Hair phenotype diversity across Indriidae lemurs

Hair (i.e., pelage/fur) is a salient feature of primate (including human) diversity and evolution-serving functions tied to thermoregulation, protection, camouflage, and signaling-but wild primate pelage biology and evolution remain relatively understudied. Specifically, assessing multiple hypotheses across distinct phylogenetic scales is essential but is rarely conducted. We examine whole body hair color and density variation across the Indriidae lemurs (Avahi, Indri, Propithecus)-a lineage that, like humans, exhibits vertical posture (i.e., their whole bodies are vertical to the sun). Our analyses consider multiple phylogenetic scales (family-level, genus-level) and hypotheses (e.g., Gloger's rule, the body cooling hypotheses). Our results show that across the Indriidae family, darker hair is typical in wetter regions (per Gloger's rule). However, within Propithecus, dark black hair is common in colder forest regions, which may implicate thermoregulation and is the first empirical evidence of Bogert's rule in mammals. Results also show pelage redness increases in populations exhibiting enhanced color vision and may thus aid conspecific communication in forested environments. Lastly, across Indriidae, we find follicle density on the crown and limbs increases in dry and open environments-rare empirical evidence supporting an early hypothesis on hominin hair evolution. We find an effect of body size on hue (red hair) and hair density but not on brightness (black hair). This study highlights how different selective pressures across distinct phylogenetic scales have likely acted on primate hair evolution. Lastly, since hair does not fossilize, the results of follicle and hair density variation across this clade offer us some potential insight into contextualizing human hair evolution.

Ecogeography of Plumage Pigmentation In Great Horned Owls

ABSTRACT Plumage pigmentation is fundamental to a bird's phenotype, with pigment deposition causing relative crypsis or conspicuousness, depending on the environmental context. Geographic variation in plumage melanin tends to be predictable, suggesting that aspects of climate cause local matching of plumage to environment via genetic adaptation. Ecogeographic rules describe this predictability: Gloger's rule predicts that populations in wetter and warmer environments will be more pigmented; Bogert's Rule predicts more pigmentation in cold environments. The Great Horned Owl (Bubo virginianus) exhibits extensive geographic variation in the degree of melanin-based pigmentation. We examined fine-scale spatial variation in owl plumage melanism along environmental gradients in southwestern North America. We tested whether variation is explained by either of two non-mutually exclusive hypotheses: (1) a history of allopatric divergence between subspecies or (2) in situ local adaptation consistent with ecogeographic rules. The allopatric divergence hypothesis predicts a bimodal distribution of plumage melanism, with a geographic cline across a zone of secondary contact, whereas the local adaptation hypothesis predicts that climate explains variation independently of geography. Using a colorimeter, we measured coloration in 101 museum specimens of breeding-season Great Horned Owls that had been obtained from variable environments and elevations. Specimens previously identified as separate subspecies were distinguishable by colorimetry. Plumage lightness, however, was continuously distributed, rather than bimodal. While accounting for males having reduced pigmentation relative to females, linear models revealed that lighter plumage was associated with low latitude, low elevation, high temperature, and low precipitation. These findings suggest that variation in Great Horned Owl plumage pigmentation is best understood as continuous ecogeographic variation, consistent with ecogeographic predictions, and currently maintained in situ along multiple environmental gradients that characterize the “sky island” topography of the southwestern USA.

First Locality Record of Melanistic Oncilla (Leopardus tigrinus) in Monteverde, Costa Rica

The persistence of the coat color polymorphism melanism has been reported for several tropical felids, but its evolutionary advantages remain an active area of research. Few publications have explored melanism in the elusive species, oncilla (Leopardus tigrinus) within the Neotropical part of their range in Costa Rica. Herein, I present the first record of a melanistic oncilla within the montane cloud forest of Monteverde, Costa Rica. Recent studies have found support for theories (e.g. Temporal Segregation Hypothesis and Gloger’s Rule) explaining the ecological advantages driving melanism in oncilla and tropical felid populations. However, it is unclear what is driving melanism in this Monteverde oncilla population due to the singular observation. Further research investigating whether melanism is occurring at a higher frequency in other individuals in the region is critical to better understanding the occurrence of melanism in local populations of this cryptic species. The montane cloud forest in Monteverde provides critical habitat to this vulnerable species within the small Neotropical part of their range. Melanistic individuals may be particularly threatened by land-use change and increasing human pressure if theories for the evolutionary advantages and ecological conditions motivating melanism are supported.

