Patterns Of Phenotypic Variation Research Articles

Southern Africa's Great Escarpment as an amphitheater of climate-driven diversification and a buffer against future climate change in bats.

Hosting 1460 plant and 126 vertebrate endemic species, the Great Escarpment (hereafter, Escarpment) forms a semi-circular "amphitheater" of mountains girdling southern Africa from arid west to temperate east. Since arid and temperate biota are usually studied separately, earlier studies overlooked the biogeographical importance of the Escarpment as a whole. Bats disperse more widely than other mammalian taxa, with related species and intraspecific lineages occupying both arid and temperate highlands of the Escarpment, providing an excellent model to address this knowledge gap. We investigated patterns of speciation and micro-endemism from modeled past, present, and future distributions in six clades of southern African bats from three families (Rhinolophidae, Cistugidae, and Vespertilionidae) having different crown ages (Pleistocene to Miocene) and biome affiliations (temperate to arid). We estimated mtDNA relaxed clock dates of key divergence events across the six clades in relation both to biogeographical features and patterns of phenotypic variation in crania, bacula and echolocation calls. In horseshoe bats (Rhinolophidae), both the western and eastern "arms" of the Escarpment have facilitated dispersals from the Afrotropics into southern Africa. Pleistocene and pre-Pleistocene "species pumps" and temperate refugia explained observed patterns of speciation, intraspecific divergence and, in two cases, mtDNA introgression. The Maloti-Drakensberg is a center of micro-endemism for bats, housing three newly described or undescribed species. Vicariance across biogeographic barriers gave rise to 29 micro-endemic species and intraspecific lineages whose distributions were congruent with those identified in other phytogeographic and zoogeographic studies. Although Köppen-Geiger climate models predict a widespread replacement of current temperate ecosystems in southern Africa by tropical or arid ecosystems by 2070-2100, future climate Maxent models for 13 bat species (all but one of those analyzed above) showed minimal range changes in temperate species from the eastern Escarpment by 2070, possibly due to the buffering effect of mountains to climate change.

Urban Life Affects Differentiation and Phenotypic Variation but not Asymmetry in a Fully Terrestrial Salamander

AbstractThe environmental transformations associated with cities are expected to affect organisms at the demographic, phenotypic, and evolutionary level, often negatively. The prompt detection of stressed populations before their viability is compromised is essential to understand species’ responses to novel conditions and to integrate urbanization with biodiversity preservation. The presumably stressful conditions of urban environments are expected to affect organisms’ developmental pathways, resulting in a reduction of the efficacy of developmental stability and canalization processes, which can be observed as increased Fluctuating Asymmetry (FA) and Phenotypic Variance (PV), respectively. Here, we investigated whether patterns of phenotypic variation of urban populations of a fully terrestrial salamander, Salamandra salamandra bernardezi, are affected by urban settings compared to surrounding native forest populations. We sampled populations within and around the city of Oviedo (northern Spain) and used geometric morphometrics to compare morphological differentiation, head shape deviance from the allometric slope, PV, and FA. We also compared morphological patterns with neutral genetic and structure patterns. We observed increased levels of differentiation among urban populations and in PV within certain of them, yet no differences in allometric deviance and FA were detected between habitats, and no morphological measures were found to be correlated with genetic traits. Our results do not support a clear negative impact of urban conditions over salamander populations, but rather suggest that other ecological and evolutionary local processes influence morphological variation in this urban system.

Evidence supporting an evolutionary trade-off between material properties and architectural design in Anolis lizard long bones.

In biology, "many-to-one mapping" occurs when multiple morphological forms can meet a particular functional demand. Knowledge of this mapping is crucial for understanding how selection on performance shapes the evolution of morphological diversity. Past research has focused primarily on the potential for geometrically alternative morphological designs to produce equivalent performance outcomes. Here, we ask whether the material properties of biological tissues hold similar potential. Through a phylogenetic comparative study of Anolis lizards, we show that the architectural design and mineral density of the femur trade off in a many-to-one functional system, yielding a morphospace featuring parallel isolines in size-relative bending strength. Anole femur evolution has largely tracked a narrow band of strength isolines over phylogenetic timescales, suggesting that geometry and mineral content shape the course of macroevolution through compensatory effects on performance. Despite this conserved evolutionary relationship, insular and continental species evolve strong bones differently, likely reflecting underlying ecological differences. Mainland anoles, which exhibit fast-paced life histories, typically have femora with lower mineralization and thinner walls than island species, which exhibit the opposite strategy. Together, our results reveal an overlooked dimension in the relationship between form and function, expanding our understanding of how many-to-one mapping can shape patterns of phenotypic diversity.

