Experimental evidence that evolutionary relatedness does not affect the ecological mechanisms of coexistence in freshwater green algae

Abstract

The coexistence of competing species depends on the balance between their fitness differences, which determine their competitive inequalities, and their niche differences, which stabilise their competitive interactions. Darwin proposed that evolution causes species' niches to diverge, but the influence of evolution on relative fitness differences, and the importance of both niche and fitness differences in determining coexistence have not yet been studied together. We tested whether the phylogenetic distances between species of green freshwater algae determined their abilities to coexist in a microcosm experiment. We found that niche differences were more important in explaining coexistence than relative fitness differences, and that phylogenetic distance had no effect on either coexistence or on the sizes of niche and fitness differences. These results were corroborated by an analysis of the frequency of the co-occurrence of 325 pairwise combinations of algal taxa in > 1100 lakes across North America. Phylogenetic distance may not explain the coexistence of freshwater green algae.

Species coexistence: macroevolutionary relationships and the contingency of historical interactions

“…Our results are striking and appear to contradict the few existing experimental studies that test whether stabilizing differences are explained by phylogenetic relatedness, and find no relationship [18,19]. This apparent contradiction might be explained by two methodological differences between our study and those that precede it.…”

“…'overdispersion') in communities are typically considered evidence of competitive filtering [7]. Although this interpretation has been called into question repeatedly in recent years [17,39], our evidence is consistent with other recent work [18,19] that competition does not likely result in phylogenetic overdispersion, at least in our annual plant system. Instead, competition is most likely to generate patterns of phylogenetic similarity (i.e.…”

Plant functional traits and the multidimensional nature of species coexistence

“…Prior work has examined the association between species traits and metrics that either aggregate stabilizing niche and average fitness differences (e.g., community membership, competitive dominance, and species abundance) (22)(23)(24) or form components of these quantities (e.g., interaction coefficients, relative yield, and competitive suppression) (25,26). Only now, with recent developments in coexistence theory (15,(27)(28)(29)(30), can we begin to directly evaluate the relationship between species traits and stabilizing niche differences and average fitness differences.…”

Genetic distance predicts trait differentiation at the subpopulation but not the individual level in eelgrass,Zostera marina

“…However, the underlying assumption that phylogenetic diversity serves as a proxy for trait differentiation is not always supported; in some cases, phylogenetic diversity influences ecosystem structure and functioning even when phylogenetic distance is not correlated with trait differences (Flynn et al., 2011; Tan, Pu, Ryberg & Jiang, 2012). Furthermore, not all traits relevant to the outcome of interactions are evolutionarily conserved (Best, Caulk & Stachowicz, 2013; Best & Stachowicz, 2013; Cavender‐Bares, Ackerly, Baum & Bazzaz, 2004; Cavender‐Bares, Keen & Miles, 2006; Moles et al., 2005; Silvertown, Dodd, Gowing, Lawson & McConway, 2006) and phylogenetic distance does not always influence ecological processes in the expected direction (Burns & Strauss, 2011; Cadotte, Davies & Peres‐Neto, 2017; Godoy, Kraft & Levine, 2014; Narwani, Alexandrou, Oakley, Carroll & Cardinale, 2013). …”