Juan Carlos Ortiz

Comparative phylogeography of codistributed species of Chilean Liolaemus (Squamata: Tropiduridae) from the central-southern Andean range

In this study, we used a recently developed supertrees method to test for shared phylogeographical signal in partially overlapping geographical ranges of lizards of the genus Liolaemus from the Andean Range in south‐central Chile. We reconstruct mtDNA gene trees for three partially codistributed species (Liolaemus tenuis, L. lemniscatus and L. pictus), and our sampling effort is sufficient to allow statistical tests of shared signal between the combinations L. tenuis–L. pictus, and L. tenuis–L. lemniscatus. For both combinations, standardized maximum agreement subtrees scores showed statistically significant signal for shared pattern in regions of overlap, as evaluated by randomization tests (P < 0.001 and < 0.05, respectively). The matrix representation with parsimony tree obtained from the combination of the three different gene trees revealed concordant phylogeographical associations of all species, and was consistent with the geographical association of intraspecific haploclades with three Chilean bioclimatic zones. A multidimensional scaling analysis of several climate variables showed highly significant differences among these zones, which further suggests that they may have contributed to similar patterns of intraspecific divergence across all three species. In the mesomorphic zone in Central Chile, the species L. tenuis and L. lemniscatus may have codiverged in response to shared orogenic vicariant events, which likely predominated over climatic events associated with cycles of glacial advance and retreat. In the hygromorphic zone in southern Chile, however, glacial cycles likely predominated in structuring the phylogeographical histories of L. tenuis and L. pictus, although important ecological differences between these two caution against broad generalizations at this point.

The reproductive cycle of Pleurodema thaul (Anura, Leptodactylidae) in central Chile

The reproductive cycle of Pleurodema. thaul is described. Males were analyzed according to their spermatogenic stage using histological sections of their testes. For females we used the size and pigmentation of the ovarian follicles. The results show a partially continuous reproductive cycle. Males produce sperm during almost all the year. Spermatogenesis is initiated in summer (February- March), when the seminiferous tubules contain abundant undifferentiated spermatozoids, which are transformed to spermatozoa as fall advances (May-June). The first spermatozoa appeared in late May, and spermatogenesis increaces from July to September, sometimes to November. Females present bimodal vitellogenic activity. The first vitellogenic phase is initiated in late February with a progressive maturation of the oocytes, reaching the post-vitellogenic stage between June and August. The breeding period is established during these months and continues until December. In September, some females can begin the vitellogenesis, with a second stage that ends in middle December, when the oocytes that were not spawned, pass massively to the atresic stage . The fat bodies show a synchronic increase with the gametogenic activity in both sexes, that coincide with the greater reproductive activity. Fat bodies are likely to be used as energetic reserve energetic for the vitellogenic activity. Resumen. Se describe el ciclo reproductivo de P. thaul. El ciclo de los machos fue analizado segun su estado espermatogenico realizando cortes histologicos de testiculos. El ciclo de las hembras se analizo de acuerdo a la variacion anual de los tamanos y pigmentacion de los foliculos ovaricos. Los resultados muestran un ciclo reproductivo parcialmente continuo. Los machos producen espermatozoides durante casi todo el ano. La espermatogenesis se inicia en verano (febrero - marzo), donde los tubulos seminiferos se encuentran con abundantes espermatidas indiferenciadas, que se transforman en espermatozoides a medida que avanza el otono (mayo - junio). Los primeros espermatozoides son liberados a mediados de mayo. La espermatogenesis se incrementa de julio a septiembre y se puede extender hasta noviembre. Las hembras presentan actividad vitelogenica bimodal. Una primera onda se inicia a fines de febrero con una maduracion progresiva de los oocitos, alcanzando el estado post-vitelogenico entre junio y agosto. El periodo de apareamiento se establece entre estos meses y continua hasta diciembre. En septiembre, algunas hembras parecen reiniciar la vitelogenica, con una segunda onda que concluye a mediados de diciembre, cuando los oocitos que no han sido desovados, pasan masivamente al estado atresico. En ambos casos, los cuerpos grasos muestran un aumento en forma sincronica con la actividad gametogenica, coincidiendo con el periodo de mayor actividad reproductiva, por lo que se estima su utilizacion como reserva energetica para la actividad vitelogenica.

Intraspecific variation in morphology and sexual dimorphism in Liolaemus tenuis (Tropiduridae)

Liolaemus tenuis is a widely distributed arboreal lizard species in central-southern Chile. Although two subspecies, L. t. tenuis and L. t. punctatissimus, have been described based on sexual dimorphism, their characteristic have not been accurately demarcated. Therefore, both traditional and geometric morphometrics were used to study the morphological variation of L. tenuis. Four specific questions were addressed: (1) Does population morphological variation occur along a latitudinal gradient, given its wide geographic distribution in a climactic gradient? (2) Does L. tenuis present sexual dimorphism? (3) In the case of dimorphism, what is the variation along a latitudinal gradient? (4) Are these subspecies morphologically distinguishable? The study was performed in a variety of locations, including the following six bioclimatic regions of Chile: arid mediterranean, semi-arid mediterranean, sub-humid mediterranean, humid mediterranean, per-humid mediterranean, and oceanic with mediterranean influence. Male and female individuals were measured and photographed. Our results suggest sexual dimorphism for all morphological variables analyzed. Geometric data indicate that the eye orbits of the males are more extended than those of the females; this is probably related to territorial defense and/or polygynic mating system. The traditional morphometric approach revealed a difference in individuals from the arid region, whereas the geometric approach revealed a difference in individuals from the oceanic region. Differences in the limits of their distribution ranges seem be related to local factors, such as topography and climatic conditions. Finally, is not possible to recognize distinct subspecies within L. tenuis, and our research concludes that the species consists of one homogenous identity.

