Nature Of Interspecific Interactions Research Articles

The nature of interspecific interactions and co-diversification patterns, as illustrated by the fig microcosm.

Summary Interactions between mutualists, competitors, and antagonists have contrasting ecological effects that, sustained over generations, can influence micro‐ and macroevolution. Dissimilar benefits and costs for these interactions should cause contrasting co‐diversification patterns between interacting clades, with prevalent co‐speciation by mutualists, association loss by competitors, and host switching by antagonists.We assessed these expectations for a local assemblage of 26 fig species (Moraceae: Ficus), 26 species of mutualistic (pollinating), and 33 species of parasitic (galling) wasps (Chalcidoidea). Using newly acquired gene sequences, we inferred the phylogenies for all three clades. We then compared the three possible pairs of phylogenies to assess phylogenetic congruence and the relative frequencies of co‐speciation, association duplication, switching, and loss.The paired phylogenies of pollinators with their mutualists and competitors were significantly congruent, unlike that of figs and their parasites. The distributions of macroevolutionary events largely agreed with expectations for mutualists and antagonists. By contrast, that for competitors involved relatively frequent association switching, as expected, but also unexpectedly frequent co‐speciation. The latter result likely reflects the heterogeneous nature of competition among fig wasps.These results illustrate the influence of different interspecific interactions on co‐diversification, while also revealing its dependence on specific characteristics of those interactions.

Biodiversity and species identity shape the antifungal activity of bacterial communities.

Soils host diverse communities of interacting microbes and the nature of interspecific interactions is increasingly recognized to affect ecosystem-level processes. Antagonistic interactions between bacteria and fungi are of particular relevance for soil functioning. A number of soil bacteria produce secondary metabolites that inhibit eukaryotic growth. Antibiosis may be stimulated in the presence of competing bacteria, and we tested if biodiversity within bacterial communities affects their antagonistic activity against fungi and fungal-like species. We set up Pseudomonas communities of increasing diversity and measured the production of the broad spectrum antifungal compound 2,4-DAPG and their antagonistic activity against different eukaryotes. Diversity increased DAPG concentration and antifungal activity, an effect due to a combination of identity and interactions between species. Our results indicate that investment of pseudomonads into broad spectrum anti-eukaryotic traits is determined by both community composition and diversity and this provides new avenues to understand interactions between bacterial and fungal communities.

Interspecific interactions and welfare implications in mixed species communities of capuchin (Sapajus apella) and squirrel monkeys (Saimiri sciureus) over 3 years

Species have complex relationships with others in the wild, and some such as capuchin (Sapajus apella) and squirrel monkeys (Saimiri sciureus) naturally choose to associate with each other. There are a number of benefits of exhibiting such species in correspondingly mixed communities in captivity to enhance welfare through increased social complexity, which is potentially environmentally enriching in restricted captive enclosures. Monitoring the interactions between species is critical, however, particularly when members of one species are considerably larger and potentially more aggressive than the other. We report on the frequency and nature of interspecific interactions between S. apella and S. sciureus during four time periods over 3 years (2008–2010) following the formation of two mixed species groups at the ‘Living Links to Human Evolution’ Research Centre in Edinburgh Zoo, Scotland. Both the rate and the distribution of interspecific interactions among aggressive, affiliative and neutral categories of behaviour varied over time (P<0.05). We predicted that S. apella would engage in more interspecific, particularly aggressive, interactions than S. sciureus than vice versa, as they are the larger, more social species and have a more pugnacious temperament. This was the case overall (P<0.05), and particularly in 2009 and 2010. We predicted that affiliative interactions would increase over time as the number of youngsters increased and as the youngsters grew up together, establishing equable relationships and “territorial” boundaries. The data did not support this prediction. Both the most affiliative and least aggressive interspecific interactions were observed following internal enclosure refurbishment in 2008 and hence we argue that good enclosure design and husbandry is the most important factor in promoting positive interactions between individuals in mixed species groups. We conclude that long-term monitoring is important, and when combined with appropriate husbandry and enclosure upkeep, the welfare of individuals is enhanced in mixed species groups by the presence of other species.

Competition and facilitation between tree species change with stand development

Processes governing tree interspecific interactions, such as facilitation and competition, may vary in strength over time. This study tried to unveil them by performing dendrometrical analyses on black spruce Picea mariana, trembling aspen Populus tremuloides and jack pine Pinus banksiana trees from pure and mixed mature boreal forest stands in the Clay Belt of northwestern Quebec and on the tills of northwestern Ontario. We cored 1430 trees and cut 120 for stem analysis across all stand composition types, tree species and study regions. Aspen annual growth rate was initially higher when mixed with conifers, but then progressively decreased over time compared to pure aspen stands, while jack pine growth rate did not differ with black spruce presence throughout all stages of stand development. When mixed with aspen, black spruce showed a contrary response to aspen, i.e. an initial loss in growth but a positive gain later. On the richer clay soil of the Quebec Clay Belt region, however, both aspen and spruce responses in mixed stands reversed between 37 and 54 years. Overall, our results demonstrate that interspecific interactions were present and tended to change with stand development and among species. Our results also suggest that the nature of interspecific interactions may differ with soil nutrient availability.

Influence of shelter availability on interactions between Caribbean spiny lobsters and moray eels: implications for artificial lobster enhancement

The Caribbean spiny lobster Panulirus argus is a valuable fishing resource, but local populations may be limited by availability of crevice shelter on juvenile (seagrass) habitats. This has prompted research into the potential density enhancement of juvenile lobsters with 'casitas', large (1.1 m 2 surface area) but low-lying (3.8 cm entrance height) artificial shelters that exclude large predators. Moray eels (Muraenidae), however, fit into casitas and could therefore pose a threat to lob- ster enhancement. In a shelter-poor reef lagoon, we examined potential interactions between juve- nile lobsters and the locally dominant morays Gymnothorax vicinus and G. moringa in the absence (four 1 ha control sites) and presence of casitas (five 1 ha 'casita sites', each with 10 casitas), before (6 surveys) and after (22 surveys) deployment. Morays and lobsters did not interact as predator-prey, as morays neither consumed nor intimidated co-occurring lobsters. Rather, the 2 taxa appeared to compete for limited shelter on the reef lagoon, as suggested by a significant increase in density and mean size of both taxa on casita sites after deployment. Casitas significantly increased cohabitation of morays and lobsters, yet they tended to co-occur less often than expected by chance, but this result likely reflects behavioral differences between the highly gregarious, more numerous lobsters and the typically solitary, cannibalistic morays. Our study exemplifies the influence of habitat complexity on the nature of interspecific interactions and shows that G. vicinus and G. moringa would not pose a threat to lobster enhancement with casitas.