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Morfometría Geométrica WA-PJJP
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Neotropical mountain streams are important contributors of biological diversity. Two species of the characid genus Rhoadsia differing for an ecologically important morphological trait, body depth, have been described from mountain streams of the western slopes of the Andes in Ecuador. Rhoadsia altipinna is a deeper-bodied species reported from low elevations in southwestern Ecuador and northern Peru, and Rhoadsia minor is a more streamlined species that was described from high elevations (>1200 m) in the Esmeraldas drainage in northwestern Ecuador. Little is known about these species and their validity as distinct species has been questioned. In this study, we examine how their body shape varies along replicated elevational gradients in different drainages of western Ecuador using geometric morphometrics and the fineness ratio. We also use sequences of the mitochondrial cytochrome oxidase c I gene and the second intron of the S7 nuclear gene to examine whether genetic data are consistent with the existence of two species. We found that body depth varies continuously among populations within drainages as a function of elevation, and that body shape overlaps among drainages, such that low elevation populations of R. minor in the Esmeraldas drainage have similar body depths to higher elevation R. altipinna in southern drainages. Although a common general trend of declining body depth with elevation is clear, the pattern and magnitude of body shape divergence differed among drainages. Sequencing of mitochondrial and nuclear genes failed to meet strict criteria for the recognition of two species (e.g., reciprocal monophyly and deep genetic structure). However, there was a large component of genetic variation for the COI gene that segregated among drainages, indicating significant genetic divergence associated with geographic isolation. Continued research on Rhoadsia in western Ecuador may yield significant insight into adaptation and speciation in Neotropical mountain streams.
Patterns of univariate trait variation across metacommunities are widely explored, as are searches for their underlying causes. Surprisingly, patterns of multivariate shape remain unknown, and the search for drivers of functional traits of communities often neglect the biogeographical distribution of phylogenetic clades. Our aim was to investigate multivariate shape distribution across metacommunities and to determine the main environmental drivers of shape beyond/taking into account the phylogenetic distribution of lineages. We obtained mean skull and mandible shape for 228 species of Neotropical sigmodontine rodents through geometric morphometrics (GM), and then calculated mean shapes for 1°x1° cells across the Neotropics based on the incidence of sigmodontines. We investigated the effects of lineage distribution on mean trait variation by using phylogenetic fuzzy weighting to calculate Principal Coordinates of Phylogenetic Structure (PCPS). Effects of environmental variables on shape variation incorporating phylogenetic composition were realized through redundancy analysis. We found that the different distributions of major lineages throughout the Neotropics were responsible for much of the mean shape variation. The association of landscape features with tribal groupings (Oryzomyini with Amazonia and Phyllotini and Abrotrichini with the Andes) were standouts. Environmental variables and lineage distribution explain the same (i.e. shared) portion of shape variation, suggesting phylogenetic niche conservatism at the metacommunity level. Seasonality in temperature and land cover were the best environmental predictors of mean shape: larger tympanic bullae, incisive foramina, and check teeth are all associated with highly seasonal and less vegetated areas. Our new approach of using GM shape across metacommunities was demonstrably useful in understanding large-scale biogeographical patterns of shape variation and identifying its underlying causes. The overlap between environmental variables and phylogenetic lineage distribution suggests that a process of niche conservatism is likely: the phenotype-environment correlation is mediated by the differential biogeographical distribution of the main clades.
Abstract:
Abstract This chapter is related to fish taxonomy, describing the importance of ladmarks-based morphometry in the context of integrative taxonomy. The general hypothesis of the chapter is that traditional morphological techniques are non conclusive in the description of new species, and thus they should be additional supported with taxonomic integrative tools. The main results achieved by our research group BIMOPE are: i) the assessing of the species validity of Mugil liza (formerly M. platanus) in relation to Mugil cephalus, based on a multidisciplinary approach which includes molecular, meristic and morfogeometric data; ii) the occurrence of only two species of Merluccius in argentine waters, based on meristic and landmarks-based analyses; iii) the assessment of lineal versus landmark-based morphometry for discriminating seven species of Mugilidae; iv) the use of geometric morphometrics and spinulation patterns to discriminate between two species of Sympterygia (Rajidae) of the Southwest Atlantic Ocean; v) the multidisciplinary analysis of the specific validity of a recently described new species of hake, M. tasmanicus; vi) the analysis of boundaries among: (A) O. bonariensis and O. argentinensis at the species level, and the eventual intermediate morphs that could inhabit Mar Chiquita Coastal Lagoon; (B) the putative populations of O. argentinensis from Mar Chiquita Coastal Lagoon and marine environments.
