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1.
Nat Ecol Evol ; 4(1): 40-45, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31844189

RESUMO

According to the competitive exclusion principle, species with low competitive abilities should be excluded by more efficient competitors; yet, they generally remain as rare species. Here, we describe the positive and negative spatial association networks of 326 disparate assemblages, showing a general organization pattern that simultaneously supports the primacy of competition and the persistence of rare species. Abundant species monopolize negative associations in about 90% of the assemblages. On the other hand, rare species are mostly involved in positive associations, forming small network modules. Simulations suggest that positive interactions among rare species and microhabitat preferences are the most probable mechanisms underpinning this pattern and rare species persistence. The consistent results across taxa and geography suggest a general explanation for the maintenance of biodiversity in competitive environments.


Assuntos
Biodiversidade , Ecologia , Geografia
2.
Sci Total Environ ; 466-467: 34-9, 2014 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-23892021

RESUMO

The effect of lead (Pb) toxicity on bone mineralization was investigated in a wild population of red-legged partridge (Alectoris rufa) inhabiting a farmland area contaminated with Pb-shot from recreational hunting activities in Albacete, a southeastern province of Spain. Femora from 40 specimens of red-legged partridge were analyzed for Pb by graphite furnace atomic absorption spectroscopy (GF-AAS), and for bone composition by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The FTIR and DRX data of bone were analyzed in detail to determine possible alterations in bone mineral chemistry and crystallinity due to Pb toxicity. Results showed a marked decrease in the degree of mineralization as Pb concentrations in bone tissue increased while XRD analyses showed that the crystallinity of apatite crystals increased with the Pb load in bone. These load-dependent effects are indicative that Pb contamination altered bone remodeling by reducing new bone mineral formation and demonstrate that bone quality is a sensitive indicator of adverse effects on wild bird populations exposed to Pb pollution.


Assuntos
Calcificação Fisiológica/efeitos dos fármacos , Exposição Ambiental , Poluentes Ambientais/toxicidade , Galliformes/metabolismo , Chumbo/toxicidade , Animais , Monitoramento Ambiental , Feminino , Armas de Fogo , Masculino , Espectrofotometria Atômica , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios X
3.
Rev Biol Trop ; 59(3): 1061-9, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22017112

RESUMO

Podocarpus angustifolius is an endangered recalcitrant-seeded small tree, endemic to mountain rain forests in the central and Pinar del Río regions in Cuba. In this study, the germination patterns of P. angustifolius seeds were evaluated and the nature of the soil seed bank was determined. Using a weighted two-factor design, we analyzed the combined germination response to seed source (i.e. freshly matured seeds directly collected from trees versus seeds extracted from soil samples) and pretreatment (i.e. seed water-immersion for 48h at room temperature). Germination was delayed for four weeks (= 30 days) in all cases, regardless of both factors analyzed. Moreover, nine additional days were necessary to achieve high germination values (in the case of fresh, pretreated seeds). These results overall may indicate the existence of a non-deep simple morphophysiological dormancy in P. angustifolius seeds. The water-immersion significantly enhanced seed germination, probably as a result of the hydration of recalcitrant seeds. Although germination of seeds extracted from soil samples was low, probably due to aging and pathogen effects throughout the time of burial, the study revealed the existence of a persistent soil seed bank (at least short-termed) of approximately 42 viable seeds per m2 in the upper 10cm of soil. Such a record is noteworthy since references to persistent soil seed banks in recalcitrant-seeded species are scarce in the literature. The population consequences derived from the formation of persistent soil seed banks in this endangered species are discussed.


Assuntos
Germinação/fisiologia , Sementes/crescimento & desenvolvimento , Solo/análise , Traqueófitas/fisiologia , Árvores , Cuba , Chuva
4.
Rev. biol. trop ; 59(3): 1061-1069, Sept. 2011. ilus, tab
Artigo em Inglês | LILACS | ID: lil-638140

RESUMO

Podocarpus angustifolius is an endangered recalcitrant-seeded small tree, endemic to mountain rain forests in the central and Pinar del Río regions in Cuba. In this study, the germination patterns of P. angustifolius seeds were evaluated and the nature of the soil seed bank was determined. Using a weighted two-factor design, we analyzed the combined germination response to seed source (i.e. freshly matured seeds directly collected from trees versus seeds extracted from soil samples) and pretreatment (i.e. seed water-immersion for 48h at room temperature). Germination was delayed for four weeks (≈30 days) in all cases, regardless of both factors analyzed. Moreover, nine additional days were necessary to achieve high germination values (in the case of fresh, pretreated seeds). These results overall may indicate the existence of a non-deep simple morphophysiological dormancy in P. angustifolius seeds. The water-immersion significantly enhanced seed germination, probably as a result of the hydration of recalcitrant seeds. Although germination of seeds extracted from soil samples was low, probably due to aging and pathogen effects throughout the time of burial, the study revealed the existence of a persistent soil seed bank (at least short-termed) of ≈42 viable seeds per m² in the upper 10cm of soil. Such a record is noteworthy since references to persistent soil seed banks in recalcitrant-seeded species are scarce in the literature. The population consequences derived from the formation of persistent soil seed banks in this endangered species are discussed. Rev. Biol. Trop. 59 (3): 1061-1069. Epub 2011 September 01.


