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GROUP SELECTION ON POPULATION SIZE AFFECTS LIFE‐HISTORY PATTERNS IN THE ENTOMOPATHOGENIC NEMATODE STEINERNEMA CARPOCAPSAE
Author(s) -
Bashey Farrah,
Lively Curtis M.
Publication year - 2009
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.2009.00637.x
Subject(s) - biology , entomopathogenic nematode , selection (genetic algorithm) , nematode , host (biology) , inbreeding , population , experimental evolution , trait , zoology , ecology , evolutionary biology , genetics , demography , gene , artificial intelligence , sociology , computer science , programming language
Selection is recognized to operate on multiple levels. In disease organisms, selection among hosts is thought to provide an important counterbalance to selection for faster growth within hosts. We performed three experiments, each selecting for a divergence in group size in the entomopathogenic nematode, Steinernema carpocapsae. These nematodes infect and kill insect larvae, reproduce inside the host carcass, and emerge as infective juveniles. We imposed selection on group size by selecting among hosts for either high or low numbers of emerging nematodes. Our goal was to determine whether this trait could respond to selection at the group level, and if so, to examine what other traits would evolve as correlated responses. One of the three experiments showed a significant response to group selection. In that experiment, the high‐selected treatment consistently produced more emerging nematodes per host than the low‐selected treatment. In addition, nematodes were larger and they emerged later from hosts in the low‐selected lines. Despite small effective population sizes, the effects of inbreeding were small in this experiment. Thus, selection among hosts can be effective, leading to both a direct evolutionary response at the population level, as well as to correlated responses in populational and individual traits.