Native Fauna of Tardigrades from Two Natural Areas of the Argentina Republic.

Understanding and preserving biodiversity in natural habitats is crucial due to their rapid degradation and destruction. The meiofauna of natural areas is less well known than the macroscopic life. Tardigrades are common in limno-terrestrial meiofauna and can indicate environmental conditions. In this study, we expand our understanding of the taxonomy and ecology of tardigrade communities in two natural reserves in Argentina by examining the environmental factors that can affect them and the species that could be used as indicators. In 2018, sampling occurred in the Parque Luro Provincial Reserve (province of La Pampa) and the Poligono A Municipal Ecological Reserve (province of Salta). Samples were taken from epiphytic communities that grow on the bark of trees. Various environmental and microhabitat factors were taken into account. In the province of La Pampa, there were 1326 specimens of five species, and in the province of Salta, there were 212 specimens of nine species. The tardigrade communities in Salta exhibited statistically higher diversity than those in La Pampa. Temperature and moisture affected the tardigrade community of Parque Luro Provincial Reserve, while the microhabitat thickness affected those of Poligono A Municipal Ecological Reserve. The species turnover shaped the community of Salta, while nesting shaped the community of La Pampa.

Postmortem Interval Estimation and Validation Through a Comparative Study of South American Flies Reared in the Field Versus Laboratory Conditions.

Studies under constant temperatures are the most common to estimate the Postmortem Interval (PMI). It is imperative that forensic sciences have data from studies carried out in the field. Therefore, this work aims to: (1) evaluate the parameters (weight, length, development time) associated with the life cycles of Lucilia ochricornis (Wiedemann) (Diptera: Calliphoridae) and Lucilia purpurascens (Walker) under experimental conditions in the field considering fluctuating temperatures, and (2) compare these results with those known and published by the same authors for cultures realized in the laboratory under constant temperatures; which will permit us to contrast the most widely used existing methodologies for forensic application in estimating the minimum postmortem interval (PMImin). For each season of the year, cultures of both species were made in the field, collecting information on temperature, humidity, and photoperiod to perform laboratory cultures, later comparing: development time, length, weight, and Accumulated Degree-Hours (ADH) in both types of cultures. Methods for estimating the PMI were obtained and validated with the information of the cultures grown in the field. The two types of cultures showed differences between each other for both species. The forensic use methods to estimate PMI were enhanced and their precision increased when maximum larval length data were used, and it was also concluded that feeding larval stages are the most accurate to be used in making estimates because the larva is growing. The estimation of the PMI through the use of necrophagous flies development remains reliable for obtaining the PMImin.

Estimation of the Postmortem Interval Through the Use of Development Time of Two South American Species of Forensic Importance of the Genus Lucilia (Diptera: Calliphoridae).

Obtaining the specific development time of each species of forensic interest is crucial for the estimation of an accurate and reliable Minimum Postmortem Interval (PMImin). In Argentina, Lucilia ochricornis (Wiedemann) and Lucilia purpurascens (Walker) (Diptera: Calliphoridae) were masked under the name Lucilia cluvia (Walker) for a long time still in forensic expertise. For this reason, the objective of this work is to deepen the study of the development time of these species and utilize this relevant information in the generation of different associated methods that can be used in forensics to estimate the PMI. Immature stages of L. ochricornis and L. purpurascens were reared in a brood chamber according to the following temperature treatments: 13.4, 15.1, 22.3, and 23.6°C. The development time of each stage/state of these flies was recorded as well as the resulting accumulated degree-hours (ADH), to build isomorphen diagrams and thermal summation models for each species. The development time and ADH were different between both species and their development stages. On the other hand, the methods provided for estimating PMImin provide the forensic entomologist more tools to reach accurate and reliable estimates.

Contributions to the Estimation of the Postmortem Interval Through the Length and Body Weight of Two Indigenous Species of South America: Lucilia ochricornis (Diptera: Calliphoridae) and Lucilia purpurascens.

