Espèces de <i>Liolaemus</i> sans pores précloacaux chez les mâles, le long des Andes méridionales (Reptilia: Squamata: Iguania: Tropiduridae)

Abstract

Our last findings in Cordilleran mountains of the Malargue Deparment, Southern Mendoza Province, Argentina, led us to evaluate the lack of secretory precloacal pores in <i>Liolaemus</i> males, considering it as a noticeable evolutionary trend of peculiar species groups, rather than a somewhat occasional morpho-physiological character (absence of pheromones?) occurring at random in different taxa of the same phyletic line, as in its usual interpretation. In fact, our recent discovery of a new species of Liolaemine iguanid whitout precloacal pores (<i>Liolaemus thermarum</i> Videla et Cei, 1996) in the basaltic landscape (2400 m) surrounding the Peteroa Volcano (4135 m) gave us the chance of a wide screening of all its nearly related forms also missing this important secondary sex character (Figs 1-4). Only four species, belonging to a major “chiliensis” group, very similar to <i>L. thermarun</i> for their somatic features, presented a total lack of precloacal pores, in the Andean and sub-Andean environments along the Chilean-Argentine frontier, between 35° and 40° South Latitude (Fig. 2). Striking biogeographical and ecological remarks point out the actual scattering of all these taxa mainly in the distribution area of the preglacial coniferous woods, such as <i>Araucaria araucana</i> formations. That is the case of <i>Liolaemus neuquensis</i> in the neighbourhood of the Copahue Volcano (1800 m) and of <i>L. coeruleus</i> from the basaltic relief of Primeros Pinos and Lonco Luan (1800) also in Neuquen Province, Argentina. <i>Liolaemus thermarum</i> and <i>L. cristiani</i> (Cerro El Peine, 2248 m, Maule, Chile) live now in biotopes wanting relics of the ancestral <i>Araucaria</i> woods, but their precursors can to have been likely in touch with this spread ecosystem during the long period of their quaternary isolation (see Fig. 5). According to our screening, another austral species group of <i>Liolaemus</i> showing the above mentioned peculiar lack of precloacal pores in males could be also put in evidence from 46° to 50° S.Lat. (Figs 2, 4). They are the lineomaculatus and “silvanae” groups (Fig. 2), spreading the first with only a species from the Atlantic coast to the Cordillerans, living the second in a very specialized periglacial habitat of Santa Cruz Province, Argentina, with the endemic <i>Liolaemus silvanae</i> from the flat summit (1400 m) of the isolated Meseta de la Laguna del Sello, near the great Patagonian ice field, and with the very localized <i>L. periglacialis</i> in some tabulated, broken sub-Andean basaltic embossments, also at the latitude of the continental inland ice still remnant alongside the Pacific borders. Conclusions of the present research were that the lack of precloacal pores in males was only proved in the here reported <i>Liolaemus</i> groups living under hard, cold environmental conditions, from the Southern Andrean valleys at about 35° - 40 °S Lat. to the most extreme periglacial habitats. Any speculation concerning the adaptive value of such a likely derived character lies yet opaque, and a further more detailed research is needed. We point out that no other species of <i>Liolaemus</i> exhibit apparently such a morphological condition. Any former bibliographic report about other taxa from other groups does not provide a suitable information, being often supported by some misleading understanding of the original species descriptions.

Recientes hallazgos en el Sur de Mendoza, Dep. Malargue, Argentina, llevaron al descubrimiento y estudio de una nueva especie de <i>Liolaemus</i>, cerca del Volcán Peteroa (Baños del Azufre, 2400 m). Este taxon (<i>Liolaemus thermarum</i>) no posee poros precloacales en los machos y junto a otras tres especies que presentan el mismo carácter constituye, según nuestras observaciones, un grupo de formas cistransandinas bien definido y distribuido en ambientes rocosos generalmente basálticos, frecuentemente en áreas todavía ocupadas por formaciones de <i>Araucaria araucana</i>, reliquias de los grandes bosques de coniferas preglaciales. Las mencionadas especies son <i>Liolaemus cristiani</i> de Cerro el Peine, Maulé, Chile, <i>L. neuquensis</i> del Volcán Copahue, Neuquén, y <i>L. coeruleus</i> de los relieves subandinos de Primeros Pinos y Lonco Luán, también en Neuquén, Argentina. Pues todos, con <i>Liolaemus thermarum</i>, entre los 35° y 40° S Lat. Además de este conjunto de especies hay otros dos grupos de <i>Liolaemus</i> carentes de poros precloacales, los grupos «lineomaculatus» y «silvanae», este último con dos taxa, <i>L. silvanae</i> y <i>L. periglacialis</i>, fuertemente especializados, aún más que <i>L. lineomaculatus</i>, para subsistir en habitats patagónicos muy fríos. Estas formas de Santa Cruz se hallan entre 45° y 50° S Lat. y seguramente son de evolución post-glacial. No resulta haber otras especies del género sin poros precloacales, cuyas secreciones son verosímilmente feromónicas : anteriores citaciones de su falta en otros taxa corresponden a datos erróneos. Se hace un breve análisis de las condiciones ambientales y biocenóticas de estos tropiduridos, y de los factores geocronológicos y paleo- climáticos que pueden haber actuado sobre sus procesos evolutivos y su aislamiento.