Spatial phenotypic variability is higher between island populations than between mainland populations worldwide

Spatial isolation is a key driver of population‐level variability in traits and genotypes worldwide. Geographical distance between populations typically increases isolation, but organisms face additional environmental barriers when dispersing between suitable habitat patches. Despite the predicted universal nature of the causes of isolation, global comparisons of isolation effects across taxa and geographic systems are few. We assessed the strength of isolation due to geographic and macroclimatic distance for paired marine island and paired mainland populations within the same species. Our meta‐analysis included published measurements of phenotypic traits and neutral genetic diversity from 1608 populations of 108 plant and animal species at a global scale. As expected, phenotypic differentiation was higher between marine islands than between populations on the mainland, but we found no consistent signal for differences in spatial patterns of neutral genetic diversity between the two systems. Geographic distance had comparatively weak effects on the spatial patterns of phenotypes and neutral genetic diversity. These results suggest that spatial patterns of phenotypic variation are determined by eco‐evolutionary pressures that differ more between islands than between mainland populations, while the spatial variability of neutral genetic diversity might be shaped by rather similar processes in the two systems. Our approach demonstrates that global biodiversity models that include island biology studies may progress our understanding of the interacting effects of spatial habitat structure, geographic‐ and environmental distances on biological processes underlying spatial population variability. We formulate future research directions for empirical tests and global syntheses in the field.

Effects of geo-climate factors on phenotypic variation in cone and seed traits of Pinus yunnanensis.

Evaluating variations in reproductive traits and the response of the variations to geo-climate conditions are essential for understanding the persistence, evolution, and range dynamics of plant populations. However, there are insufficient studies to attempt to analyze the importance of geo-climate factors in explaining within- or among-population variation in reproductive traits. We examined 14 traits for 2671 cones of Pinus yunnanensis collected from nine populations in the mountains of Southwest China to characterize the patterns of phenotypic variation of traits and estimate environmental effects on these trait performances and trait variation. We found the contribution of intrapopulation variation to the overall variation was greater than the interpopulation variation and the larger coefficients of variation for the populations lying at the edge of northern and southern regions. Climatic variables are more important than geographical and tree size variables in their relationships to cone and seed traits. Populations in more humid and warmer climate expressed greater cone and seed weight and seed number but lower seed abortion rate, while the larger coefficients of variation in seed weight and number were detected in northern and southern marginal regions with drier or colder climate. Our study illustrates that intraspecific trait variation should be considered when examining plant species response to changing climate and suggests that the high variability rather than high quality of seed traits in the marginal regions with drier or colder climate might foster plant-population persistence in stressful conditions.

Ecological correlates of cranial evolution in the megaradiation of dipsadine snakes

BackgroundDipsadine snakes represent one of the most spectacular vertebrate radiations that have occurred in any continental setting, with over 800 species in South and Central America. Their species richness is paralleled by stunning ecological diversity, ranging from arboreal snail-eating and aquatic eel-eating specialists to terrestrial generalists. Despite the ecological importance of this clade, little is known about the extent to which ecological specialization shapes broader patterns of phenotypic diversity within the group. Here, we test how habitat use and diet have influenced morphological diversification in skull shape across 160 dipsadine species using micro-CT and 3-D geometric morphometrics, and we use a phylogenetic comparative approach to test the contributions of habitat use and diet composition to variation in skull shape among species.ResultsWe demonstrate that while both habitat use and diet are significant predictors of shape in many regions of the skull, habitat use significantly predicts shape in a greater number of skull regions when compared to diet. We also find that across ecological groupings, fossorial and aquatic behaviors result in the strongest deviations in morphospace for several skull regions. We use simulations to address the robustness of our results and describe statistical anomalies that can arise from the application of phylogenetic generalized least squares to complex shape data.ConclusionsBoth habitat and dietary ecology are significantly correlated with skull shape in dipsadines; the strongest relationships involved skull shape in snakes with aquatic and fossorial lifestyles. This association between skull morphology and multiple ecological axes is consistent with a classic model of adaptive radiation and suggests that ecological factors were an important component in driving morphological diversification in the dipsadine megaradiation.

