Pelage Color Variation Research Articles

Melanism in a Wild Sifaka Population: Darker Where Cold and Fragmented

Pigmentation is one of the most striking examples of diversity in the natural world. Specifically, primate pelage (hair/fur) pigmentation provides a substrate for selection, and is tied to functions such as crypsis, signaling, and thermoregulation. However, most of our hypotheses on the forces responsible for primate pelage pigmentation are based solely on macro-evolutionary studies. Here, we test how distinct hypotheses around climate, age, and sex might be influencing pelage color variation in a wild primate population. We characterize pelage color and pattern variation within a population of wild diademed sifakas (Propithecus diadema) exhibiting striking diversity in coloration (melanic to tri-colored). Our approach jointly assesses climate and pelage variation across the region. We score pelage using a semi-quantitative methodology (n = 87 individuals). We then test if pelage variation is associated with climatic or demographic factors (i.e., sex–class, age–class) across the Tsinjoarivo forest, Madagascar. We find darker bodies and greater facial complexity in colder and more fragmented forests. We conclude that three explanations may explain the phenotypic pattern: isolation by distance, an environmental gradient, or local adaptation. Although it is difficult to reach a causal conclusion without genetic data, each scenario signals the need for enhanced conservation of diademed sifakas in the Tsinjoarivo forest. More studies on primate pigmentation in wild populations will be needed to contextualize if this pattern is exceptional or typical. We argue that primate color in wild populations may also foretell either adaptation or maladaptation (i.e., via environmental mismatch).

Reconsidering the taxonomy of thePithecia irrorataspecies group (Primates: Pitheciidae)

The number of Pithecia species has considerably increased in recent years. In the first comprehensive taxonomic revision for the genus, five species were recognized, among these, Pithecia irrorata, with two subspecies: P. irrorata irrorata and P. irrorata vanzolinii. These subspecies were elevated to full species in the most recent taxonomic revision of the genus, which was based primarily on pelage color. Additionally, it was proposed that P. irrorata was a group of undescribed species, and three additional species were described from P. irrorata: P. mittermeieri, P. rylandsi, and P. pissinattii. However, diagnoses and geographic distributions are not well defined for the species proposed, bringing confusion to subsequent studies. To address the current hypothesis on the species diversity in the P. irrorata species group, we conducted comparative analyses using the same source of evidence: pelage color variation. Material analyzed includes specimens throughout the distribution of the group in Peru, Bolivia, and Brazil. Based on our results, we recognize two groups that are morphologically diagnosable and correspond to geographically isolated populations. The senior names available for these groups are P. irrorata and P. vanzolinii. We recognize P. mittermeieri, P. rylandsi, and P. pissinattii as junior synonyms of P. irrorata. We also discuss some taxonomic inaccuracies regarding the type localities and type material for the senior and junior names, provide synonymy lists based on extensive literature review, and provide distribution maps for the valid species we recognized.

Examination of Cranial and Pelage Color Variation between Two Subspecies of Gray Squirrel (Sciurus carolinensis)

Whether cranial measurements or pelage color is most appropriate for identifying two subspecies of gray squirrel (Sciurus c. carolinensis and S. c. fuliginosus) has been a matter of debate. The objective of this research was to examine populations of gray squirrels in Louisiana, Arkansas, and Mississippi to determine which aspects of variation are more useful for identifying subspecies. Cranial variation was assessed using 14 cranial measurements of museum specimens. Pelage color was assessed from digital pictures of the dorsal pelage. We used multivariate analysis of variance (MANOVA) to test for differences in cranial and pelage color variation. Cranial size was significantly different among populations of gray squirrels, with a north to south cline of larger to smaller individuals. However, we were not able to definitively assign populations in the zone of intergradation to a subspecies based on cranial morphology. Pelage color showed no discernable pattern of geographic variation among populations. Based on these results, we suggest that the differences observed among populations could be due to clinal variation and the legitimacy of S. carolinensis subspecies is tentative at best.

Intra-specific pelage color variation in a South American small rodent species.

