Scielo RSS <![CDATA[Revista chilena de historia natural]]> vol. 90 num. lang. es <![CDATA[SciELO Logo]]> <![CDATA[Composition, structure and diversity of a mesquite in Pesquería (Northeastern Mexico)]]> Abstract Background: Although the mesquite (mesquital or mezquital in Spanish) is one of the representative ecosystems of the landscapes in the north of Mexico, it is also one of the least studied. This study evaluated the structure (horizontal and vertical) and diversity of a plant community of mesquite in Northeastern Mexico. Three plots of 1,600 m2 each were established. All trees and shrubs with a basal diameter (d0.10) ≥ 0.5 cm were recorded, and total height (h) and crown diameter (dcrown) were measured. Results: There were 8 families, 12 genera and 14 species. The genus presenting the most species was Acacia (three species). The most representative family was Fabaceae with seven species. The evaluated community presents a density of 375 N/ha and a crown area of 6,600 m2/ha. The species with the highest values on the Importance Value Index (IVI) were Prosopis glandulosa (15.95%), Acacia amentacea (14.50%), Havardia pallens (14.27%) and Acacia farnesiana (11.22%). These four species account for 55.94% of IVI. The value obtained from the Vertical Species Profile Index (A) was 3.03, with an Amax of 3.74 and an Arel of 81.15%, indicating high structural diversity in the high strata. The evaluated plant community had a Margalef Diversity Index value of DMg = 2.50 and a Shannon Index value of H' = 2.28, values which are intermediate and considered to be common in the scrublands of Northeastern Mexico. Conclusions: 1) The studied community presents intermediate values that are considered as common in comparison to other arid and semi-arid vegetation associations of Northeastern Mexico. 2) The abundance curve of the species was well adjusted to the geometric model, and the distribution is associated with adverse environments such as semi-arid. 3) The family with greater importance for its contribution to the community is Fabaceae, while the genus with more species was Acacia. The research generated quantitative information of the plant community of a mesquite which is in a phase of mature ecological succession. <![CDATA[Agricultural landscapes as habitat for birds in central Chile]]> Abstract Background: Understanding the role of agroecosystems as habitat for wildlife is crucial for long-term conservation planning, as different crop stratification and landscape elements can influence bird communities, which are also affected by seasonality. The goal of our study was to determine how agricultural landscapes varying in land cover characteristics affect bird richness and abundance. Bird surveys were conducted at 110 locations within agricultural landscapes in central Chile. The surveyed areas were characterized by land cover at two scales (50 and 500 m radii) through direct observation and photo-interpretation, during winter and spring seasons. Generalized Linear Mixed Models were used to evaluate the effects of different agricultural land covers on bird species and communities. Results: Our results show that birds were more abundant during winter, in particular for insectivorous and granivorous birds, and that bird species richness was significantly increased due to cover provided by hedgerows at the plot scale. Conclusions: We found that abundance of some bird species in agroecosystems in central Chile was higher in winter than in spring, and that overall bird richness was favored by structural diversity including non-crop structures such as hedgerows, which thus may be relevant for improving bird conservation management in temperate agroecosystems. Our results suggest that native vegetation proximity and area may affect seasonal changes in bird communities at larger scales, relationships which warrant further study. <![CDATA[Molecular phylogenetic analyses reveal the importance of taxon sampling in cryptic diversity: <em>Liolaemus nigroviridis</em> and <em>L. monticola</em> (Liolaeminae) as focal species]]> Abstract Background Mitochondrial markers are widely used as a first approach in determining evolutionary relationships among vertebrate taxa at different hierarchical scales. Cytochrome b and cytochrome oxidase I are among the most common markers; they are particularly useful in phylogeography and species delineation studies. Simulation and empirical studies show that increasing the taxon sampling has a clear and strong effect on the accuracy of the inferred trees and therefore on hypothesized phylogenetic relationships (and eventually in new taxonomic rearrangements); this should be considered in the design of studies. The lizard genus Liolaemus is widely distributed in southern South America and includes more than 250 described species. The number of taxa and the distribution of Liolaemus species/populations makes them a good model for testing different hypotheses in systematics. Methods We studied two Liolaemus species, Liolaemus nigroviridis and L. monticola as focal species to evaluate their monophyly and the influence of adding new samples from related taxa in the resulting phylogenies. We performed phylogenetic analyses (maximum likelihood and Bayesian inference) using 141 sequences of the mitochondrial DNA Cytochrome b (cyt-b) of 11 Liolaemus species. Results Our study show that using intensive taxon sampling for phylogenetic reconstructions, two species (L. uniformis and L. nitidus) are placed within the clades of the two focal species (L. nigroviridis and L. monticola, respectively). Conclusions Our study confirms the importance of taxon sampling to infer more accurate phylogenetic relationships, particularly to reveal hidden polyphyly or paraphyly, which may have a strong impact on taxonomic proposals and/or inferring cryptic diversity. <![CDATA[Temporal variations in macroinvertebrate communities from the tributaries in the Three Gorges Reservoir Catchment, China]]> Abstract Background The seasonal variations in macroinvertebrate communities in tropical, temperate and subarctic regions have been observed and well documented to date, but similar studies conducted in subtropical rivers at the regional scale are relatively rare. In this paper, the