This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Social prey species respond to predation risk by modifying habitat selection and grouping behavio... more Social prey species respond to predation risk by modifying habitat selection and grouping behaviour. These responses may depend on both actual predation risk (predator probability of occurrence) and/or on perceived predation risk associated with habitat structure. Other factors like food availability and co-occurrence with other species may also affect habitat selection and group formation. We analyse habitat selection and grouping behaviour (group size and cohesion) of lesser rhea (Rhea pennata subsp. pennata), a ratite endemic of South America inhabiting steppe shrublands and grasslands, in relation to actual (puma probability of occurrence) and perceived (habitat structure: openness, visibility) predation risk, co-occurrence with other herbivore species and forage availability in the Chilean Patagonia. We used data from 9 sampling seasons in 5 years. Results show that habitat selection, group size and cohesion in lesser rhea were mainly driven by variables associated with perceived predation risk and by co-occurrence with other herbivores both during breeding and non–breeding season. As expected, lesser rhea preferred open habitats (vegas and grasslands) that allow a behaviour of ‘watch and run’ to avoid predation and formed larger groups in them. Moreover, lesser rhea positively selected year-round habitats where livestock occur, forming large groups during non–breeding season there. Group size and co-occurrence with other herbivores significantly decreased group cohesion, suggesting a reduction of perceived predation risk. Therefore, lesser rhea seems to take advantage of forming mixed interspecific groups to reduce predation risk. These results suggest that lesser rhea habitat selection and grouping behaviour are preferentially driven by factors related to perceived predation risk than by actual predator occurrence or food availability.
Social prey species respond to predation risk by modifying habitat selection and grouping behavio... more Social prey species respond to predation risk by modifying habitat selection and grouping behaviour. These responses may depend on both actual predation risk (predator probability of occurrence) and/or on perceived predation risk associated with habitat structure. Other factors like food availability and co-occurrence with other species may also affect habitat selection and group formation. We analyse habitat selection and grouping behaviour (group size and cohesion) of lesser rhea (Rhea pennata subsp. pennata), a ratite endemic of South America inhabiting steppe shrublands and grasslands, in relation to actual (puma probability of occurrence) and perceived (habitat structure: openness, visibility) predation risk, co-occurrence with other herbivore species and forage availability in the Chilean Patagonia. We used data from 9 sampling seasons in 5 years. Results show that habitat selection, group size and cohesion in lesser rhea were mainly driven by variables associated with perceived predation risk and by co-occurrence with other herbivores both during breeding and non–breeding season. As expected, lesser rhea preferred open habitats (vegas and grasslands) that allow a behaviour of ‘watch and run’ to avoid predation and formed larger groups in them. Moreover, lesser rhea positively selected year-round habitats where livestock occur, forming large groups during non–breeding season there. Group size and co-occurrence with other herbivores significantly decreased group cohesion, suggesting a reduction of perceived predation risk. Therefore, lesser rhea seems to take advantage of forming mixed interspecific groups to reduce predation risk. These results suggest that lesser rhea habitat selection and grouping behaviour are preferentially driven by factors related to perceived predation risk than by actual predator occurrence or food availability.
Growth of wild ungulate populations within protected areas can cause an expansion towards surroun... more Growth of wild ungulate populations within protected areas can cause an expansion towards surrounding non-protected areas and lead to conflicts with human activities. The spatial and demographic structure of colonizing populations inform about their state and potential trends, since the initial colonization by dispersing individuals precedes the establishment of a population with potential for further growth and expansion. Once colonization has succeeded, the spatial pattern of animal abundance is associated with intra-and interspecific interactions and environmental factors (e.g., habitat and food availability) and the population shows similar demographic features throughout the whole occupation area, which has been called a diffusive dispersal pattern. Here, we analyze the current status of colonization by a guanaco population of ranches surrounding a protected area in Chilean Patagonia with data gathered along three consecutive years. We thus compared animal abundance and social structure between the protected and unprotected areas and evaluated throughout the whole area the effect of environmental factors on guanaco abundance, proportion of family groups, and reproductive success. Guanaco abundance significantly declined with increasing distance from the center of the local distribution and marginally with predation risk. Moreover, social structure showed only minor differences between areas, pointing to a diffusive dispersal pattern. These results suggest that the population is already well established and has the potential to grow and continue its expansion. The case exemplifies a challenging outcome of successful animal conservation, and it presents a useful approach to evaluate the state of wild ungulate populations colonizing new areas.
