One-character evolutionary histories reconstructed through Bayesian stochastic character mapping on a phylogeny of mantellid frogs (from Wollenberg et al. 2011). Inset photos show exemplary species for the various character states. (A) presence/ absence of frenal streak (as indicated by arrows in the upper three inset photos); (B) presence/absence of dark tympanic patch (as indicated by arrows in the upper three inset photos). Inset photos from top to bottom: (A) Mantella betsileo, Gephyromantis granulatus, Boophis rhodoscelis, Mantidactylus melanopleura, Mantella laevigata, Gephyromantis zavona, Boophis arcanus, Mantidactylus aerum­ nalis; (B) Aglyptodactylus madagascariensis, Mantidactylus sp. aff. aerumnalis, Boophis doulioti, Laliostoma labrosum, Mantidactylus sp. aff. biporus, Boophis majori. 

One-character evolutionary histories reconstructed through Bayesian stochastic character mapping on a phylogeny of mantellid frogs (from Wollenberg et al. 2011). Inset photos show exemplary species for the various character states. (A) presence/ absence of frenal streak (as indicated by arrows in the upper three inset photos); (B) presence/absence of dark tympanic patch (as indicated by arrows in the upper three inset photos). Inset photos from top to bottom: (A) Mantella betsileo, Gephyromantis granulatus, Boophis rhodoscelis, Mantidactylus melanopleura, Mantella laevigata, Gephyromantis zavona, Boophis arcanus, Mantidactylus aerum­ nalis; (B) Aglyptodactylus madagascariensis, Mantidactylus sp. aff. aerumnalis, Boophis doulioti, Laliostoma labrosum, Mantidactylus sp. aff. biporus, Boophis majori. 

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With more than 250 species, the Mantellidae is the most species-rich family of frogs in Madagascar. These frogs are highly diversified in morphology, ecology and natural history. Based on a molecular phylogeny of 248 mantellids, we here examine the distribution of three characters reflecting the diversity of eye colouration and two characters of he...

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... of ecology, habitat, eye and head colours in the Mantellidae Bayesian analysis of character evolution indicates a com- plex history of ecological diversification in mantellid frogs. The ancestral general ecology at the mantellid root could not be reliably resolved; both a saxicolous state (posteri- or probability of this character state: PP = 0.431; Supple- mentary Table S2; Fig. 1A) as observed in some deep man- tellid clades of low species diversity (Tsingymantis and Boehmantis), and an arboreal origin (PP = 0.315) received comparable posterior probabilities. In general terms, most mantellid genera are relatively uniform and well-defined regarding their general ecology and habits (Fig. 1A). Sev- eral independent evolutionary transitions leading to arbo- real, semiarboreal, terrestrial and saxicolous habits are re- constructed within the family (Fig. 1A). For example, ar- boreality might have evolved directly from saxicolous an- cestors in Boophis, from terrestrial forms in Spinomantis, or through intermediate semiarboreal stages as in Guibe­ mantis. Semiarboreal habits evolved from terrestrial ances- tors in Blommersia, or from terrestrial-rheophilous ones in Gephyromantis and Mantidactylus argenteus, in this latter case clearly supported by the nested position of the species within its genus. Remarkably, progressive adaptation to streams has occurred from terrestrial-rheophilous general- ists to rheophilous specialists four times. Saxicolous habits appear derived from arboreal and terrestrial-rheophilous ancestors in three cases. All mantellids have horizontal pupils, but iris colour and pattern has been modified multiple times across the mantellid tree ( Fig. 1B; Supplementary Table S2). Uni- formly black eyes evolved exclusively (and most prob- ably twice convergently) in the genus Mantella but this state is not derived from the densely reticulated iris that is found in some Mantidactylus and Blommersia. Bright iris colour arranged in an annular pattern evolved con- vergently in various clades of the genus Boophis, exclud- ing the pond-breeding subgenus Sahona. A contrasted iris colour also originated in two other clades of arbore- al and semi arboreal frogs (Mantidactylus argenteus and Guibe mantis), although in these species, the iris is clearly less bright than in most Boophis and has no annular pat- tern (Fig. 1C). All Boophis have a brightly coloured iris periphery (sclera) (Fig. 1D), and this character state also evolved in several other, mainly arboreal or saxicolous clades, e.g., Spino mantis or Guibemantis frogs. Generally, clades with a brightly coloured iris typically contain spe- cies with different iris periphery colours (blue, bluish, yel- low, and white). Green sclera, however, were only present in one clade of Boophis. Of the head colour characters an- alysed, our reconstruction indicates that a dark tympanic patch and a frenal streak (which might however be weak- ly expressed) are ancestral in mantellids, and both these characters experienced many independent secondary losses ( Fig. 2 and Supplementary Table S2). Aposematic colouration is exclusive to the genus Mantella and is re- constructed as having been present in the ancestor of this clade, with two reversals within the clade (Supplementary Table ...