macroinvertebrate communities from the main tributaries in the Three Gorges Reservoir Catchment (TGRC) were investigated as a function of the four seasons to explore the temporal variations in macroinvertebrate communities and further tests the temporal stability of certain metrics that are based on macroinvertebrates under a routine bioassessment framework. Results The taxa richness reached the highest point in spring, followed by winter, autumn and summer. The taxa Chironomidae, Heptageniidae, Corbiculidae and Baetidae dominated the communities across seasons. The temporal variations in communities were mainly reflected in the changes in taxa proportions between seasons. The percentages of the taxa Heptageniidae and Baetidae were the highest in autumn (normal discharge period) and lowest in summer (high discharge period). The abundance of macroinvertebrates was the lowest in summer, increased in autumn and winter, and then decreased in spring. Natural fluctuations of aquatic ecosystems (temporal effects) resulted in variations that were apparent in macroinvertebrate-based metrics, such as EPT%, Baetidae%, Caenidae%, Ephemerellidae% and Hydropsychidae%. Conclusions The results of our study demonstrated that the macroinvertebrate communities in the main tributaries of the TGRC varied as a function of seasons. This variation was fundamentally similar to the seasonal patterns in subarctic and temperate streams. Different hydro-morphological characteristics and water quality during the high discharge period (summer), low discharge period (winter) and normal discharge period (spring and autumn) strongly affected the distribution patterns of macroinvertebrate communities. Discharge variation among seasons resulted in seasonal fluctuations in the density of macroinvertebrates. In the TGRC, autumn was the important hatching period for mayflies (Ephemeroptera). The variations in metrics related to macroinvertebrates indicated that temporal effects should not be neglected under a biomonitoring framework in future studies. <![CDATA[Winter diet of the long-eared owl <em>Asio otus</em> (Strigiformes: Strigidae) in the grasslands of Janos, Chihuahua, Mexico]]> Abstract Background The long-eared owl (Asio otus) has a Holarctic distribution, including much of North America. This nocturnal species is considered to be extremely secretive, and poorly known in the Great Plains of the United States and Canada, as well as to México, where no previous studies on its diet have been conducted. Findings We analyzed 120 pellets collected during January 2007 in roosts in a 2-3 m height mesquite scrub within a grassland area of Reserva Ecológica El Uno, located in the Natural Protected Area Janos. We registered and identified three orders, four families, eight genera and ten species of mammals and two orders and one family of insects. Winter diet is dominated by mammals, especially rodents in both frequency and biomass. Cricetidae and Perognathus flavus were the most frequent family and species, respectively. On the other hand, when analyzing biomass, Sigmodon species were dominant, achieving almost 70% of the consumed biomass. Levin's standardized niche breath based on frequency was calculated as 0.40, while based on biomass was 0.38. Also, two previously unrecorded rodent species were identified as long-eared owl prey. Conclusion Although 18 different types of items were identified, the long-eared owl tends to be selective, with a single genera (Sigmodon) comprising almost 70% of its consumed biomass during winter. Perognathus flavus was also important in frequency (21%); however, it barely constitutes 2% of the consumed biomass.<hr/>Resumen El búho orejas largas es una especie Holártica, que se distribuye en gran parte de Norteamérica y que ha sido poco estudiada, especialmente en las Grandes Planicies de Estados Unidos y en México, donde no existe un estudio previo sobre su dieta invernal. Se colectaron y analizaron 120 egagrópilas en la Reserva Ecológica El Uno, dentro del Área Natural Protegida Reserva de la Biósfera Janos. Se identificaron un total de 18 tipos de presa, pero la especie mostró selectividad por dos géneros/especies, ya que cerca del 70% de la biomasa consumida fueron especies del género Sigmodon, mientras que el 21% de las muestras contenían Perognathus flavus. Además, dos especies de roedores identificadas constituyen nuevos registros de presa para la especie. <![CDATA[Persistence of <em>Dromiciops gliroides</em> in landscapes dominated by <em>Pinus radiata</em> plantations]]> Abstract Background Monitos del monte (Dromiciops gliroides) are old-growth forest specialists and, thus, believed to be very sensitive to habitat transformation, although some recent studies show some level of plasticity of their habitat selection patterns. Findings In this note we report on records of D. gliroides living in a very modified environment, composed mostly by industrial pine plantations and small fragments of Nothofagus spp. forests and we report the extension of the northernmost limit of its currently known distribution. Conclusions Although highly reliant on native vegetation, Dromiciops gliroides has been able to persist in industrial forest landscapes dominated by pine plantations. <![CDATA[The ecological value of long-term studies of birds and mammals in Central America, South America and Antarctica]]> Abstract This review covers long-term ecological studies in Central America, South America, and Antarctica that include at least 10 years of data on both terrestrial and marine mammals as well as birds. Specifically, we compiled long-term research on social systems, population ecology, and community ecology. Long-term research is necessary to understand decadal trends and dynamics that would otherwise go unnoticed in short-term studies. This review highlights the impact of ecological conditions as well as territoriality and conflict on social organization and structure, the role that environmental perturbations and climate change have on populations, and how interaction between biotic and abiotic factors influence entire ecological communities. It especially highlights the need for additional long-term studies to assess climate change trends and the ecological changes that will follow.