The early arrival and colonization of species belonging to the family Calliphoridae (Insecta: Diptera) on a corpse represent one of the most reliable means of estimating minimum postmortem interval (PMImin). However, information on the development and life cycles of some Argentine species in this family is not complete. The objective of this work was to contribute new information regarding the larval body size of neotropical species that allow, through the construction of forensic methods, the estimation of a more precise and specific PMImin. This work was conducted on laboratory cultures of larvae of Lucilia ochricornis (Wiedemann) and Lucilia purpurascens (Walker) using as average temperatures: 13.4, 15.1, 22.6, and 23.3°C, which represent the four seasons of the year for the province of Salta. With this information, we constructed isomegalen diagrams and growth models for the obtained variables of larval length and body weight. The mean values of length and body weight differ between both species, indicating that L. purpurascens exceeded L. ochricornis in both variables. In contrast, within each species the mean length and weight remained unchanged between culture temperatures for the three larval instars. Isomegalen diagrams can be used for the entire range of temperatures worked in the laboratory, but the body size entered is approximate. The growth models allow the use of point data but are specific for each culture temperature used.

Eficiencia de trampas de caída y suficiencia taxonómica en comunidades de arañas (Araneae) epigeas en tres ecorregiones del noroeste argentino / Efficiency of pitfall traps and taxonomic sufficiency for epigeal spider communities (Araneae) in three ecoregions of northwestern Argentina

Resumen El incremento de la degradación de los hábitats naturales ha fortalecido la necesidad de conocer y evaluar los patrones de biodiversidad; siendo los inventarios biológicos y la suficiencia taxonómica herramientas que permiten describir y monitorear la diversidad en cortos períodos de tiempo. El estudio de la araneofauna en el norte Argentino es escaso en particular en ecorregiones donde se considera prioritario conservar sus ambientes. Las arañas son utilizadas como taxón indicador para comparar patrones de biodiversidad, donde el estudio de las familias y de los gremios puede potencialmente servir como sustitutos ecológicos de las especies dando indicación del uso del hábitat y de las estrategias de forrajeo. En este estudio, analizamos la diversidad alfa y beta de las comunidades de arañas epigeas en diferentes ecorregiones de la provincia de Salta (Chaco Serrano, Monte de Sierras y Bolsones, y Puna) utilizando trampas de caída y muestreos en las cuatro estaciones del año; y testeamos si el nivel taxonómico familia, en el caso de las arañas, puede actuar como potencial sustituto del nivel especie en las evaluaciones rápidas de biodiversidad. Para ello, en cada ecorregión seleccionamos tres sitios ampliamente separados que fueron muestreados durante el otoño, invierno, primavera y verano del 2005-2007. En cada sitio se colocaron 10 trampas de caída separadas por 10 m a lo largo de una transecta lineal y con una actividad de 7 días por estación. Se recolectaron 886 arañas de 100 especies/morfoespecies correspondientes a 19 familias. La ecorregión Chaco (S = 56, N = 495) reportó la mayor riqueza de especies y abundancia comparada con el Monte (S = 44, N = 262) y la Puna (S = 23, N = 129). La completitud del inventario obtenido para cada ecorregión fue completa, superando el 70 %. La diversidad alfa y beta evidenciaron que las comunidades ecorregionales de arañas fueron diferentes. Las estaciones más frías (otoño e invierno) demostraron ser claves a la hora de evaluar la diversidad de arañas en las ecorregiones, aportando a la diversidad regional conjuntamente con la diversidad de las estaciones cálidas (primavera y verano). Además, el nivel taxonómico de familia evidenció reflejar, de igual manera que el nivel especie, los cambios en la diversidad alfa y beta. El uso de trampas de caída en todas las estaciones del año y el reconocimiento de las familias de arañas para la fauna epigea son de gran utilidad para realizar futuras evaluaciones rápidas de biodiversidad en el área en estudio; permitiendo así incorporar este grupo taxonómico en los estudios de monitoreo de biodiversidad que se lleven a cabo en estas ecorregiones.

