Cristián F. Estades

Strengthened insectivory in a temperate fragmented forest

Habitat fragmentation modifies ecological patterns and processes through changes in species richness and abundance. In the coastal Maulino forest, central Chile, both species richness and abundance of insectivorous birds increases in forest fragments compared to continuous forest. Through a field experiment, we examined larvae predation in fragmented forests. Higher richness and abundance of birds foraging at forest fragments translated into more insect larvae preyed upon in forest fragments than in continuous forest. The assessed level of insectivory in forest fragments agrees with lower herbivory levels in forest fragments. This pattern strongly suggests the strengthening of food interactions web in forest fragments of coastal Maulino forest.

Providing habitat for native mammals through understory enhancement in forestry plantations.

The Convention on Biological Diversity (CBD) expects forestry plantations to contribute to biodiversity conservation. A well-developed understory in forestry plantations might serve as a surrogate habitat for native species and mitigate the negative effect of plantations on species richness. We experimentally tested this hypothesis by removing the understory in Monterey pine (Pinus radiata) plantations in central Chile and assessing changes in species richness and abundance of medium-sized mammals. Frequency of occurrence of mammals, including kodkods (Leopardus guigna), culpeo foxes (Pseudalopex culpaeus), lesser grisons (Conepatus chinga), and Southern pudu deer (Pudu puda), was low in forest stands with little to no understory relative to stands with well-developed undergrowth vegetation. After removing the understory, their frequency of occurrence decreased significantly, whereas in control stands, where understory was not removed, their frequency did not change. This result strongly supports the idea that facilitating the development of undergrowth vegetation may turn forestry stands into secondary habitats as opposed to their containing no habitat for native mammals. This forestry practice could contribute to conservation of biological diversity as it pertains to CBD targets.

Effects of habitat loss, habitat fragmentation, and isolation on the density, species richness, and distribution of ladybeetles in manipulated alfalfa landscapes

Abstract 1. Habitat loss and fragmentation are the main causes of changes in the distribution and abundance of organisms, and are usually considered to negatively affect the abundance and species richness of organisms in a landscape. Nevertheless, habitat loss and fragmentation have often been confused, and the reported negative effects may only be the result of habitat loss alone, with habitat fragmentation having nil or even positive effects on abundance and species richness.

Niche segregation between wild and domestic herbivores in Chilean Patagonia.

Competition arises when two co-occuring species share a limiting resource. Potential for competition is higher when species have coexisted for a short time, as it is the case for herbivores and livestock introduced in natural systems. Sheep, introduced in the late 19th century in Patagonia, bear a great resemblance in size and diet to the guanaco, the main native herbivore in Patagonia. In such circumstances, it could be expected that the two species compete and one of them could be displaced. We investigated spatial overlap and habitat selection by coexisting sheep and guanaco in winter and in summer. Additionally, we studied habitat selection of the guanaco in a control situation free from sheep, both in summer and winter. We also determined overlap between species in areas with different intensity of use (named preferred and marginal areas) in order to further detect the potential level of competition in the case of overlapping. Guanaco and sheep showed significantly different habitat preferences through all seasons, in spite of their spatial overlap at landscape scale. Additionally, the habitat used by guanaco was similar regardless of the presence or absence of livestock, which further indicates that sheep is not displacing guanaco where they coexist. These results suggest that habitat segregation between guanaco and sheep is due to a differential habitat selection and not to a competitive displacement process. Therefore, the potential for competition is considered low, contrary to what has been previously observed, although this could be a density-dependent result.

