High temporal variability in the occurrence of consumer-resource interactions in ecological networks

Ecological networks are theoretical abstractions that represent ecological communities. These networks are usually defined as static entities, in which the occurrence of a particular interaction between species is considered fixed despite the intrinsic dynamics of ecological systems. However, empirical analysis of the temporal variation of trophic interactions is constrained by the lack of data with high spatial, temporal, and taxonomic resolution. Here, we evaluate the spatiotemporal variability of multiple consumer-resource interactions of large marine networks. The tropic interactions of all of the analyzed networks had low temporal persistence, which was well described by a common exponential decay in the rank-frequency relationship of consumer-resource interactions. This common pattern of low temporal persistence was evident despite the dissimilarities of environmental conditions among sites. Between-site rank correlations of frequency of occurrence of interactions ranged from 0.59 to 0.73. After removing the interactions with <50% frequency, the between-site correlations decreased to values between 0.60 and 0.28, indicating that low-frequency interactions accounted for the apparent similarities between sites. Our results showed that the communities studied were characterized by few persistent interactions and a large number of transient trophic interactions. We suggest that consumer-resource temporal asynchrony in addition to varying local environmental conditions and opportunistic foraging could be among the mechanisms generating the observed rank-frequency relationship of trophic interactions. Therefore, our results question the analysis of ecological communities as static and persistent natural entities and stress the need for strengthening the analysis of temporal variability in ecological networks and long-term studies.Comment: 21 pages, 3 figure

Educación Científica y Evolutiva en Chile: Problemas Funcionales y Confictos entre Enseñar y Aprender Science and Evolution Education in Chile: Functional Problems and Conficts between Teaching and Learning

En Chile, la educación media (secundaria) y universitaria de pregrado, y la conexión entre ellas, son los puntos más sensibles de la educación científca en biología y evolución, que estuvo seriamente deprimida hacia fnes del siglo XX. No obstante, hoy enfrentamos un escenario de transición favorable donde convergen tres factores capaces de potenciar la alfabetización biológica en sentido amplio: un nuevo currículum secundario que incluye un fuerte componente biológico, con énfasis en evolución y ecología; una reactivación de la formación pedagógica a nivel universitario; y un desarrollo científco creciente en el área de biología evolutiva. Sin embargo, estos factores aún están conectados débilmente, y su mejor articulación podría contribuir a mejorar signifcativamente la retroalimentación entre los componentes del sistema educativo, y a resolver algunos confictos dialécticos entre enseñar y aprender que se generan en diferentes niveles jerárquicos del mismo sistema. El reforzamiento de la interdisciplinaridad entre biología y pedagogía en la formación de nuevos profesores sería un factor clave, ya que el profesor secundario parece ser la piedra angular del sistema educativo, además de jugar un rol crucial en la formación inicial de los futuros científcos.<br>In Chile, high school (secondary) and university undergraduate levels, and their connection, are the most sensitive points of science education in biology and evolution, which was seriously depressed at the end of the 20th century. Nonetheless, we face today a favourable transitional scenario where three converging factors are able to foster science literacy in a wide sense: a new high school curriculum including a strong biological component, with emphasis on evolution and ecology; a reactivation of university formation of secondary pedagogues; and a growing scientifc development in the feld of evolutionary biology. However, these factors are still weakly connected, and strengthening their articulation might improve signifcantly the feedback between all components of the Chilean educational system, helping to solve some dialectic conficts between teaching and learning that originate at different hierarchical levels of the same system. The reinforcement of interdisciplinarity between biology and pedagogy in the process of formation of new teachers would be a key factor, because the high school teacher turns to be the cornerstone of the educational system, in addition playing a crucial role in the initial formation of the future scientists