L'ecologie reproductive de Cistus ladanifer a ete associee traditionnellement a l'apparit... more L'ecologie reproductive de Cistus ladanifer a ete associee traditionnellement a l'apparition des incendies, bien que la dispersion des graines de cette espece par le cerf puisse jouer un role important dans la capacite colonisatrice de l'espece et etre en rapport avec la dormance des graines. On a analyse a chaque saison le contenu en graines des fumees du cerf et le pouvoir germinatif des graines obtenues directement sur la plante ainsi que de celles contenues dans les excrements. Le cerf disperse un grand nombre de semences de cette espece, plus de 250.000 par individu entre fevrier et aout, avec un maximum en ete d'environ 8.000 par individu -1 jour -1 ; elles ont un pourcentage de germination rapide plus grand que celui des graines recoltees sur la plante (46% vs. 30%). Ces resultats completent la vision traditionnelle que l'on a de la reproduction de ce ciste, surtout en ce qui concerne des graines des epoques anterieures a l'augmentation des incendies par les activites humaines.
Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departam... more Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Ecología. Fecha de lectura 11-05-2007 Bibliogr.: p. 167-180
Apart from safety issues, most scientific literature on the road/wildlife conflict has been focus... more Apart from safety issues, most scientific literature on the road/wildlife conflict has been focused on the analysis of the impacts of roads on animal populations. However, the integration of roads into ecosystems does not follow straightforwardly from such analyses as it depends on interactions between the infrastructure, the management operations and the biological communities in the surroundings. Thus, the involvement of companies that operate motorways is key in designing strategies to the environmental integration. From this perspective, we surveyed companies operating eight motorway sections in Spain (c. 225km in total) in order to identify: i) the types of fauna-related problems they faced, ii) the mitigation measures they take in response, and iii) the importance given to such problems in decision making, both subjectively and in terms of cost. A total of eight questionnaires were answered and six road-kill databases were gathered. Results show that the perception of wildlife problems and the implementation of mitigation measures varied between motorway sections, the highest-scored problems being road kills (cited in 100% of cases,), effects on the stability of roadslopes (50%), damage to fencing (50%) and carriageway deterioration (12%). Furthermore, the typology and extent of the problems differed significantly depending on the type of landscape crossed, with differences between those affecting motorways crossing urban zones and those seen at motorways in less disturbed areas. Companies adopt several mitigation and management actions that focus on these problems, with costs regarded as nonexistent or low in 62% of cases or moderate in 38%. The effectiveness of such actions is scarcely analyzed. In this regard, 38% of responders considered that the public image of their companies suffers from the road/wildlife conflict and 50% of them think that new mitigation measures should be implemented. In conclusion, and with the caution imposed by the small sample size, the survey shows i) road operating companies show disposition to take measures aimed at diminishing the road/wildlife conflict, and ii) highway management could benefit from improving scientific analyses of the implemented measures. Improved management could thus result from knowledge generated by their own monitoring of the effects of roads on wildlife.
Plant communities are often dispersal-limited and zoochory can be an efficient mechanism for plan... more Plant communities are often dispersal-limited and zoochory can be an efficient mechanism for plants to colonize new patches of potentially suitable habitat. We predicted that seed dispersal by ungulates acts as an ecological filterwhich differentially affects individuals according to their characteristics and shapes species assemblagesand that the filter varies according to the dispersal mechanism (endozoochory, fur-epizoochory and hoof-epizoochory). We conducted two-step individual participant data meta-analyses of 52 studies on plant dispersal by ungulates in fragmented landscapes, comparing eight plant traits and two habitat indicators between dispersed and non-dispersed plants. We found that ungulates dispersed at least 44% of the available plant species. Moreover, some plant traits and habitat indicators increased the likelihood for plant of being dispersed. Persistent or nitrophilous plant species from open habitats or bearing dry or elongated diaspores were more likely to be dispersed by ungulates, whatever the dispersal mechanism. In addition, endozoochory was more likely for diaspores bearing elongated appendages whereas epizoochory was more likely for diaspores released relatively high in vegetation. Hoof-epizoochory was more likely for light diaspores without hooked appendages. Fur-epizoochory was more likely for diaspores with appendages, particularly elongated or hooked ones. We thus observed a gradient of filtering effect among the three dispersal mechanisms. Endozoochory had an effect of rather weak intensity (impacting six plant characteristics with variations between ungulate-dispersed and nondispersed plant species mostly below 25%), whereas hoof-epizoochory had a stronger effect (eight characteristics included five ones with above 75% variation), and fur-epizoochory an even stronger one (nine characteristics included six ones with above 75% variation). Our results demonstrate that seed dispersal by ungulates is an ecological filter whose intensity varies according to the dispersal mechanism considered. Ungulates can thus play a key role in plant community dynamics and have implications for plant spatial distribution patterns at multiple scales.
