TY - BOOK
T1 - Interspecific Interactions between the Invasive Beetle Harmonia axyridis, Native Anthocorids and Entomopathogenic Fungi
AU - Howe, Andrew Gordon
PY - 2014
Y1 - 2014
N2 - The Earth’s biodiversity encompasses dynamic arrangements of ecosystems, species and their inherent genetic diversity. Biodiversity is an integral component underlying functional ecosystems. Human well-being is dependent on a variety of services provided by ecosystems, e.g. climate regulation, pest suppression and provision of clean water. Concurrently, direct and indirect human influences can impinge biodiversity thereby disrupting ecosystem services. Understanding humanmediated drivers of biodiversity change will enhance sustainable use of ecosystems now and in the future. Increased global trade, travel and tourism are linked to biodiversity change. These drivers can inadvertently increase biotic exchange of species between regions, countries and continents, while deliberate species introductions have the same effect, e.g. release of biological control agents. Biotic exchange is considered negative when introduced species cause negative impacts on ecosystems, or cause economic or human detriment, i.e. biological invasions. Rates of biological invasion are more intense now than previously detected in prehistoric records and are recognized as a major threat to global biodiversity.
The harlequin ladybird Harmonia axyridis Pallas (Coleoptera: Coccinellidae) was introduced to North America from Asia in the early 20th century as a biological control agent against insect
agricultural pests. In the late 20th century a specific population in eastern North America became
invasive. Invasive H. axyridis have since spread to many countries on 4 continents. Evidence shows
native predatory insect species are negatively impinged. There is concern that decline of native
predatory insects may alter the regulating ecosystem service provided by these natural enemies, i.e.
pest suppression. Most of our knowledge of H. axyridis impacts on biodiversity stem from studies
on ladybirds associated with agricultural habitat. Furthermore, studies largely focus on intraguild
predation, a direct trophic interaction whereby H. axyridis attacks a native species with which it
competes with for a resource, e.g. aphids. However, a vast assemblage of predators other than
ladybirds may be affected by invasive H. axyridis, while other interspecific interactions may also be
implicated.
This PhD thesis addresses an indirect trophic interaction, namely interspecific competition, between
H. axyridis and Anthocoris nemoralis (Heteroptera: Anthocoridae), a European flower bug which
shares habitat and prey with invasive H. axyridis in urban habitats. Interspecific competition occurs
when species compete for limited resources, and can reduce predator fitness and contribute to
species displacement. This was approached through laboratory assays which assessed the relative
strength of interspecific competition compared to intraguild predation and possible effects thereof
on predators. A field-based study using DNA gut-content analysis tested whether trophic
interactions between co-occurring predators in urban arboreal habitats reflected findings from
laboratory assays. In addition, infection of H. axyridis by naturally occurring entomopathogenic
fungi was assessed in order to determine whether fungi co-occur with ladybirds in arboreal habitats
and whether entomopathogenic fungi exploit H. axyridis. Finally, in an attempt to shed light on the
role of insect behaviour in biological invasions, a supplementary dataset compared behavioural 8
traits (tendency to fly/mate and activity) relevant to successful invasion between five
native/invasive H. axyridis populations.
Findings from laboratory assays strongly suggested interspecific competition with H. axyridis is a
stronger interaction for A. nemoralis than intraguild predation by H. axyridis. This was manifest
through reduced survival and a sublethal effect on A. nemoralis fitness (weight gain). In urban
arboreal habitats, DNA gut-content analysis revealed a low level of intraguild predation by H.
axyridis, but a high level of prey overlap between predators, thereby confirming the relative
strengths of interspecific interactions among wild populations. Coupled with high temporal and spatial niche overlap of predators these findings demonstrate that interspecific competition for
resources by H. axyridis has the potential to affect local populations of native predatory insects
whose habitat is invaded by H. axyridis.
Five species of naturally occurring entomopathogenic fungi from three genera were distributed in
arboreal habitats, however two of these genera were responsible for most fungi prevalence in H.
axyridis and native ladybirds. These novel findings demonstrate that trees are a source of infection,
which suggests that entomopathogenic fungi contribute to regulation of H. axyridis populations in
invaded urban habitats. Finally, comparison of behaviours revealed that an invasive eastern North
American and native Chinese population displayed greater dispersal activity than three other
populations. Although an invasive/native dichotomy was not established, results suggest that trait
differences may reflect population-level adaptions. Findings underline that intraspecific
comparisons of an invasive species’ native and introduced populations may uncover traits which
play a role in biological invasions.
This PhD thesis contributes novel insights into interspecific interactions involving the harlequin
ladybird which have implications for species coexistence in invaded ecosystems. Concurrently, the
strength of trophic interactions between ladybirds and fungi were assessed in urban ecosystems,
which addresses the paucity of knowledge in ecosystems beyond agricultural habitats while also
contributing to basic ecological knowledge of fungi. Findings highlight the importance of assessing
indirect interspecific trophic interactions as they potentially affect a wider range of taxa than direct
interspecific interactions, e.g. intraguild predation.
