Alejandra Troncoso | Universidad Mayor de San Simon (original) (raw)
Papers by Alejandra Troncoso
Revista Chilena de Historia Natural
Ecosystems provide a variety of benefits to human society and humanity’s utilization of ecosystem... more Ecosystems provide a variety of benefits to human society and humanity’s utilization of ecosystems affects their composition, structure, and functions. Global change drivers demand us to study the interactions between ecological and social systems, and advise strategies to protect the large fraction of Chilean unique ecosystems. Long-term research and monitoring are vital for meaningful understanding of human impacts and socio-ecological feedback, which occur over multiple spatial and time-scales and can be invisible to traditional grant-sponsored short-term studies.Despite the large fraction of unique ecosystems, Chilean government agencies have not established long-term monitoring programs to inform and guide management decisions for use, conservation, and adaptation to climate change. Responding to this void, the Chilean Long-Term Socio-Ecological Research Network (LTSER-Chile) was created, comprising nine study sites funded by a variety of private and public institutions, that b...
Ecological Modelling, 2018
We determined the composition and organization of avian mixed-species foraging flocks during the ... more We determined the composition and organization of avian mixed-species foraging flocks during the non-breeding season from April to August 2000 in a high-Andean forest fragment of Polylepis besseri (Rosaceae) (3710-3880 m a.s.l., 11 ha) in Cochabamba, Bolivia. Forest birds were color-banded monthly starting December 1999. Sixty-three observations of flocks were made containing a total of 10 species with a mean (± SD) of 2.8 ± 0.9 species and 5.4 ± 1.8 individuals per flock. The entire Polylepis bird community contained 30 core species. Since the forest was small, most flocks contained at least some of the same individuals. Three species occurred in > 70% (Giant Conebill Oreomanes fraseri, Tawny Tit-Spinetail Leptasthenura yanacensis, and White-throated Tyrannulet Mecocerculus leucophrys, with 2.6 ± 0.6, 1.9 ± 0.6, and 1.6 ± 0.5 individuals per flock respectively), one species (Asthenes dorbignyi with 1.4 ± 0.5 individuals per flock) in 21%, and the remaining six species in 5% of...
European Journal of Entomology, 2009
European Journal of Entomology, 2009
European Journal of Entomology, 2008
... AND CONSERVATION OF HIGH-ANDEAN POLYLEPIS FORESTS Sebastian K. Herzog1, Jennifer Cahjll M.1, ... more ... AND CONSERVATION OF HIGH-ANDEAN POLYLEPIS FORESTS Sebastian K. Herzog1, Jennifer Cahjll M.1, Jon Fjeldsa2, Michael Kessler3, EricYensen4 ... in a landscape otherwise characterized by a harsh climate unsuitable for tree growth (eg, Weberbauer 1930, Koepcke ...
uchile.academia.edu
HERZOG ETAL. INTRODUCTION Mixed-species foraging flocks are one of the most con-spicuous elements... more HERZOG ETAL. INTRODUCTION Mixed-species foraging flocks are one of the most con-spicuous elements of many tropical forest bird com-munities. They often contain large numbers of spe-cies and individuals (Munn &Terborgh 1979, Powell 1985, Hutto 1987) and are ...
Scientific Reports
Assessing population evolutionary potential has become a central tenet of conservation biology. S... more Assessing population evolutionary potential has become a central tenet of conservation biology. Since adaptive responses require allelic variation at functional genes, consensus has grown that genetic variation at genes under selection is a better surrogate for adaptive evolutionary potential than neutral genetic diversity. Although consistent with prevailing theory, this argument lacks empirical support and ignores recent theoretical advances questioning the very concept of neutral genetic diversity. In this study, we quantified genome-wide responses of single nucleotide polymorphism loci linked to climatic factors over a strong latitudinal gradient in natural populations of the high Andean wetland plant, Carex gayana, and then assessed whether genetic variation of candidate climate-selected loci better predicted their genome-wide responses than genetic variation of non-candidate loci. Contrary to this expectation, genomic responses of climate-linked loci only related significantly...