Page 1. biodiversity Letters (1996) 3, 54-57 BIODIVERSITY RESEARCH New insights into pasture dive... more Page 1. biodiversity Letters (1996) 3, 54-57 BIODIVERSITY RESEARCH New insights into pasture diversity: the consequences of seed dispersal in herbivore dung JUAN E. MALO and FRANCISCO SUAREZ Departamento Interuniversitario ...
The percentage of central Iberian herbaceous percentage of anemochorous, endo-and exozoochorous s... more The percentage of central Iberian herbaceous percentage of anemochorous, endo-and exozoochorous species is somewhat higher in the dispersive spectrum of the species introduced into the Mediterranean zone of Chile is alien species introduced in Chile. These results suggest analysed in terms of the most usual types of dispersal: endothat the seed dispersal systems associated with animals are and exo-zoochory and anemochory. Almost 15% of the particularly favourable for the introduction of species, and herbaceous species from Central Iberia are naturalized in that herbivores have facilitated the naturalization and Chile. This proportion is significantly higher for the endospread of alien herbaceous species from their initial points and exozoochorous species (21% and 23%), and not of introduction. significantly for the anemochorous species (20%). In contrast, only 8% of the species not covered by these three
Columnar cacti are an important feature of the arid “cardonal” landscape in South America. The pr... more Columnar cacti are an important feature of the arid “cardonal” landscape in South America. The predominant columnar cactus in the southern zone is Echinopsis (= Trichocereus) terscheckii. At some sites, the species suffers considerable trunk damage, attributed in previous studies to feral livestock grazing (donkey and cattle). In order to understand the potential impact of this damage on columnar cactus populations, we investigated whether reproductive output (flower, fruit and seed production) of Echinopsis terscheckii ...
1. This paper presents a method for modelling unimodal flowering phenology based on fitting data ... more 1. This paper presents a method for modelling unimodal flowering phenology based on fitting data to an exponential sine function with a minimum number of parameters. 2. Such parameters have the advantage of being direct surrogates for the most relevant features of any phenology (start, duration, intensity, skewness and length of the tails). 3. The use of the proposed function is exemplified using flowering data collected from populations of five Cistaceae species (four from the genus Cistus and one from Halimium). 4. The fitted models account for a large part (> 90%) of the variance in the data, and their parameters are easily interpreted in ecological terms.
The study of rodent population cycles has greatly contributed, both theoretically and empirically... more The study of rodent population cycles has greatly contributed, both theoretically and empirically, to our understanding of the circumstances under which predator-prey interactions destabilize populations. According to the specialist predator hypothesis, reciprocal interactions between voles and small predators that specialize on voles, such as weasels, can cause multiannual cycles. A fundamental feature of classical weasel-vole models is a long time-lag in the numerical response of the predator to variations in prey abundance: weasel abundance increases with that of voles and peaks approximately 1 yr later. We investigated the numerical response of the common weasel (Mustela nivalis) to fluctuating abundances of common voles (Microtus arvalis) in recently colonized agrosteppes of Castilla-y-L eon, northwestern Spain, at the southern limit of the species' range. Populations of both weasels and voles exhibited multiannual cycles with a 3-yr period. Weasels responded quickly and numerically to changes in common-vole abundance, with a time lag between prey and weasel abundance that did not exceed 4 months and occurred during the breeding season, reflecting the quick conversion of prey into predator offspring and/or immigration to sites with high vole populations. We found no evidence of a sustained, high weasel abundance following vole abundance peaks. Weasel population growth rates showed spatial synchrony across study sites approximately 60 km apart. Weasel dynamics were more synchronized with that of common voles than with other prey species (mice or shrews). However, asynchrony within, as well as among sites, in the abundance of voles and alternative prey suggests that weasel mobility could allow them to avoid starvation during low-vole phases, precluding the emergence of prolonged time lag in the numerical response to voles. Our observations are inconsistent with the specialist predator hypothesis as currently formulated, and suggest that weasels might follow rather than cause the vole cycles in northwestern Spain. The reliance of a specialized predator on a functional group of prey such as small rodents does not necessarily lead to a long delay in the numerical response by the predator, depending on the spatial and interspecific synchrony in prey dynamics.