Intra-specific color variation is often underestimated by researchers, and among mammals, intra-specific differences in coloration are poorly documented for most species. The main goal of this study was to apply an objective color measurement methodology to the study of a specific problem: the detection, if any, of patterns of changes in the fur color of specimens of Akodon budini in relation to biological (i.e., sex) and environmental (i.e., season) variables. We hypothesize that coat color will be more homogeneous in males than in females and that coat color will be darker in winter than in summer, the latter being orange. We measured the pelage color on five points over the dorsal surface of 26 A. budini museum specimens using a spectroradiometer and a diffuse illumination cabin. We used Principal Component Analysis to describe the association between the color variables, sex and season, and each of the observations. We then used general linear models of Analysis of Variance to examine relationships between color data, season, and sex. The results clearly confirm the hypothesis related to seasonal coat color change but do not directly confirm the hypothesis related to changes in coat color in relation to sex, and we show the complexity of the studied pattern. In conclusion, undoubtedly, the studied variables should accordingly be considered when studying the coloration of specimens for characterization, identification and discrimination of different taxonomic units based on color.

Morphological Variation in Wild Marmosets (Callithrix penicillata and C. geoffroyi) and Their Hybrids

Evolutionary theory and observation predict wider phenotypic variation in hybrids than parental species. Emergent phenotypic novelty in hybrids may in turn drive new adaptations or speciation by breaking parental phenotypic constraints. Primate hybridization is often documented through genetic evidence, but knowledge about the primate hybrid phenotype remains limited due to a small number of available studies on hybrid primate morphology. Here, we examine pelage and morphometric variation in two Brazilian marmoset species (Callithrix penicillata and C. geoffroyi) and their hybrids. Hybrids were sampled in an anthropogenic hybrid zone in the municipality of Viçosa, Minas Gerais state, Brazil. We analyzed hybrid facial and body pelage color variation, and compared 13 morphometric measures between hybrids and parental species. Five different hybrid facial morphotypes were observed, varying from intermediate to parental-like. Hybrid facial morphotypes were biased towards C. penicillata, suggesting that the pelage of this species may be dominant to that of C. geoffroyi in this context, and indicating that mate preference, and therefore gene flow/introgression, may be biased towards C. penicillata within the hybrid zone. Hybrid morphometric features were on average intermediate to parental species traits, but transgressive hybrids were also observed, suggesting that morphometric variation for the studied traits is consistent with Rieseberg’s complementary allele model. Finally, we observed a decoupling of facial patterning and size/shape in hybrids, relative to parent phenotypes, suggesting that an important factor driving phenotypic novelty within the Viçosa marmoset hybrid zone might be the loosening of evolutionary constraints on phenotypic trait integration.

Morphometric and pelage color variation of two sibling species of shrew (Mammalia: Soricomorpha)

Pelage color variants have been documented in some small mammals, but there is not any reported about coat color variation in shrews. Here, pelage color variants of the two sibling species (Sorex cylindricauda and Sorex bedfordiae) were uncovered in different sampling sites. Our data may initiate new interest to pelage color variants in small mammals. Furthermore, the classification of two striped shrews has been controversial for several decades. We conducted a detailed examination of the morphometric characters for the two sibling shrews. Significant differences between the two species morphologically confirmed the two-species classification status.

True lemurs…true species - species delimitation using multiple data sources in the brown lemur complex

BackgroundSpecies are the fundamental units in evolutionary biology. However, defining them as evolutionary independent lineages requires integration of several independent sources of information in order to develop robust hypotheses for taxonomic classification. Here, we exemplarily propose an integrative framework for species delimitation in the “brown lemur complex” (BLC) of Madagascar, which consists of seven allopatric populations of the genus Eulemur (Primates: Lemuridae), which were sampled extensively across northern, eastern and western Madagascar to collect fecal samples for DNA extraction as well as recordings of vocalizations. Our data base was extended by including museum specimens with reliable identification and locality information for skull shape and pelage color analysis.ResultsBetween-group analyses of principal components revealed significant heterogeneity in skull shape, pelage color variation and loud calls across all seven populations. Furthermore, post-hoc statistical tests between pairs of populations revealed considerable discordance among different data sets for different dyads. Despite a high degree of incomplete lineage sorting among nuclear loci, significant exclusive ancestry was found for all populations, except for E. cinereiceps, based on one mitochondrial and three nuclear genetic loci.ConclusionsUsing several independent lines of evidence, our results confirm the species status of the members of the BLC under the general lineage concept of species. More generally, the present analyses demonstrate the importance and value of integrating different kinds of data in delimiting recently evolved radiations.

