The effects of morphology,phylogeny and prey availability on trophic resource partitioning in an anuran community

Several factors influence the partitioning of trophic resources in ecological communities, such as morphology, evolutionary history, and resource availability. Although the effects of morphology, phylogeny, and resource availability on trophic ecology have long been explored by theoretical studies, little has been done to empirically test these relationships. Here, we tested whether phylogenetic and morphological distances correlate with trophic niche overlap using a path analysis of multiple partial regression of distance matrices. Also, we tested whether niche breadth is influenced by body size using Phylogenetic Generalized Least Squares analysis. Trophic niche overlap was better explained by morphology per se than by the phylogenetic distance. We also found that predator's body size influences niche breadth calculated considering prey traits and availability, but not when we do not include these availability data. Additionally, trophic niche breadth was usually smaller when we considered prey traits and availability, differently from niche overlap, whose values increased when we did not consider these data. Our findings show that the interpretation of trophic niche in communities changes if we consider availability data, affecting inferences about coexistence and trophic specialization. Our study contributes to understanding trophic specialization and emphasizes the importance of incorporating prey availability and their traits into diet analysis.     

Molecular investigation of Phryganella acropodia Hertwig et Lesser, 1874 (Arcellinida,Amoebozoa)

Phryganella acropodia Hertwig and Lesser, 1874, is one of the most common and abundant testate amoeba species. It represents the type species of the genus Phryganella Penard, 1902, which in turn is the type genus for the suborder Phryganellina (Arcellinida) Bovee, 1985, but despite its taxonomic importance it was not yet analyzed with molecular methods. We established two cultures of putative Phryganella acropodia, designed Phryganellina-specific primers, amplified SSU rDNA data and subjected these sequences to phylogenetic analyses. Morphological and genetic differences were found between both strains. With SSU rDNA phylogenetic analyses we confirm that Phryganella acropodia branches with Phryganella paradoxa Penard, 1902 and Cryptodifflugia Penard, 1890 in the Phryganellina. We thus give further evidence that pseudopodia morphology in the Arcellinida is a character of high taxonomic value, as suggested by Bovee and Jung when erecting the suborder Phryganellina. Moreover, we provide evidence for cryptic diversity and for the first time confirm the existence of a naked life stage in Arcellinida by molecular means.     

Morphology, sociality, and ecology: can morphology predict pairing behavior in coral reef fishes?

Morphology can contain valuable information about the ecological performance of reef fishes, but it has rarely been used in combination with social traits. Social behavior is known to influence the ecological role of fishes; however, the ecological basis for pairing in reef fishes is not well understood. Field observations of 2,753 individuals, in 47 species in six families of biting reef fishes (Acanthuridae, Chaetodontidae, Kyphosidae, Labridae, Pomacanthidae, Siganidae), were used in combination with six morphological measurements, to examine the morphology of fishes in different social systems. A principal components analysis of morphological traits segregated species with high proportions of pairing individuals from non-pairing species along principal component 1, explaining 40.8 % of the variation. Pairing species were characterized by large eyes, concave foreheads, pointed snouts, deep bodies, and small maximum sizes. There was a significant positive relationship between these morphological traits (i.e., scores on PC1) and the prevalence of pairing within the Chaetodontidae (r ² = 0.59; P = 0.026), Siganidae (r ² = 0.72; P = 0.004), and Acanthuridae (r ² = 0.82; P < 0.001). This was consistent when traits were corrected for phylogenetic effects. No pattern was evident in the scarine Labridae (r ² = 0.15; P = 0.17). The morphological characteristics found among pairing species suggest that pairing species share common ecological traits, including foraging for small prey items in micro-topographically complex environments such as reef crevices. These ecological traits may have played a role in the evolution of pairing behavior and subsequently led to the development of reproductive patterns based on monogamy.     