We analyse the hypothesis that predictable gradients occur in plant-pollinator interactions along... more We analyse the hypothesis that predictable gradients occur in plant-pollinator interactions along altitudinal gradients due to thermal constraints on insect body size and floral traits being selected for by pollinators. Pollinators' size should follow Bergmann's rule in mountains (larger body size at higher altitudes) and selection should, in turn, lead to larger flower size at higher altitudes. The study focuses on the flower and pollinator size variation in 11 Cytisus scoparius populations located between 680 and 1300 m a.s.l., and on the relationship between flower size and pollination success of plants in each population. Significant differences among populations were found in flower size, pollinator size and fruiting success ( , P < 0.001 in all cases). Regression models show that (i) pollinator size increases significantly with altitude, (ii) a parallel quadratic increase in flower size and (iii) a quadratic decrease in pollination success with altitude. Moreover, there is a tendency of plants with smaller flowers in each population to have a higher percentage of flowers initiating development into fruits ( , P < 0.05). All these observations support the presence of the predicted gradient in the studied species and they suggest the possibility of it to be somewhat common among plants that occupy large altitudinal ranges due to the simple basis on which it could be rooted.
Understanding how roads affect the persistence of animal populations is one of the challenges of ... more Understanding how roads affect the persistence of animal populations is one of the challenges of road ecology. Small mammals are of great interest on account of their value as indicators of environmental impacts and their key role in ecosystems. Nevertheless, there is a large gap in our knowledge of small mammal communities in the proximity of roads. An intensive study was conducted of the effect of a motorway on the small mammal communities in an extensively managed Mediterranean landscape. Live-trapping methods were used over a 2-year period to characterise the structure and dynamics of small mammal populations at increasing distances from the motorway (0-500-1000 m). In total, 1004 individuals of three species were captured. All three were significantly more abundant nearest to the motorway. In addition, in the case of the wood mouse, a higher proportion of juveniles was found at 0 m and 500 m from the motorway and its abundance was independent of other, habitat-related, characteristics. The greater abundance of small mammals in close vicinity to the motorway became more obvious during the second year, when a population crash reduced captures by over 60%. Thus, the ratio of captures alongside the motorway relative to those at the other distances analysed rose from approximately 3:2 to 9:2. The results point to roadside verges being an important refuge for small mammals in terms both of greater abundance and population stability. This finding has important implications from the viewpoint of conservation biology and for management of the environmental impacts of roads.
Cytisus scoparius (L.) Link (Fabaceae) has a ballistic type of primary seed-dispersal mechanism i... more Cytisus scoparius (L.) Link (Fabaceae) has a ballistic type of primary seed-dispersal mechanism in which its legumes dehisce suddenly when they dry. This paper presents an experimental approach to the measurement and modeling of distances reached by seeds under optimum dispersal conditions. Branchlets of the species carrying mature legumes were collected and attached to 1.20-m-high platforms on a flat roof terrace. For 2 weeks, daily measurements were made of distances attained by seeds ejected from legumes in the previous 24 h. Seeds were found at a distance of 2343 ± 113 mm (mean ± s.e., n = 245), with 10.2% of recorded distances greater than 5 m and some about 7 m. The mixture model fitted to the distances traveled by seeds allows the mathematical isolation of two underlying processes, the ballistic projection of seeds by dehiscent legumes (nearly 49% of seeds, reaching 3686 ± 1797 mm) and the barochorous dispersal of the remaining seeds in the platform environs (1254 ± 1254 mm)....