Resumen:
El presente capítulo trata sobre taxonomía de peces, describiendo el rol de la morfometría basada en puntos homólogos (landmarks) en el contexto de la taxonomía integrativa. Se plantea como hipótesis general de trabajo que las técnicas morfológicas tradicionales no son concluyentes en la descripción de nuevas especies de peces, y por ende deben complementarse con herramientas taxonómicas integrativas. Los principales resultados relativos al tema obtenidos por nuestro grupo de investigación BIMOPE incluyen: i) el esclarecimiento del estatus taxonómico de la lisa del Atlántico Sudoccidental Mugil liza (anteriormente Mugil platanus), en relación a Mugil cephalus, sobre la base de un análisis multidisciplinario, empleando secuencias del gen mitochondrial Citocromo b, datos merísticos y morfometría basada en landmarks; ii) la presencia de solo dos especies de Merluccius en aguas de Argentina: M. australis y M. hubbsi, basada en el análisis de datos merísticos y distancias entre puntos homólogos de especímenes de Merluccius, junto a la reexaminación de ejemplares tipo; iii) la evaluación del porcentaje de discriminación de siete especies de la Familia Mugilidae, mediante distintas técnicas morfogeométricas y de morfometría lineal; iv) el empleo de patrones de espinulación y técnicas morfogeométricas para evaluar la discriminación de dos especies de rayas del Género Sympterygia: S.acuta y S. bonapartii; v) el análisis multidisciplinario de la validez específica de una reciente especie de merluza, M. tasmanicus, descripta en 2006; vi) el establecimiento de los límites entre: A) dos especies de pejerreyes: Odontesthes bonariensis y O. argentinensis a nivel específico, y sus posibles formas intermedias (morfotipos); y B) la población de O. argentinensis de la Laguna Costera Mar Chiquita y sus conespecíficos marinos.
Palabras clave: ictiología; morfometría geométrica; análisis multivariados; puntos homólogos; taxonomía integrativa.
Fear lives among Everest’s mighty ice-fluted faces and howls across its razor-sharp crags. Gnawing at reason and enslaving minds, it has killed many and defeated countless others. But in 1953, Edmund Hillary and Tenzing Norgay stared into its dark eye and did not waver. On May 29, they pushed spent bodies and aching lungs past the achievable to pursue the impossible. At a terminal altitude of 29,028 feet, they stood triumphant atop the highest peak in the world. With nimble words and a straightforward style, New Zealand mountaineering legend Hillary recollects the bravery and frustration, the agony and glory that marked his Everest odyssey. From the 1951 expedition that led to the discovery of the Southern Route, through the grueling Himalayan training of 1952, and on to the successful 1953 expedition led by Colonel John Hunt, Hillary conveys in precise language the mountain’s unforgiving conditions. In explicit detail he recalls an Everest where chaotic icefalls force costly detours, unstable snow ledges promise to avalanche at the slightest misstep, and brutal weather shifts from pulse-stopping cold to fiendish heat in mere minutes. In defiance of these torturous conditions, Hillary remains enthusiastic and never hesitates in his quest for the summit. Despite the enormity of his and Norgay’s achievement, he regards himself, Norgay, and the other members of his expedition as hardworking men, not heroes. And while he never would have reached the top without practiced skill and technical competence, his thrilling memoir speaks first to his admiration of the human drive to explore, to understand, to risk, and to conquer.
