Adaptive genomic evolution of opsins reveals that early mammals flourished in nocturnal environments.

Background: Based on evolutionary patterns of the vertebrate eye, Walls (1942) hypothesized that early placental mammals evolved primarily in nocturnal habitats. However, not only Eutheria, but all mammals show photic characteristics (i.e.

Did trichromatic color vision and red hair color coevolve in primates?

Reddish pelage and red hair ornaments have evolved many times, independently, during primate evolution. It is generally assumed that these red-coat phenotypes, like red skin phenotypes, play a role in sociosexual signaling and, thus evolved in tandem with conspecific color vision. This study examines the phylogenetic distribution of color vision and pelage coloration across the primate order to ask: (1) did red pelage and trichromacy coevolve; or (2) did trichromacy evolve first, and then subsequently red pelage evolved as an exaptation? We collected quantitative, color-corrected photographic color data for 142 museum research skins from 92 species representing 41 genera spanning all major primate lineages.

A novel method for comparative analysis of retinal specialization traits from topographic maps.

Vertebrates possess different types of retinal specializations that vary in number, size, shape, and position in the retina. This diversity in retinal configuration has been revealed through topographic maps, which show variations in neuron density across the retina. Although topographic maps of about 300 vertebrates are available, there is no method for characterizing retinal traits quantitatively.

Anatomical specializations for nocturnality in a critically endangered parrot, the Kakapo (Strigops habroptilus).

The shift from a diurnal to nocturnal lifestyle in vertebrates is generally associated with either enhanced visual sensitivity or a decreased reliance on vision. Within birds, most studies have focused on differences in the visual system across all birds with respect to nocturnality-diurnality. The critically endangered Kakapo (Strigops habroptilus), a parrot endemic to New Zealand, is an example of a species that has evolved a nocturnal lifestyle in an otherwise diurnal lineage, but nothing is known about its' visual system.

Retinogeniculostriate pathway components scale with orbit convergence only in primates and not in other mammals.

Studies of the relative sizes of brain components in mammals suggest that areas responsible for sensory processing, including visual processing, are correlated with aspects of ecology, especially activity pattern. Some studies suggest that primate orbit convergence and binocular vision are correlated with the overall size of the brain as well as components of the visual pathway, such as the lateral geniculate nucleus. However, the question remains whether components of the visual pathway are correlated with orbit convergence and binocular visual field overlap in nonprimate mammals.

The nocturnal bottleneck and the evolution of mammalian vision.

Evidence from the early paleontological record of mammalian evolution has often been interpreted as supporting the idea that mammals were nocturnal for most of their early history. Multiple features of extant mammal sensory systems, such as evolutionary modifications to the light-regulated circadian system, photoreceptor complement, and retinal morphology, support this nocturnal hypothesis for mammalian evolution. Here, we synthesize data on eye shape and orbit orientation in mammals as these data compare to other amniotes.

Relative Wulst volume is correlated with orbit orientation and binocular visual field in birds.

In mammals, species with more frontally oriented orbits have broader binocular visual fields and relatively larger visual regions in the brain. Here, we test whether a similar pattern of correlated evolution is present in birds. Using both conventional statistics and modern comparative methods, we tested whether the relative size of the Wulst and optic tectum (TeO) were significantly correlated with orbit orientation, binocular visual field width and eye size in birds using a large, multi-species data set.

Ecomorphology of orbit orientation and the adaptive significance of binocular vision in primates and other mammals.

Primates are characterized by forward-facing, or convergent, orbits and associated binocular field overlap. Hypotheses explaining the adaptive significance of these traits often relate to ecological factors, such as arboreality, nocturnal visual predation, or saltatory locomotion in a complex nocturnal, arboreal environment. This study re-examines the ecological factors that are associated with high orbit convergence in mammals.

Malagasy primate origins: phylogenies, fossils, and biogeographic reconstructions.

The geographic origin of Malagasy primates is a rich source of debate, providing a useful context for understanding effects of differing phylogenetic interpretations upon area of origin reconstructions. This study has evaluated the biogeographic implications of competing primate phylogenies in order to reconstruct the area of origin of Malagasy strepsirhines. The robusticity of biogeographic inference is examined based on sensitivity to tree topology.

Function of the mammalian postorbital bar.

Complete postorbital bars, bony arches that encompass the lateral aspect of the eye and form part of a circular orbit, have evolved homoplastically multiple times during mammalian evolution. Numerous functional hypotheses have been advanced for postorbital bars, the most promising being that postorbital bars function to stiffen the lateral orbit in taxa that have significant angular deviation between the temporal fossa and the bony orbit. Without a stiff lateral orbit the anterior temporalis muscle and fascia potentially would pull on the postorbital ligament, deform the orbit, and cause disruption of oculomotor precision.

On the relationship between orbit orientation and binocular visual field overlap in mammals.

The orbital apertures of Primates are among the most convergent (i.e., facing in the same direction) among mammals.