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Social prey species respond to predation risk by modifying habitat selection and grouping behavio... more Social prey species respond to predation risk by modifying habitat selection and grouping behaviour. These responses may depend on both actual predation risk (predator probability of occurrence) and/or on perceived predation risk associated with habitat structure. Other factors like food availability and co-occurrence with other species may also affect habitat selection and group formation. We analyse habitat selection and grouping behaviour (group size and cohesion) of lesser rhea (Rhea pennata subsp. pennata), a ratite endemic of South America inhabiting steppe shrublands and grasslands, in relation to actual (puma probability of occurrence) and perceived (habitat structure: openness, visibility) predation risk, co-occurrence with other herbivore species and forage availability in the Chilean Patagonia. We used data from 9 sampling seasons in 5 years. Results show that habitat selection, group size and cohesion in lesser rhea were mainly driven by variables associated with perceived predation risk and by co-occurrence with other herbivores both during breeding and non–breeding season. As expected, lesser rhea preferred open habitats (vegas and grasslands) that allow a behaviour of ‘watch and run’ to avoid predation and formed larger groups in them. Moreover, lesser rhea positively selected year-round habitats where livestock occur, forming large groups during non–breeding season there. Group size and co-occurrence with other herbivores significantly decreased group cohesion, suggesting a reduction of perceived predation risk. Therefore, lesser rhea seems to take advantage of forming mixed interspecific groups to reduce predation risk. These results suggest that lesser rhea habitat selection and grouping behaviour are preferentially driven by factors related to perceived predation risk than by actual predator occurrence or food availability.
Social prey species respond to predation risk by modifying habitat selection and grouping behavio... more Social prey species respond to predation risk by modifying habitat selection and grouping behaviour. These responses may depend on both actual predation risk (predator probability of occurrence) and/or on perceived predation risk associated with habitat structure. Other factors like food availability and co-occurrence with other species may also affect habitat selection and group formation. We analyse habitat selection and grouping behaviour (group size and cohesion) of lesser rhea (Rhea pennata subsp. pennata), a ratite endemic of South America inhabiting steppe shrublands and grasslands, in relation to actual (puma probability of occurrence) and perceived (habitat structure: openness, visibility) predation risk, co-occurrence with other herbivore species and forage availability in the Chilean Patagonia. We used data from 9 sampling seasons in 5 years. Results show that habitat selection, group size and cohesion in lesser rhea were mainly driven by variables associated with perceived predation risk and by co-occurrence with other herbivores both during breeding and non–breeding season. As expected, lesser rhea preferred open habitats (vegas and grasslands) that allow a behaviour of ‘watch and run’ to avoid predation and formed larger groups in them. Moreover, lesser rhea positively selected year-round habitats where livestock occur, forming large groups during non–breeding season there. Group size and co-occurrence with other herbivores significantly decreased group cohesion, suggesting a reduction of perceived predation risk. Therefore, lesser rhea seems to take advantage of forming mixed interspecific groups to reduce predation risk. These results suggest that lesser rhea habitat selection and grouping behaviour are preferentially driven by factors related to perceived predation risk than by actual predator occurrence or food availability.
Growth of wild ungulate populations within protected areas can cause an expansion towards surroun... more Growth of wild ungulate populations within protected areas can cause an expansion towards surrounding non-protected areas and lead to conflicts with human activities. The spatial and demographic structure of colonizing populations inform about their state and potential trends, since the initial colonization by dispersing individuals precedes the establishment of a population with potential for further growth and expansion. Once colonization has succeeded, the spatial pattern of animal abundance is associated with intra-and interspecific interactions and environmental factors (e.g., habitat and food availability) and the population shows similar demographic features throughout the whole occupation area, which has been called a diffusive dispersal pattern. Here, we analyze the current status of colonization by a guanaco population of ranches surrounding a protected area in Chilean Patagonia with data gathered along three consecutive years. We thus compared animal abundance and social structure between the protected and unprotected areas and evaluated throughout the whole area the effect of environmental factors on guanaco abundance, proportion of family groups, and reproductive success. Guanaco abundance significantly declined with increasing distance from the center of the local distribution and marginally with predation risk. Moreover, social structure showed only minor differences between areas, pointing to a diffusive dispersal pattern. These results suggest that the population is already well established and has the potential to grow and continue its expansion. The case exemplifies a challenging outcome of successful animal conservation, and it presents a useful approach to evaluate the state of wild ungulate populations colonizing new areas.