Phylogenetic structure of a palm community in the central Amazon: changes along a hydro-edaphic gradient

The concepts of phylogenetic community structure (PCS) and phylogenetic niche conservatism (PNC) allow ecologists to address the role of species’ evolutionary history in community assembly. It is important to test the role of historical legacies relative to environmental constraints at local scales, where communities are assembled. We studied phylogenetic structure and niche conservatism for palms (Arecaceae) in the 64-km² Ducke Reserve in the central Amazon, near Manaus. The 72 study plots, each covering 0.1 ha, were distributed regularly in a terra firme forest along a hydro-edaphic gradient. We compared the observed palm PCS with assemblages generated by null models. We also analyzed whether morphological and ecological traits are labile or conserved along the phylogeny and quantified the spatial structure of morphological traits in each plot. We found an overall neutral PCS in combination with low PNC (labile traits), suggesting that evolutionary history poses little constraint on palm community assembly in this Amazonian landscape. Still, there was a tendency towards phylogenetic overdispersion in bottomlands, suggesting competitive exclusion among close relatives or, more likely, environmental filtering acting on convergent traits that affect co-occurrence in flood-prone areas. We conclude that (1) PCS of local communities is random as a whole and morphological traits are overall labile, but that (2) the hydro-edaphic gradient within terra firme forests leads to differences in species co-occurrence so that closely related species occur less often than expected in bottomlands due to diffuse competition among close relatives or environmental filtering on convergent traits.     

ASYNCHRONOUS EVOLUTION OF PHYSIOLOGY AND MORPHOLOGY IN ANOLIS LIZARDS

Species‐rich adaptive radiations typically diversify along several distinct ecological axes, each characterized by morphological, physiological, and behavioral adaptations. We test here whether different types of adaptive traits share similar patterns of evolution within a radiation by investigating patterns of evolution of morphological traits associated with microhabitat specialization and of physiological traits associated with thermal biology in Anolis lizards. Previous studies of anoles suggest that close relatives share the same “structural niche” (i.e., use the same types of perches) and are similar in body size and shape, but live in different “climatic niches” (i.e., use habitats with different insolation and temperature profiles). Because morphology is closely tied to structural niche and field active body temperatures are tied to climatic niches in Anolis, we expected phylogenetic analyses to show that morphology is more evolutionarily conservative than thermal physiology. In support of this hypothesis, we find (1) that thermal biology exhibits more divergence among recently diverged Anolis taxa than does morphology; and (2) diversification of thermal biology among all species often follows diversification in morphology. These conclusions are remarkably consistent with predictions made by anole biologists in the 1960s and 1970s.     

Variation in Body Shape across Species and Populations in a Radiation of Diaptomid Copepods

Inter and intra-population variation in morphological traits, such as body size and shape, provides important insights into the ecological importance of individual natural populations. The radiation of Diaptomid species (~400 species) has apparently produced little morphological differentiation other than those in secondary sexual characteristics, suggesting sexual, rather than ecological, selection has driven speciation. This evolutionary history suggests that species, and conspecific populations, would be ecologically redundant but recent work found contrasting ecosystem effects among both species and populations. This study provides the first quantification of shape variation among species, populations, and/or sexes (beyond taxonomic illustrations and body size measurements) to gain insight into the ecological differentiation of Diaptomids. Here we quantify the shape of five Diaptomid species (family Diaptomidae) from four populations each, using morphometric landmarks on the prosome, urosome, and antennae. We partition morphological variation among species, populations, and sexes, and test for phenotype-by-environment correlations to reveal possible functional consequences of shape variation. We found that intraspecific variation was 18-35% as large as interspecific variation across all measured traits. Interspecific variation in body size and relative antennae length, the two traits showing significant sexual dimorphism, were correlated with lake size and geographic location suggesting some niche differentiation between species. Observed relationships between intraspecific morphological variation and the environment suggest that divergent selection in contrasting lakes might contribute to shape differences among local populations, but confirming this requires further analyses. Our results show that although Diaptomid species differ in their reproductive traits, they also differ in other morphological traits that might indicate ecological differences among species and populations.     

