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Using functional traits to investigate the determinants of crustacean zooplankton community structure 总被引:1,自引:0,他引:1
Understanding the various processes contributing to community assembly is among the central aims of ecology. As a means of exploring this topic we quantified the relative influences of habitat filtering and competition in establishing patterns of community functional trait diversity across a landscape of lakes. Habitat filtering has been invoked in shaping community structure when co‐occurring taxa are more similar in their traits than expected by chance (under‐dispersion), and competition has been inferred as a structuring agent when co‐occurring taxa are less similar (over‐dispersion). We tested these hypotheses in crustacean zooplankton communities using a functional trait‐based approach based on five traits defining zooplankton feeding and habitat preferences across 51 lakes spanning several large limnological gradients. In general, zooplankton communities were functionally less diverse than random assemblages created from the same regional species pool. Furthermore, functional diversity was strongly correlated with variables related to lake productivity, suggesting that access to resources was the chief habitat filtering process constraining zooplankton functional diversity. This pattern was driven by the predominantly herbivorous cladocerans as opposed to the more commonly omnivorous, and sometimes carnivorous, copepods. 相似文献
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Andrew T. Miller Carol Dahlberg Mark L. Sandberg Ben G. Wen Daniel R. Beisner John A. H. Hoerter Albert Parker Christian Schmedt Monique Stinson Jacqueline Avis Cynthia Cienfuegos Mark McPate Pamela Tranter Martin Gosling Paul J. Groot-Kormelink Janet Dawson Shifeng Pan Shin-Shay Tian H. Martin Seidel Michael P. Cooke 《PloS one》2015,10(6)
Emerging approaches to treat immune disorders target positive regulatory kinases downstream of antigen receptors with small molecule inhibitors. Here we provide evidence for an alternative approach in which inhibition of the negative regulatory inositol kinase Itpkb in mature T lymphocytes results in enhanced intracellular calcium levels following antigen receptor activation leading to T cell death. Using Itpkb conditional knockout mice and LMW Itpkb inhibitors these studies reveal that Itpkb through its product IP4 inhibits the Orai1/Stim1 calcium channel on lymphocytes. Pharmacological inhibition or genetic deletion of Itpkb results in elevated intracellular Ca2+ and induction of FasL and Bim resulting in T cell apoptosis. Deletion of Itpkb or treatment with Itpkb inhibitors blocks T-cell dependent antibody responses in vivo and prevents T cell driven arthritis in rats. These data identify Itpkb as an essential mediator of T cell activation and suggest Itpkb inhibition as a novel approach to treat autoimmune disease. 相似文献
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Jonathan T. Hovius Beatrix E. Beisner Kevin S. McCann Norman D. Yan 《Biological invasions》2007,9(3):233-243
As a recent invader of North American lakes, Bythotrephes longimanus has induced large changes in crustacean zooplankton communities through direct predation effects. Here we demonstrate that
Bythotrephes can also have indirect food web effects, specifically on rotifer fauna. In historical time series data, the densities of
the colonial rotifer Conochilus unicornis significantly increased after Bythotrephes invasion in Harp Lake, Ontario. No such changes were observed in a non-invaded reference lake, the nearby Red Chalk Lake.
Evidence for two mechanisms explaining the Conochilus increase was examined based on changes to the crustacean zooplankton community over time. Rapid and severe declines in several
herbivorous species of cladoceran zooplankton after Bythotrephes detection indicated a decrease in exploitative competition pressure on Conochilus. Secondly, a later and significant decline to virtual extinction of native invertebrate predators (Mesocyclops and Leptodora) could account for the observed Conochilus increase which also began 1–2 years after invasion by Bythotrephes. Ultimately, it appears that both reduced competition followed by a loss of native invertebrate predators were necessary
to lead to the large Conochilus densities observed following invader establishment. From this analysis of long-term community data, it appears that Bythotrephes has important indirect, as well as direct, food web effects in newly invaded North American lakes with implications for trophic
relationships. 相似文献
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Beatrix E. Beisner Jonathan Hovius April Hayward Jurek Kolasa Tamara N. Romanuk 《Biological invasions》2006,8(4):655-664
Productivity influences the availability of resources for colonizing species. Biodiversity may also influence invasibility of communities because of more complete use of resource types with increasing species richness. We hypothesized that communities with higher environmental productivity and lower species richness should be more invasible by a competitor than those where productivity is low or where richness is high. We experimentally examined the invasion resistance of herbivorous meiofauna of Jamaican rock pools by a competitor crustacean (Ostracoda: Potamocypris sp. (Brady)) by contrasting three levels of nutrient input and four levels of species richness. Although relative abundance (dominance) of the invasive was largely unaffected by resource availability, increasing resources did increase the success rate of establishment. Effects of species richness on dominance were more pronounced with a trend towards the lowest species richness treatment of 2 resident species being more invasible than those with 4, 6, or 7 species. These results can be attributed to a ‘sampling effect associated with the introduction of Alona davidii (Richard) into the higher biodiversity treatments. Alona dominated the communities where it established and precluded dominance by the introduced ostracod. Our experimental study supports the idea that niche availability and community interactions define community invasibility and does not support the application of a neutral community model for local food web management where predictions of exotic species impacts are needed. 相似文献
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Rhesus macaques, like many other primates, live in stable, multi-male multi-female groups in which adult females typically outnumber adult males. The number of males in multi-male/multi-female groups is most commonly discussed in terms of mate competition, where the sex ratio is a function of an adult male's ability to monopolize a group of females. However, the relationship between sex ratio and group stability is unclear because the presence of many males may either reduce stability by increasing mate competition or may improve stability if adult males are key conflict managers. We investigated the relationship between sex ratio, male intervention behavior, and trauma in seven groups of captive rhesus macaques. Our results show that high-ranking adult males intervene twice as frequently as adult females (P<0.0001) and are about twice as successful (P<0.0001). Furthermore, the type of adult males present in the group affects the relationship between intervention behavior and rate of traumas: males must be unrelated to the highest-ranking matrilines. Groups with a lower ratio of females per male unrelated to the alpha and beta matrilines had better intervention success (P<0.04) and fewer traumas requiring veterinary care (P=0.003). We conclude that conflict management behavior by adult males, particularly those unrelated to the highest-ranking matrilines, is the mechanism by which sex ratio influences the frequency of traumas, and thus group stability. We therefore suggest that monitoring and managing the sex ratio of captive primate groups is one of many measurements to predict group stability. 相似文献
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