Abstract The increased degradation of natural habitats has strengthened the need to know and assess biodiversity patterns. Particularly, the study of the spider fauna in the North of Argentina is scarce in ecoregions with priority interests of conservation. Generally, spiders are used as indicators to compare biodiversity patterns, and here we tested whether the spider family-level can act as a substitute of the species-level in biodiversity rapid assessments. For this, we analyzed the alpha and beta diversity of the epigeal spider communities in three separate sites of three ecoregions of Salta province (Chaco Serrano, Monte de Sierras and Bolsones, and Puna), during the fall, winter, spring and summer of 2005-2007. In each site, 10 pitfall traps, located along a linear transect and 10 meters apart, were placed for seven days per season of continuous activity. A total of 886 spiders were collected from 100 species/morphospecies of 19 families. The completeness of the inventory obtained for each ecoregion surpassed 70 %. The Chaco ecoregion (S = 56, N = 495) reported the highest species richness and abundance compared to Monte (S = 44, N = 262) and Puna (S = 23, N = 129). Alpha and beta diversity showed that ecoregional spider communities were different, sharing few species (0.7 %). The Chaco reported a high dissimilarity of its assemblage with respect to the other ecoregions. The colder seasons (autumn and winter) are important in assessing the diversity of spiders, contributing to regional diversity in conjunction with the diversity of warm seasons (spring and summer). Four guilds were reported (ground hunters, specialists, other hunters and ambush hunters), but the latter was absent in Monte, and the specialists dominated Chaco. Zodariidae was dominant in Chaco Serrano, where Leprolochus birabeni is an indicator of native environments. On the other hand, Lycosidae, Philodromidae, Anyphaenidae and Oonopidae were important for Monte and Puna. Year-round pitfall traps and identification of epigeal spider families are useful for biodiversity rapid assessments in this area. Like the species-level, the taxonomic family-level evidenced changes in alpha and beta diversity. This allows the inclusion of this taxonomic group for future biodiversity monitoring. Rev. Biol. Trop. 66(1): 204-217. Epub 2018 March 01.

Changes of arthropod diversity across an altitudinal ecoregional zonation in Northwestern Argentina.

This study examined arthropod community patterns over an altitudinal ecoregional zonation that extended through three ecoregions (Yungas, Monte de Sierras y Bolsones, and Puna) and two ecotones (Yungas-Monte and Prepuna) of Northwestern Argentina (altitudinal range of 2,500 m), and evaluated the abiotic and biotic factors and the geographical distance that could influence them. Pitfall trap and suction samples were taken seasonally in 15 sampling sites (1,500-4,000 m a.s.l) during one year. In addition to climatic variables, several soil and vegetation variables were measured in the field. Values obtained for species richness between ecoregions and ecotones and by sampling sites were compared statistically and by interpolation-extrapolation analysis based on individuals at the same sample coverage level. Effects of predictor variables and the similarity of arthropods were shown using non-metric multidimensional scaling, and the resulting groups were evaluated using a multi-response permutation procedure. Polynomial regression was used to evaluate the relationship between altitude with total species richness and those of hyperdiverse/abundant higher taxa and the latter taxa with each predictor variable. The species richness pattern displayed a decrease in species diversity as the elevation increased at the bottom wet part (Yungas) of our altitudinal zonation until the Monte, and a unimodal pattern of diversity in the top dry part (Monte, Puna). Each ecoregion and ecotonal zone evidenced a particular species richness and assemblage of arthropods, but the latter ones displayed a high percentage of species shared with the adjacent ecoregions. The arthropod elevational pattern and the changes of the assemblages were explained by the environmental gradient (especially the climate) in addition to a geographic gradient (the distance of decay of similarity), demonstrating that the species turnover is important to explain the beta diversity along the elevational gradient. This suggests that patterns of diversity and distribution of arthropods are regulated by the dissimilarity of ecoregional environments that establish a wide range of geographic and environmental barriers, coupled with a limitation of species dispersal. Therefore, the arthropods of higher taxa respond differently to the altitudinal ecoregional zonation.