Morphological Similarity and Ecological Overlap in Two Rotifer Species

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.e., niche retention), these species will have similar ecological requirements and are expected to have strong competitive interactions. 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. plicatilis and B. manjavacas. We focus on three key ecological features related to body size: (1) functional response, expressed by clearance rates; (2) tolerance to starvation, measured by growth and reproduction; and (3) vulnerability to copepod predation, measured by the number of preyed upon neonates. No major differences between B. plicatilis and B. manjavacas were found in the response to these features. Our results demonstrate the existence of a substantial niche overlap, suggesting that the subtle size differences between these two cryptic species are not sufficient to explain their coexistence. This lack of evidence for ecological differentiation in the studied biotic niche features is in agreement with the phylogenetic limiting similarity hypothesis but requires a mechanistic explanation of the coexistence of these species not based on differentiation related to biotic niche axes.     

Flow cytometric analysis in Lagenaria siceraria (Cucurbitaceae) indicates correlation of genome size with usage types and growing elevation

The occurrence and extent of genome size variation within species is controversially discussed and thorough analyses are rare. Given the large morphological variation in Lagenaria siceraria (bottle gourds) and its wide distribution in Africa we here analysed (1) the genome size variation within cultivars of L. siceraria, (2) the correlation between genome size and morphological traits, and (3) the geographical patterns of DNA content within the species. We measured 2C-values of 366 individuals from 117 accessions of L. siceraria (2n = 22) from Africa, America and Asia via flow cytometry with propidium iodide as DNA stain. We found that 2C-value in L. siceraria (0.683–0.776 pg/2C) is about two times lower than previously reported and varies by about 12% among all accessions. Moreover, our results indicated a clear correlation of genome size with two different seed or usage types and with growing elevations in West Africa. Within the seed types genome size varies by 6.6 and 7.5%, respectively. The genome size differences in seed types of L. siceraria might indicate differences in their evolutionary history and necessitates a re-evaluation of the phylogenetic relationships within L. siceraria while the correlation between 2C-value and the elevation of the collecting sites might indicate an adaptation of genome size to an unknown ecological parameter connected to altitude.     

A phylogenetic analysis of macroevolutionary patterns in fermentative yeasts

When novel sources of ecological opportunity are available, physiological innovations can trigger adaptive radiations. This could be the case of yeasts (Saccharomycotina), in which an evolutionary novelty is represented by the capacity to exploit simple sugars from fruits (fermentation). During adaptive radiations, diversification and morphological evolution are predicted to slow‐down after early bursts of diversification. Here, we performed the first comparative phylogenetic analysis in yeasts, testing the “early burst” prediction on species diversification and also on traits of putative ecological relevance (cell‐size and fermentation versatility). We found that speciation rates are constant during the time‐range we considered (ca., 150 millions of years). Phylogenetic signal of both traits was significant (but lower for cell‐size), suggesting that lineages resemble each other in trait‐values. Disparity analysis suggested accelerated evolution (diversification in trait values above Brownian Motion expectations) in cell‐size. We also found a significant phylogenetic regression between cell‐size and fermentation versatility (R² = 0.10), which suggests correlated evolution between both traits. Overall, our results do not support the early burst prediction both in species and traits, but suggest a number of interesting evolutionary patterns, that warrant further exploration. For instance, we show that the Whole Genomic Duplication that affected a whole clade of yeasts, does not seems to have a statistically detectable phenotypic effect at our level of analysis. In this regard, further studies of fermentation under common‐garden conditions combined with comparative analyses are warranted.     

To What Extent Do Food Preferences Explain the Trophic Position of Heterotrophic and Mixotrophic Microbial Consumers in a Sphagnum Peatland?

Although microorganisms are the primary drivers of biogeochemical cycles, the structure and functioning of microbial food webs are poorly studied. This is the case in Sphagnum peatlands, where microbial communities play a key role in the global carbon cycle. Here, we explored the structure of the microbial food web from a Sphagnum peatland by analyzing (1) the density and biomass of different microbial functional groups, (2) the natural stable isotope (δ ¹³C and δ ¹⁵N) signatures of key microbial consumers (testate amoebae), and (3) the digestive vacuole contents of Hyalosphenia papilio, the dominant testate amoeba species in our system. Our results showed that the feeding type of testate amoeba species (bacterivory, algivory, or both) translates into their trophic position as assessed by isotopic signatures. Our study further demonstrates, for H. papilio, the energetic benefits of mixotrophy when the density of its preferential prey is low. Overall, our results show that testate amoebae occupy different trophic levels within the microbial food web, depending on their feeding behavior, the density of their food resources, and their metabolism (i.e., mixotrophy vs. heterotrophy). Combined analyses of predation, community structure, and stable isotopes now allow the structure of microbial food webs to be more completely described, which should lead to improved models of microbial community function.     

