The insect microbiome and its effects on community interactions Julia Ferrari

julia.ferrari@york.ac.uk

Outline

• Why insects?

• Microbial symbionts – what are they?

• Some case studies: • nutritional obligate symbionts

• reproductive parasites – the Great Eggfly

• facultative symbionts – protection from natural enemies and community interactions in aphids

• microbial symbionts in pollinators

Why insects?

• most diverse group of animals, ca. 1 million described species, perhaps 10 million

• many important roles in the ecosystem, e.g. • pollination

• decomposition

• herbivory

• predation

• parasitism

Image: Barta IV, CC BY 2.0 via flickr

Why insects?

Pollination

• more than 80% of crop species

• every third mouthful - pollination

• globally £120 billion, £690 million each year UK

By Vera Buhl CC BY-SA 3.0 via Wikimedia Commons

Why insects?

Pests

• Losses: 14% of all agricultural production

• > 50% loss in cotton, rice, potato, maize, wheat

Disease transmission

• Vector-borne diseases: 17% of all infectious diseases, causing more than 700,000 deaths annually

By Rasbak CC-BY-SA-3.0 via Wikimedia Commons

What are insect symbionts?

• microbial partners, live inside insect

• usually transmitted from mother to offspring

• play major roles in insect biology: • nutrition

• defence against natural enemies

• other environmental stresses

• reproduction

By Scott O'Neill CC BY 2.5 via Wikimedia Commons

Obligate symbionts

• Obligate • usually nutritional role

• allow radiation in species on imbalanced diets

• But: use resources and might overproliferate

Moran, NA (2007) PNAS 104 (S1) :8627-8633

©2007 by National Academy of Sciences

Seabrooke Leckie via flickr (CC BY-NC-ND 2.0)

Sitophilus

Reproductive manipulators

• symbionts usually transmitted from mothers to offspring

• males are a dead end

• can affect sex ratios of natural populations up to risk of extinction

By Vtbijoy CC BY-SA 3.0 via Wikimedia Commons

Wolbachia in the Great Eggfly (Hypolimnas bolina)

Dyson et al. PNAS 101: 6520

Great Eggfly

Charlat et al. Science 19: 789

Facultative symbionts

• Facultative • many functions

• benefit often dependent on environment

• protection from stresses • natural enemies

• extreme temperatures

By Piotr Łukasik CC BY-NC-SA 2.0

Symbionts protect from natural enemies

By Piotr Łukasik CC BY-NC-SA 2.0

Łukasik et al. Ecology Letters 16: 214

Symbionts protect in the field

Hrček et al. Journal of Animal Ecology 85: 1605

Symbiont protection can lead to extinction cascades

Sanders et al. Ecology Letters 19: 789

Symbiont protection can lead to extinction cascades

Image of M. viciae: InfluentialPoints.com CC BY 3.0 via Wikimedia Commons Sanders et al. Ecology Letters 19: 789

The microbiome in pollinators

• Honey bees: simple specialized microbial gut community, 8 to 10 bacterial species

• social transmission, possibly due to specialized behaviours like trophallaxis

• in some bee groups, evidence that association is ancient.

By Vera Buhl CC BY-SA 3.0 via Wikimedia Commons

Bee diseases

• 54% decline in bee colonies between 1985 to 2008

• Gut bacteria can inhibit honey bee bacterial pathogens: • American Foulbrood

(Paenibacillus larvae) and

• European Foulbrood (Melissococcus plutonius)

By Pollinator CC-BY-SA-3.0 via Wikimedia Commons

Forsgren et al. Apidologie 41:99 Vásquez et al. PLoS one 7: e33188

By Jrmgkia CC BY-SA 3.0 via Wikimedia Commons

Conclusions

• Microbial symbionts are widespread in insects and have diverse roles

• Symbionts can protect from natural enemies and affect species interactions and entire communities

• Symbionts affect economically important species, e.g. honey bees

• Understanding microbial symbionts is crucial to understanding insect biology, and sustainable management