Efectos del disturbio antrópico sobre las poblaciones de Leprolochus birabeni (Araneae, Zodariidae) en el Chaco Seco del noroeste de Argentina / Effects of anthropogenic disturbance on the populations of Leprolochus birabeni (Araneae, Zodariidae) in the Chaco Seco northwestern Argentina

Se conoce poco sobre la biología y la ecología de la especie mirmecófaga Leprolochus birabeni Mello-Leitão, 1942 (Zodariidae), el único representante de este género en la Argentina. Esta especie es típica de ambientes áridos del norte del país, y su estudio en el Chaco Seco es relevante, por ser una ecorregión altamente perturbada con uno de los pocos bosques subtropicales secos del mundo. El objetivo de este trabajo es estudiar la demografía de la especie teniendo en cuenta su variación estacional en ambientes nativos, y sí la ganadería y la agricultura, dos de las actividades antropogénicas más comunes de la ecorregión Chaco Seco en la provincia de Salta (Argentina) producen cambios en sus poblaciones. Se consideraron tres tipos de ambientes: nativo (NA); afectados por el ganado vacuno y caprino (NP); y afectados por la agricultura (NC). Este último correspondió a parches de vegetación nativa en medio de una matriz agrícola. En cada tipo de ambiente se consideraron tres sitios de muestreo donde se realizaron muestreos estacionales utilizando trampas de caída durante el otoño, invierno y primavera de 2006 y el verano de 2007. Se recolectaron 549 ejemplares de L. birabeni , siendo la mayoría juveniles con el 64,12% de la abundancia total, seguidos por machos (26,41%) y hembras (9,47%). A nivel de paisaje, la primavera presentó el mayor número de individuos, llegando al 44,99% de la abundancia total; mientras que el otoño mostró el porcentaje más bajo (7,83%). El incremento de los juveniles durante el invierno podría indicar una adaptación de los estadios de desarrollo a las condiciones ambientales. El mismo patrón se observó en ambientes NA y NC, pero no en los NP. Estos últimos mostraron una disminución en la abundancia de adultos a lo largo del año; mientras que las poblaciones NC mostraron un incremento en la abundancia de los machos durante la primavera, con una fuerte reducción de las hembras y los juveniles durante todo el año. [...]

Little is known about the biology and ecology of the myrmecophagic species Leprolochus birabeni Mello-Leitão, 1942 (Zodariidae), the only representative of this genus in Argentina. This species is typical of arid environments of the north of Argentina, and their study in the Chaco Seco is relevant, because is a highly disturbed ecoregion and one of the few with dry subtropical forests in the World. The aim of this work is to study the demography of this species, considering its seasonal variation in native environments, and if the livestock grazing and the agriculture, two of the most common anthropogenic activities of the Chaco Seco ecoregion, produce changes in their populations in the province of Salta (Argentina). We consider three type of environments: native (NA); affected by cattle and goats (NP); and affected by agriculture (NC). The latter corresponds to patches of native vegetation in an agricultural matrix. Three sampling sites were selected on each type of environment, where seasonal samplings using pitfall traps were performed during autumn, winter and spring (2006) and summer (2007). We collected 549 spiders of L. birabeni , with the juveniles reaching until the 64.12% of total abundance, followed by males (26.41%) and females (9.47%). At landscape level, spring season showed the highest number of individuals, reaching 44.99% of the total abundance, while autumn reported the lowest percentage (7.83%). The juveniles increase observed during the winter would indicate an adaptation to environmental conditions. The same pattern was observed in NA and NC environments, but not in NP ones. The later environments showed a decrease in the adult abundances across the seasons, while the NC populations showed an increase of male abundances during spring season with a sharp reduction of females and juveniles throughout the year. [...]

Evaluación de la diversidad en comunidades de tardígrados (Ecdysozoa: Tardigrada) en hábitats urbano y rural de la ciudad de Salta (Argentina) / Diversity assessment in tardigrades communities (Ecdysozoa, Tardigrada) in urban and rural habitats of the city of Salta (Argentina)

Este trabajo se realizó bajo la hipótesis de que existe una pérdida creciente de diversidad en las comunidades de tardígrados, desde las áreas rurales hacia las urbanas, incrementando la homogenización de sus comunidades producto de la urbanización. Para la ciudad de Salta, se tomaron muestras en áreas con tránsito vehicular alto y muestras en áreas rurales circundantes. Se identificaron en total ocho especies/morfoespecies. El inventario tuvo una completitud mayor al 94%. La comunidad rural fue más diversa y estructuralmente más uniforme que la comunidad urbana. Macrobiotus hufelandi Schultze, 1834 resultó especie indicadora y Milnesium sp. como detectora para el hábitat urbano, mientras que Paramacrobiotus areolatus Murray, 1907 resultó indicadora para el hábitat rural.