AB - The Earth’s biodiversity encompasses dynamic arrangements of ecosystems, species and their inherent genetic diversity. Biodiversity is an integral component underlying functional ecosystems. Human well-being is dependent on a variety of services provided by ecosystems, e.g. climate regulation, pest suppression and provision of clean water. Concurrently, direct and indirect human influences can impinge biodiversity thereby disrupting ecosystem services. Understanding humanmediated drivers of biodiversity change will enhance sustainable use of ecosystems now and in the future. Increased global trade, travel and tourism are linked to biodiversity change. These drivers can inadvertently increase biotic exchange of species between regions, countries and continents, while deliberate species introductions have the same effect, e.g. release of biological control agents. Biotic exchange is considered negative when introduced species cause negative impacts on ecosystems, or cause economic or human detriment, i.e. biological invasions. Rates of biological invasion are more intense now than previously detected in prehistoric records and are recognized as a major threat to global biodiversity.
The harlequin ladybird Harmonia axyridis Pallas (Coleoptera: Coccinellidae) was introduced to North America from Asia in the early 20th century as a biological control agent against insect
agricultural pests. In the late 20th century a specific population in eastern North America became
invasive. Invasive H. axyridis have since spread to many countries on 4 continents. Evidence shows
native predatory insect species are negatively impinged. There is concern that decline of native
predatory insects may alter the regulating ecosystem service provided by these natural enemies, i.e.
pest suppression. Most of our knowledge of H. axyridis impacts on biodiversity stem from studies
on ladybirds associated with agricultural habitat. Furthermore, studies largely focus on intraguild
predation, a direct trophic interaction whereby H. axyridis attacks a native species with which it
competes with for a resource, e.g. aphids. However, a vast assemblage of predators other than
ladybirds may be affected by invasive H. axyridis, while other interspecific interactions may also be
implicated.
This PhD thesis addresses an indirect trophic interaction, namely interspecific competition, between
H. axyridis and Anthocoris nemoralis (Heteroptera: Anthocoridae), a European flower bug which
shares habitat and prey with invasive H. axyridis in urban habitats. Interspecific competition occurs
when species compete for limited resources, and can reduce predator fitness and contribute to
species displacement. This was approached through laboratory assays which assessed the relative
strength of interspecific competition compared to intraguild predation and possible effects thereof
on predators. A field-based study using DNA gut-content analysis tested whether trophic
interactions between co-occurring predators in urban arboreal habitats reflected findings from
laboratory assays. In addition, infection of H. axyridis by naturally occurring entomopathogenic
fungi was assessed in order to determine whether fungi co-occur with ladybirds in arboreal habitats
and whether entomopathogenic fungi exploit H. axyridis. Finally, in an attempt to shed light on the
role of insect behaviour in biological invasions, a supplementary dataset compared behavioural 8
traits (tendency to fly/mate and activity) relevant to successful invasion between five
native/invasive H. axyridis populations.
Findings from laboratory assays strongly suggested interspecific competition with H. axyridis is a
stronger interaction for A. nemoralis than intraguild predation by H. axyridis. This was manifest
through reduced survival and a sublethal effect on A. nemoralis fitness (weight gain). In urban
arboreal habitats, DNA gut-content analysis revealed a low level of intraguild predation by H.
axyridis, but a high level of prey overlap between predators, thereby confirming the relative
strengths of interspecific interactions among wild populations. Coupled with high temporal and spatial niche overlap of predators these findings demonstrate that interspecific competition for
resources by H. axyridis has the potential to affect local populations of native predatory insects
whose habitat is invaded by H. axyridis.
Five species of naturally occurring entomopathogenic fungi from three genera were distributed in
arboreal habitats, however two of these genera were responsible for most fungi prevalence in H.
axyridis and native ladybirds. These novel findings demonstrate that trees are a source of infection,
which suggests that entomopathogenic fungi contribute to regulation of H. axyridis populations in
invaded urban habitats. Finally, comparison of behaviours revealed that an invasive eastern North
American and native Chinese population displayed greater dispersal activity than three other
populations. Although an invasive/native dichotomy was not established, results suggest that trait
differences may reflect population-level adaptions. Findings underline that intraspecific
comparisons of an invasive species’ native and introduced populations may uncover traits which
play a role in biological invasions.
This PhD thesis contributes novel insights into interspecific interactions involving the harlequin
ladybird which have implications for species coexistence in invaded ecosystems. Concurrently, the
strength of trophic interactions between ladybirds and fungi were assessed in urban ecosystems,
which addresses the paucity of knowledge in ecosystems beyond agricultural habitats while also
contributing to basic ecological knowledge of fungi. Findings highlight the importance of assessing
indirect interspecific trophic interactions as they potentially affect a wider range of taxa than direct
interspecific interactions, e.g. intraguild predation.
UR - https://rex.kb.dk/primo-explore/fulldisplay?docid=KGL01008977090&context=L&vid=NUI&search_scope=KGL&tab=default_tab&lang=da_DK
M3 - Ph.D. thesis
BT - Interspecific Interactions between the Invasive Beetle Harmonia axyridis, Native Anthocorids and Entomopathogenic Fungi
PB - Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen
ER -
