title: A novel method for comparative analysis of retinal specialization traits from topographic maps.
abstract: 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. Our goal is to present a novel method to standardize information on the position of the retinal specializations and changes in retinal ganglion cell (RGC) density across the retina from published topographic maps. We measured the position of the retinal specialization using two Cartesian coordinates and the gradient in cell density by sampling ganglion cell density values along four axes (nasal, temporal, ventral, and dorsal). Using this information, along with the peak and lowest RGC densities, we conducted discriminant function analyses (DFAs) to establish if this method is sensitive to distinguish three common types of retinal specializations (fovea, area, and visual streak). The discrimination ability of the model was higher when considering terrestrial (78%-80% correct classification) and aquatic (77%-86% correct classification) species separately than together. Our method can be used in the future to test specific hypotheses on the differences in retinal morphology between retinal specializations and the association between retinal morphology and behavioral and ecological traits using comparative methods controlling for phylogenetic effects.
authors.affiliation: Dept. of Biological Sciences, Purdue Univ., West Lafayette, IN, USA.
authors.forename: Bret A
authors.initials: BA
authors.lastname: Moore
authors.forename: Jason M
authors.initials: JM
authors.lastname: Kamilar
authors.forename: Shaun P
authors.initials: SP
authors.lastname: Collin
authors.forename: Olaf R P
authors.initials: OR
authors.lastname: Bininda-Emonds
authors.forename: Nathaniel J
authors.initials: NJ
authors.lastname: Dominy
authors.forename: Margaret I
authors.initials: MI
authors.lastname: Hall
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Heesy
authors.forename: Sönke
authors.initials: S
authors.lastname: Johnsen
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Lisney
authors.forename: Ellis R
authors.initials: ER
authors.lastname: Loew
authors.forename: Gillian
authors.initials: G
authors.lastname: Moritz
authors.forename: Saúl S
authors.initials: SS
authors.lastname: Nava
authors.forename: Eric
authors.initials: E
authors.lastname: Warrant
authors.forename: Kara E
authors.initials: KE
authors.lastname: Yopak
authors.forename: Esteban
authors.initials: E
authors.lastname: Fernández-Juricic
mesh_terms: D025042:Amacrine Cells / Q000502:physiology; D000818:Animals; D004463:Ecology; D005584:Fovea Centralis / Q000166:cytology* / Q000502:physiology*; D006801:Humans; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology; D010802:Phylogeny; D012160:Retina / Q000166:cytology* / Q000502:physiology*; D051245:Retinal Bipolar Cells / Q000502:physiology; D012165:Retinal Ganglion Cells / Q000502:physiology; D051248:Retinal Horizontal Cells / Q000502:physiology; D013045:Species Specificity; D014714:Vertebrates