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75 results for “intraspecific competition”

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Data from: Evolution of increased intraspecific competitive ability following introduction: the importance of relatedness among genotypes.

1.A long‐standing explanation for invasion success is that invasive plants could evolve to be more competitive following introduction. This evolution of increased competitive ability (EICA) hypothesis, however, has seldom been tested with regard to intraspecific competition. Given that plants can display different responses to related and unrelated conspecifics, the evolution of intraspecific competitive ability might be specific to genotypes of different relatedness. 2.Here, we grew five native (South American) and five introduced (North American) genotypes of the clonal herbaceous invasive plant Alternanthera philoxeroides alone, with aboveground competition from kin (the same genotype) or from one of two types of strangers (another genotype from the same range or another genotype from the other range). 3.When grown alone, introduced and native genotypes produced similar total biomass and storage‐root biomass. However, in response to intraspecific competition, introduced genotypes showed increases in total biomass and stem length, and a decrease in specific stem length, whereas native genotypes showed the opposite pattern. When grown with kin instead of strangers, introduced genotypes showed an increase in branch number, whereas native genotypes showed the opposite. 4.Synthesis. Our study provided evidence for evolution of increased intraspecific competitive responses in an invasive plant. We also found, for the first time, that the interactions among kin were likely to shift from competition towards facilitation following introduction.

opencc-zeroDec 2017View details →

dryad28/100

Data from: Intraspecific competition and inbreeding depression: increased competitive effort by inbred males is costly to outbred opponents

A recent theoretical model suggests that intraspecific competition is an important determinant of the severity of inbreeding depression. The reason for this is that intraspecific competition is density dependent, leading to a stronger negative effect on inbred individuals if they are weaker competitors than outbred ones. In support of this prediction, previous empirical work shows that inbred individuals are weaker competitors than outbred ones and that intraspecific competition often exacerbates inbreeding depression. Here, we report an experiment on the burying beetle Nicrophorus vespilloides, in which we recorded the outcome of competition over a small vertebrate carcass between an inbred or outbred male resident caring for a brood and a size-matched inbred or outbred male intruder. We found that inbred males were more successful as intruders in taking over a carcass from a male resident and were injured more frequently as either residents or intruders. Furthermore, inbred males gained less mass during the breeding attempt and had a shorter adult life span than outbred males. Finally, successful resident males reared a substantially smaller brood comprised of lighter larvae when the intruder was inbred than when it was outbred. Our results shows that inbred males increased their competitive effort, thus contradicting previous work suggesting that inbred males are weaker competitors. Furthermore, our results shows that inbred intruders impose a greater cost to resident males, suggesting that outbred individuals can suffer fitness costs as a result of competition with inbred ones.

opencc-zeroDec 2016View details →

dryad28/100

Data from: Egg chemoattractants moderate intraspecific sperm competition

Interactions among eggs and sperm are often assumed to generate intraspecific variation in reproductive fitness, but the specific gamete-level mechanisms underlying competitive fertilization success remain elusive in most species. Sperm chemotaxis–the attraction of sperm by egg-derived chemicals—is a ubiquitous form of gamete signaling, occurring throughout the animal and plant kingdoms. The chemical cues released by eggs are known to act at the interspecific level (e.g., facilitating species recognition), but recent studies have suggested that they could have roles at the intraspecific level by moderating sperm competition. Here, we exploit the experimental tractability of a broadcast spawning marine invertebrate to test this putative mechanism of gamete-level sexual selection. We use a fluorescently labeled mitochondrial dye in mussels to track the real-time success of sperm as they compete to fertilize eggs, and provide the first direct evidence in any species that competitive fertilization success is moderated by differential sperm chemotaxis. Furthermore, our data are consistent with the idea that egg chemoattractants selectively attract ejaculates from genetically compatible males, based on relationships inferred from both nuclear and mitochondrial genetic markers. These findings for a species that exhibits the ancestral reproductive strategy of broadcast spawning have important implications for the numerous species that also rely on egg chemoattractants to attract sperm, including humans, and have potentially important implications for our understanding of the evolutionary cascade of sexual selection.

opencc-zeroDec 2016View details →

dryad28/100

Data from: Commonness and rarity of alien and native plant species – the relative roles of intraspecific competition and plant–soil feedback

The success of invasive alien and common native species may be explained by the same underlying mechanisms. Differences in intraspecific competition as well as differences in plant–soil feedback have been put forward as potential determinants of plant success. We teased apart the relative roles of competition and plant–soil feedback in a greenhouse experiment with 30 common and rare alien and native species from nine plant families. We tested whether plant biomass decreased less for common than rare species, regardless of origin, when grown at higher relative frequencies (1, 3 or 6 out of 9 plants per pot) in a community and in soil previously conditioned by the same species at different frequencies (0, 1, 3 or 6 out of 9 plants per pot) in an orthogonal design for these two factors. Plant survival decreased slightly, but non-significantly, for all species when grown in soil previously occupied by conspecifics. Among surviving plants, we found a decrease in biomass with increasing intraspecific competition across all species (regardless of origin or commonness), and alien species were more negatively affected by previous high plant frequency than native species, but only marginally significantly so. Our findings suggest that, while intraspecific competition limits individual biomass in a density-dependent manner, these effects do not depend on species origin or commonness. Notably, alien species but not natives showed a decrease in performance when grown in soil pre-conditioned with a higher frequency of conspecifics. In conclusion, soil-borne pathogen accumulation might be weak in its effects on plant performance compared to intraspecific competition, with neither being clearly linked to species commonness.

opencc-zeroDec 2015View details →

dryad28/100

Data from: Evolution of size-dependent intraspecific competition predicts body size scaling of metabolic rate

1. Growth in body size is accompanied by changes in foraging capacity and metabolic costs, which lead to changes in competitive ability during ontogeny. The resulting size-dependent competitive asymmetry influences population dynamics and community structure, but it is not clear whether natural selection leads to asymmetry in intraspecific competition. 2. We address this question by using a size-structured consumer-resource model, in which the strength and direction of competitive asymmetry between different consumer individuals depends on the scaling of maximum ingestion and maintenance metabolism with consumer body size. We use adaptive dynamics to study selection on the scaling exponents of these processes. 3. Selection leads to an identical scaling of maximum ingestion and maintenance metabolism with consumer body size. Equal scaling exponents neutralise strong competitive differences within the consumer population, because all consumer individuals require the same amount of resources to cover maintenance requirements. Furthermore, the scaling exponents respond adaptively to changes in mortality such that biomass production through growth or reproduction increases in the life stage that is subject to increased mortality. Also, decreasing size at birth leads to increased investment in juvenile growth, while increasing maximum size leads to increased investment in post-maturation growth and reproduction. 4. These results provide an explanation for observed variation in the ontogenetic scaling of metabolic rate with body size. Data of teleost fish are presented that support these predictions. However, selection towards equal scaling exponents is contradicted by empirical findings, which suggests that additional ecological complexity beyond this basic consumer-resource interaction is required to understand the evolution of size-dependent asymmetry in intraspecific competition.

opencc-zeroDec 2017View details →

dryad28/100