This work was carried out under the hypothesis that there is a growing loss of diversity in communities of tardigrades, from rural to urban areas, increasing the homogenization of its communities due to the urbanization. Samples were taken from the city of Salta in areas with high vehicular traffic and samples in surrounding rural areas. We identified a total of eight species/morphospecies. The inventory completeness was greater than 94%. The rural community was more diverse and structurally more uniform compared with the urban one, shown that both communities were different. Macrobiotus hufelandi Schultze, 1834 results as an indicator species, and Milnesium sp. as detector species from urban habitat; meanwhile Paramacrobiotus areolatus Murray 1907 was an indicator species for rural areas.

Efectos del disturbio antrópico sobre las poblaciones de Leprolochus birabeni (Araneae, Zodariidae) en el Chaco Seco del noroeste de Argentina

RESUMEN Se conoce poco sobre la biología y la ecología de la especie mirmecófaga Leprolochus birabeni Mello-Leitão, 1942 (Zodariidae), el único representante de este género en la Argentina. Esta especie es típica de ambientes áridos del norte del país, y su estudio en el Chaco Seco es relevante, por ser una ecorregión altamente perturbada con uno de los pocos bosques subtropicales secos del mundo. El objetivo de este trabajo es estudiar la demografía de la especie teniendo en cuenta su variación estacional en ambientes nativos, y sí la ganadería y la agricultura, dos de las actividades antropogénicas más comunes de la ecorregión Chaco Seco en la provincia de Salta (Argentina) producen cambios en sus poblaciones. Se consideraron tres tipos de ambientes: nativo (NA); afectados por el ganado vacuno y caprino (NP); y afectados por la agricultura (NC). Este último correspondió a parches de vegetación nativa en medio de una matriz agrícola. En cada tipo de ambiente se consideraron tres sitios de muestreo donde se realizaron muestreos estacionales utilizando trampas de caída durante el otoño, invierno y primavera de 2006 y el verano de 2007. Se recolectaron 549 ejemplares de L. birabeni , siendo la mayoría juveniles con el 64,12% de la abundancia total, seguidos por machos (26,41%) y hembras (9,47%). A nivel de paisaje, la primavera presentó el mayor número de individuos, llegando al 44,99% de la abundancia total; mientras que el otoño mostró el porcentaje más bajo (7,83%). El incremento de los juveniles durante el invierno podría indicar una adaptación de los estadios de desarrollo a las condiciones ambientales. El mismo patrón se observó en ambientes NA y NC, pero no en los NP. Estos últimos mostraron una disminución en la abundancia de adultos a lo largo del año; mientras que las poblaciones NC mostraron un incremento en la abundancia de los machos durante la primavera, con una fuerte reducción de las hembras y los juveniles durante todo el año. La abundancia de L. birabeni en ambientes NA fue mayor (41,06% de la abundancia total), siendo los valores mínimos registrados en NC (24,67%). Las dos actividades antropogénicas más comunes que afectan al Chaco Seco de la provincia de Salta modifican tanto los cambios estacionales como la representación de las diferentes etapas de desarrollo y sexos de las poblaciones nativas de L. birabeni , siendo la modificación de los ambientes nativos por la agricultura, el factor más perjudicial.