The Endangered Sardinian Grass Snake: Distribution Update, Bioclimatic Niche Modelling, Dorsal Pattern Characterisation, and Literature Review.

The Sardinian grass snake, Natrix helvetica cetti, is an endangered endemic snake subspecies with a restricted and highly fragmented geographic distribution. Information on its ecology and detailed geographic distribution are scarce and may negatively impact on its conservation status. Therefore, a literature review on its taxonomy, morphology, ecology, and conservation is presented here. Moreover, field records from the authors, citizen science and the existing literature provide an updated geographic distribution highlighting its presence within 13 new and 7 historic 10 × 10 km cells. Bioclimatic niche modelling was then applied to explore patterns of habitat suitability and phenotypic variation within N. h. cetti. The geographic distribution of the species was found to be positively correlated with altitude and precipitation values, whereas temperature showed a negative correlation. Taken together, these outcomes may explain the snake's presence, particularly in eastern Sardinia. In addition, analysis of distribution overlap with the competing viperine snake (N. maura) and the urodeles as possible overlooked trophic resources (Speleomantes spp. and Euproctus platycephalus) showed overlaps of 66% and 79%, respectively. Finally, geographical or bioclimatic correlations did not explain phenotypic variation patterns observed in this highly polymorphic taxon. Perspectives on future research to investigate N. h. cetti's decline and support effective conservation measures are discussed.

The evolutionary ecology of variation in labile traits: selection on its among- and within-individual components.

Closer integration between behavioral ecology and quantitative genetics has resulted in a recent increase in studies partitioning sources of variation in labile traits. Repeatable between-individual differences are commonly documented, and their existence is generally explained using adaptive arguments, implying that selection has shaped variation at the among- and within-individual level. However, predicting the expected pattern of non-adaptive phenotypic variation around an optimal phenotypic value is difficult, hampering our ability to provide quantitative assessments of the adaptive nature of observed patterns of phenotypic variation within a population. We argue that estimating the strength of selection on trait variation among and within individuals provides a way to test adaptive theory concerned with phenotypic variation. To achieve this aim, we describe a nonlinear selection analysis that enables the study of the selective pressures on trait means and their among- and within-individual variation. By describing an integrative approach for studying the strength of selection on phenotypic variation at different levels, we hope to stimulate empirical studies investigating the ecological factors that can shape the repeatability, heritability, and coefficients of variation of labile and other repeatedly expressed traits.

Ecological factors drive the divergence of morphological, colour and behavioural traits in cactus wrens (Aves, Troglodytidae).

The study of ecological mechanisms influencing organisms' phenotypic variation is a central subject of evolutionary biology. In this study, we characterized morphological, plumage colour and acoustic variation in cactus wrens Campylorhynchus brunneicapillus throughout its distribution. We assessed whether Gloger's, Allen's and Bergmann's ecogeographical rules, and the acoustic adaptation hypothesis relate to geographical trait variation. We analysed specimen coloration in belly and crown plumage, beak shape and structural song characteristics. We tested whether the subspecific classification or the peninsular/mainland groups mirrored the geographical variation in phenotypes and whether ecological factors were associated with patterns of trait variation. Our results suggest that colour, beak shape and acoustic traits varied across the range, in agreement with two lineages described by genetics. The simple versions of Gloger's and Allen's rules are related to variations in colour traits and morphology. Conversely, patterns of phenotypic variation did not support Bergmann's rule. The acoustic adaptation hypothesis supported song divergence for frequency-related traits. Phenotypic variation supports the hypothesis of two taxa: C. affinis in the Baja California peninsula and C. brunneicapillus in the mainland. The ecological factors are associated with phenotypic trait adaptations, suggesting that divergence between lineages could result from ecological divergence.