L'ecologie reproductive de Cistus ladanifer a ete associee traditionnellement a l'apparit... more L'ecologie reproductive de Cistus ladanifer a ete associee traditionnellement a l'apparition des incendies, bien que la dispersion des graines de cette espece par le cerf puisse jouer un role important dans la capacite colonisatrice de l'espece et etre en rapport avec la dormance des graines. On a analyse a chaque saison le contenu en graines des fumees du cerf et le pouvoir germinatif des graines obtenues directement sur la plante ainsi que de celles contenues dans les excrements. Le cerf disperse un grand nombre de semences de cette espece, plus de 250.000 par individu entre fevrier et aout, avec un maximum en ete d'environ 8.000 par individu -1 jour -1 ; elles ont un pourcentage de germination rapide plus grand que celui des graines recoltees sur la plante (46% vs. 30%). Ces resultats completent la vision traditionnelle que l'on a de la reproduction de ce ciste, surtout en ce qui concerne des graines des epoques anterieures a l'augmentation des incendies par les activites humaines.
Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departam... more Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Ecología. Fecha de lectura 11-05-2007 Bibliogr.: p. 167-180
Apart from safety issues, most scientific literature on the road/wildlife conflict has been focus... more Apart from safety issues, most scientific literature on the road/wildlife conflict has been focused on the analysis of the impacts of roads on animal populations. However, the integration of roads into ecosystems does not follow straightforwardly from such analyses as it depends on interactions between the infrastructure, the management operations and the biological communities in the surroundings. Thus, the involvement of companies that operate motorways is key in designing strategies to the environmental integration. From this perspective, we surveyed companies operating eight motorway sections in Spain (c. 225km in total) in order to identify: i) the types of fauna-related problems they faced, ii) the mitigation measures they take in response, and iii) the importance given to such problems in decision making, both subjectively and in terms of cost. A total of eight questionnaires were answered and six road-kill databases were gathered. Results show that the perception of wildlife problems and the implementation of mitigation measures varied between motorway sections, the highest-scored problems being road kills (cited in 100% of cases,), effects on the stability of roadslopes (50%), damage to fencing (50%) and carriageway deterioration (12%). Furthermore, the typology and extent of the problems differed significantly depending on the type of landscape crossed, with differences between those affecting motorways crossing urban zones and those seen at motorways in less disturbed areas. Companies adopt several mitigation and management actions that focus on these problems, with costs regarded as nonexistent or low in 62% of cases or moderate in 38%. The effectiveness of such actions is scarcely analyzed. In this regard, 38% of responders considered that the public image of their companies suffers from the road/wildlife conflict and 50% of them think that new mitigation measures should be implemented. In conclusion, and with the caution imposed by the small sample size, the survey shows i) road operating companies show disposition to take measures aimed at diminishing the road/wildlife conflict, and ii) highway management could benefit from improving scientific analyses of the implemented measures. Improved management could thus result from knowledge generated by their own monitoring of the effects of roads on wildlife.
Plant communities are often dispersal-limited and zoochory can be an efficient mechanism for plan... more Plant communities are often dispersal-limited and zoochory can be an efficient mechanism for plants to colonize new patches of potentially suitable habitat. We predicted that seed dispersal by ungulates acts as an ecological filterwhich differentially affects individuals according to their characteristics and shapes species assemblagesand that the filter varies according to the dispersal mechanism (endozoochory, fur-epizoochory and hoof-epizoochory). We conducted two-step individual participant data meta-analyses of 52 studies on plant dispersal by ungulates in fragmented landscapes, comparing eight plant traits and two habitat indicators between dispersed and non-dispersed plants. We found that ungulates dispersed at least 44% of the available plant species. Moreover, some plant traits and habitat indicators increased the likelihood for plant of being dispersed. Persistent or nitrophilous plant species from open habitats or bearing dry or elongated diaspores were more likely to be dispersed by ungulates, whatever the dispersal mechanism. In addition, endozoochory was more likely for diaspores bearing elongated appendages whereas epizoochory was more likely for diaspores released relatively high in vegetation. Hoof-epizoochory was more likely for light diaspores without hooked appendages. Fur-epizoochory was more likely for diaspores with appendages, particularly elongated or hooked ones. We thus observed a gradient of filtering effect among the three dispersal mechanisms. Endozoochory had an effect of rather weak intensity (impacting six plant characteristics with variations between ungulate-dispersed and nondispersed plant species mostly below 25%), whereas hoof-epizoochory had a stronger effect (eight characteristics included five ones with above 75% variation), and fur-epizoochory an even stronger one (nine characteristics included six ones with above 75% variation). Our results demonstrate that seed dispersal by ungulates is an ecological filter whose intensity varies according to the dispersal mechanism considered. Ungulates can thus play a key role in plant community dynamics and have implications for plant spatial distribution patterns at multiple scales.
