: The role of bryophytes for tree seedling responses to winter climate change: implications for the stress gradient hypothesis

1.When tree seedlings establish beyond the current tree line due to climate warming, they encounter existing vegetation, such as bryophytes that often dominate in arctic and alpine tundra. The stress gradient hypothesis (SGH) predicts that plant interactions in tundra become increasingly negative as climate warms and conditions become less harsh. However, for seedlings climate warming might not result in lower winter stress, if insulating snow cover is reduced. 2.We aimed to understand to if bryophytes facilitate seedling survival in a changing winter climate and if these effects of bryophytes on tree seedlings comply with the SGH along elevational gradients under contrasting snow conditions. 3.In the Swedish subarctic, we transplanted intact bryophyte cores covered by each of three bryophyte species and bryophyte-free control soil from above the tree line to two field common-garden sites, representing current and future tree line air temperature conditions (i.e. current tree line elevation and a lower, warmer, elevation below the tree line). We planted seedlings of Betula pubescens and Pinus sylvestris into these cores and subjected them to experimental manipulation of snow cover during one winter. 4.In agreement with the SGH, milder conditions caused by increased snow cover enhanced the generally negative or neutral effects of bryophytes on seedlings immediately after winter. Further, survival of P. sylvestris seedlings after one full year was higher at lower elevation, especially when snow cover was thinner. However, in contrast with the SGH, impacts of bryophytes on over-winter survival of seedlings did not differ between elevations, and impacts on survival of B. pubescens seedlings after one year was more negative at lower elevation. Bryophyte species differed in their effect on seedling survival after winter, but these differences were not related to their insulating capacity. 5.Synthesis: Our study demonstrates that interactions from bryophytes can modify the impacts of winter climate change on tree seedlings, and vice versa. These responses do not always comply with SGH, but could ultimately have consequences for large-scale ecological processes such as tree-line shifts. These new insights need to be taken into account in predictions of plant species responses to climate change.

opencc-zeroDec 2011View details →

Data from: The Black Queen Hypothesis: evolution of dependencies through adaptive gene loss

Reductive genomic evolution is common in endosymbiotic bacteria, where it is driven by genetic drift. Genome reduction is less common in free-living organisms, but it has occurred in the numerically dominant open-ocean bacterioplankton Prochlorococcus and Pelagibacter, and in these cases the reduction appears to be driven by natural selection rather than drift. The loss of certain genes in free-living organisms may leave them dependent on co-occurring microbes for the lost metabolic functions. We present the Black Queen Hypothesis (BQH), a novel theory of reductive evolution that explains how selection leads to such dependencies; its name refers to the queen of spades in the game Hearts, where the usual strategy is to avoid taking this card. Gene loss can provide a selective advantage by conserving an organism's limiting resources, provided that the gene's function is dispensable. Many vital genetic functions are leaky, thereby unavoidably producing public goods that are available to the entire community. Such leaky functions are thus dispensable for individuals, provided they are not lost entirely from the community. The BQH predicts that the loss of a costly, leaky function is selectively favored at the individual level and will proceed until the production of public goods is just sufficient to support the equilibrium community; at that point, the benefit of any further loss would be offset by the cost. Evolution in accordance with the BQH thus generates "beneficiaries" of reduced genomic content that are dependent on leaky "helpers," and it may explain the observed non-universality of prototrophy, stress resistance, and other cellular functions in the microbial world.

opencc-zeroDec 2016View details →

Data from: Aerobic power and flight capacity in birds: a phylogenetic test of the heart-size hypothesis

Flight capacity is one of the most important innovations in animal evolution; it only evolved in insects, birds, mammals and the extinct pterodactyls. Given that powered flight represents a demanding aerobic activity, an efficient cardiovascular system is essential for the continuous delivery of oxygen to the pectoral muscles during flight. It is well known that the limiting step in the circulation is stroke volume (the volume of blood pumped from the ventricle to the body during each beat), which is determined by the size of the ventricle. Thus, the fresh mass of the heart represents a simple and repeatable anatomic measure of aerobic power of an animal. Although several authors have already compared heart masses across bird species, a phylogenetic comparative analysis of these comparisons is still lacking. Compiling heart sizes for 915 species and applying several statistical procedures controlling for body size and/or testing for adaptive trends in the dataset (e.g., model selection approaches, phylogenetic generalized linear models), we found that (residuals of) heart sizes are consistently associated with four categories of flight capacity. In general, our results indicate that species exhibiting continuous hovering flight (i.e., hummingbirds) have substantially larger hearts than do other groups, that species that use flapping flight and gliding show intermediate values, and that species categorized as poor flyers show the smallest values. Our study shows that at a broad scale, routine flight modes seem to have shaped the energetic requirements of birds sufficiently to be anatomically detected at the comparative level.

opencc-zeroDec 2012View details →

Data from: Neurospora and the dead-end hypothesis: genomic consequences of selfing in the model genus.

It is becoming increasingly evident that adoption of different reproductive strategies, such as sexual selfing and asexuality, greatly impacts genome evolution. In this study, we test theoretical predictions on genomic maladaptation of selfing lineages using empirical data from the model fungus Neurospora. We sequenced the genomes of four species representing distinct transitions to selfing within the history of the genus, as well as the transcriptome of one of these, and compared with available data from three outcrossing species. Our results provide evidence for a relaxation of purifying selection in protein-coding genes and for a reduced efficiency of transposable element silencing by Repeat Induced Point mutation. A reduction in adaptive evolution was also identified in the form of reduced codon usage bias in highly expressed genes of selfing Neurospora, but this result may be confounded by mutational bias. Potentially counteracting these negative effects, the nucleotide substitution rate and the spread of transposons is reduced in selfing species. We suggest that differences in substitution rate relate to the absence of the asexual pathway producing conidia in selfing Neurospora. Our results support the dead-end theory and show that Neurospora genomes bear signatures of both sexual and asexual reproductive mode.