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Decreased coevolutionary potential and increased symbiont fecundity during the biological invasion of a legume‐rhizobium mutualism
Author(s) -
Wendlandt Camille E.,
Helliwell Emily,
Roberts Miles,
Nguyen Kyle T.,
Friesen Maren L.,
Wettberg Eric,
Price Paul,
Griffitts Joel S.,
Porter Stephanie S.
Publication year - 2021
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/evo.14164
Subject(s) - mutualism (biology) , biology , rhizobia , symbiosis , ecology , coevolution , fecundity , evolutionary biology , population , genetics , demography , sociology , bacteria
Although most invasive species engage in mutualism, we know little about how mutualism evolves as partners colonize novel environments. Selection on cooperation and standing genetic variation for mutualism traits may differ between a mutualism's invaded and native ranges, which could alter cooperation and coevolutionary dynamics. To test for such differences, we compare mutualism traits between invaded‐ and native‐range host‐symbiont genotype combinations of the weedy legume, Medicago polymorpha , and its nitrogen‐fixing rhizobium symbiont, Ensifer medicae , which have coinvaded North America. We find that mutualism benefits for plants are indistinguishable between invaded‐ and native‐range symbioses. However, rhizobia gain greater fitness from invaded‐range mutualisms than from native‐range mutualisms, and this enhancement of symbiont fecundity could increase the mutualism's spread by increasing symbiont availability during plant colonization. Furthermore, mutualism traits in invaded‐range symbioses show lower genetic variance and a simpler partitioning of genetic variance between host and symbiont sources, compared to native‐range symbioses. This suggests that biological invasion has reduced mutualists’ potential to respond to coevolutionary selection. Additionally, rhizobia bearing a locus ( hrrP ) that can enhance symbiotic fitness have more exploitative phenotypes in invaded‐range than in native‐range symbioses. These findings highlight the impacts of biological invasion on the evolution of mutualistic interactions.