Nematodes, mites and Collembola as predators of nematodes, and the role of generalist predators.

Allee effects driven by predation can play a strong role in the decline of small populations but are conventionally thought to occur when generalist predators target specific prey (i.e. type II functional response). However, aside from direct consumption, fear of predators could also increase vigilance and reduce time spent foraging as population size decreases, as has been observed in wild mammals living in social groups. To investigate the role of fear on fitness in relation to population density in a species with limited sociality, we exposed varying densities of Drosophila melanogaster to mantid predators either during an experimental breeding season or non-breeding season. The presence of mantids in either season decreased the reproductive performance of individuals but only at low breeding densities, providing evidence for an Allee effect. We then used our experimental results to parametrize a mathematical model to examine the population consequences of fear at low densities. Fear tended to destabilize population dynamics and increase the risk of extinction up to sevenfold. Our study provides unique experimental evidence that the indirect effects of the presence of predators can cause an Allee effect and has important consequences for our understanding of the dynamics of small populations.

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Monoclonal antibodies reveal the potential of the tetragnathid spider Pachygnatha degeeri (Araneae: Tetragnathidae) as an aphid predator

Bulletin of Entomological Research ◽

10.1079/ber2004346 ◽

2005 ◽

Vol 95 (2) ◽

pp. 161-167 ◽

Cited By ~ 40

Author(s):

J.D. Harwood ◽

K.D. Sunderland ◽

W.O.C. Symondson

Keyword(s):

Monoclonal Antibodies ◽

Integrated Approach ◽

High Rate ◽

Generalist Predators ◽

Large Numbers ◽

Aphid Predators ◽

Predator Complex ◽

The Uk ◽

Establishment Phase

AbstractThe drive towards a more sustainable and integrated approach to pest management has engendered a renewed interest in conservation biological control, the role of natural enemy communities and their interactions with prey. Monoclonal antibodies have provided significant advances in enhancing our knowledge of trophic interactions and can be employed to help quantify predation on target species. The tetragnathid spider Pachygnatha degeeri Sundevall was collected from fields of winter wheat in the UK and assayed by ELISA for aphid proteins. It was demonstrated that this spider did not simply consume greater quantities of aphids because it was bigger. In addition, P. degeeri contained significantly greater concentrations of aphid in their guts than other spiders, showing that aphids comprised a greater proportion of their diet. Although P. degeeri constituted only 6% of the spider population numerically, females and males respectively contained 16% and 37% of total aphid proteins within all spiders screened, significantly more than their density would predict. These spiders also preyed upon aphids at a disproportionately high rate in June, during the aphid establishment phase, theoretically the best time for limiting growth in the aphid population. Although less abundant than other generalist predators, the capability of these hunting spiders to consume large numbers of aphids highlights them as a more significant component of the predator complex than had previously been realized. Limitation of aphid numbers early in the year by generalist predators provides more time for the specialist aphid predators and parasitoids to move in.

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Development of a multi-primer metabarcoding approach to understand trophic interactions in agroecosystems

10.1101/2021.05.19.444782 ◽

2021 ◽

Author(s):

Iván Batuecas ◽

Oscar Alomar ◽

Cristina Casta&ntildee ◽

Josep Pi&ntildeol ◽

Stephane Boyer ◽

...

Keyword(s):

Trophic Interactions ◽

High Throughput Sequencing ◽

Trophic Relationships ◽

Generalist Predators ◽

Plant Resources ◽

Molecular Approaches ◽

Trophic Links ◽

Anthocoris Nemoralis ◽

Predatory Insects

Knowing which arthropod and plant resources are used by generalist predators in agroecosystems is important to understand trophic interactions and the precise ecological role of each predatory species. To achieve this objective, molecular approaches, such as the use of high-throughput sequencing (HTS) platforms are key. This study develops a multi-primer metabarcoding approach and explores its suitability for the screening of the most common trophic interactions of two predatory species of arthropod with contrasted morphology, Rhagonycha fulva (Coleoptera: Cantharidae) and Anthocoris nemoralis (Hemiptera: Anthocoridae) collected in an organic peach crop. To save time and cost in this metabarcoding approach, we first evaluated the effect of two different predator-pool sizes (10 and 23 individuals of the same species), as well as the performance of using one or two primer pairs in the same library. Our results show that the analysis of 23 individuals together with the use of two primer pairs in the same library optimizes the HTS analysis. With these best-performing conditions, we analyzed whole bodies of field-collected predators as well as the washing solutions used to clean the insect bodies. Results showed that we were able to identify both, gut content (i.e. diet) as well as external pollen load (i.e. on the insects body), respectively. This study also demonstrates the need of washing predatory insects prior to HTS analysis when the target species have a considerable size and hairy structures. This metabarcoding approach has a high potential for the study of trophic links in agriculture, revealing both expected and unexpected trophic relationships.