Testing the simple and complex versions of Gloger’s rule in the Variable Antshrike (Thamnophilus caerulescens, Thamnophilidae)

Gloger’s rule is a classic ecogeographical principle that, in its simplest version, predicts animals should be darker in warmer and wetter climates. In a rarely tested more complex version, it also predicts animals should be more rufous in warmer and drier climates. The Variable Antshrike (Thamnophilus caerulescens) is a widely distributed South American passerine that presents an impressive amount of plumage color variation and occupies a wide variety of climatic conditions. Moreover, genetic and vocal evidence indicate ongoing hybridization in south-central Bolivia among 3 populations with very distinct plumages. We collected color data from 232 specimens from throughout this species’ distribution to test the predictions of Gloger’s rule. We found a negative correlation between brightness and precipitation, consistent with the simple version of Gloger’s rule. In contrast, we found that birds were darker in cooler climates, contrary to the simple version of Gloger’s rule, but consistent with recent findings in other taxa. We found support for both predictions of the complex Gloger’s rule and suggest it might be driven by background matching. We conclude by concurring with a recent suggestion that the simple version of Gloger’s rule should be reformulated exclusively in terms of humidity.

Climate, crypsis and Gloger’s rule in a large family of tropical passerine birds (Furnariidae)

Gloger’s rule predicts endothermic animals should have darker colors under warm and rainy climates, but empirical studies have typically found that animals tend to be darker under cool and rainy climates. Moreover, Gloger’s rule has rarely been tested jointly with the prediction that animals occupying dark habitats should have darker colors to enhance crypsis. We aimed to disentangle the effects of climate and light environments (habitat type) as correlates of plumage brightness in a large Neotropical passerine family. We found that cooler and rainier climates are associated with darker plumage, even after accounting for habitat types, and that darker habitats are associated with darker plumage, even after accounting climate. There was an important interaction between precipitation and temperature, whereby the negative effect of temperature on brightness becomes stronger under cooler temperatures. Climate and light environments have separate but complementary effects in driving macroevolutionary patterns of plumage color variation in birds.

Ecotypic changes of alpine birds to climate change

In endotherm animals, several traits are related to climate. For example, Bergmann’s rule predicts a decrease in body size within species and across closely related species with increasing temperature, whereas Gloger’s rule states that birds and mammals should be darker in humid and warm environments compared to colder and drier areas. However, it is still not clear whether ecotypic responses to variation in the local environment can also apply to morphological and colouration changes through time in response to climate change. We present a 100-year-long time series on morphological and melanin-based colours of snowfinch (325 Montifringilla, 92 Pyrgilauda and 30 Onychostruthus) museum specimens. Here we show that the tarsus length of the species has decreased and the saturation of the melanin-based colour has increased, which was correlated with the increase of temperature and precipitations. As ecotypic variations are tightly linked to individual behavioural and physiological responses to environmental variations, differently sized and coloured individuals are expected to be differently penalized by global changes. This study opens the pertinent question about whether ecotypic responses can enhance population persistence in the context of global change.

Shallow genetic divergence and distinct phenotypic differences between two Andean hummingbirds: Speciation with gene flow?

Ecological speciation can proceed despite genetic interchange when selection counteracts the homogenizing effects of migration. We tested predictions of this divergence-with-gene-flow model in Coeligena helianthea and C. bonapartei, 2 parapatric Andean hummingbirds with marked plumage divergence. We sequenced putatively neutral markers (mitochondrial DNA [mtDNA] and nuclear ultraconserved elements [UCEs]) to examine genetic structure and gene flow, and a candidate gene (MC1R) to assess its role underlying divergence in coloration. We also tested the prediction of Gloger’s rule that darker forms occur in more humid environments, and examined morphological variation to assess adaptive mechanisms potentially promoting divergence. Genetic differentiation between species was low in both ND2 and UCEs. Coalescent estimates of migration were consistent with divergence with gene flow, but we cannot reject incomplete lineage sorting reflecting recent speciation as an explanation for patterns of genetic variation. MC1R variation was unrelated to phenotypic differences. Species did not differ in macroclimatic niches but were distinct in morphology. Although we reject adaptation to variation in macroclimatic conditions as a cause of divergence, speciation may have occurred in the face of gene flow driven by other ecological pressures or by sexual selection. Marked phenotypic divergence with no neutral genetic differentiation is remarkable for Neotropical birds, and makes C. helianthea and C. bonapartei an appropriate system in which to search for the genetic basis of species differences employing genomics.