Intertidal zone is a significant wetland between land and ocean. It plays an important rolein maintaining local ecological balance. Both Mai Po and Futian intertidal mudflats are located in Shenzhen Bay and are import...Intertidal zone is a significant wetland between land and ocean. It plays an important rolein maintaining local ecological balance. Both Mai Po and Futian intertidal mudflats are located in Shenzhen Bay and are important 'refueling' point along the East Asian/Australian flyway of migratory birds. The environmental quality of Mai Po and Futian mudflats have aroused great concern due to rapid economic developments in Hong Kong and Shenzhen in recent decades. Macroinfauna of Mai Po and Futian mudflats was investigated in December 2000 and the faunal data were used to assess their environmental quality. Two other mudflats, namely Ma Wan Typhoon Shelter (a more disturbed area) and Luk Keng intertidal mudflat (a place with relatively less human disturbance), were also sampled for macroinfauna and used as reference mudflats. Shannon - Weaver species diversity index (Isd), biotic coefficient (Cb) and macrofaunal pollution index (Imp) of the macrofauna community on four intertidal mudflats were used to determine their environmental quality. The results showed that Luk Keng intertidal mudflat was unpolluted, Mai Po and Futian mudflats were slightly polluted, and Ma Wan was moderately polluted. The pollution in Ma Wan Typhoon Shelter mainly came from various types of rubbish and fishing boats that disturbed the sediment, while pollution sources in Mai Po and Futian mudflats were discharges of industrial water, municipal sewage and from nearby rivers.展开更多
Mechanisms that drive species co-occurrence are poorly documented for intermittent rivers of semiarid regions. Here, we investigated fish community assembly in response to habitat types and physicochemical conditions ...Mechanisms that drive species co-occurrence are poorly documented for intermittent rivers of semiarid regions. Here, we investigated fish community assembly in response to habitat types and physicochemical conditions in intermittent rivers of the lower Okavango Delta, Botswana. Using Joint Species Distribution Models, we inferred relative influences of environmental filtering and species interactions on patterns of species co-occurrence. Fishes were surveyed from multiple locations during drought and flood phases of the annual hydrological cycle. Species were classified into trophic guilds to facilitate inference about the types of species interactions that influence community structure. Water physicochemistry (depth, temperature, and dissolved oxygen concentration) was significantly associated with species distributions, whereas habitat type (ephemeral vs. permanent) was not significantly associated with species distribution. Controlling for the influence of environmental covariates resulted in three negative residual correlations, of which two involved non-predatory fishes from different trophic guilds, suggesting a behavioral selection of, or enhanced survival within, habitats with different environmental conditions. There was a negative residual correlation between a predator and a potential prey species, suggesting a role for predation mortality or threat in species segregation. Our results demonstrate that using trophic guilds in conjunction with JSDMs can enhance inferences about mechanisms of community assembly.展开更多
A central tenet of coevolutionary theory,including theory of the coevolutionary relationship between brood parasites and their hosts,is that temporal and spatial patterns may reveal important information about ecologi...A central tenet of coevolutionary theory,including theory of the coevolutionary relationship between brood parasites and their hosts,is that temporal and spatial patterns may reveal important information about ecological and evolutionary dynamics.For instance,level of genetic structure of populations provides important information about the role of genetics and gene ow in determining local patterns of selection on hosts due to parasitism(i.e.,egg rejection) and on parasites due to selection by hosts(i.e.,egg mimicry).Furthermore,abiotic(i.e.,climatic conditions) and biotic(phenotypic characteristics of animals) factors that also vary spatially may directly or indirectly a ect populations of hosts and brood parasites and,therefore,their interaction.By reviewing the literature,we found considerable evidence for an e ect of the spatially and temporally structured abiotic environment on the phenotype of both parasite and host eggs and the degree of mimicry.Moreover,we found examples suggesting that speci c life history characteristics of hosts that vary geographically and/or temporally may a ect the probability of initial colonization of a new host species and the direction and the speed of coevolution.We provide an exhaustive review of studies investigating temporal and spatial patterns of the interaction between brood parasites and their hosts.Such temporal and spatial trends in parasite and host traits are,together with genetic information on rejection and signi cant e ects of gene ow,consistent with coevolutionary dynamics.However,gene ow and changes in the temporal and spatial patterns of abundance of both parasites and hosts may result in frequent cases of counter-intuitive relationships between the phenotype of the parasite and that of the host(i.e.,poor or no mimicry),which may suggest limits to the degree of adaptation.We provide a list of scienti c questions in need of further investigation,concluding that studies of brood parasites and their hosts may play a central role in testing the geographic theory of coevolution and several alternative hypotheses.展开更多