Inventory of on-farm sorghum landrace diversity and climate adaptation in Tigray, Northern Ethiopia: implications for sorghum breeding and conservation

The study was conducted with the aim of inventorying and assessing the level of sorghum landraces richness, estimating the extent and patterns of phenotypic diversity, identifying race type, and predicting suitable areas of production using future climate scenarios in Tigray, Northern Ethiopia. Overall, 358 landraces from 125 independent farmers’ fields in 20 districts belonging to four zones of Tigray were surveyed. Landraces richness, frequency of character states, and diversity levels were estimated via Margalef’s, Menhinick’s and Shannon–Weaver (H′) indices for each zone and altitude classes. Suitable areas for sorghum cultivation in the future were predicted using DIVA-GIS. Altogether, 140 distinctly named landraces were identified and collected. Southern zone has the highest richness (DMg = 10.74, DMn = 5.0) followed by central (DMg = 8.54, DMn = 3.80). The estimated H′ for the phenotypic character states ranged from 0.24 (seed form) to 0.95 (rachis branch length). Highest diversity estimate was found in northwest (H′ = 0.71) followed by central zone (H′ = 0.64). Respectively, H′ was 0.70, 0.68, and 0.61 in lowland, intermediate, and highland elevations. In general, lowlands of northwest, central, and southern zones are identified as potential sites for germplasm conservation and utilization. The races durra, bicolor, caudatum, and durra-bicolor were found with durra as the dominant race (79%). All the currently surveyed areas and many other sites in Tigray are predicted to be suitable for future sorghum production under the changing climate scenario. Copies of all the 358 sorghum landraces are deposited in the national gene bank for use in future sorghum breeding work. The wealth of sorghum landraces diversity could be used in sorghum improvement programs.

The energetics of childhood: Current knowledge and insights into human variation, evolution, and health.

How organisms capture and ultimately use metabolic energy-a limiting resource of life-has profound implications for understanding evolutionary legacies and current patterns of phenotypic variation, adaptation, and health. Energetics research among humans has a rich history in biological anthropology and beyond. The energetics of childhood, however, remains relatively underexplored. This shortcoming is notable given the accepted importance of childhood in the evolution of the unique human life history pattern as well as the known sensitivity of childhood development to local environments and lived experiences. In this review, I have three objectives: (1) To overview current knowledge regarding how children acquire and use energy, highlighting work among diverse human populations and pointing to recent advances and remaining areas of uncertainty; (2) To discuss key applications of this knowledge for understanding human variation, evolution, and health; (3) To recommend future avenues for research. A growing body of evidence supports a model of trade-offs and constraint in childhood energy expenditure. This model, combined with advancements on topics such as the energetics of immune activity, the brain, and the gut, provides insights into the evolution of extended human subadulthood and the nature of variation in childhood development, lifetime phenotype, and health.

Hierarchical Variation in Phenotypic Flexibility across Timescales and Associated Survival Selection Shape the Dynamics of Partial Seasonal Migration.

AbstractPopulation responses to environmental variation ultimately depend on within-individual and among-individual variation in labile phenotypic traits that affect fitness and resulting episodes of selection. Yet complex patterns of individual phenotypic variation arising within and between time periods, as well as associated variation in selection, have not been fully conceptualized or quantified. We highlight how structured patterns of phenotypic variation in dichotomous threshold traits can theoretically arise and experience varying forms of selection, shaping overall phenotypic dynamics. We then fit novel multistate models to 10 years of band-resighting data from European shags to quantify phenotypic variation and selection in a key threshold trait underlying spatioseasonal population dynamics: seasonal migration versus residence. First, we demonstrate substantial among-individual variation alongside substantial between-year individual repeatability in within-year phenotypic variation ("flexibility"), with weak sexual dimorphism. Second, we demonstrate that between-year individual variation in within-year phenotypes ("supraflexibility") is structured and directional, consistent with the threshold trait model. Third, we demonstrate strong survival selection on within-year phenotypes-and hence on flexibility-that varies across years and sexes, including episodes of disruptive selection representing costs of flexibility. By quantitatively combining these results, we show how supraflexibility and survival selection on migratory flexibility jointly shape population-wide phenotypic dynamics of seasonal movement.

