title: Diversity in Morphology and Locomotory Behavior Is Associated with Niche Expansion in the Semi-aquatic Bugs.
abstract: Acquisition of new ecological opportunities is a major driver of adaptation and species diversification [1-4]. However, how groups of organisms expand their habitat range is often unclear [3]. We study the Gerromorpha, a monophyletic group of heteropteran insects that occupy a large variety of water surface-associated niches, from small puddles to open oceans [5, 6]. Due to constraints related to fluid dynamics [7-9] and exposure to predation [5, 10], we hypothesize that selection will favor high speed of locomotion in the Gerromorpha that occupy water-air interface niches relative to the ancestral terrestrial life style. Through biomechanical assays and phylogenetic reconstruction, we show that only species that occupy water surface niches can generate high maximum speeds. Basally branching lineages with ancestral mode of locomotion, consisting of tripod gait, achieved increased speed on the water through increasing midleg length, stroke amplitude, and stroke frequency. Derived lineages evolved rowing as a novel mode of locomotion through simultaneous sculling motion almost exclusively of the midlegs. We demonstrate that this change in locomotory behavior significantly reduced the requirement for high stroke frequency and energy expenditure. Furthermore, we show how the evolution of rowing, by reducing stroke frequency, may have eliminated the constraint on body size, which may explain the evolution of larger Gerromorpha. This correlation between the diversity in locomotion behaviors and niche specialization suggests that changes in morphology and behavior may facilitate the invasion and diversification in novel environments.
authors.affiliation: Institut de Génomique Fonctionnelle de Lyon, Université de Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5242, Ecole Normale Supérieure de Lyon, 46, allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: Antonin J J
authors.initials: AJJ
authors.lastname: Crumière
authors.affiliation: Institut de Génomique Fonctionnelle de Lyon, Université de Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5242, Ecole Normale Supérieure de Lyon, 46, allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: M Emilia
authors.initials: ME
authors.lastname: Santos
authors.affiliation: Laboratoire de Biologie et de Modélisation de la Cellule, Ecole Normale Supérieure de Lyon, CNRS, Université de Lyon, 69007 Lyon, France.
authors.forename: Marie
authors.initials: M
authors.lastname: Sémon
authors.affiliation: Institut de Génomique Fonctionnelle de Lyon, Université de Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5242, Ecole Normale Supérieure de Lyon, 46, allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: David
authors.initials: D
authors.lastname: Armisén
authors.affiliation: Laboratório de Biodiversidade Entomológica, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro 21040-360, Brazil.
authors.forename: Felipe F F
authors.initials: FFF
authors.lastname: Moreira
authors.affiliation: Institut de Génomique Fonctionnelle de Lyon, Université de Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5242, Ecole Normale Supérieure de Lyon, 46, allée d'Italie, 69364 Lyon Cedex 07, France. Electronic address: abderrahman.khila@ens-lyon.fr.
authors.forename: Abderrahman
authors.initials: A
authors.lastname: Khila
mesh_terms: D000818:Animals; D044822:Biodiversity; D005075:Biological Evolution; D017753:Ecosystem; D005121:Extremities / Q000033:anatomy & histology / Q000502:physiology; D005684:Gait; D007313:Insecta / Q000033:anatomy & histology* / Q000235:genetics / Q000502:physiology*; D009043:Motor Activity; D014741:Video Recording
keywords: Gerromorpha ecology; evolution; rowing gait; tripod gait; water surface locomotion