Evaluación del estado de conservación de los anfibios en Chile

Los anfibios son uno de los grupos con mayores problemas de conservacion en la actualidad. La declinacion que se produce en numerosas poblaciones a nivel mundial ha llevado a los herpetologos a reconocer la urgencia de abordar temas relacionados a la biologia y estado de conservacion de este grupo. En Chile existen numerosas propuestas para categorizar en estados de conservacion, tanto a flora como fauna. De alli, que el estado de conservacion de la fauna de anfibios haya sido evaluado a nivel nacional y regional. Sin embargo, la revision de estos trabajos denota el uso reiterado de analisis cualitativos que carecen de datos cuantificables, estando sujetas a observaciones de campo y a la experiencia de los investigadores. Se hace necesario aplicar un metodo mas cuantificable en la categorizacion de anfibios de manera que sea posible detectar y reconocer los factores que podrian incidir en la disminucion de las poblaciones. El presente trabajo recopila la informacion disponible para los diversos taxa de anfibios chilenos, y evalua el estado de conservacion de la fauna de anfibios que habita en Chile por medio de la adicion del indice SUMIN elaborado por Reca et al. (1994) y la propuesta por la Union Internacional para la Conservacion de la Naturaleza (IUCN 2001). Se comparan los resultados de la aplicacion de estas metodologias con las evaluaciones previas.

Age, Size, and Growth of the Chilean Frog Pleurodema thaul (Anura: Leiuperidae): Latitudinal and Altitudinal Effects

Abstract Age, longevity, size, and the effects of climate on growth and age at sexual maturity were analyzed in four populations of Pleurodema thaul (Leiuperidae) from Chile by comparing two populations at different latitudes but similar altitude (Limarí and Chaitén), and two populations at similar latitude but different altitudes (Itata and Laja). Body size was measured and age was estimated by skeletochronology applied to phalanges. In each population there was a positive relationship between body size and age, and growth decreased gradually after maturity. The longevity was estimated to be five years for females and males; age structures were similar between sexes. Pleurodema thaul showed intra-population variation in the degree of sexual dimorphism in growth patterns, age at sexual maturity, and size. Females were larger than males in the low altitude and latitude populations (Limarí and Itata), but did not differ significantly at high altitude and latitude populations (Chaitén and Laja). In all populations, sexual maturity was reached at two years of age by both sexes except that some females at high altitude and latitude did not mature until three years of age. The growth coefficient, according to von Bertalanffys model, was greater in females than in males from Chaitén, greater in males from Limarí, and was similar between sexes in Itata and Laja. Pleurodema thaul populations from high latitude and altitude showed slower growth than populations from low latitude and altitude, but individuals achieved larger body size. The mean annual growth rate was greater in populations located at high altitude or latitude for males and females. These results allow inference of the responses of amphibians to changes in the environment, which is key for generating conservation strategies.

Hantavirus en roedores de la Octava Región de Chile

La Octava Region de Chile corresponde a la segunda region con el mayor numero de casos de Sindrome Cardiopulmonar por Hantavirus (SCPH). Por tal motivo se realizo un estudio para detectar la presencia de anticuerpos contra hantavirus en roedores y su distribucion local en la Octava Region. El estudio comprendio las cuatro provincias de la region y considero once sitios de muestreo. Se capturaron siete especies de roedores, Abrothrix olivaceus fue la mas abundante seguida de Oligoryzomys longicaudatus. De los 300 roedores analizados, cinco ejemplares (1,66 %) resultaron ser positivos a hantavirus y correspondieron a tres especies de sigmodontinos: a saber, Loxodontomys micropus, que corresponde al unico registro de este tipo para la especie en Chile, Abrotrix longipilis y Oligoryzomys longicaudatus

Sexual and age differences in ecological variables of the lizard Microlophus atacamensis (Tropiduridae) from northern Chile

ABSTRACT Microlophus is a lizard genus of South-America which has many species with sexual size dimorphism. An ecologicalstudy was performed on M. atacamensis, a species inhabiting the intertidal zone of the coast of northern Chile. Thefollowing questions were addressed: (1) does M. atacamensis exhibit sexual dimorphism? (2) do individuals of differentage and sex segregate spatially? (3) do individuals of different age and sex use different type of microhabitat? and (4)do individuals of different sexes exhibit differences in thermoregulatory characteristics? The study was conducted indifferent localities from northern Chile, which include two types of rocky systems used by this species, a high and alow type. At the moment of lizard capture, type of microhabitat, height of perch, body, air and substrate temperatures,were recorded. Individuals were then measured and weighted, and separated by age class and sex. Results indicate thatthis species exhibits sexual dimorphism, males being larger. There were no intersexual differences in microhabitat usedand height of perch in the high type system, although adults and subadults were spatially segregated from juveniles. Inthe low type system adult females shared microhabitat with juveniles, a probable consequence of behaviors related tothe burying of eggs. There were no differences between sexes in thermal characteristics, and body temperature of lizardsshowed independence from external thermal conditions.Key words: Tropiduridae, Microlophus atacamensis , sexual dimorphism, thermoregulation, spatial segregation,Chile.