Environmentally driven phenotypic convergence and niche conservatism accompany speciation in hoary bats

Species that are geographically widespread may exist across environmentally heterogeneous landscapes that could influence patterns of occupation and phylogeographic structure. Previous studies have suggested that geographic range size should be positively correlated with niche breadth, allowing widespread species to sustain viable populations over diverse environmental gradients. We examined the congruence of phenotypic and phylogenetic divergence with the environmental factors that help maintain species level diversity in the geographically widespread hoary bats (Lasiurus cinereus sensu lato) across their distribution. Genetic sequences were analyzed using multiple phylogenetic and species delimitation methods, and phenotypic data were analyzed using supervised and unsupervised machine learning approaches. Spatial data from environmental, geographic, and topographic features were analyzed in a multiple regression analysis to determine their relative effect on phenotypic diversity. Ecological niches of each hoary bat species were examined in environmental space to quantify niche overlap, equivalency, and the magnitude of niche differentiation. Phylogenetic and species delimitation analyses support existence of three geographically structured species of hoary bat, each of which is phenotypically distinct. However, the Hawaiian hoary bat is morphologically more similar to the South American species than to the North American species despite a closer phylogenetic relationship to the latter. Multiple regression and niche analyses revealed higher environmental similarities between the South American and Hawaiian species. Hoary bats thus exhibit a pattern of phenotypic variation that disagrees with well-supported genetic divergences, instead indicating phenotypic convergence driven by similar environmental features and relatively conserved niches occupied in tropical latitudes.

Inter- and Intraspecific Variation Patterns of Leaf Phenotypic Traits in Two Sympatric Pine Species

Individual persistence under changing climate conditions can be aided by phenotypic plasticity. Needle morphology reflects pine species’ adaptation to their habitats, and adaptive plasticity is beneficial to pine survival. As two closely related pines, Pinusmassoniana Lamb. and Pinus hwangshanensis W. Y. Hsia sympatrically occur in the subtropical region of China, forming hilly forests (i.e., subtropical evergreen needleleaf forests) at lower elevations and montane forests (i.e., temperate evergreen needleleaf forests) at medium and high elevations. However, little is known about the intraspecific phenotypic variation patterns of the two pine species and their relationship with environmental factors. Here, we investigated the interspecific and intraspecific variation patterns of needle traits in the two sympatric pine species, focusing on six traits—i.e., leaf length, leaf thickness, leaf width, leaf area, specific leaf area, and leaf dry matter content—as well as the relationship between needle traits and environmental factors. We found significant phenotypic trait differences among populations of each species. Except for leaf length and leaf width, variation within species was greater than variation between species in the needle traits measured. Even more intriguingly, the leaf size traits (i.e., length, width, thickness) were more conservative than the leaf economic traits (i.e., specific leaf area and leaf dry matter content). In other words, the intraspecific variability of the former was weaker than that of the latter. The nature of P. massoniana needle traits was mainly shaped by latitude, while the needle traits of P. hwangshanensis were significantly affected by annual precipitation. Therefore, phenotypic plasticity may be an essential mechanism for the two pine species to better cope with changing external conditions. The intraspecific variation patterns found in the two pine species and the relationships between traits and environmental factors can provide substantial scientific data for large-scale exploration of intraspecific phenotypic variation in pine species and their breeding practice.

Systematics of Thraupis (Aves, Passeriformes) reveals an extensive hybrid zone between T. episcopus (Blue-gray Tanager) and T. sayaca (Sayaca Tanager).