Congruence between comparative morphology and molecular phylogenies: Evolution of the male genital skeletal/muscular system in the subtribe Polyommatina (Lepidoptera,Lycaenidae)

The skeleton and musculature of male genitalia were studied in species of a model butterfly group (subtribe Polyommatina, Lycaenidae). In total, we analyzed 45 species of the tribe Polyommatini most of which were previously used in the molecular phylogenetic study (Talavera et al., 2013). The studied morphological characters were mapped on the molecular trees, which allowed us to reveal trends of morphological changes and to estimate the age of their origin. As a result, chronology of evolution of skeleton and musculature traits was established. It was shown that periods of slow morphological evolution alternated in the subtribe Polyommatina with those of a high rate of origin of new traits. For example, topography of the intravalvar muscles has not changed for 26 MY preserving their initial fan-shaped attachment. The evolution of intravalvar muscles started 10 MYA, proceeded slowly during the first 5 MY, and then accelerated during the last 5 MY resulting in the extensive splitting of the musculature in most monophyletic lineages. Mapping the morphological characters on the phylogeny demonstrated that the rates of skeleton and muscle evolution within the skeleton/musculature apparatus were different. In most cases the intravalvar musculature evolved much faster than the skeleton. The cladistic interpretation of states of morphological traits was found to be consistent with phylogenetic reconstructions based on analysis of multiple molecular markers. Moreover, morphological synapomorphies were found for the lineages Alpherakya + Glabroculus and Aricia + (Alpherakya + Glabroculus), which had low statistical support in molecular phylogenetic analysis. Additionally, in some cases molecular studies helped to reveal trends in the evolution of morphological traits. For example, the unpaired uncus and the compact juxta are not plesiomorphic for Cupidina as previously thought; instead, they were shown to have evolved secondarily within this subtribe.     

Multigene phylogeny reveals convergent evolution in small interstitial catfishes from the Amazon and Atlantic forests (Siluriformes: Trichomycteridae)

Interstitial trichomycterid catfishes of the Glanapteryginae and Sarcoglanidinae with uncommon morphology have been known for long time from taxa endemic to the Amazon. In most recent decades, two genera, Listrura and Microcambeva, respectively, placed in Glanapteryginae and Sarcoglanidinae on the basis of morphological characters, have been described from the Atlantic Forest of eastern South America, about 1,500 km from the area inhabited by those Amazon taxa. Herein, we first test the phylogenetic positioning of Listrura and Microcambeva using a multigene data set, including two nuclear and three mitochondrial genes for nine species of Listrura and Microcambeva and 11 species representing all closely related subfamilies (TSVSG-clade), as well as five used as outgroups. The phylogenetic analyses generated a robust tree with high support values in all nodes, where monophyly of Glanapteryginae and Sarcoglanidinae is refuted. In contrast, Listrura and Microcambeva form a highly supported clade, herein formally described as a new subfamily, sister to a clade containing taxa representing the Glanapteryginae, Sarcoglanidinae, Stegophilinae, Tridentinae and Vandelliinae. This study also indicates that Microcambeva and Listrura exhibit divergent evolutionary trends in ecological and morphological attributes. Species of Microcambeva inhabit patches of loose sand and possess morphological traits that were convergently acquired by Amazon sand-dwelling sarcoglanidines, including loss of body pigmentation and long maxilla. Species of Listrura live burrowed inside small stretches of dense leaf litter and have morphological traits that were convergently acquired by Amazon glanapterygines inhabiting leaf litter bottom rivers, including elongate body, with numerous vertebrae and loss or reduction of all fins.     

