Phylogenetic relatedness predicts priority effects in nectar yeast communities

Abstract

Priority effects, in which the outcome of species interactions depends on the order of their arrival, are a key component of many models of community assembly. Yet, much remains unknown about how priority effects vary in strength among species in a community and what factors explain this variation. We experimented with a model natural community in laboratory microcosms that allowed us to quantify the strength of priority effects for most of the yeast species found in the floral nectar of a hummingbirdpollinated shrub at a biological preserve in northern California. We found that priority effects were widespread, with late-arriving species experiencing strong negative effects from early-arriving species. However, the magnitude of priority effects varied across species pairs. This variation was phylogenetically non-random, with priority effects stronger between closer relatives. Analysis of carbon and amino acid consumption profiles indicated that competition between closer relatives was more intense owing to higher ecological similarity, consistent with Darwin's naturalization hypothesis. These results suggest that phylogenetic relatedness between potential colonists may explain the strength of priority effects and, as a consequence, the degree to which community assembly is historically contingent.

Nectar bacteria, but not yeast, weaken a plant–pollinator mutualism

“…Bombus vosnesenskii and Xylocopa micans) may also visit M. aurantiacus flowers. Flowers can persist for approximately 6 -10 days [22] and contain up to 10 ml of nectar [21], in which both yeasts [23] and bacteria frequently attain densities of 10 4 CFUs (colony forming units) per ml, similar to densities reported in other systems [24]. At JRBP, bacterial densities ranged from 0 to 10 4 CFUs per ml, with an average of 350 CFUs per ml among flowers exposed to pollinators (n ¼ 82 flowers).…”

“…Stigmas of M. aurantiacus flowers close upon contact and stay closed if much pollen is received, but reopen if little pollen is received [21]. For this reason, stigma closure can be used as an indicator of pollination in this species [22]. At the Jasper Ridge Biological Preserve (JRBP), located in the Santa Cruz Mountains of California (37824 0 N, 122813 0 30 00 W), we frequently observe floral visitation by Anna's hummingbird (Calypte anna), although Allen's hummingbird (Selasphorus sasin), Rufous hummingbird (Selasphorus rufus) and occasionally bees (e.g.…”

Species coexistence: macroevolutionary relationships and the contingency of historical interactions

“…Signatures of this past evolution frequently emerge in the strength of the interactions among current-day species [1] in ways that have potential to further perpetuate divergence and the evolution of interaction strengths [2]. This dynamic feedback between the ecology and evolution of organisms is a central theme in microevolutionary [3,4], macroevolutionary [5] and recent ecological perspectives [6][7][8], as it promises a more complete picture of the processes that generate and maintain biological diversity.…”

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

“…However, the magnitude of genetic differentiation at the site level did predict site‐level trait differentiation, although our sample size was relatively small (five sites). Thus, the correlation between genetic relatedness and trait differentiation among eelgrass genotypes appears to be scale dependent, just as has been found for correlations between phylogenetic distance and trait distance among species (Cavender‐Bares, Keen & Miles, 2006; Peay, Belisle & Fukami, 2011). …”

“…The scale‐dependence of the within‐species relatedness versus trait differentiation relationship (a lack of relationship among individuals, but positive relationship among subpopulations) is analogous to the idea that the relationship between phylogenetic and trait differentiation among species depends on the phylogenetic scale under consideration (e.g., Cavender‐Bares, Keen & Miles, 2006; Peay et al., 2011; Stegen, Lin, Konopka & Fredrickson, 2012). Many of the issues we discuss for predicting within‐species ecological differentiation from genetic differentiation at neutral loci have analogies at the among‐species level.…”