Pelage color variation in pocket gophers (Rodentia: Geomyidae) in relation to sex, age and differences in habitat

Pelage coloration is a phenotypic characteristic in mammals that could be associated with an individual's survival and fitness; thus coloration gains adaptive importance. In geomyids, pelage coloration shows a relationship with the color of soils on which they live, mainly freshly dug soil of their burrows. This characteristic could be due to a camouflage adaptation to avoid predators. Pocket gophers disperse aboveground to establish a territory before they reach reproductive condition, and males disperse longer distances than females. The aim of this study was to evaluate pelage color variation in pocket gophers (Thomomys anitae) in relation to habitat differences, sex, and age, and determine its association to the color of the soil on which they live. Brightness of T. anitae's dorsal pelage coloration and that of soil samples from five different habitats in the Baja California peninsula, Mexico were measured to test four hypotheses: (1) Subadults show a wide coloration range, but extreme colors are lost in adulthood due to natural selection. (2) Males are more vulnerable to depredation than females; therefore, males’ coloration is more homogenous as a protective camouflage. (3) In open habitats pocket gophers are more exposed to being detected by predators, therefore their pelage coloration pattern is less variable than that of individuals from habitats with more vegetation cover. (4) Pelage coloration better matches soil coloration in moist conditions similar to that of freshly dug soil of their burrows. The results confirmed our predictions; however, selection does not impose an equal pressure on pelage coloration on the five habitats evaluated; other factors such as population density and predator presence need to be assessed. The strongest effects are found in the most open habitat, and there is less strong support for predictions in habitats where predator assemblage is diminished.

Genetic characterization of Okinawan black rats showing coat color polymorphisms of white spotting and melanism

We examined pelage color variation in wild populations of black rats (the Rattus rattus species complex) in the Yambaru forest area, northern Okinawa Island, Ryukyu Archipelago, Japan. Our field study revealed that 8.7% (38/438) and 0.2% (4/2500) of rats exhibited two types of coat color: white spotting and melanism, respectively. Using 34 representative animals, the phylogeography of the population was inferred using a nuclear gene marker, i.e., sequences (954 bp) of the melanocortin-1 receptor (Mc1r) gene responsible for the melanistic form in black rats. Four sequences from Okinawa were characterized as R. tanezumi, the Asian strain of black rat. Notably, neither of the phenotypic characters of white spotting or melanism was associated with the Mc1r haplotypes. Analysis of mitochondrial cytochrome b (Cytb) sequences (1140 bp) revealed that four haplotypes recovered from Okinawa clustered with the clade of R. tanezumi and differed by one or more bases from haplotypes at other localities in Japan and Asian countries. Thus, both variants may have arisen in the native rat population of Okinawa without interaction with the lineage of R. rattus, which exhibits a worldwide distribution and displays such coat color variants. The Yambaru population of black rats has thus experienced its own evolutionary history in allopatry for a substantial period of time (e.g., 10,000 years), which has preserved valuable genetic polymorphisms and will be useful for assessing the ecological consequences of genetic variation in natural populations.

