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Symbiotic interactions may change depending on third parties like predators or prey. Third-party interactions with prey bacteria are central to the symbiosis betweenDictyostelium discoideumsocial amoeba hosts andParaburkholderiabacterial symbionts. Symbiosis with inedibleParaburkholderiaallows hostD. discoideumto carry prey bacteria through the dispersal stage where hosts aggregate and develop into fruiting bodies that disperse spores. Carrying prey bacteria benefits hosts when prey are scarce but harms hosts when prey bacteria are plentiful, possibly because hosts leave some prey bacteria behind while carrying. Thus, understanding benefits and costs in this symbiosis requires measuring how many prey bacteria are eaten, carried and left behind by infected hosts. We found thatParaburkholderiainfection makes hosts leave behind both symbionts and prey bacteria. However, the number of prey bacteria left uneaten was too small to explain why infected hosts produced fewer spores than uninfected hosts. Turning to carried bacteria, we found that hosts carry prey bacteria more often after developing in prey-poor environments than in prey-rich ones. This suggests that carriage is actively modified to ensure hosts have prey in the harshest conditions. Our results show that multi-faceted interactions with third parties shape the evolution of symbioses in complex ways.
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Who gets left behind by left behind places?
Abstract We document that children growing up in places left behind by today’s economy experience lower levels of social mobility as adults. Using a longitudinal database that tracks over 20,000 places in the USA from 1980 to 2018, we identify two kinds of left behind places: the ‘long-term left behind’ that have struggled over long periods of history; and ‘recently left-behind’ places where conditions have deteriorated. Compared to children of similar baseline household income levels, we find that exposure to left behind places is associated with a 4-percentile reduction in adult income rank. Children fare considerably better when exposed to places where conditions are improving. These outcomes vary across prominent social and spatial categories and are compounded when nearby places are also experiencing hardship. Based on these findings, we argue that left behind places are having ‘scarring effects’ on children that could manifest long into the future, exacerbating the intergenerational challenges faced by low-income households and communities. Improvements in local economic conditions and outmigration to more prosperous places are, therefore, unlikely to be full remedies for the problems created by left behind places.
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- Award ID(s):
- 1924670
- PAR ID:
- 10492060
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Cambridge Journal of Regions, Economy and Society
- Volume:
- 17
- Issue:
- 1
- ISSN:
- 1752-1378
- Format(s):
- Medium: X Size: p. 37-58
- Size(s):
- p. 37-58
- Sponsoring Org:
- National Science Foundation
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