Page 1. biodiversity Letters (1996) 3, 54-57 BIODIVERSITY RESEARCH New insights into pasture dive... more Page 1. biodiversity Letters (1996) 3, 54-57 BIODIVERSITY RESEARCH New insights into pasture diversity: the consequences of seed dispersal in herbivore dung JUAN E. MALO and FRANCISCO SUAREZ Departamento Interuniversitario ...
The percentage of central Iberian herbaceous percentage of anemochorous, endo-and exozoochorous s... more The percentage of central Iberian herbaceous percentage of anemochorous, endo-and exozoochorous species is somewhat higher in the dispersive spectrum of the species introduced into the Mediterranean zone of Chile is alien species introduced in Chile. These results suggest analysed in terms of the most usual types of dispersal: endothat the seed dispersal systems associated with animals are and exo-zoochory and anemochory. Almost 15% of the particularly favourable for the introduction of species, and herbaceous species from Central Iberia are naturalized in that herbivores have facilitated the naturalization and Chile. This proportion is significantly higher for the endospread of alien herbaceous species from their initial points and exozoochorous species (21% and 23%), and not of introduction. significantly for the anemochorous species (20%). In contrast, only 8% of the species not covered by these three
Columnar cacti are an important feature of the arid “cardonal” landscape in South America. The pr... more Columnar cacti are an important feature of the arid “cardonal” landscape in South America. The predominant columnar cactus in the southern zone is Echinopsis (= Trichocereus) terscheckii. At some sites, the species suffers considerable trunk damage, attributed in previous studies to feral livestock grazing (donkey and cattle). In order to understand the potential impact of this damage on columnar cactus populations, we investigated whether reproductive output (flower, fruit and seed production) of Echinopsis terscheckii ...
1. This paper presents a method for modelling unimodal flowering phenology based on fitting data ... more 1. This paper presents a method for modelling unimodal flowering phenology based on fitting data to an exponential sine function with a minimum number of parameters. 2. Such parameters have the advantage of being direct surrogates for the most relevant features of any phenology (start, duration, intensity, skewness and length of the tails). 3. The use of the proposed function is exemplified using flowering data collected from populations of five Cistaceae species (four from the genus Cistus and one from Halimium). 4. The fitted models account for a large part (> 90%) of the variance in the data, and their parameters are easily interpreted in ecological terms.
The study of rodent population cycles has greatly contributed, both theoretically and empirically... more The study of rodent population cycles has greatly contributed, both theoretically and empirically, to our understanding of the circumstances under which predator-prey interactions destabilize populations. According to the specialist predator hypothesis, reciprocal interactions between voles and small predators that specialize on voles, such as weasels, can cause multiannual cycles. A fundamental feature of classical weasel-vole models is a long time-lag in the numerical response of the predator to variations in prey abundance: weasel abundance increases with that of voles and peaks approximately 1 yr later. We investigated the numerical response of the common weasel (Mustela nivalis) to fluctuating abundances of common voles (Microtus arvalis) in recently colonized agrosteppes of Castilla-y-L eon, northwestern Spain, at the southern limit of the species' range. Populations of both weasels and voles exhibited multiannual cycles with a 3-yr period. Weasels responded quickly and numerically to changes in common-vole abundance, with a time lag between prey and weasel abundance that did not exceed 4 months and occurred during the breeding season, reflecting the quick conversion of prey into predator offspring and/or immigration to sites with high vole populations. We found no evidence of a sustained, high weasel abundance following vole abundance peaks. Weasel population growth rates showed spatial synchrony across study sites approximately 60 km apart. Weasel dynamics were more synchronized with that of common voles than with other prey species (mice or shrews). However, asynchrony within, as well as among sites, in the abundance of voles and alternative prey suggests that weasel mobility could allow them to avoid starvation during low-vole phases, precluding the emergence of prolonged time lag in the numerical response to voles. Our observations are inconsistent with the specialist predator hypothesis as currently formulated, and suggest that weasels might follow rather than cause the vole cycles in northwestern Spain. The reliance of a specialized predator on a functional group of prey such as small rodents does not necessarily lead to a long delay in the numerical response by the predator, depending on the spatial and interspecific synchrony in prey dynamics.