Is Chytridiomycosis Driving Darwin’s Frogs to Extinction?

Darwin’s frogs (Rhinoderma darwinii and R. rufum) are two species of mouth brooding frogs from Chile and Argentina that have experienced marked population declines. Rhinoderma rufum has not been found in the wild since 1980. We investigated historical and current evidence of Batrachochytrium dendrobatidis (Bd) infection in Rhinoderma spp. to determine whether chytridiomycosis is implicated in the population declines of these species. Archived and live specimens of Rhinoderma spp., sympatric amphibians and amphibians at sites where Rhinoderma sp. had recently gone extinct were examined for Bd infection using quantitative real-time PCR. Six (0.9%) of 662 archived anurans tested positive for Bd (4/289 R. darwinii; 1/266 R. rufum and 1/107 other anurans), all of which had been collected between 1970 and 1978. An overall Bd-infection prevalence of 12.5% was obtained from 797 swabs taken from 369 extant individuals of R. darwinii and 428 individuals representing 18 other species of anurans found at sites with current and recent presence of the two Rhinoderma species. In extant R. darwinii, Bd-infection prevalence (1.9%) was significantly lower than that found in other anurans (7.3%). The prevalence of infection (30%) in other amphibian species was significantly higher in sites where either Rhinoderma spp. had become extinct or was experiencing severe population declines than in sites where there had been no apparent decline (3.0%; x 2 = 106.407, P<0.001). This is the first report of widespread Bd presence in Chile and our results are consistent with Rhinoderma spp. declines being due to Bd infection, although additional field and laboratory investigations are required to investigate this further.

Intraspecific variation in a physiological thermoregulatory mechanism: the case of the lizard Liolaemus tenuis (Liolaeminae)

La variacion interespecifica en las tasas de calentamiento de Liolaemus pareciera ser un mecanismo fisiologico adaptativo que permitiria a los lagartos enfrentar restricciones termicas ambientales impuestas a la termorregulacion conductual. Esta tendencia ha sido raramente analizada a nivel intraespecifico y en este estudio exploramos si existe variacion intraespecifica en las tasas de calentamiento de Liolaemus tenuis, una especie con rango de distribucion relativamente amplio en Chile central. Probamos la hipotesis de que las tasas de calentamiento estan relacionadas con la condicion termica ambiental, a traves de comparaciones de las tasas de calentamiento de tres poblaciones (a lo largo de un rango latitudinal), que habitan en ambientes termicos diferentes. Ademas, exploramos si el factor intrinseco, sexo, modula estas tasas de calentamiento. Las tasas de calentamiento tienen una variacion intraespecifica significativa a nivel poblacional y sexual. Sin embargo, estas tasas estan solo parcialmente relacionadas a las condiciones ambientales a la que estan sometidas las poblaciones. La poblacion nortena, que habita a mas altas temperaturas, se calienta mas lento, lo que podria reducir el riesgo de sobrecalentamiento. Por otra parte, independiente de la poblacion, las hembras se calientan mas lento que los machos. El significado de esta variacion sexual no es claro, pero podria ser consecuencia de las significativas diferencias en las conductas sociales de ambos sexos. Debido a que los machos defienden un territorio con un haren, un calentamiento mas rapido les permitiria asignar mayor tiempo a las conductas asociadas a la defensa y mantencion del territorio.

Thermoregulation and activity pattern of the high-mountain lizard Phymaturus palluma (Tropiduridae) in Chile

Behavioral and physiological mechanisms of thermoregulation in ectotherms are conditioned by thermal constraints. These mechanisms may be even more restrictive when environmental conditions are unfavorable for indi- viduals, especially when sexual dimorphism segregates the sexes spatially. In order to understand behavioral and physi- ological regulation mechanisms, we investigated the thermal biology of Phymaturus palluma (Molina, 1782), a sexually size dimorphic, high-mountain lizard that inhabits extreme climatic conditions. P. palluma showed a bimodal activity pattern, a major peak in the morning (11:00-13:30h) and in the afternoon (15:30-18:00 h). The lizards were more active when substrate temperatures were between 25 and 28° C. The highest abundance was found around 27o C (between 11:00-12:30). Females showed greater activity than males in the early morning. Sub-adults and juveniles did not show differences in their activity pattern. There was a positive relationship between body temperature and air and substrate temperatures, suggesting typically thigmothermal regulation.