Effect of Clearcutting Operations on the Survival Rate of a Small Mammal

Clearcutting is a common timber harvesting technique that represents a significant and abrupt change in habitat conditions for wildlife living in industrial forests. Most research on this type of impact has focused on comparing populations or communities in mature forests/plantations and the resulting clearcut stands. However, this approach does not separate the effect of changes in habitat attributes from direct mortality produced by the intensive use of heavy machinery required for cutting down trees and dragging them to a road. Because knowing the fate of individuals after a disturbance is important for modelling landscape-scale population dynamics in industrial forests, we conducted a study in South-Central Chile to understand the short-term response to clearcutting operations of the long-haired Akodont (Abrothrix longipillis), a forest specialist mouse. Between 2009 and 2013 we radiotracked a total of 51 adult male Akodonts, before, during and after the clearcutting of the pine plantations in which they lived. A minimum of 52.4% of the individuals died as a direct cause of the timbering operations, being crushed by vehicles or logs during logging operations. Our observations suggest that, instead of fleeing the area, the response of long-haired Akodonts to the approaching machinery is to hide under the forest litter or in burrows, which exposes them to a serious risk of death. The real mortality rate associated to clearcutting may be higher than that estimated by us because of some methodological biases (i.e. individuals with crushed radiotransmitters not recorded) and the fact that additional mortality sources may affect the population in the weeks following logging operations (e.g. higher exposure to predation, effects of site preparation for the new plantation, etc).

Invasive African clawed frog Xenopus laevis in southern South America: key factors and predictions

The African clawed frog Xenopus laevis is one of the most widely distributed amphibians in the world. It has invaded an area of approximately 21,200 km2 since its naturalization in Chile in the early 1980s. Currently, there is scant knowledge on the factors and processes underlying its distributional pattern. We constructed a bioclimatic niche model considering areas susceptible to be invaded (coarse model). At a local scale, we explored topographic, ecological, and anthropic variables, to identify which of these have the greatest predictive power for the expansion of this African species in southern South America. Not surprisingly, the projection of the distribution of Xenopus laevis laevis in southern Africa had the highest probabilities associated with the mediterranean area of the Cape region. From the habitat projection on southern South America, we predict high habitat suitability for this species in the mediterranean region of Chile. Nonetheless, the coastal desert of northern Chile, the Atlantic coasts of Argentina (32° to 54° S), Uruguay, southern Brazil, the north-central part of Argentina (22° to 35° S) and the central-southern region of Bolivia, are potentially suitable as well. At a local scale, we confirm that lentic aquatic environments, with slow drainage and murky waters, highly connected, human-disturbed, and part of an irrigation system of small streams and canals, account for the highest probabilities of successful establishment of X. laevis within the area of invasion. Based on our habitat suitability models, we expect the African clawed frog to invade farther north and farther south in Chile. We warn that the pet trade and subsequent release of African clawed frog to the wild pose a serious invasion risk to other countries of the southern cone of South America.

Is natural selection promoting sexual dimorphism in the Green-backed Firecrown Hummingbird (Sephanoides Sephaniodes)?

In many hummingbird species there is an opposite pattern of sexual dimorphism in bill length and other morphometric measures of body size. These differences seem to be closely related with differences in foraging ecology directly associated with a different resource exploitation strategy. The aim of this study was to assess if natural selection is acting on wing length and bill size in hummingbird males and females with different resource exploitation strategies (i.e., territorial males and non-territorial females). If competition for resources promotes sexual dimorphism as a selective pressure, males should be subjected to negative directional selection pressure for wing length and no selection pressure over bill size, while females should undergo positive directional selection pressure for both bill size and wing length. The morphometric data we collected suggests that there is no selection for wing length and bill size in male hummingbirds. In contrast, our females exhibited positive directional selection for both wing length and bill size. Although we cannot reject sexual selection acting on sexually dimorphic traits, this study suggests that natural selection may promote sexual dimorphism in traits that are closely related with hummingbird foraging ecology and resource exploitation strategies.