Pelage Color Variation of Macaca arctoides and Its Evolutionary Implications

Stump-tailed macaques (Macaca arctoides) exhibit significant intraspecific variation in pelage color. Based on their pelage color and geographical distribution, they are classified into 2 subspecies: northern bright brown Macaca arctoides arctoides and southern black Macaca arctoides melanota. However, studies on the natural population are extremely scarce, and researchers have occasionally questioned the subspecific classification. We quantitatively examined pelage color variation of Macaca arctoides in 3 free-ranging populations in Thailand. Pelage color difference between populations is significant. The population distributed south of the Isthmus of Kra showed wide intrapopulational variation, including bright brown, dark brown, and completely black, whereas the northern populations primarily had dark brown hairs. Thus, we conclude that one cannot classify the color variants into subspecies. Further, we hypothesize that the distinctive polymorphism in southern Thailand resulted from geographical isolation caused by the Pleistocene eustatic fluctuations and subsequent recovery of land connection and subsequent gene flow.

Coat color and biochemical variation in Amazonian wild populations of Alouatta belzebul

A comparative study of 13 blood genetic systems and pelage color variation was performed in four wild populations of Alouatta belzebul. The animals from the west bank of the Tocantins River showed less color variation than those from the east bank, as well as less than those from Tocantins Island. The blood genetic markers, however, revealed an opposite pattern of variation. A previously undescribed morphological variant (completely red) was observed in one specimen of the east bank, where pelage color of the local population varied from completely black to completely red. Levels of heterozygosity and inter- and intralocus variances for the blood systems are compared with those observed in five other species of New World primates.

Subspecies of Pocket Gophers: Causal Bases for Geographic Differentiation in Thomomys bottae

Geographic races of pocket gophers, Thomomys bottae, have been defined classically by differences in cranial dimensions, augmented by pelage color variation. Here, we distinguish between size and non-size related components of cranial variation and show that overall size is predicted mainly by features reflecting the nutritional quality of the available vegetation among the habitats occupied by gophers. Body size thus has a strong non-genetic, or environmental, basis. Cranial shape, on the other hand, identifies geographically homogeneous units that are concordant with electromorphically determined segments of the species' range. Cranial shape is, therefore, considered to represent underlying genetic influences and to identify more closely historical (phyletic) evolutionary units. In our view, these evolutionary units should form the basis for the infraspecific taxonomy of pocket gophers, and other organisms as well. The number of formal subspecies of T. bottae for the region of study (the deserts of eastern California) would be reduced from 11 to three by application of this criterion.

Adaptive variation of pelage color within and between species of the subterranean mole rat (Spalax ehrenbergi) in Israel

Color notations of dorsal pelage were analyzed in 451 adult subterranean mole rats, comprising 19 populations and 4 chromosomal species (2n=52, 54, 58 and 60) of the Spalax ehrenbergi superspecies in Israel. In addition, the color notations of soil samples from the collection sites were measured. In an attempt to evaluate the degree of correlation between pelage color of mole rats and the local soil color, each color was compared both macro- and microgeographically. The macrogeographic comparisons were among populations of the 4 chromosomal species, and the microgeographic comparisons were among pairs of geographically neighboring subpopulations which occur under similar climatic conditions but differ in soil type and color. The results indicate that 1. no differences in pelage color notation exist between the sexes; 2. pelage of mole rats is generally characterized by an over-all grayish color, but its shades vary regionally and locally in accordance with varying soil color; 3. a positive correlation was found between pelage and local soil colors in the macrogeographic analysis and this correlation was verified in a microgeographic comparison; 4. specimens from populations of the northern chromosomal species (2n=52, 54) mainly inhabit terra rossa and basalt soils, respectively, with reddish brown tones, and they tend to have a more reddish shade, whereas animals from the central species (2n=58), which inhabits mainly dark soils including alluvial clays, terra rossa and brown rendzina and the souther species 2n=60, which occurs mainly in light soil types such as pale rendzina, sandy loams and loess, tend to have a more yellowish shade. The general appearance of specimens from 2n=58 was dark gray while that of 2n=60 specimens was light gray; 5. mole rats living in xeric environments (particularly 2n=60, but also 2n=54) are lighter than those which live in mesic environments (2n=52, 58). The results support the conclusion that pelage color of strictly subterranean mole rats is subject to selection pressures of overground predation of disharmonious types with their background soil color. The possibility that the pelage color variation and patterns also contributes to better thermoregulation while mole rats are above ground is discussed.