Dynamic Transmission, Host Quality, and Population Structure in a Multihost Parasite of Bumblebees

Abstract

The evolutionary ecology of multihost parasites is predicted to depend upon patterns of host quality and the dynamics of transmission networks. Depending upon the differences in host quality and transmission asymmetries, as well as the balance between intra-and interspecific transmission, the evolution of specialist or generalist strategies is predicted. Using a trypanosome parasite of bumblebees, we ask how host quality and transmission networks relate to parasite population structure across host species, and thus the potential for the evolution of specialist strains adapted to different host species. Host species differed in quality, with parasite growth varying across host species. Highly asymmetric transmission networks, together with differences in host quality, likely explain local population structure of the parasite across host species. However, parasite population structure across years was highly dynamic, with parasite populations varying significantly from one year to the next within individual species at a given site. This suggests that, while host quality and transmission may provide the opportunity for short-term host specialization by the parasite, repeated bottlenecking of the parasite, in combination with its own reproductive biology, overrides these smaller scale effects, resulting in the evolution of a generalist parasite.

A sting in the spit: widespread cross‐infection of multiple RNA viruses across wild and managed bees

“…2012). B. lapidarius is common in England and Wales, while B. hortorum is widespread across Great Britain (Goulson 2009), so there is no clear pattern of pathogen prevalence and bumblebee rarity among our samples.…”

Parasites in bloom: flowers aid dispersal and transmission of pollinator parasites within and between bee species

“…These honeybee colonies had been determined by PCR screening (see below) to be infected by the Nosema apis and N. ceranae parasites, while the bumblebee colonies had been determined by PCR to be infected by A. bombi, C. bombi and Nosema bombi; the colonies of neither bee species were infected by the parasites of the other bee species. Nosema apis is apparently unable to infect bumblebees, and C. bombi and N. bombi are unable to infect honeybees, whereas N. ceranae and A. bombi are capable of infecting both hosts [15,22,40]. Three additional honeybee colonies and three additional bumblebee colonies, which had been confirmed by PCR to be free of any of these parasite infections, were selected to provide the 'vector bees' for the experiment.…”

“…Remarkably, however, the epidemiology and transmission of pollinator parasites is still very poorly understood and the potentially profound role of shared flower use, in particular, little investigated [15,16]. Several studies have detected the presence of parasites in bee collected pollen [22,42,44], but it is unclear if these parasites were on the flowers and collected along with the pollen or if they originate from the foraging bee [45].…”

“…While some plantpollinator systems are specific, in the vast majority of cases flowers are visited by multiple pollinator species in a complex web of interactions [13,14]. It then follows that vectoring of parasites by non-host species during shared flower use may be of great importance in pollinator-parasite interactions [15,16]. There is currently great interest in the stress factors affecting pollinators, many of which are showing substantial population declines with knock-on effects on the plants that rely on them for pollination [17][18][19].…”

Gene expression differences underlying genotype-by-genotype specificity in a host–parasite system

“…C. bombi is genetically highly diverse (37)(38)(39)(40) and infects a high proportion of B. terrestris in the wild (31,41,42). Different parasite genotypes have different infection success in different colonies of this host (43).…”