Oecologia, 2010
Host-plants can mediate the interactions between herbivores and their mutualists and also between... more Host-plants can mediate the interactions between herbivores and their mutualists and also between parasitic plants and their mutualists. The present study reveals how a hemiparasitic plant parasitizing three host species gives rise to three distinct hemiparasite-host neighborhoods which differ in terms of volatile composition and pollinator attractiveness. The study was performed in a population of the mistletoe Tristerix verticillatus infecting three different species of hosts occurring in sympatry within a small area, thus exposing all individuals studied to similar abiotic conditions and pollinator diversity; we assessed the effect of hosts on the hemiparasites’ visual and olfactory cues for pollinator attraction. During the study period, the hemiparasite individuals were flowering but the hosts were past their flowering stage. We collected volatile organic compounds from the hemiparasite and its hosts, measured floral display characteristics and monitored bird and insect visitors to inflorescences of T. verticillatus. We showed that: (1) floral patches did not differ in terms of floral display potentially involved in the attraction of pollinators, (2) hosts and hemiparasites on each host were discriminated as distinct chemical populations in terms of their volatile chemical profiles, (3) insect visitation rates differed between hemiparasites parasitizing different hosts, and (4) volatile compounds from the host and the hemiparasite influenced the visitation of hemiparasite flowers by insects. The study showed that a species regarded as “ornithophilic” by its floral morphology was actually mostly visited by insects that interacted with its sexual organs during their visits and carried its pollen, and that host-specific plant-volatile profiles within the T. verticillatus population were associated with differential attractiveness to pollinating insects.
Bulletin of Entomological Research, 2005
Entomologia Experimentalis Et Applicata, 2005
Host plant selection and acceptance by aphids involves four consecutive steps: (1) prealighting b... more Host plant selection and acceptance by aphids involves four consecutive steps: (1) prealighting behaviour, (2) leaf surface exploration and probing of subepidermal tissues, (3) deep probing of plant tissues, and (4) evaluation of the phloem sap. Host specialisation in aphids may involve not only different performances on potential hosts, but also different strategies for host selection and acceptance. Myzus persicae s.s. (Sulzer) (Homoptera: Aphididae) is one of the most polyphagous aphid species, although a tobacco-adapted subspecies, M. persicae nicotianae, has been described. These two taxa constitute a good system for studying the effect of host range on host selection strategies. We studied the first two steps in the host selection process by alate virginoparae of M. persicae s.s. and M. persicae nicotianae on host and non-host plants, using three types of behavioural assays: wind tunnel, olfactometry, and video-recording. Alate virginoparae of M. persicae nicotianae recognised and chose their host plant more efficiently than M. persicae s.s., on the basis of olfactory and visual cues, and factors residing at cuticular and subcuticular levels. Host recognition was evident before phloem tissues were contacted. Olfactory cues were apparently not involved in host selection by M. persicae s.s.
Bulletin of Entomological Research, 2007
The mistletoe Tristerix verticillatus (Loranthaceae) parasitizes within a small area of the Yerba... more The mistletoe Tristerix verticillatus (Loranthaceae) parasitizes within a small area of the Yerba Loca Nature Sanctuary near Santiago, Chile, three co-occurring hosts: Schinus montanus (Anacardiaceae), Fabiana imbricata (Solanaceae) and Berberis montana (Berberidaceae). Previous studies suggest that T. verticillatus may be favoured when parasitizing S. montanus relative to the other two host species. We hypothesize that infection of S. montanus is not proportional to its local abundance or appearance, that S. montanus is more intensively parasitized than other available hosts, and that host provenance is a determinant of the fate of the infecting seed.