The Neotropical avian genus Thraupis (Passeriformes, Thraupidae) currently comprises seven species that are widespread and abundant throughout their ranges. However, no phylogenetic hypothesis with comprehensive intraspecific sampling is available for the group and, therefore, currently accepted species limits remain untested. We obtained sequence data for two mitochondrial (ND2, cyt-b) and three non-coding nuclear (TGFB2, MUSK, and βF5) markers from 118 vouchered museum specimens. We conducted population structure and coalescent-based species-tree analyses using a molecular clock calibration. We integrated these results with morphometric and coloration analyses of 1,003 museum specimens to assess species limits within Thraupis. Our results confirm that Thraupis is a monophyletic group and support its origin in the late Miocene and subsequent diversification during the Pleistocene. However, we found conflicts with previous phylogenies. We recovered Thraupis glaucocolpa to be sister to all other species in the genus, and T. cyanoptera to the remaining five species. Our phylogenetic trees and population structure analyses uncovered phylogeographic structure within Thraupis episcopus that is congruent with geographic patterns of phenotypic variation and distributions of some named taxa. The first genetic and phenotypic cluster in T. episcopus occurs east of the Andes and is diagnosed by the white patch on the lesser and median wing coverts, whereas the second group has a blue patch on the wing and distributes to the west of Colombia's eastern Andes. Finally, we present evidence of hybridization and ongoing gene flow between several taxa at different taxonomic levels and discuss its taxonomic implications.

Sexually mediated phenotypic variation within and between sexes as a continuum structured by ecology: The mosaic nature of skeletal variation across body regions in Threespine stickleback (Gasterosteus aculeatus L.).

Ecological character displacement between the sexes, and sexual selection, integrate into a convergent set of factors that produce sexual variation. Ecologically modulated, sexually mediated variation within and between sexes may be a major contributor to the amount of total variation that selection can act on in species. Threespine stickleback (Gasterosteus aculeatus) display rapid adaptive responses and sexual variation in many phenotypic traits. We examined phenotypic variation in the skull, pectoral and pelvic girdles of threespine stickleback from two freshwater and two coastal marine sites on the Sunshine Coast of British Columbia, Canada, using an approach that avoids a priori assumptions about bimodal patterns of variation. We quantified shape and size of the cranial, pectoral and pelvic regions of sticklebacks in marine and freshwater habitats using 3D geometric morphometrics and an index of sexually mediated variation. We show that the expression of phenotypic variation is structured in part by the effects of both habitat marine vs freshwater and the effects of individual sites within each habitat. Relative size exerts variable influence, and patterns of phenotypic variation associated with sex vary among body regions. This fine‐grained quantification of sexually mediated variation in the context of habitat difference and different anatomical structures indicates a complex relationship between genetically inferred sex and environmental factors, demonstrating that the interplay between shared genetic background and sexually mediated, ecologically based selective pressures structures the phenotypic expression of complex traits.

The Biological Hierarchy, Time, and Temporal 'Omics in Evolutionary Biology: A Perspective.

Sequencing data-genomics, transcriptomics, epigenomics, proteomics, and metabolomics-have revolutionized biological research, enabling a more detailed study of processes, ranging from subcellular to evolutionary, that drive biological organization. These processes, collectively, are responsible for generating patterns of phenotypic variation and can operate over dramatically different timescales (milliseconds to billions of years). While researchers often study phenotypic variation at specific levels of biological organization to isolate processes operating at that particular scale, the varying types of sequence data, or 'omics, can also provide complementary inferences to link molecular and phenotypic variation to produce an integrated view of evolutionary biology, ranging from molecular pathways to speciation. We briefly describe how 'omics has been used across biological levels and then demonstrate the utility of integrating different types of sequencing data across multiple biological levels within the same study to better understand biological phenomena. However, single-time-point studies cannot evaluate the temporal dynamics of these biological processes. Therefore, we put forward temporal 'omics as a framework that can better enable researchers to study the temporal dynamics of target processes. Temporal 'omics is not infallible, as the temporal sampling regime directly impacts inferential ability. Thus, we also discuss the role the temporal sampling regime plays in deriving inferences about the environmental conditions driving biological processes and provide examples that demonstrate the impact of the sampling regime on biological inference. Finally, we forecast the future of temporal 'omics by highlighting current methodological advancements that will enable temporal 'omics to be extended across species and timescales. We extend this discussion to using temporal multi-omics to integrate across the biological hierarchy to evaluate and link the temporal dynamics of processes that generate phenotypic variation.

Burrowing constrains patterns of skull shape evolution in wrasses.