Nesting of the Thorn-Tailed Rayadito (Aphrastura spinicauda) in a Pine Plantation in Southcentral Chile

Abstract We installed nest boxes for Thorn-tailed Rayaditos (Aphrastrura spinicauda) and monitored their use in a Monterrey pine (Pinus radiata) plantation in the Maule Region, southcentral Chile. Thirty-four breeding pairs built nests in boxes, of which 75% began laying eggs. Nest establishment began in early September and construction lasted 12.8 ± 4.9 days (n  =  23). Rayaditos used mainly pine needles, together with mosses, epiphytes, herbs, and animal hair in their nests. Clutch size ranged from two to four eggs (mode  =  3) that were incubated for 15.8 ± 1.2 days. Brood size negatively affected mass of nestlings, but was positively related to mass of the parents. Adults had higher body mass and built larger nests than those reported previously for the species on Chiloé Island, where broods are larger and the incubation period is shorter. The provision of artificial cavities allowed Thorn-tailed Rayaditos to nest in the pine plantation. Nest boxes combined with other management tools, such as maintaining snags and understory enhancement, may be important factors in mitigation of negative effects of pine plantations on secondary cavity-nesting birds.

Behavioural and genetic interactions between an endangered and a recently-arrived hummingbird

The invasion or expansion of non-native species into new geographic areas can pose a major threat to the conservation of biodiversity. These threats are augmented when the newly-arrived species interacts with native species that are already threatened by other ecological or anthropogenic processes. Potential interactions can include both competition for scarce resources and reproductive interference, including hybridisation. Understanding the dynamics of these interactions forms a crucial component of conservation management strategies. A recent contact zone occurs in the north of Chile between the endangered Chilean woodstar (Eulidia yarrellii) and the closely-related and recently-arrived Peruvian sheartail (Thaumastura cora), which expanded its range from Peru into Chile during the 1970s. We characterised the interactions between the species by combining population size estimates with molecular, morphological and behavioural data. We show that a low degree of hybridisation, but not introgression, is occurring between the two species. Despite interspecific morphological similarities, behavioural observations indicate that food niche overlap between the species is relatively low, and that the dietary breadth of sheartails is larger, which may have aided the species’ range expansion. Finally, woodstars dominate the sheartails in male–male territorial interactions. However, potentially increased energetic costs for woodstars associated with frequent territorial chases and courtship displaying with sheartails may exacerbate the effects of other threats on woodstar viability, such as human-induced habitat modification. This study highlights the value of implementing multidisciplinary approaches in conservation biology to gain a more complete understanding of interactions between recently-arrived and endangered species.

Revisión de la clasificación de especies en categorías de amenaza en Chile

A partir de 1985 comienzan los esfuerzos del Estado de Chile, con el apoyo de especialistas, para generar listas de especies de plantas (1985) y animales (1987) con altos a moderados riesgos de extincion en el corto plazo producto de actividades antropicas (i.e., especies amenazadas). Las siete categorias de amenazas utilizadas para la fauna coinciden con las empleadas por la Union Internacional para la Conservacion de la Naturaleza (UICN) en 1982; para la flora hubo coincidencia en solo cinco de las categorias utilizadas. En el ano 1994, la Ley 19300 de Bases del Medio Ambiente establecio seis categorias de estados de conservacion. El Reglamento para la Clasificacion de Especies Silvestres, promulgado el 2005, definio estas seis categorias haciendo una combinacion entre lo propuesto por la UICN en 2001 y 1982. La generacion de este sistema hibrido que no era comparable con el utilizado ampliamente en el mundo, restringio severamente la posibilidad de clasificar a las especies con amenaza inferior al nivel de Vulnerable. Complicaciones adicionales se generaron con la inclusion de categorias de conservacion en la Ley 19473 de Caza (1996), la Ley 20283 sobre Recuperacion del Bosque Nativo y Fomento Forestal (2008), y sus respectivos reglamentos. La Ley 20417 (publicada el 26 de enero 2010) modifico la ley 19300 e incorporo las categorias recomendadas por la UICN. Ahora el Estado requiere adecuar varios cuerpos legales para avanzar en el conocimiento del estado de conservacion de la flora y la fauna nacional, y consecuentemente, asegurar la implementacion de medidas efectivas de proteccion de la biodiversidad.