A REVIEW OF LIZARDS OF THE LIOLAEMUS WIEGMANNII GROUP (SQUAMATA, IGUANIA, TROPIDURIDAE), AND A HISTORY OF MORPHOLOGICAL CHANGE IN THE SAND-DWELLING SPECIES

Abstract

The wiegmannii group of Liolaemus includes L. lutzae, L. occipitalis, L. multima- culatus, L. rabinoi, L. riojanus, L. salinicola, L. scapularis, and L. wiegmannii; the status of L. cranwelli is uncertain, but is here considered a synonym of L. wiegmannii. The morphological characteristics of the wiegmannii group as a whole are described, and a taxonomic review, together with descriptions, distributions, and natural histories are presented for each species. This study then investigates the sequence of morphological changes that accompanied the evolution of the wieg- mannii group. Seven of these, referred to here as the "sand-lizards" are confined to a substrate of loose, aeolean sand with extensive open dunes or sand flats. All of these species are members of a more inclusive clade, the boulengeri group. A phylogenetic analysis of the boulengeri group, based on 39 morphological and one behavioral character, produced a single most parsimonious tree that included the wiegmannii group as a fully resolved clade. This clade has a pectinate topology, with the following relationships: wiegmannii (lutzae (salinicola (scapularis (occipitalis (multimaculatus (riojanus + rabinoi)))))), with sand lizards represented by the last seven species, i.e., L. wiegmannii is the sister taxon to the sand lizards. Many of the morphological and behavioral transformations that occur at the origin of, and sub- sequently within the sand lizards, facilitate life on and under the surface of loose, wind-blown sand. Rapid diving and burial under the sand may be facilitated by a wedge-shaped snout with numerous small scales on the dorsal and lateral surfaces of the head, a sharp keel formed by the scales of the lower jaw, and a serrate margin on the shoulders and edges of the tail. Breathing under sand by vertical movement of the sternum may be facilitated by a wider sternum, with the fontanel reduced or absent, and a short median interclavicle process. A small ear opening, projecting ciliary scales, and a partly countersunk lower jaw should help to exclude sand from body openings. Fringes of projecting scales on the toes, and smooth, non-imbricate scales on the palms and soles should facilitate surface locomotion on sand. Reduction in dorsal sexual dicromatism, and close substrate color and pattern matching render them cryptic on the sand. Burial as a means of nocturnal retreat occurs in the sand lizards and most other species of the boulengeri group, but rapid diurnal burial as a means of escape occurs only in L. wiegmannii and the sand lizards. RESUMEN: El grupo wiegmannii de Liolaemus incluye L. lutzae, L. occipitalis, L. multimacu- latus, L. rabinoi, L. riojanus, L. salinicola, L. scapularis, y L. wiegmannii; la posicion taxonomica de L. cranwelli es incierta pero es considerada aqui un sin6nimo de L. wiegmannii. Se describen los caracteres morfologicos del grupo wiegmannii y se presenta para cada una revision taxonomica, junto con descripciones, distribuciones e historias naturales. Luego se investiga la secuencia de cambios morfolo6gicos que acompafiaron la evolucion del grupo wiegmannii. Siete de estas especies, referidas aqul como los "lagartos arenfcolas," estdn confinados a un sustrato de arena e6olica suelta, con medanos abiertos extensos o llanos de arena. Todas estas especies son miembros de un clado mas inclusivo, el grupo boulengeri. Un analisis filogenetico del grupo boulengeri, basado en 39 caracteres morfolo6gicos y uno de comportamiento, dio un unico arbol mas parsimonioso que incluye el grupo wiegmannii como un clado completamente resuelto. Este clado tiene una topologia pec- tinada, con las siguientes relaciones: wiegmannii (lutzae (salinicola (scapularis (occipitalis (multi- maculatus (riojanus + rabinoi)))))), con los lagartos arenicolas representados por las ultimas siete especies, siendo L. wiegmannii el tax6n hermano de estos. Muchas de las transformaciones morfolo6gicas y de comportamiento que ocurren en el origen y