Studies dealing with interactions between vertebrate frugivores and fleshy-fruited plants have fo... more Studies dealing with interactions between vertebrate frugivores and fleshy-fruited plants have focused on the selective role of vertebrates upon fruit or plant traits (le, dispersal syndromes), assuming that these systems are coevolved (Howe & Estabrook. 1977. ...
Response to comments on " Uncertainty principle in niche assessment: A solution to the d... more Response to comments on " Uncertainty principle in niche assessment: A solution to the dilemma redundancy vs. competitive exclusion, and some analytical consequences " a b s t r a c t The influence of quantum ecological uncertainty (QEU: a discrete statistical trade-off between the standard deviations of species diversity and energy, two indicators that are essential to define the ecological niche of every species), has been proposed as a plausible explanation to the debate between the competitive exclusion principle (CEP) and the hypothesis of functional redundancy (HFR). The debate CEP ↔ HFR is a manifestation of the wide spectrum of issues connected with a very important problem in ecology: the so-called " biodiversity paradox " (i.e.: How is it possible that so many species can coexist despite the underlying influence of interspecific competition?). Any testable theoretical alternative to explain species coexistence depends on an accurate assessment of the ecological niche in practice. However, under QEU, the assessment of ecological niche cannot be as accurate as we want due to an objective limitation of nature: the above-mentioned trade-off. Consequently, it is nonsense following the debate about this topic in the conventional way; it is necessary to change our traditional point of view about this issue in order to develop a non-conventional interpretation of ecosystem functioning. However, QEU has been strongly criticized in a recently published article. This article is devoted to clarify certain misunderstandings whose nature is evident by reading the above-mentioned criticism and its precursory publications in comparison with the spectrum of articles that supports QEU. The general fulfillment of QEU has also been questioned by the above-mentioned criticism, so it is additionally supported in this article by a noticeably abbreviated inclusion of results from field data, surveyed under different circumstances in comparison with previous data, from two inland water taxocenes (zooplankton rotifers and crustaceans, Acton Lake, Ohio, U.S.A.) to which this model has not been applied so far. Our general conclusion is that the criticism to QEU has been groundlessly proposed due to epistemological inaccuracies; fragmentary understanding about the principles connected with QEU; as well as an incomplete literature review.
The introduction of non-native gastropods on islands has repetitively been related to a decline o... more The introduction of non-native gastropods on islands has repetitively been related to a decline of the endemic fauna. So far, no quantitative information is available even for the native gastropod fauna from the laurel forests (the so-called Laurisilva) of the Canary Islands. Much of the original laurel forest has been logged in recent centuries. Based on vegetation studies, we hypothesized that densities and the number of introduced species decline with the age of the regrowth forests. We sampled 27 sites from which we collected thirty native and seven introduced species. Two introduced species, Milax nigricans and Oxychilus alliarius, were previously not reported from the Canary Islands. Assemblage composition was mainly structured by disturbance history and altitude. Overall species richness was correlated with slope inclination, prevalence of rocky outcrops, amounts of woody debris and leaf litter depth. Densities were correlated with the depth of the litter layer and the extent of herb layer cover and laurel canopy cover. Introduced species occurred in 22 sites but were neither related to native species richness nor to the time that elapsed since forest regrowth. One introduced slug, Lehmannia valentiana, is already wide-spread, with densities strongly related to herb cover. Overall species richness seemed to be the outcome of invasibility, thus factors enhancing species richness likely also enhance invasibility. Although at present introduced species contribute to diversity, the potential competition between introduced slugs and the rich native semi-slug fauna, and the effects of introduced predatory snails ( Oxychilus spp. and Testacella maugei) warrant further monitoring.
Studies dealing with interactions between vertebrate frugivores and fleshy-fruited plants have fo... more Studies dealing with interactions between vertebrate frugivores and fleshy-fruited plants have focused on the selective role of vertebrates upon fruit or plant traits (le, dispersal syndromes), assuming that these systems are coevolved (Howe & Estabrook. 1977. ...
Response to comments on " Uncertainty principle in niche assessment: A solution to the d... more Response to comments on " Uncertainty principle in niche assessment: A solution to the dilemma redundancy vs. competitive exclusion, and some analytical consequences " a b s t r a c t The influence of quantum ecological uncertainty (QEU: a discrete statistical trade-off between the standard deviations of species diversity and energy, two indicators that are essential to define the ecological niche of every species), has been proposed as a plausible explanation to the debate between the competitive exclusion principle (CEP) and the hypothesis of functional redundancy (HFR). The debate CEP ↔ HFR is a manifestation of the wide spectrum of issues connected with a very important problem in ecology: the so-called " biodiversity paradox " (i.e.: How is it possible that so many species can coexist despite the underlying influence of interspecific competition?). Any testable theoretical alternative to explain species coexistence depends on an accurate assessment of the ecological niche in practice. However, under QEU, the assessment of ecological niche cannot be as accurate as we want due to an objective limitation of nature: the above-mentioned trade-off. Consequently, it is nonsense following the debate about this topic in the conventional way; it is necessary to change our traditional point of view about this issue in order to develop a non-conventional interpretation of ecosystem functioning. However, QEU has been strongly criticized in a recently published article. This article is devoted to clarify certain misunderstandings whose nature is evident by reading the above-mentioned criticism and its precursory publications in comparison with the spectrum of articles that supports QEU. The general fulfillment of QEU has also been questioned by the above-mentioned criticism, so it is additionally supported in this article by a noticeably abbreviated inclusion of results from field data, surveyed under different circumstances in comparison with previous data, from two inland water taxocenes (zooplankton rotifers and crustaceans, Acton Lake, Ohio, U.S.A.) to which this model has not been applied so far. Our general conclusion is that the criticism to QEU has been groundlessly proposed due to epistemological inaccuracies; fragmentary understanding about the principles connected with QEU; as well as an incomplete literature review.
The introduction of non-native gastropods on islands has repetitively been related to a decline o... more The introduction of non-native gastropods on islands has repetitively been related to a decline of the endemic fauna. So far, no quantitative information is available even for the native gastropod fauna from the laurel forests (the so-called Laurisilva) of the Canary Islands. Much of the original laurel forest has been logged in recent centuries. Based on vegetation studies, we hypothesized that densities and the number of introduced species decline with the age of the regrowth forests. We sampled 27 sites from which we collected thirty native and seven introduced species. Two introduced species, Milax nigricans and Oxychilus alliarius, were previously not reported from the Canary Islands. Assemblage composition was mainly structured by disturbance history and altitude. Overall species richness was correlated with slope inclination, prevalence of rocky outcrops, amounts of woody debris and leaf litter depth. Densities were correlated with the depth of the litter layer and the extent of herb layer cover and laurel canopy cover. Introduced species occurred in 22 sites but were neither related to native species richness nor to the time that elapsed since forest regrowth. One introduced slug, Lehmannia valentiana, is already wide-spread, with densities strongly related to herb cover. Overall species richness seemed to be the outcome of invasibility, thus factors enhancing species richness likely also enhance invasibility. Although at present introduced species contribute to diversity, the potential competition between introduced slugs and the rich native semi-slug fauna, and the effects of introduced predatory snails ( Oxychilus spp. and Testacella maugei) warrant further monitoring.
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Papers by Juan D Delgado