We compare the incidence of infection of T. verticillatus in relation to local availability and appearance variables, and the intensity of infection of T. verticillatus, on the three co-occurring host species.We then test the effects of host provenance on mistletoe seed establishment success with a seed cross inoculation experiment varying the donor and receptor hosts. Finally, we test whether there are differences in establishment success between manually processed seeds and seeds defecated by the avian disperser Mimus thenca (Passeriformes: Mimidae). Our results show that the three hosts have an aggregated spatial distribution. Schinus montanus was parasitized at a higher rate than expected by its local availability and appearance, and inoculated seeds showed differential development depending on the origin of the seeds: seeds from T. verticillatus parasitizing S. montanus inoculated to S. montanus twigs showed higher germination and lower mortality than seeds from T. verticillatus parasitizing F. imbricata inoculated to S. montanus twigs. Furthermore, seeds defecated by the avian disperser, M. thenca, had higher adherence and reduced mortality when compared to manually processed seeds. The disproportional host infection found is discussed in terms of the differential establishment of mistletoe seeds, morphological characteristics of hosts and the behaviour of dispersing birds.
Host-plants can mediate the interactions between herbivores and their mutualists and also between... more Host-plants can mediate the interactions between herbivores and their mutualists and also between parasitic plants and their mutualists. The present study reveals how a hemiparasitic plant parasitizing three host species gives rise to three distinct hemiparasite-host neighborhoods which differ in terms of volatile composition and pollinator attractiveness. The study was performed in a population of the mistletoe Tristerix verticillatus infecting three different species of hosts occurring in sympatry within a small area, thus exposing all individuals studied to similar abiotic conditions and pollinator diversity; we assessed the effect of hosts on the hemiparasites’ visual and olfactory cues for pollinator attraction. During the study period, the hemiparasite individuals were flowering but the hosts were past their flowering stage. We collected volatile organic compounds from the hemiparasite and its hosts, measured floral display characteristics and monitored bird and insect visitors to inflorescences of T. verticillatus. We showed that: (1) floral patches did not differ in terms of floral display potentially involved in the attraction of pollinators, (2) hosts and hemiparasites on each host were discriminated as distinct chemical populations in terms of their volatile chemical profiles, (3) insect visitation rates differed between hemiparasites parasitizing different hosts, and (4) volatile compounds from the host and the hemiparasite influenced the visitation of hemiparasite flowers by insects. The study showed that a species regarded as ‘‘ornithophilic’’ by its floral morphology was actually mostly visited by insects that interacted with its sexual organs during their visits and carried its pollen, and that host-specific plant-volatile profiles within the T. verticillatus population were associated with differential attractiveness to pollinating insects.
The feeding behaviour of specialist butterflies may be affected by the mechanical and chemical ch... more The feeding behaviour of specialist butterflies may be affected by the mechanical and chemical characteristics of the tissues of their host-plants. Larvae of the butterfly, Battus polydamas archidamas feed only on Aristolochia chilensis, which contains aristolochic acids. We studied the oviposition pattern of adults and the foraging of larvae of B. polydamas archidamas over time in relation to variations in hardness of the substrate and concentration of aristolochic acids in different plant tissues. We further tested the effect of two artificial diets containing different concentrations of aristolochic acids on larval performance. B. polydamas archidamas oviposited mostly on young leaves and the larvae fed on this tissue until the second instar. Third instar larvae fed also on mature leaves and fourth and higher instars fed also on stems. Young leaves are softer and contain higher concentrations of aristolochic acids than mature leaves, and stems are both harder and contain a high concentration of aristolochic acids. Larvae reared on artificial diets containing a high concentration of aristolochic acids suffered less mortality and were heavier than those reared on a diet with a lower concentration of aristolochic acids, which suggests they are phagostimulatory. A strategy of host use regulated by aristolochic acid content and tissue hardness is discussed.
