Head shape evolution in Tropidurinae lizards: does locomotion constrain diet?

Abstract

Different components of complex integrated systems may be specialized for different functions, and thus the selective pressures acting on the system as a whole may be conflicting and can ultimately constrain organismal performance and evolution. The vertebrate cranial system is one of the most striking examples of a complex system with several possible functions, being associated to activities as different as locomotion, prey capture, display and defensive behaviours. Therefore, selective pressures on the cranial system as a whole are possibly complex and may be conflicting. The present study focuses on the influence of potentially conflicting selective pressures (diet vs. locomotion) on the evolution of head shape in Tropidurinae lizards. For example, the expected adaptations leading to flat heads and bodies in species living on vertical structures may conflict with the need for improved bite performance associated with the inclusion of hard or tough prey into the diet, a common phenomenon in Tropidurinae lizards. Body size and six variables describing head shape were quantified in preserved specimens of 23 species, and information on diet and substrate usage was obtained from the literature. No phylogenetic signal was observed in the morphological data at any branch length tested, suggesting adaptive evolution of head shape in Tropidurinae. This pattern was confirmed by both factor analysis and independent contrast analysis, which suggested adaptive co‐variation between the head shape and the inclusion of hard prey into the diet. In contrast to our expectations, habitat use did not constrain or drive head shape evolution in the group.

Effects of different substrates on the sprint performance of lizards

“…For example, living in relatively open areas might be selective for highspeed sprinting over long distances; conversely, inhabiting highly structured habitats might favor short bursts of locomotion (Fuller et al, 2011). A considerable body of literature has focused on relationships between morphology and ecology (Miles and Ricklefs, 1984;Pounds, 1988;Herrel et al, 2002;Herrel et al, 2008;Herrel et al, 2011;Bickel and Losos, 2002;Irschick, 2002;Goodman et al, 2007;Goodman et al, 2008;Essner, 2007;Kohlsdorf et al, 2001;Kohlsdorf et al, 2004;Kohlsdorf et al, 2008;Marshall et al, 2008;McElroy et al, 2008;Collar et al, 2010;Grizante et al, 2010;Vanhooydonck et al, 2011) or between habitat use and performance (Losos, 1990a;Losos, 1990b;Irschick and Losos, 1999;Melville and Swain, 2000;Vanhooydonck et al, 2005;Mattingly and Jayne, 2004;Autumm et al, 2006;Goodman et al, 2008;Johnson et al, 2010;Bonino et al, 2011;Fuller et al, 2011). However, there are relatively few studies about how habitat structure might influence the relationships between morphology and ecology (e.g.…”

Correlaciones Morfológicas entre la Forma de la Cabeza, Dieta y uso de Hábitat de Algunos Sceloporus de México: Un Análisis Cuantitativo

“…grammicus, S. jalapae, S. jarrovi, S. magister, S. mucronatus, S. undulatus y S. utirformis, que consumen presas duras y evasivas o intermedias, como: coleópteros, lepidópteros, formícidos y vertebrados (otras lagartijas). De igual forma se han visto estas relaciones en otros grupos, como el género Tropidurus (Kohlsdorf et al, 2008), aunque el alto de la cabeza se ha correlacionado con una fuerza de la mordida mayor en estudios realizados con Podarcis muralis y Lacerta vivípara (Herrel et al, 2001) y, Sauromalus ater (Lappin et al), ya que les permite acomodar músculos mandibulares grandes y mejorar el desempeño de la mordida (Herrel et al, 1999;2001: Lappin et al;Verwaijen et al, 2002).…”

“…Por otro lado, el nivel de evasión de las presas se encuentra relacionado con la velocidad y precisión para capturar las presas con esta estrategia de escape (Kohlsdorf et al;Measey et al, 2011). Para esto se requieren de hocicos y mandíbulas más largos, para una mayor apertura en la palanca de la mandíbula (Harmon et al, 2005).…”

“…bicanthalis, S. clarkii, S, formosus, S. gadoviae, S. grammicus, S. horridus, S. jalapae, S. jarrovi, S. magister, S. megalepidurus, S. mucronatus, S. nelsoni, S. occidentalis, S. poinsetti, S. spinosus, S. torquatus, S. undulatus, S. utiformis y S. variabilis. Para minimizar la varianza debido a las diferentes clases de edad, en el presente estudio se tomaron datos úni-camente a machos adultos. Se consideraron en la mayoría de las especies los organismos de una sola población, sin embargo, en algunas especies que presentaron densidades poblacionales bajas, se analizó más de una población y, para descartar posibles diferencias entre distintas poblaciones, se realizó una ANOVA que permitió considerar los datos como una sola muestra (Kohlsdorf et al, 2008). Finalmente, el tamaño de muestra considerado en los análisis fue variable y se evaluaron entre 5 y 15 organismos para cada especie.…”

Ecomorfologia em serpentes neotropicais: um estudo de caso com a tribo Pseudoboini

“…Conflicting selective pressures acting on morphology were also suggested by Kohlsdorf et al (2008) in a lineage of lizards. These authors studied the conflicts imposed by a diet based on "hard prey" and those imposed by locomotion in different habitat types on the head morphology of tropidurid lizards.…”