Morphometrics has undergone a revolutionary transformation in the past two decades as new methods have been developed to address shortcomings in the traditional multivirate analysis of linear distances, angles, and indices. While there is much active research in the field, the new approaches to shape analysis are already making significant and ever-increasing contributions to biological research, including physical anthropology. Modern Morphometrics in Physical Anthropology highlights the basic machinery of the most important methods, while introducing novel extensions to these methods and illustrating how they provide enhanced results compared to more traditional approaches. Modern Morphometrics in Physical Anthropology provides a comprehensive sampling of the applications of modern, sophisticated methods of shape analysis in anthropology, and serves as a starting point for the exploration of these practices by students and researchers who might otherwise lack the local expertise or training to get started. This text is an important resource for the general morphometric community that includes ecologists, evolutionary biologists, systematists, and medical researchers.
Developmental changes through an animal's life are generally understood to contribute to the resulting adult morphology. Possible exceptions are species with complex life cycles, where individuals pass through distinct ecological and morphological life stages during their ontogeny, ending with metamorphosis to the adult form. Antagonistic selection is expected to drive low genetic correlations between life stages, theoretically permitting stages to evolve independently. Here we describe, using Australian frog radiation, the evolutionary consequences on morphological evolution when life stages are under different selective pressures. We use morphometrics to characterize body shape of tadpoles and adults across 166 species of frog and investigate similarities in the two resulting morphological spaces (morphospaces) to test for concerted evolution across metamorphosis in trait variation during speciation. A clear pattern emerges: Australian frogs and their tadpoles are evolving independently; their markedly different morphospaces and contrasting estimated evolutionary histories of body shape diversification indicate that different processes are driving morphological diversification at each stage. Tadpole morphospace is characterized by rampant homoplasy, convergent evolution and high lineage density. By contrast, the adult morphospace shows greater phylogenetic signal, low lineage density and divergent evolution between the main clades. Our results provide insight into the macroevolutionary consequences of a biphasic life cycle.
Birds are the most diversified forms of modern terrestrial vertebrates. They are archosaurs, and are related to Theropoda within Dinosauria. Even though bird morphology has been a subject of interest for centuries, most studies have focused solely on discrete morphological characters, leaving a gap in the understanding of morphological organization and integration in macroevolution. We present this chapter to exemplify a quantitative exploration of the macroevolutionary trends of skull morphological diversity in theropod dinosaurs including modern birds. Using a sample with taxa representative of all of known modern avian Orders, skull disparity is described over a morphospace modeled from shape variables obtained by General Procrustes methods. High taxonomical categories imply large-scale morphological difference, thus landmarks were selected according to evolutionary homologous and developmental conservative areas. Morphological diversity of the skull relies mainly on craniofacial variation, and can be found within the first four dimension of a PCA. Modern avian forms have a strikingly localized, but not morphologically independent, variation at the rostrum. Craniofacial variation unfolds in a range of structurally straight-flexed appearance dependant on the covariation between the rostrum and braincase, structurally mediated by the antorbital cavity. Extinct theropods occupy a region within morphospace resembling an extreme straight skull. Major macroevolutionary changes are likely associated to expansion of the braincase.
Most geometric morphometric studies are underpinned by sets of photographs of specimens. The camera lens distorts the images it takes, and the extent of the distortion will depend on factors such as the make and model of the lens and camera and user-controlled variation such as the zoom of the lens. Any study that uses populations of geometric data digitized from photographs will have shape variation introduced into the data set simply by the photographic process. We illustrate the nature and magnitude of this error using a 30-specimen data set of Recent New Zealand Mactridae (Mollusca: Bivalvia) using only a single camera and camera lens with four different photographic setups. We then illustrate the use of retrodeformation in Adobe Photoshop and test the magnitude of the variation in the data set using multivariate Procrustes analysis of variance. The effect of photographic method on the variance in the data set is significant, systematic, and predictable and, if not accounted for, could lead to misleading results, suggest clustering of specimens in ordinations that has no biological basis, or induce artificial oversplitting of taxa. Recommendations to minimize and quantify distortion include: (1) that studies avoid mixing data sets from different cameras, lenses, or photographic setups; (2) that studies avoid placing specimens or scale bars near the edges of the photographs; (3) that the same camera settings are maintained (as much as practical) for every image in a data set; (4) that care is taken when using full-frame cameras; and (5) that a reference grid is used to correct for and/or quantify distortion.