Papilionid butterflies of the tribe Troidini are specialists on plants of the family Aristolochia... more Papilionid butterflies of the tribe Troidini are specialists on plants of the family Aristolochiaceae. The role of plant volatiles in host recognition by adult and larval stages of these insects remains unknown. We used Battus polydamas archidamas (Papilionidae: Troidini) and its host-plant, Aristolochia chilensis (Aristolochiaceae), to study: (i) the olfactory and electrophysiological responses of adults to headspace volatiles of the host-plant, (ii) the chemical composition of the headspace volatiles of the host-plant, (iii) the patterns of aggregation of larvae in the field in order to ascertain the time when they leave the plant where the eggs were laid, and (iv) the olfactory responses of solitary-feeding fourth-instar larvae to headspace volatiles of the host-plant. Larvae left their initial host-plant during the third or fourth instar. Host-plant headspace volatiles attracted fourth-instar larvae as well as adults; adult females were more responsive than males. Taken together, these results reveal changes in the responsiveness to host-plant volatiles during development, and provide an insight into the host-plant specialization of this butterfly.
The importance of interspecific competition as a force promoting specialization in phytophagous i... more The importance of interspecific competition as a force promoting specialization in phytophagous insects has been long debated. Myzus persicae sensu stricto (Hemiptera: Aphididae) is one of the most polyphagous aphids. Its subspecies, M. persicae nicotianae, is found mainly on tobacco, although it can survive and reproduce on a relatively wide range of plant species in the laboratory. Since life history traits of these taxa make competitive interactions likely, we hypothesize that asymmetrical competition occurs between M. p. nicotianae and M. persicae s.s., and accounts for the exclusion of the former when they share a common resource. This hypothesis was tested in laboratory experiments, which examined the population growth of colonies of both taxa coexisting on sweet pepper. A replacement series experiment was set up with both aphid taxa on sweet pepper plants, and the rates of population growth (RPG) evaluated at 5 day intervals for 25 days. M. p. nicotianae showed a significantly lower RPG when interacting with M. persicae s.s. than when in monotypic colonies, while M. persicae s.s. RPG was unaffected by competition. The relative population growth from the second census onwards of M. persicae s.s. was consistently higher than that of M. p. nicotianae. Finally, the RPG of M. p. nicotianae was significantly reduced when the plant was infested with M. persicae s.s. The results suggest that the absence of M. p. nicotianae from sweet pepper in the field in Chile can be partly explained by competitive exclusion by M. persicae s.s.
Revista Chilena de Historia Natural
Ecosystems provide a variety of benefits to human society and humanity’s utilization of ecosystem... more Ecosystems provide a variety of benefits to human society and humanity’s utilization of ecosystems affects their composition, structure, and functions. Global change drivers demand us to study the interactions between ecological and social systems, and advise strategies to protect the large fraction of Chilean unique ecosystems. Long-term research and monitoring are vital for meaningful understanding of human impacts and socio-ecological feedback, which occur over multiple spatial and time-scales and can be invisible to traditional grant-sponsored short-term studies.Despite the large fraction of unique ecosystems, Chilean government agencies have not established long-term monitoring programs to inform and guide management decisions for use, conservation, and adaptation to climate change. Responding to this void, the Chilean Long-Term Socio-Ecological Research Network (LTSER-Chile) was created, comprising nine study sites funded by a variety of private and public institutions, that b...
Ecological Modelling, 2018
We determined the composition and organization of avian mixed-species foraging flocks during the ... more We determined the composition and organization of avian mixed-species foraging flocks during the non-breeding season from April to August 2000 in a high-Andean forest fragment of Polylepis besseri (Rosaceae) (3710-3880 m a.s.l., 11 ha) in Cochabamba, Bolivia. Forest birds were color-banded monthly starting December 1999. Sixty-three observations of flocks were made containing a total of 10 species with a mean (± SD) of 2.8 ± 0.9 species and 5.4 ± 1.8 individuals per flock. The entire Polylepis bird community contained 30 core species. Since the forest was small, most flocks contained at least some of the same individuals. Three species occurred in > 70% (Giant Conebill Oreomanes fraseri, Tawny Tit-Spinetail Leptasthenura yanacensis, and White-throated Tyrannulet Mecocerculus leucophrys, with 2.6 ± 0.6, 1.9 ± 0.6, and 1.6 ± 0.5 individuals per flock respectively), one species (Asthenes dorbignyi with 1.4 ± 0.5 individuals per flock) in 21%, and the remaining six species in 5% of...