Highlighting convergent evolution in morphological traits in response to climatic gradient in African tropical tree species: The case of genus Guibourtia Benn.

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A longirostrine tyrannosauroid from the Early Cretaceous of China

The fossil record of tyrannosauroid theropods is marked by a substantial temporal and morphological gap between small-bodied, Barremian taxa, and extremely large-bodied taxa from the latest Cretaceous. Here we describe a new tyrannosauroid, Xiongguanlong baimoensis n. gen. et sp., from the Aptian–Albian Xinminpu Group of western China that represents a phylogenetic, morphological, and temporal link between these disjunct portions of tyrannosauroid evolutionary history. Xiongguanlong is recovered in our phylogenetic analysis as the sister taxon to Tyrannosauridae plus Appalachiosaurus, and marks the appearance of several tyrannosaurid hallmark features, including a sharp parietal sagittal crest, a boxy basicranium, a quadratojugal with a flaring dorsal process and a flexed caudal edge, premaxillary teeth bearing a median lingual ridge, and an expanded axial neural spine surmounted by distinct processes at its corners. Xiongguanlong is characterized by a narrow and elongate muzzle resembling that of Alioramus. The slender, unornamented nasals of Xiongguanlong are inconsistent with recent hypotheses of correlated progression in tyrannosauroid feeding mechanics, and suggest more complex patterns of character evolution in the integration of feeding adaptations in tyrannosaurids. Body mass estimates for the full-grown holotype specimen of Xiongguanlong fall between those of Late Cretaceous tyrannosaurids and Barremian tyrannosauroids, suggesting that the trend of increasing body size observed in North American Late Cretaceous Tyrannosauridae may extend through the Cretaceous history of Tyrannosauroidea though further phylogenetic work is required to corroborate this.     

Foraging strategies,craniodental traits,and interaction in the bite force of Neotropical frugivorous bats (Phyllostomidae: Stenodermatinae)

1. Bats in the family Phyllostomidae exhibit great diversity in skull size and morphology that reflects the degree of resource division and ecological overlap in the group. In particular, the subfamily Stenodermatinae has high morphological diversification associated with cranial and mandibular traits that are associated with the ability to consume the full range of available fruits (soft and hard).
2. We analyzed craniodental traits and their relationship to the bite force in 343 specimens distributed in seven species of stenodermatine bats with two foraging strategies: nomadic and sedentary frugivory. We evaluated 19 traits related to feeding and bite force in live animals by correcting bite force with body size.
3. We used a generalized linear model (GLM) and post hoc tests to determine possible relationships and differences between cranial traits, species, and sex. We also used Blomberg''s K to measure the phylogenetic signal and phylogenetic generalized least‐squares (PGLS) to ensure the phylogenetic independence of the traits.
4. We found that smaller nomadic species, A. anderseni and A. phaeotis , have a similar bite force to the large species A. planirostris and A. lituratus; furthermore, P. helleri registered a bite force similar to that of the sedentary bat, S. giannae. Our study determined that all the features of the mandible and most of the traits of the skull have a low phylogenetic signal. Through the PGLS, we found that the diet and several cranial features (mandibular toothrow length, dentary length, braincase breadth, mastoid breadth, greatest length of skull, condylo‐incisive length, and condylo‐canine length) determined bite force performance among Stenodermatiane.
5. Our results reinforce that skull size is a determining factor in the bite force, but also emphasize the importance of its relationships with morphology, ecology, and phylogeny of the species, which gives us a better understanding of the evolutionary adaptions of this highly diverse Neotropical bat group.

