Abstract
Darwin’s naturalization hypothesis (DNH) proposes that colonization is less likely when the colonizing species is related to members of the invaded community, because evolutionary closeness intensifies competition among species that share similar resources. Studies that have evaluated DNH from correlational evidence have yielded controversial results with respect to its occurrence and generality. In the present study we carried out a set of manipulative experiments in which we controlled the phylogenetic relatedness of one colonizing species (Lactuca sativa) with five assemblages of plants (the recipient communities), and evaluated the colonizing success using five indicators (germination, growth, flowering, survival, and recruitment). The evolutionary relatedness was calculated as the mean phylogenetic distance between Lactuca and the members of each assemblage (MPD) and by the mean phylogenetic distance to the nearest neighbor (MNND). The results showed that the colonization success of Lactuca was not affected by MPD or MNND values, findings that do not support DNH. These results disagree with experimental studies made with communities of microorganisms, which show an inverse relation between colonization success and phylogenetic distances. We suggest that these discrepancies may be due to the high phylogenetic distance used, since in our experiments the colonizing species (Lactuca) was a distant relative of the assemblage members, while in the other studies the colonizing taxa have been related at the congeneric and conspecific levels. We suggest that under field conditions the phylogenetic distance is a weak predictor of competition, and it has a limited role in determining colonization success, contrary to prediction of the DNH. More experimental studies are needed to establish the importance of phylogenetic distance between colonizing species and invaded community on colonization success.
Highlights
Biological invasions have attracted the attention of modern ecologists and biogeographers [1] because of their leading role as components of global change [2]
Using an experimental gradient of phylogenetic relatedness between five plant species and a colonizing species (Lactuca sativa), we found that phylogenetic relatedness did not influence the colonization success of the inoculated species
These findings do not support Darwin’s naturalization hypothesis (DNH), and this is valid for a combination of five measures of colonizing success and two of phylogenetic relatedness (MPDLactuca and MNNDLactuca)
Summary
Biological invasions have attracted the attention of modern ecologists and biogeographers [1] because of their leading role as components of global change [2]. A intriguing and controversial role is that played by Darwin’s naturalization hypothesis (DNH), which states that naturalization success depends on the phylogenetic relatedness between the colonizer and the members of the recipient community [10] If this relatedness is close, the colonization process will be inhibited as a result of the greater competitive intensity that there is – supposedly– between closely related species [11]. If the phylogenetic relationship is distant, the establishment would be favored as a result of a lower competitive intensity Underlying this relationship between phylogenetic distance and invasion success, it is assumed that closely related species shares similar resources and natural enemies [11]
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