European Journal of Entomology, 2009
European Journal of Entomology, 2009
European Journal of Entomology, 2008
... AND CONSERVATION OF HIGH-ANDEAN POLYLEPIS FORESTS Sebastian K. Herzog1, Jennifer Cahjll M.1, ... more ... AND CONSERVATION OF HIGH-ANDEAN POLYLEPIS FORESTS Sebastian K. Herzog1, Jennifer Cahjll M.1, Jon Fjeldsa2, Michael Kessler3, EricYensen4 ... in a landscape otherwise characterized by a harsh climate unsuitable for tree growth (eg, Weberbauer 1930, Koepcke ...
uchile.academia.edu
HERZOG ETAL. INTRODUCTION Mixed-species foraging flocks are one of the most con-spicuous elements... more HERZOG ETAL. INTRODUCTION Mixed-species foraging flocks are one of the most con-spicuous elements of many tropical forest bird com-munities. They often contain large numbers of spe-cies and individuals (Munn &Terborgh 1979, Powell 1985, Hutto 1987) and are ...
Scientific Reports
Assessing population evolutionary potential has become a central tenet of conservation biology. S... more Assessing population evolutionary potential has become a central tenet of conservation biology. Since adaptive responses require allelic variation at functional genes, consensus has grown that genetic variation at genes under selection is a better surrogate for adaptive evolutionary potential than neutral genetic diversity. Although consistent with prevailing theory, this argument lacks empirical support and ignores recent theoretical advances questioning the very concept of neutral genetic diversity. In this study, we quantified genome-wide responses of single nucleotide polymorphism loci linked to climatic factors over a strong latitudinal gradient in natural populations of the high Andean wetland plant, Carex gayana, and then assessed whether genetic variation of candidate climate-selected loci better predicted their genome-wide responses than genetic variation of non-candidate loci. Contrary to this expectation, genomic responses of climate-linked loci only related significantly...
Oecologia, 2010
Host-plants can mediate the interactions between herbivores and their mutualists and also between... more Host-plants can mediate the interactions between herbivores and their mutualists and also between parasitic plants and their mutualists. The present study reveals how a hemiparasitic plant parasitizing three host species gives rise to three distinct hemiparasite-host neighborhoods which differ in terms of volatile composition and pollinator attractiveness. The study was performed in a population of the mistletoe Tristerix verticillatus infecting three different species of hosts occurring in sympatry within a small area, thus exposing all individuals studied to similar abiotic conditions and pollinator diversity; we assessed the effect of hosts on the hemiparasites’ visual and olfactory cues for pollinator attraction. During the study period, the hemiparasite individuals were flowering but the hosts were past their flowering stage. We collected volatile organic compounds from the hemiparasite and its hosts, measured floral display characteristics and monitored bird and insect visitors to inflorescences of T. verticillatus. We showed that: (1) floral patches did not differ in terms of floral display potentially involved in the attraction of pollinators, (2) hosts and hemiparasites on each host were discriminated as distinct chemical populations in terms of their volatile chemical profiles, (3) insect visitation rates differed between hemiparasites parasitizing different hosts, and (4) volatile compounds from the host and the hemiparasite influenced the visitation of hemiparasite flowers by insects. The study showed that a species regarded as “ornithophilic” by its floral morphology was actually mostly visited by insects that interacted with its sexual organs during their visits and carried its pollen, and that host-specific plant-volatile profiles within the T. verticillatus population were associated with differential attractiveness to pollinating insects.