Abstract Little is known about the biology and ecology of the myrmecophagic species Leprolochus birabeni Mello-Leitão, 1942 (Zodariidae), the only representative of this genus in Argentina. This species is typical of arid environments of the north of Argentina, and their study in the Chaco Seco is relevant, because is a highly disturbed ecoregion and one of the few with dry subtropical forests in the World. The aim of this work is to study the demography of this species, considering its seasonal variation in native environments, and if the livestock grazing and the agriculture, two of the most common anthropogenic activities of the Chaco Seco ecoregion, produce changes in their populations in the province of Salta (Argentina). We consider three type of environments: native (NA); affected by cattle and goats (NP); and affected by agriculture (NC). The latter corresponds to patches of native vegetation in an agricultural matrix. Three sampling sites were selected on each type of environment, where seasonal samplings using pitfall traps were performed during autumn, winter and spring (2006) and summer (2007). We collected 549 spiders of L. birabeni , with the juveniles reaching until the 64.12% of total abundance, followed by males (26.41%) and females (9.47%). At landscape level, spring season showed the highest number of individuals, reaching 44.99% of the total abundance, while autumn reported the lowest percentage (7.83%). The juveniles increase observed during the winter would indicate an adaptation to environmental conditions. The same pattern was observed in NA and NC environments, but not in NP ones. The later environments showed a decrease in the adult abundances across the seasons, while the NC populations showed an increase of male abundances during spring season with a sharp reduction of females and juveniles throughout the year. The abundance of L. birabeni in NA environments was higher (41.06% of total abundance) and the least value was reported in NC environments (24.67%). The two most common anthropogenic activities affecting the Chaco Seco of the province of Salta modify both the seasonal changes as the representation of the different developmental stages and sexes of the native populations of L. birabeni , being the most damaging factor the modification of the native environments by the agriculture.

Evaluación de la diversidad en comunidades de tardígrados (Ecdysozoa: Tardigrada) en hábitats urbano y rural de la ciudad de Salta (Argentina)

RESÚMEN Este trabajo se realizó bajo la hipótesis de que existe una pérdida creciente de diversidad en las comunidades de tardígrados, desde las áreas rurales hacia las urbanas, incrementando la homogenización de sus comunidades producto de la urbanización. Para la ciudad de Salta, se tomaron muestras en áreas con tránsito vehicular alto y muestras en áreas rurales circundantes. Se identificaron en total ocho especies/morfoespecies. El inventario tuvo una completitud mayor al 94%. La comunidad rural fue más diversa y estructuralmente más uniforme que la comunidad urbana. Macrobiotus hufelandi Schultze, 1834 resultó especie indicadora y Milnesium sp. como detectora para el hábitat urbano, mientras que Paramacrobiotus areolatus Murray, 1907 resultó indicadora para el hábitat rural.

ABSTRACT This work was carried out under the hypothesis that there is a growing loss of diversity in communities of tardigrades, from rural to urban areas, increasing the homogenization of its communities due to the urbanization. Samples were taken from the city of Salta in areas with high vehicular traffic and samples in surrounding rural areas. We identified a total of eight species/morphospecies. The inventory completeness was greater than 94%. The rural community was more diverse and structurally more uniform compared with the urban one, shown that both communities were different. Macrobiotus hufelandi Schultze, 1834 results as an indicator species, and Milnesium sp. as detector species from urban habitat; meanwhile Paramacrobiotus areolatus Murray 1907 was an indicator species for rural areas.

Evaluación de la diversidad en comunidades de tardígrados (Ecdysozoa: Tardigrada) en hábitats urbano y rural de la ciudad de Salta (Argentina) / Diversity assessment in tardigrades communities (Ecdysozoa, Tardigrada) in urban and rural habitats of the city of Salta (Argentina)

Este trabajo se realizó bajo la hipótesis de que existe una pérdida creciente de diversidad en las comunidades de tardígrados, desde las áreas rurales hacia las urbanas, incrementando la homogenización de sus comunidades producto de la urbanización. Para la ciudad de Salta, se tomaron muestras en áreas con tránsito vehicular alto y muestras en áreas rurales circundantes. Se identificaron en total ocho especies/morfoespecies. El inventario tuvo una completitud mayor al 94%. La comunidad rural fue más diversa y estructuralmente más uniforme que la comunidad urbana. Macrobiotus hufelandi Schultze, 1834 resultó especie indicadora y Milnesium sp. como detectora para el hábitat urbano, mientras que Paramacrobiotus areolatus Murray, 1907 resultó indicadora para el hábitat rural.(AU)