文摘Intertidal zone is a significant wetland between land and ocean. It plays an important rolein maintaining local ecological balance. Both Mai Po and Futian intertidal mudflats are located in Shenzhen Bay and are important 'refueling' point along the East Asian/Australian flyway of migratory birds. The environmental quality of Mai Po and Futian mudflats have aroused great concern due to rapid economic developments in Hong Kong and Shenzhen in recent decades. Macroinfauna of Mai Po and Futian mudflats was investigated in December 2000 and the faunal data were used to assess their environmental quality. Two other mudflats, namely Ma Wan Typhoon Shelter (a more disturbed area) and Luk Keng intertidal mudflat (a place with relatively less human disturbance), were also sampled for macroinfauna and used as reference mudflats. Shannon - Weaver species diversity index (Isd), biotic coefficient (Cb) and macrofaunal pollution index (Imp) of the macrofauna community on four intertidal mudflats were used to determine their environmental quality. The results showed that Luk Keng intertidal mudflat was unpolluted, Mai Po and Futian mudflats were slightly polluted, and Ma Wan was moderately polluted. The pollution in Ma Wan Typhoon Shelter mainly came from various types of rubbish and fishing boats that disturbed the sediment, while pollution sources in Mai Po and Futian mudflats were discharges of industrial water, municipal sewage and from nearby rivers.
文摘Mechanisms that drive species co-occurrence are poorly documented for intermittent rivers of semiarid regions. Here, we investigated fish community assembly in response to habitat types and physicochemical conditions in intermittent rivers of the lower Okavango Delta, Botswana. Using Joint Species Distribution Models, we inferred relative influences of environmental filtering and species interactions on patterns of species co-occurrence. Fishes were surveyed from multiple locations during drought and flood phases of the annual hydrological cycle. Species were classified into trophic guilds to facilitate inference about the types of species interactions that influence community structure. Water physicochemistry (depth, temperature, and dissolved oxygen concentration) was significantly associated with species distributions, whereas habitat type (ephemeral vs. permanent) was not significantly associated with species distribution. Controlling for the influence of environmental covariates resulted in three negative residual correlations, of which two involved non-predatory fishes from different trophic guilds, suggesting a behavioral selection of, or enhanced survival within, habitats with different environmental conditions. There was a negative residual correlation between a predator and a potential prey species, suggesting a role for predation mortality or threat in species segregation. Our results demonstrate that using trophic guilds in conjunction with JSDMs can enhance inferences about mechanisms of community assembly.
文摘A central tenet of coevolutionary theory,including theory of the coevolutionary relationship between brood parasites and their hosts,is that temporal and spatial patterns may reveal important information about ecological and evolutionary dynamics.For instance,level of genetic structure of populations provides important information about the role of genetics and gene ow in determining local patterns of selection on hosts due to parasitism(i.e.,egg rejection) and on parasites due to selection by hosts(i.e.,egg mimicry).Furthermore,abiotic(i.e.,climatic conditions) and biotic(phenotypic characteristics of animals) factors that also vary spatially may directly or indirectly a ect populations of hosts and brood parasites and,therefore,their interaction.By reviewing the literature,we found considerable evidence for an e ect of the spatially and temporally structured abiotic environment on the phenotype of both parasite and host eggs and the degree of mimicry.Moreover,we found examples suggesting that speci c life history characteristics of hosts that vary geographically and/or temporally may a ect the probability of initial colonization of a new host species and the direction and the speed of coevolution.We provide an exhaustive review of studies investigating temporal and spatial patterns of the interaction between brood parasites and their hosts.Such temporal and spatial trends in parasite and host traits are,together with genetic information on rejection and signi cant e ects of gene ow,consistent with coevolutionary dynamics.However,gene ow and changes in the temporal and spatial patterns of abundance of both parasites and hosts may result in frequent cases of counter-intuitive relationships between the phenotype of the parasite and that of the host(i.e.,poor or no mimicry),which may suggest limits to the degree of adaptation.We provide a list of scienti c questions in need of further investigation,concluding that studies of brood parasites and their hosts may play a central role in testing the geographic theory of coevolution and several alternative hypotheses.