Bulletin of Entomological Research, 2005
Entomologia Experimentalis Et Applicata, 2005
Host plant selection and acceptance by aphids involves four consecutive steps: (1) prealighting b... more Host plant selection and acceptance by aphids involves four consecutive steps: (1) prealighting behaviour, (2) leaf surface exploration and probing of subepidermal tissues, (3) deep probing of plant tissues, and (4) evaluation of the phloem sap. Host specialisation in aphids may involve not only different performances on potential hosts, but also different strategies for host selection and acceptance. Myzus persicae s.s. (Sulzer) (Homoptera: Aphididae) is one of the most polyphagous aphid species, although a tobacco-adapted subspecies, M. persicae nicotianae, has been described. These two taxa constitute a good system for studying the effect of host range on host selection strategies. We studied the first two steps in the host selection process by alate virginoparae of M. persicae s.s. and M. persicae nicotianae on host and non-host plants, using three types of behavioural assays: wind tunnel, olfactometry, and video-recording. Alate virginoparae of M. persicae nicotianae recognised and chose their host plant more efficiently than M. persicae s.s., on the basis of olfactory and visual cues, and factors residing at cuticular and subcuticular levels. Host recognition was evident before phloem tissues were contacted. Olfactory cues were apparently not involved in host selection by M. persicae s.s.
Bulletin of Entomological Research, 2007
The mistletoe Tristerix verticillatus (Loranthaceae) parasitizes within a small area of the Yerba... more The mistletoe Tristerix verticillatus (Loranthaceae) parasitizes within a small area of the Yerba Loca Nature Sanctuary near Santiago, Chile, three co-occurring hosts: Schinus montanus (Anacardiaceae), Fabiana imbricata (Solanaceae) and Berberis montana (Berberidaceae). Previous studies suggest that T. verticillatus may be favoured when parasitizing S. montanus relative to the other two host species. We hypothesize that infection of S. montanus is not proportional to its local abundance or appearance, that S. montanus is more intensively parasitized than other available hosts, and that host provenance is a determinant of the fate of the infecting seed.
We compare the incidence of infection of T. verticillatus in relation to local availability and appearance variables, and the intensity of infection of T. verticillatus, on the three co-occurring host species.We then test the effects of host provenance on mistletoe seed establishment success with a seed cross inoculation experiment varying the donor and receptor hosts. Finally, we test whether there are differences in establishment success between manually processed seeds and seeds defecated by the avian disperser Mimus thenca (Passeriformes: Mimidae). Our results show that the three hosts have an aggregated spatial distribution. Schinus montanus was parasitized at a higher rate than expected by its local availability and appearance, and inoculated seeds showed differential development depending on the origin of the seeds: seeds from T. verticillatus parasitizing S. montanus inoculated to S. montanus twigs showed higher germination and lower mortality than seeds from T. verticillatus parasitizing F. imbricata inoculated to S. montanus twigs. Furthermore, seeds defecated by the avian disperser, M. thenca, had higher adherence and reduced mortality when compared to manually processed seeds. The disproportional host infection found is discussed in terms of the differential establishment of mistletoe seeds, morphological characteristics of hosts and the behaviour of dispersing birds.
Host-plants can mediate the interactions between herbivores and their mutualists and also between... more Host-plants can mediate the interactions between herbivores and their mutualists and also between parasitic plants and their mutualists. The present study reveals how a hemiparasitic plant parasitizing three host species gives rise to three distinct hemiparasite-host neighborhoods which differ in terms of volatile composition and pollinator attractiveness. The study was performed in a population of the mistletoe Tristerix verticillatus infecting three different species of hosts occurring in sympatry within a small area, thus exposing all individuals studied to similar abiotic conditions and pollinator diversity; we assessed the effect of hosts on the hemiparasites’ visual and olfactory cues for pollinator attraction. During the study period, the hemiparasite individuals were flowering but the hosts were past their flowering stage. We collected volatile organic compounds from the hemiparasite and its hosts, measured floral display characteristics and monitored bird and insect visitors to inflorescences of T. verticillatus. We showed that: (1) floral patches did not differ in terms of floral display potentially involved in the attraction of pollinators, (2) hosts and hemiparasites on each host were discriminated as distinct chemical populations in terms of their volatile chemical profiles, (3) insect visitation rates differed between hemiparasites parasitizing different hosts, and (4) volatile compounds from the host and the hemiparasite influenced the visitation of hemiparasite flowers by insects. The study showed that a species regarded as ‘‘ornithophilic’’ by its floral morphology was actually mostly visited by insects that interacted with its sexual organs during their visits and carried its pollen, and that host-specific plant-volatile profiles within the T. verticillatus population were associated with differential attractiveness to pollinating insects.