     

Variability of quantitative morphological traits of mosquito larvae in some species of the <Emphasis Type="Italic">Culex pipiens</Emphasis> complex (Diptera,Culicidae)

The variability of 13 larval morphological characteristics in the urban mosquito, Culex pipiens f. molestus and Culex torrentium, was investigated. These species, belonging to the Culex pipiens complex, are characterized by rapid ecological and evolutionary processes following the human-induced environmental changes. A comparison of 4 geographical larval populations of C. pipiens f. molestus and Culex torrentium revealed different rates of divergence of different morphological traits. In the older form in terms of evolutionary development, C. torrentium, the two local populations differed in the structures of the trophic morphological complex characterized by a higher functional trophic load, while the structures with a lower functional load did not differ between the populations. On the contrary, the populations of the younger form, C. pipiens f. molestus, which had recently colonized new urban sites, differed in the structures with a low functional trophic load (some structures of siphon and abdominal segment IX), whereas structures of the trophic morphological complex were similar in different populations. The possible mechanisms of these morphological transformations and their role in the evolution of mosquito larvae are discussed.     

Linking intraspecific variability in trophic and functional niches along an environmental gradient

1. Intraspecific trophic variability has important ecological and evolutionary implications, and is driven by multiple interacting factors. Functional traits and environmental conditions are important in mediating the trophic niche of individuals because they determine their ability to consume certain prey, their energetic requirements, and resource availability. In this study, we aimed at investigating the interacting effects of functional traits and environmental conditions on several attributes of trophic niche in natural populations.
2. Here, we quantified intraspecific variability in the trophic niche of 12 riverine populations of European minnow (Phoxinus phoxinus) using stable isotope analyses. Functional traits (i.e. morpho-anatomical traits) and environmental conditions (i.e. upstream–downstream gradient, forest cover) were quantified to identify the determinants of (1) trophic position and resource origin, (2) trophic niche size, and (3) trophic differentiation (β-diversity) among populations.
3. We demonstrated that trophic position and resource origin covaried with functional traits related to body size and locomotion performance, and that the strength and shape of these relationships varied according to local environmental conditions. The trophic niche size also differed among populations, although no determinant was identified. Finally, trophic β-diversity was correlated to environmental differentiation among sites.
4. Overall, the determinants of intraspecific variability in trophic niche appeared highly context-dependent, and related to the interactions between functional traits and environmental conditions. Because populations are currently facing important environmental changes, understanding this context-dependency is important for predicting food web structure and ecosystem dynamics in a changing world.

     

Adaptive Radiation in Mediterranean Cistus (Cistaceae)

Background

Adaptive radiation in Mediterranean plants is poorly understood. The white-flowered Cistus lineage consists of 12 species primarily distributed in Mediterranean habitats and is herein subject to analysis.

Methodology/Principal Findings

We conducted a “total evidence” analysis combining nuclear (ncpGS, ITS) and plastid (trnL-trnF, trnK-matK, trnS-trnG, rbcL) DNA sequences and using MP and BI to test the hypothesis of radiation as suggested by previous phylogenetic results. One of the five well-supported lineages of the Cistus-Halimium complex, the white-flowered Cistus lineage, comprises the higher number of species (12) and is monophyletic. Molecular dating estimates a Mid Pleistocene (1.04±0.25 Ma) diversification of the white-flowered lineage into two groups (C. clusii and C. salviifolius lineages), which display asymmetric characteristics: number of species (2 vs. 10), leaf morphologies (linear vs. linear to ovate), floral characteristics (small, three-sepalled vs. small to large, three- or five-sepalled flowers) and ecological attributes (low-land vs. low-land to mountain environments). A positive phenotype-environment correlation has been detected by historical reconstructions of morphological traits (leaf shape, leaf labdanum content and leaf pubescence). Ecological evidence indicates that modifications of leaf shape and size, coupled with differences in labdanum secretion and pubescence density, appear to be related to success of new species in different Mediterranean habitats.

Conclusions/Significance

The observation that radiation in the Cistus salviifolius lineage has been accompanied by the emergence of divergent leaf traits (such as shape, pubescence and labdanum secretion) in different environments suggets that radiation in the group has been adaptive. Here we argued that the diverse ecological conditions of Mediterranean habitats played a key role in directing the evolution of alternative leaf strategies in this plant group. Key innovation of morphological characteristics is supported by our dated phylogeny, in which a Mediterranean climate establishment (2.8 Ma) predated the adaptive radiation of the white-flowered Cistus.