We analyse the hypothesis that predictable gradients occur in plant-pollinator interactions along... more We analyse the hypothesis that predictable gradients occur in plant-pollinator interactions along altitudinal gradients due to thermal constraints on insect body size and floral traits being selected for by pollinators. Pollinators' size should follow Bergmann's rule in mountains (larger body size at higher altitudes) and selection should, in turn, lead to larger flower size at higher altitudes. The study focuses on the flower and pollinator size variation in 11 Cytisus scoparius populations located between 680 and 1300 m a.s.l., and on the relationship between flower size and pollination success of plants in each population. Significant differences among populations were found in flower size, pollinator size and fruiting success ( , P < 0.001 in all cases). Regression models show that (i) pollinator size increases significantly with altitude, (ii) a parallel quadratic increase in flower size and (iii) a quadratic decrease in pollination success with altitude. Moreover, there is a tendency of plants with smaller flowers in each population to have a higher percentage of flowers initiating development into fruits ( , P < 0.05). All these observations support the presence of the predicted gradient in the studied species and they suggest the possibility of it to be somewhat common among plants that occupy large altitudinal ranges due to the simple basis on which it could be rooted.
Understanding how roads affect the persistence of animal populations is one of the challenges of ... more Understanding how roads affect the persistence of animal populations is one of the challenges of road ecology. Small mammals are of great interest on account of their value as indicators of environmental impacts and their key role in ecosystems. Nevertheless, there is a large gap in our knowledge of small mammal communities in the proximity of roads. An intensive study was conducted of the effect of a motorway on the small mammal communities in an extensively managed Mediterranean landscape. Live-trapping methods were used over a 2-year period to characterise the structure and dynamics of small mammal populations at increasing distances from the motorway (0-500-1000 m). In total, 1004 individuals of three species were captured. All three were significantly more abundant nearest to the motorway. In addition, in the case of the wood mouse, a higher proportion of juveniles was found at 0 m and 500 m from the motorway and its abundance was independent of other, habitat-related, characteristics. The greater abundance of small mammals in close vicinity to the motorway became more obvious during the second year, when a population crash reduced captures by over 60%. Thus, the ratio of captures alongside the motorway relative to those at the other distances analysed rose from approximately 3:2 to 9:2. The results point to roadside verges being an important refuge for small mammals in terms both of greater abundance and population stability. This finding has important implications from the viewpoint of conservation biology and for management of the environmental impacts of roads.
Cytisus scoparius (L.) Link (Fabaceae) has a ballistic type of primary seed-dispersal mechanism i... more Cytisus scoparius (L.) Link (Fabaceae) has a ballistic type of primary seed-dispersal mechanism in which its legumes dehisce suddenly when they dry. This paper presents an experimental approach to the measurement and modeling of distances reached by seeds under optimum dispersal conditions. Branchlets of the species carrying mature legumes were collected and attached to 1.20-m-high platforms on a flat roof terrace. For 2 weeks, daily measurements were made of distances attained by seeds ejected from legumes in the previous 24 h. Seeds were found at a distance of 2343 ± 113 mm (mean ± s.e., n = 245), with 10.2% of recorded distances greater than 5 m and some about 7 m. The mixture model fitted to the distances traveled by seeds allows the mathematical isolation of two underlying processes, the ballistic projection of seeds by dehiscent legumes (nearly 49% of seeds, reaching 3686 ± 1797 mm) and the barochorous dispersal of the remaining seeds in the platform environs (1254 ± 1254 mm)....
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Papers by Juan Malo