Chemical and behavioural strategies along the spectrum of host specificity in ant-associated silverfish.

BACKGROUND: Host range is a fundamental trait to understand the ecological and evolutionary dynamics of symbionts. Increasing host specificity is expected to be accompanied with specialization in different symbiont traits. We tested this specificity-specialization association in a large group of 16 ant-associated silverfish species by linking their level of host specificity to their degree of behavioural integration into the colony and to their accuracy of chemically imitating the host's recognition system, i.e. the cuticular hydrocarbon (CHC) profile. RESULTS: As expected, facultative associates and host generalists (targeting multiple unrelated ants) tend to avoid the host, whereas host-specialists (typically restricted to Messor ants) were bolder, approached the host and allowed inspection. Generalists and host specialists regularly followed a host worker, unlike the other silverfish. Host aggression was extremely high toward non-ant-associated silverfish and modest to low in ant-associated groups. Surprisingly, the degree of chemical deception was not linked to host specificity as most silverfish, including facultative ant associates, imitated the host's CHC profile. Messor specialists retained the same CHC profile as the host after moulting, in contrast to a host generalist, suggesting an active production of the cues (chemical mimicry). Host generalist and facultative associates flexibly copied the highly different CHC profiles of alternative host species, pointing at passive acquisition (chemical camouflage) of the host's odour. CONCLUSIONS: Overall, we found that behaviour that seems to facilitate the integration in the host colony was more pronounced in host specialist silverfish. Chemical deception, however, was employed by all ant-associated species, irrespective of their degree of host specificity.

The Genus Anelpistina (Insecta, Zygentoma, Nicoletiidae) in Puerto Rico, with the Description of a New Species.

Samples of Nicoletiidae (order Zygentoma = Thysanura s. str.) collected in two localities from Puerto Rico belonging to the genus Anelpistina Silvestri, 1905 are studied. One of them, collected in the same cave where A. puertoricensis Espinasa and Baker Alpheis, 2003 was found, allows for the description of the female of this species, together with some additional information on the variability and postembryonic development of this troglobitic insect. The second consists of specimens collected in litter of the islet of Palominos, near the northeastern coast of the main island of Puerto Rico; these specimens are identified as a new species. This species, named Anelpistina naarae sp. nov., is described and compared with related species. A genetic analysis of its DNA and 16S rRNA compared with the available data of the remaining species points to the chronology of the lineages of Anelpistina in this island and their relationships with continental species of the genus.