Color Pattern Variation in a Cryptic Amphibian, Anaxyrus fowleri

Oliveira

et al. 2022

PeerJ

Quantifying variability is important for understanding how evolution operates in polymorphic species such as those of the genus Proceratophrys Miranda-Ribeiro, 1920, which is widely distributed in South America. P. cristiceps distribution is limited to the Caatinga biome in Brazil. We examined its chromatic variation from a populational perspective, looking at different phenetic polymorphism levels and probable chromotypic association by applying statistical and GIS tools that could facilitate future taxonomic research regarding this and other species. We characterized P. cristiceps colour patterns and re-evaluated its geographic variation, highlighting potential consequences for the taxonomy of the genus. Our results revealed six principle chromotypes whose frequencies varied among sex and ontogenetic classes. Phenotypic expression appeared to respect defined proportions and evidenced selective value for the species. We conclude that individual variation, together with typological traditionalism may overestimate the polymorphic magnitude at the population level and cause taxonomic inflation. Our data support the usefulness of P. cristiceps as a model for microevolutionary studies.

Section: Methodsmentioning

confidence: 99%

Polymorphism in a Neotropical toad species: ontogenetic, populational and geographic approaches to chromatic variation inProceratophrys cristiceps(Müller, 1883) (Amphibia, Anura, Odontophrynidae)

Oliveira

et al. 2022

PeerJ

“…While much of the research on colour patterning in vertebrates has focused on birds and teleost fish 1 , amphibians have been an important system in this topic as well 2 , 26 – 28 . A characteristic feature of many amphibians is their complex life cycle, which most typically consists of an aquatic larval stage and a terrestrial adult phase 29 .…”

Section: Introductionmentioning

confidence: 99%

Shifts in the developmental rate of spadefoot toad larvae cause decreased complexity of post-metamorphic pigmentation patterns

Hyeun-Ji

Rendón

Liedtke

et al. 2020

Sci Rep

Amphibian larvae are plastic organisms that can adjust their growth and developmental rates to local environmental conditions. The consequences of such developmental alterations have been studied in detail, both at the phenotypic and physiological levels. While largely unknown, it is of great importance to assess how developmental alterations affect the pigmentation pattern of the resulting metamorphs, because pigmentation is relevant for communication, mate choice, and camouflage and hence influences the overall fitness of the toads. Here we quantify the variation in several aspects of the pigmentation pattern of juvenile spadefoot toads experimentally induced to accelerate their larval development in response to decreased water level. It is known that induced developmental acceleration comes at the cost of reduced size at metamorphosis, higher metabolic rate, and increased oxidative stress. In this study, we show that spadefoot toads undergoing developmental acceleration metamorphosed with a less complex, more homogeneous, darker dorsal pattern consisting of continuous blotches, compared to the more contrasted pattern with segregated blotches and higher fractal dimension in normally developing individuals, and at a smaller size. We also observed a marked effect of population of origin in the complexity of the pigmentation pattern. Complexity of the post-metamorphic dorsal pigmentation could therefore be linked to pre-metamorphic larval growth and development.

“…Variation in colour and pattern are of the more vivid examples of morphological variability in nature. Taxa as diverse as spiders (Cotoras et al., ; De Busschere, Baert, Van Belleghem, Dekoninck, & Hendrickx, ), insects (Katakura, Saitoh, Nakamura, & Abbas, ; Williams, ), fish (Endler, ; Houde, ), amphibians and reptiles (Allen, Baddeley, Scott‐samuel, & Cuthill, ; Balogová & Uhrin, ; Calsbeek, Bonneaud, & Smith, ; Rabbani, Zacharczenko, Green, Abbani, & Acharczenko, ), mammals (Hoekstra, Hirschmann, Bundey, Insel, & Crossland, ; Nekaris & Jaffe, ) and plants (Clegg & Durbin, ; Mascó, Noy‐Meir, & Sérsic, ) display natural variation in pigment or structural colorations. The distribution of colours in specific patterns play an important role in mate preference (Endler, ; Kronforst et al., ), thermal regulation (Forsman, Ringblom, Civantos, & Ahnesjö, ), aposematism (Rojas, Valkonen, & Nokelainen, ) and crypsis (Nosil & Crespi, ) and represent evolutionary adaptations that in many cases have promoted diversification within lineages.…”

Section: Introductionmentioning

confidence: 99%

patternize: An R package for quantifying colour pattern variation

et al. 2017

Abstract1. The use of image data to quantify, study and compare variation in the colours and patterns of organisms requires the alignment of images to establish homology, followed by colour-based segmentation of images. Here, we describe an R package for image alignment and segmentation that has applications to quantify colour patterns in a wide range of organisms.2. patternize is an R package that quantifies variation in colour patterns obtained from image data. patternize first defines homology between pattern positions across specimens either through manually placed homologous landmarks or automated image registration. Pattern identification is performed by categorizing the distribution of colours using an RGB threshold, k-means clustering or watershed transformation.3. We demonstrate that patternize can be used for quantification of the colour patterns in a variety of organisms by analysing image data for butterflies, guppies, spiders and salamanders. Image data can be compared between sets of specimens, visualized as heatmaps and analysed using principal component analysis.4. patternize has potential applications for fine scale quantification of colour pattern phenotypes in population comparisons, genetic association studies and investigating the basis of colour pattern variation across a wide range of organisms. K E Y W O R D Scolour patterns, heatmap, image registration, image segmentation, landmarks | INTRODUCTIONNatural populations often harbour great phenotypic diversity. Variation in colour and pattern are of the more vivid examples of morphological variability in nature. Taxa as diverse as spiders (Cotoras et al., 2016;De Busschere, Baert, Van Belleghem, Dekoninck, & Hendrickx, 2012), insects (Katakura, Saitoh, Nakamura, & Abbas, 1994;Williams, 2007), fish (Endler, 1983;Houde, 1987), amphibians and reptiles (Allen, Baddeley, Scott-samuel, & Cuthill, 2013;Balogová & Uhrin, 2015;Calsbeek, Bonneaud, & Smith, 2008;Rabbani, Zacharczenko, Green, Abbani, & Acharczenko, 2015), mammals (Hoekstra, Hirschmann, Bundey, Insel, & Crossland, 2006;Nekaris & Jaffe, 2007) and plants (Clegg & Durbin, 2000;Mascó, Noy-Meir, & Sérsic, 2004) | ALIGNMENTSuperimposing colour patterns to quantify variation in their expression requires the homologous alignment of the anatomical structures they occur in. Image transformations for this alignment can be obtained from landmark based transformations or image registration techniques. | Landmark based transformationsLandmark based transformations use discrete anatomical points that are homologous among individuals in the analysis. Non-rigid, but uniform transformations from one set of "source" landmarks to a set of "target" landmarks such as affine transformations include translation, rotation, scaling and skewing (Hazewinkel, 2001). Additionally, nonuniform changes in shape between the source and target landmarks can be accounted for by storing the transformation as if it were "the bending of a thin sheet of metal," the so-called thin plate spline (TPS) transformation (Duchon, 1...