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Feeding and decoration preferences of the epialtidae crab Acanthonyx scutiforms

Brazilian Journal of Oceanography ◽

10.1590/s1679-87592009000200006 ◽

2009 ◽

Vol 57 (2) ◽

pp. 137-143 ◽

Cited By ~ 7

Author(s):

Marcelo Augusto Vasconcelos ◽

Thiago Costa Mendes ◽

Wagner Luiz Soares Fortes ◽

Renato Crespo Pereira

Keyword(s):

Generalist Predators ◽

Red Seaweed ◽

Crab Species ◽

Feeding Preferences ◽

Dictyota Menstrualis ◽

The Family ◽

Decorator Crab ◽

Choice Feeding ◽

Plocamium Brasiliense

Studies on the feeding preferences of marine herbivores are very important for our better understanding of the biology and the ecological role of these organisms. Members of the family Epialtidae are usually herbivores that mask themselves with pieces of seaweed and other materials to avoid predation. In order to better understand the mechanisms of food and decorating choices of the decorator crab Acanthonyx scutiformis, two multiple-choice feeding assays were performed using fresh seaweeds and artificial food containing crude extracts of the four seaweeds Osmundaria obtusiloba, Plocamium brasiliense, Sargassum sp., and Dictyota menstrualis, offered simultaneously to this crab species. In both assays the seaweed most consumed was O. obtusiloba, followed by P. brasiliense and Sargassum sp., while D. menstrualis was the least consumed. It is suggested that A. scutiformis is a generalist feeder, but with some preference for the perennial red seaweed O. obtusiloba and the chemically-defended seaweed P. brasiliense. Decorating behavior observations revealed the preferences of A. scutiformis by P. brasiliense. This decorating behavior can be interpreted as a mechanism to avoid generalist predators, since feeding and decorating preference were not associated and the crab used only small pieces of chemically defended algae.

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Host range in phytophagous insects: the potential role of generalist predators

Evolutionary Ecology ◽

10.1007/bf02285261 ◽

1989 ◽

Vol 3 (4) ◽

pp. 299-311 ◽

Cited By ~ 72

Author(s):

E. A. Bernays

Keyword(s):

Host Range ◽

Potential Role ◽

Phytophagous Insects ◽

Generalist Predators

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The role of spatial scale in understanding responses of medium-sized carnivores to forest fragmentation

Canadian Journal of Zoology ◽

10.1139/z96-235 ◽

1996 ◽

Vol 74 (11) ◽

pp. 2070-2079 ◽

Cited By ~ 114

Author(s):

James D. Oehler ◽

John A. Litvaitis

Keyword(s):

Spatial Scale ◽

Habitat Diversity ◽

Generalist Predators ◽

Wild Canids ◽

Close Proximity ◽

Proximate Factor ◽

Agricultural Areas ◽

Free Ranging ◽

Felis Domesticus

Increased predation has been suggested as a proximate factor causing the decline of vertebrate diversity in many human-altered landscapes. Previous studies on this topic have provided conflicting results, perhaps as a consequence of the limited spatial scale used in these investigations. We incorporated a multiscaled approach (using site, plot (1.44 km2), and landscape (54 km2)) to investigate the distribution of activity of medium-sized carnivores relative to habitat edges and the numeric responses of these predators to habitat diversity. Among the taxa surveyed, raccoons (Procyon lotor) did not show an affinity for habitat edges at any spatial scale. However, raccoons were more abundant in landscapes characterized by a diversity of cover types. Free-ranging domestic dogs (Canis familiaris) and cats (Felis domesticus) did not respond to the proximity of habitat edges in summer but showed a strong affinity for edge habitats (especially those associated with human dwellings) during winter. Wild canids (Vulpes vulpes and Canis latrans) also selected sites in close proximity to edges in winter and were more abundant in diverse landscapes. Although human-dominated habitats (agricultural areas, grass–brushland, and developed sites) represented only 7–27% of the three landscapes studied, populations of generalist predators (raccoons and wild canids) increased as landscapes became more diverse. As a result, even moderate levels of habitat fragmentation may elevate predation rates and subsequently alter the composition of prey communities.

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