Podocarpus angustifolius es un árbol endémico de los bosques lluviosos de la región de Pinar del Río y la parte central de Cuba, que se encuentra en peligro de extinción. En este estudio se evaluó la germinación de sus semillas y la naturaleza del banco de semillas del suelo. Específicamente, se analizó la respuesta germinativa de las semillas a dos factores: su procedencia (recolectadas directamente de los árboles versus extraídas de muestras de suelo) y el pretratamiento (inmersión en agua durante 48h a temperatura ambiente). La germinación no comenzó hasta las cuatro semanas (≈30 días) en todos los casos. Además, fueron necesarios 9 días más para alcanzar un valor elevado de germinación (en el caso de semillas recolectadas del árbol con pretratamiento), lo que parece indicar la existencia de un letargo de tipo morfofisiológico simple no profundo. El pretratamiento incrementó significativamente la germinación, posiblemente por hidratación de las semillas recalcitrantes. El estudio demostró la existencia de un banco de semillas persistente en el suelo, al menos de corta duración de ≈42 semillas viables por m² en los 10 primeros cm del suelo. Dicho hallazgo es destacable, ya que los casos descritos en la literatura sobre bancos persistentes en especies con semillas recalcitrantes son escasos. Además, se discute la importancia que tiene para esta especie amenazada la existencia de un banco de semillas persistente.


Assuntos
Coniferophyta/fisiologia , Germinação/fisiologia , Sementes/crescimento & desenvolvimento , Solo/análise , Árvores , Cuba , Chuva
5.
Ann Bot ; 107(6): 1003-16, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21335326

RESUMO

BACKGROUND AND AIMS: Only very few studies have been carried out on seed dormancy/germination in the large monocot genus Narcissus. A primary aim of this study was to determine the kind of seed dormancy in Narcissus hispanicus and relate the dormancy breaking and germination requirements to the field situation. METHODS: Embryo growth, radicle emergence and shoot growth were studied by subjecting seeds with and without an emerged radicle to different periods of warm, cold or warm plus cold in natural temperatures outdoors and under controlled laboratory conditions. KEY RESULTS: Mean embryo length in fresh seeds was approx. 1·31 mm, and embryos had to grow to 2·21 mm before radicle emergence. Embryos grew to full size and seeds germinated (radicles emerged) when they were warm stratified for 90 d and then incubated at cool temperatures for 30 d. However, the embryos grew only a little and no seeds germinated when they were incubated at 9/5, 10 or 15/4 °C for 30 d following a moist cold pre-treatment at 5, 9/5 or 10 °C. In the natural habitat of N. hispanicus, seeds are dispersed in late May, the embryo elongates in autumn and radicles emerge (seeds germinate) in early November; however, if the seeds are exposed to low temperatures before embryo growth is completed, they re-enter dormancy (secondary dormancy). The shoot does not emerge until March, after germinated seeds are cold stratified in winter. CONCLUSION: Seeds of N. hispanicus have deep simple epicotyl morphophysiological dormancy (MPD), with the dormancy formula C(1b)B(root) - C(3)(epicotyl). This is the first study on seeds with simple MPD to show that embryos in advanced stages of growth can re-enter dormancy (secondary dormancy).


Assuntos
Germinação , Narcissus/fisiologia , Dormência de Plantas , Sementes/fisiologia , Narcissus/crescimento & desenvolvimento , Brotos de Planta/crescimento & desenvolvimento , Brotos de Planta/fisiologia , Sementes/crescimento & desenvolvimento , Temperatura Ambiente
6.
Environ Sci Technol ; 42(16): 6271-7, 2008 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-18767698

RESUMO

The goal of the study was to investigate the accumulation and spatial patterns of spent lead (Pb) shot pellets and the prevalence of shot ingestion in red-legged partridge in a driven shooting estate. Soil was collected using a regular sampling design perpendicular to three shooting lines. Factors involved in shot spatial distribution were investigated by a causal structural equation model (SEM). Shot ingestion prevalence and liver and bone Pb concentrations were studied in partridges hunted in 2004 and 2006. Shot soil-burden averaged 73,600 units/ha (i.e., 8.1 kg/ha). Shot density was significantly higher in front of than behind shooting lines, with greatest accumulation occurring at between 40-110 m and in certain ecotones (i.e., shrubland-dry cropland). Analyses revealed 7.8% of partridges with evidence of Pb shot ingestion. Particle size in diet, grit-size composition, and shot ingestion prevalence were significantly higher in 2004 than in 2006, indicating that supplying partridges with large seeds (i.e., corn) may increase the risk of Pb shot ingestion. Moving shooting lines into croplands and controlling seed size used for diet supplementation may reduce shot ingestion.


Assuntos
Exposição Ambiental , Galliformes/metabolismo , Intoxicação por Chumbo , Animais , Ecossistema , Monitoramento Ambiental , Comportamento Alimentar , Poluentes do Solo , Espanha
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