The feeding behaviour of specialist butterflies may be affected by the mechanical and chemical ch... more The feeding behaviour of specialist butterflies may be affected by the mechanical and chemical characteristics of the tissues of their host-plants. Larvae of the butterfly, Battus polydamas archidamas feed only on Aristolochia chilensis, which contains aristolochic acids. We studied the oviposition pattern of adults and the foraging of larvae of B. polydamas archidamas over time in relation to variations in hardness of the substrate and concentration of aristolochic acids in different plant tissues. We further tested the effect of two artificial diets containing different concentrations of aristolochic acids on larval performance. B. polydamas archidamas oviposited mostly on young leaves and the larvae fed on this tissue until the second instar. Third instar larvae fed also on mature leaves and fourth and higher instars fed also on stems. Young leaves are softer and contain higher concentrations of aristolochic acids than mature leaves, and stems are both harder and contain a high concentration of aristolochic acids. Larvae reared on artificial diets containing a high concentration of aristolochic acids suffered less mortality and were heavier than those reared on a diet with a lower concentration of aristolochic acids, which suggests they are phagostimulatory. A strategy of host use regulated by aristolochic acid content and tissue hardness is discussed.
Papilionid butterflies of the tribe Troidini are specialists on plants of the family Aristolochia... more Papilionid butterflies of the tribe Troidini are specialists on plants of the family Aristolochiaceae. The role of plant volatiles in host recognition by adult and larval stages of these insects remains unknown. We used Battus polydamas archidamas (Papilionidae: Troidini) and its host-plant, Aristolochia chilensis (Aristolochiaceae), to study: (i) the olfactory and electrophysiological responses of adults to headspace volatiles of the host-plant, (ii) the chemical composition of the headspace volatiles of the host-plant, (iii) the patterns of aggregation of larvae in the field in order to ascertain the time when they leave the plant where the eggs were laid, and (iv) the olfactory responses of solitary-feeding fourth-instar larvae to headspace volatiles of the host-plant. Larvae left their initial host-plant during the third or fourth instar. Host-plant headspace volatiles attracted fourth-instar larvae as well as adults; adult females were more responsive than males. Taken together, these results reveal changes in the responsiveness to host-plant volatiles during development, and provide an insight into the host-plant specialization of this butterfly.
The importance of interspecific competition as a force promoting specialization in phytophagous i... more The importance of interspecific competition as a force promoting specialization in phytophagous insects has been long debated. Myzus persicae sensu stricto (Hemiptera: Aphididae) is one of the most polyphagous aphids. Its subspecies, M. persicae nicotianae, is found mainly on tobacco, although it can survive and reproduce on a relatively wide range of plant species in the laboratory. Since life history traits of these taxa make competitive interactions likely, we hypothesize that asymmetrical competition occurs between M. p. nicotianae and M. persicae s.s., and accounts for the exclusion of the former when they share a common resource. This hypothesis was tested in laboratory experiments, which examined the population growth of colonies of both taxa coexisting on sweet pepper. A replacement series experiment was set up with both aphid taxa on sweet pepper plants, and the rates of population growth (RPG) evaluated at 5 day intervals for 25 days. M. p. nicotianae showed a significantly lower RPG when interacting with M. persicae s.s. than when in monotypic colonies, while M. persicae s.s. RPG was unaffected by competition. The relative population growth from the second census onwards of M. persicae s.s. was consistently higher than that of M. p. nicotianae. Finally, the RPG of M. p. nicotianae was significantly reduced when the plant was infested with M. persicae s.s. The results suggest that the absence of M. p. nicotianae from sweet pepper in the field in Chile can be partly explained by competitive exclusion by M. persicae s.s.