The evolution of behavioral and ecological specialization can have marked effects on the tempo and mode of phenotypic evolution. Head-first burrowing has been shown to exert powerful selective pressures on the head and body shapes of many vertebrate and invertebrate taxa. In wrasses, burrowing behaviors have evolved multiple times independently, and are commonly used in foraging and predator avoidance behaviors. While recent studies have examined the kinematics and body shape morphology associated with this behavior, no study to-date has examined the macroevolutionary implications of burrowing on patterns of phenotypic diversification in this clade. Here, we use three-dimensional geometric morphometrics and phylogenetic comparative methods to study the evolution of skull shape in fossorial wrasses and their relatives. We test for skull shape differences between burrowing and non burrowing wrasses and evaluate hypotheses of shape convergence among the burrowing wrasses. We also quantify rates of skull shape evolution between burrowing and non burrowing wrasses to test for whether burrowing constrains or accelerates rates of skull shape evolution in this clade. We find that while burrowing and non burrowing wrasses exhibit similar degrees of morphological disparity, for burrowing wrasses, it took nearly twice as long to amass this disparity. Furthermore, while the disparities between groups are evenly matched, we find that most burrowing species are confined to a particular region of shape space with most species exhibiting narrower heads than many non-burrowing species. These results suggest head-first burrowing constrains patterns of skull shape diversification in wrasses by potentially restricting the range of phenotypes that can perform this behavior.

Patterns of Phenotypic Evolution Associated with Marine/Freshwater Transitions in Fishes.

Evolutionary transitions between marine and freshwater ecosystems have occurred repeatedly throughout the phylogenetic history of fishes. The theory of ecological opportunity predicts that lineages that colonize species-poor regions will have greater potential for phenotypic diversification than lineages invading species-rich regions. Thus, transitions between marine and freshwaters may promote phenotypic diversification in trans-marine/freshwater fish clades. We used phylogenetic comparative methods to analyze body size data in nine major fish clades that have crossed the marine/freshwater boundary. We explored how habitat transitions, ecological opportunity, and community interactions influenced patterns of phenotypic diversity. Our analyses indicated that transitions between marine and freshwater habitats did not drive body size evolution, and there are few differences in body size between marine and freshwater lineages. We found that body size disparity in freshwater lineages is not correlated with the number of independent transitions to freshwaters. We found a positive correlation between body size disparity and overall species richness of a given area, and a negative correlation between body size disparity and diversity of closely related species. Our results indicate that the diversity of incumbent freshwater species does not restrict phenotypic diversification, but the diversity of closely related taxa can limit body size diversification. Ecological opportunity arising from colonization of novel habitats does not seem to have a major effect in the trajectory of body size evolution in trans-marine/freshwater clades. Moreover, competition with closely related taxa in freshwaters has a greater effect than competition with distantly related incumbent species.

God playing dice, revisited: determinism and indeterminism in studies of stochastic phenotypic variation.

Empirical studies of phenotypic variation show that genetic and environmental heterogeneity account for only part of it. Usually, the magnitude of the residual variation is comparable with that of the genetic component, while notably exceeding the magnitude of the environmental component. This can be interpreted in two ways. A deterministic interpretation associates it with artifacts such as measurement error and genetic and environmental heterogeneity that is unaccounted for. An indeterministic interpretation argues that it is random or stochastic phenotypic variation (SPV) resulting from developmental instability - a developing organism's inability to produce a consistent phenotype in a given environment. Classical example of debates between determinists and indeterminists took place about a century ago in quantum physics. In discussing Heidelberg's Uncertainty Principle, Einstein metaphorically expressed his deterministic position: 'God does not play dice with universe'. The indeterministic Uncertainty Principle, however, was eventually widely accepted. Currently, most biologists implicitly or explicitly support deterministic interpretations of phenotypic variation patterns. Here, a wide range of data on morphological traits (studied with analysis of fluctuating asymmetry) and non-morphological traits are analyzed to provide evidence that SPV is not an artifact, but a valid phenomenon. This evidence supports conclusions that observed associations between SPV and stress can be analyzed in the framework of dynamic energy budget theory, and are inextricably linked through energy homeostasis.