This work was carried out under the hypothesis that there is a growing loss of diversity in communities of tardigrades, from rural to urban areas, increasing the homogenization of its communities due to the urbanization. Samples were taken from the city of Salta in areas with high vehicular traffic and samples in surrounding rural areas. We identified a total of eight species/morphospecies. The inventory completeness was greater than 94%. The rural community was more diverse and structurally more uniform compared with the urban one, shown that both communities were different. Macrobiotus hufelandi Schultze, 1834 results as an indicator species, and Milnesium sp. as detector species from urban habitat; meanwhile Paramacrobiotus areolatus Murray 1907 was an indicator species for rural areas.(AU)

Efectos del disturbio antrópico sobre las poblaciones de Leprolochus birabeni (Araneae, Zodariidae) en el Chaco Seco del noroeste de Argentina / Effects of anthropogenic disturbance on the populations of Leprolochus birabeni (Araneae, Zodariidae) in the Chaco Seco northwestern Argentina

Se conoce poco sobre la biología y la ecología de la especie mirmecófaga Leprolochus birabeni Mello-Leitão, 1942 (Zodariidae), el único representante de este género en la Argentina. Esta especie es típica de ambientes áridos del norte del país, y su estudio en el Chaco Seco es relevante, por ser una ecorregión altamente perturbada con uno de los pocos bosques subtropicales secos del mundo. El objetivo de este trabajo es estudiar la demografía de la especie teniendo en cuenta su variación estacional en ambientes nativos, y sí la ganadería y la agricultura, dos de las actividades antropogénicas más comunes de la ecorregión Chaco Seco en la provincia de Salta (Argentina) producen cambios en sus poblaciones. Se consideraron tres tipos de ambientes: nativo (NA); afectados por el ganado vacuno y caprino (NP); y afectados por la agricultura (NC). Este último correspondió a parches de vegetación nativa en medio de una matriz agrícola. En cada tipo de ambiente se consideraron tres sitios de muestreo donde se realizaron muestreos estacionales utilizando trampas de caída durante el otoño, invierno y primavera de 2006 y el verano de 2007. Se recolectaron 549 ejemplares de L. birabeni , siendo la mayoría juveniles con el 64,12% de la abundancia total, seguidos por machos (26,41%) y hembras (9,47%). A nivel de paisaje, la primavera presentó el mayor número de individuos, llegando al 44,99% de la abundancia total; mientras que el otoño mostró el porcentaje más bajo (7,83%). El incremento de los juveniles durante el invierno podría indicar una adaptación de los estadios de desarrollo a las condiciones ambientales. El mismo patrón se observó en ambientes NA y NC, pero no en los NP. Estos últimos mostraron una disminución en la abundancia de adultos a lo largo del año; mientras que las poblaciones NC mostraron un incremento en la abundancia de los machos durante la primavera, con una fuerte reducción de las hembras y los juveniles durante todo el año. [...](AU)

Little is known about the biology and ecology of the myrmecophagic species Leprolochus birabeni Mello-Leitão, 1942 (Zodariidae), the only representative of this genus in Argentina. This species is typical of arid environments of the north of Argentina, and their study in the Chaco Seco is relevant, because is a highly disturbed ecoregion and one of the few with dry subtropical forests in the World. The aim of this work is to study the demography of this species, considering its seasonal variation in native environments, and if the livestock grazing and the agriculture, two of the most common anthropogenic activities of the Chaco Seco ecoregion, produce changes in their populations in the province of Salta (Argentina). We consider three type of environments: native (NA); affected by cattle and goats (NP); and affected by agriculture (NC). The latter corresponds to patches of native vegetation in an agricultural matrix. Three sampling sites were selected on each type of environment, where seasonal samplings using pitfall traps were performed during autumn, winter and spring (2006) and summer (2007). We collected 549 spiders of L. birabeni , with the juveniles reaching until the 64.12% of total abundance, followed by males (26.41%) and females (9.47%). At landscape level, spring season showed the highest number of individuals, reaching 44.99% of the total abundance, while autumn reported the lowest percentage (7.83%). The juveniles increase observed during the winter would indicate an adaptation to environmental conditions. The same pattern was observed in NA and NC environments, but not in NP ones. The later environments showed a decrease in the adult abundances across the seasons, while the NC populations showed an increase of male abundances during spring season with a sharp reduction of females and juveniles throughout the year. [...](AU)