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... This latter example confirms that colour anomalies can affect the eyes and body separately. Given that both the pigment cells of iris and body skin are derived from the neural crest, this indicates that either the neural crest cells of the two tissues undergo separate cell regulation processes, or the mutations underlying colour anomalies may affect their migration in different ways (Amat et al., 2013). ...
... Results of our quantitative morphometric analysis indicated that the three known species in the genus Alexteroon exhibit highly conserved general body plans and external morphology, rendering a quantitative distinction between species based on preserved material alone difficult, particularly when comparing the two superficially similar patterned yet genetically well separated A. obstetricans and A. jynx. Meanwhile, phenotypic features that can only be observed in live specimens, such as the gular coloration observed in reproductively active males of A. hypsiphonus and A. obstetricans or marked differences in coloration between A. hypsiphonus on one hand and A. obstetricans and A. jynx on the other hand appear to be more useful for ad hoc species delimitation (compare Amat et al. 2013;Glaw et al. 2018 for similar findings in mantellid frogs). These observations call for detailed morphological studies, as well as for photo-documentations of live specimens that should be a standard feature of anuran species descriptions. ...
Article
The African reedfrog taxon Alexteroon consists of only three described species with rather restricted geographical ranges. Although the assignment to a distinct genus is supported by multiple evidence, its position within the larger African hyperoliid radiation has been disputed. Available molecular data are scarce and the geographic records are few and scattered. The partially formalin fixed type series were previously not accessible to molecular analyses. This changed only very recently with the advancement of Next Generation Sequencing and ancient DNA techniques. Here we provide a reassessment of the current distribution and identity of all known species in this taxon based on (a) historical and new records, (b) morphological reanalyses of the type material and newly collected specimens from Angola and Gabon, and (c) newly established, nearly complete mitochondrial genome data from historical type and modern non-type material. We also present a molecular phylogeny (five mitochondrial loci 12S, 16S, ND1, ND2, COI, Cytb) for 78 sequences from 75 different species of Hyperolius retrieved from GenBank and 14 newly established Alexteroon sequences. We demonstrate that Alexteroon is more widely distributed than previously thought with records from northern Angola representing major southern range extensions. Results of the quantitative morphometric analyses show that the group has a rather conserved general body plan. Therefore qualitative phenotypic features observable in live specimens appear to be more useful for ad hoc species delimitation. We found Alexteroon to be nested within Hyperolius, corroborating previous findings. However, the combination of molecular data and consistent differences observed in morphology and ecology provide strong support for the distinctiveness of this evolutionary lineage within Hyperolius sensu lato. We therefore treat Alexteroon as a subgenus of Hyperolius and argue that the large and diverse genus Hyperolius is in need of revision that may result in new generic arrangements.
... Phenotypic eye color has been suggested as an indicator of genetic predisposition toward certain behaviors, where dark-eyed subjects would tend to display behaviors requiring sensitivity, speed, and reactive responses, while with ones with light-colored eyes, behaviors requiring hesitation, inhibition, and self-paced responses, both in humans and in animals (Elias et al., 2008). Furthermore, it has been proposed that eye coloration in various species may be related to social ranks, aggression, mate recognition, and sexual selection (e.g., Volpato et al., 2003, Amat et al., 2013. Chicken eye color is largely determined by genetics, but age, diet, and disease can affect it as well (Nelson, 1947). ...
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... Boophis are notorious for lacking distinct morphological differences between closely related species and their intraspecific variability in body colour and pattern can be substantial (e.g. in B. picturatus, see Glaw et al. 2001). In contrast, the colouration of the eyes turned out to be species-specific for numerous Boophis species and therefore is a crucial character for their taxonomy (Glaw & Vences 1997, Amat et al. 2013. Similarly, the colour of the webbing between toes and fingers can be a reliable character to distinguish closely related species (e.g. ...
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... It is often assumed, for example, that vertically elongated pupils are associated with an arboreal lifestyle. However, while vertical pupils are common to all phyllomedusine frogs (Tyler and Davies, 1978), a genus of Central and South American tree frogs, among mantellid frogs both arboreal and terrestrial species have horizontally elongated pupils (Amat et al., 2013). Similarly, a genus of African hyperoliid tree frog has a horizontally elongate pupil, while those of close relatives are vertical (Roedel et al., 2009). ...
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... By contrast, other primates have round, dark eyes, which may be beneficial when concealing gaze from competitors and appearing less conspicuous to predators [4]. Many birds [5], amphibians [6] and fish [7] have conspicuous eyes, but the function of iris colour and its role in communication outside the primate lineage is poorly understood. ...
... It has been proposed that eye coloration may be related to ecology [5,6], aggression (e.g. [7]), mate recognition and/or sexual selection (e.g. ...
... [7]), mate recognition and/or sexual selection (e.g. [6]). Passeriformes is the largest order of birds, and has a wide range of iris colour across species, making it an ideal system for studying the evolution and function of eye coloration. ...
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Strong selection pressures are known to act on animal coloration. Although many animals vary in eye colour, virtually no research has investigated the functional significance of these colour traits. Passeriformes have a range of iris colours, making them an ideal system to investigate how and why iris colour has evolved. Using phylogenetic comparative methods, we tested the hypothesis that conspicuous iris colour in passerine birds evolved in response to (a) coordination of offspring care and (b) cavity nesting, two traits thought to be involved in intra-specific gaze sensitivity. We found that iris colour and cooperative offspring care by two or more individuals evolved independently, suggesting that bright eyes are not important for coordinating parental care through eye gaze. Furthermore, we found that evolution between iris colour and nesting behaviour did occur in a dependent manner, but contrary to predictions, transitions to coloured eyes were not more frequent in cavity nesters than non-cavity nesters. Instead, our results indicate that selection away from having bright eyes was much stronger in non-cavity nesters than cavity nesters, perhaps because conspicuous eye coloration in species not concealed within a cavity would be more visible to predators.