The Smell of New Competitors: The Response of American Mink, Mustela vison, to the Odours of Otter, Lutra lutra and Polecat, M. putorius

We tested the response of wild American mink (an established alien species in the UK), to the odours of unfamiliar mink, European polecat and Eurasian otter. Polecats are similar in size and habits to mink, otters are larger than mink and a dominant competitor; both are native to the UK and both were absent during the original colonization by mink but are now undergoing natural population recoveries. The response of mink to experimental odours was assessed by counting the numbers of tracks (footprints) on rafts treated with anal gland secretions, and compared with response to a control raft, on two rivers in the Upper Thames valley, UK. Remote video showed that the number of tracks was positively correlated with the time that mink spent investigating an odour. We found that mink were attracted to the odours of both unfamiliar mink and polecats. There was little evidence that mink avoided the odour of otters. We suggest that, during an encounter with a polecat, mink may behave much as they would to a conspecific. We infer from the response of mink to the odour of otters, that, if mink do avoid otters, the mechanism of avoidance is likely to be complex, situation-dependent and perhaps affected by prior experience.     

THE POPCORN WOLBACHIA INFECTION OF DROSOPHILA MELANOGASTER: CAN SELECTION ALTER WOLBACHIA LONGEVITY EFFECTS?

Wolbachia popcorn ( w MelPop), a life-shortening strain of Wolbachia, has been proposed as an agent for suppressing transmission of dengue fever following infection of the vectoring mosquito Aedes aegypti . However, evolutionary changes in the host and Wolbachia genomes might attenuate any life span effects mediated by w MelPop. Here we test for attenuation by selecting strains of Drosophila melanogaster infected with w MelPop for early and late reproduction in three independent outcrossed populations. Selection caused divergence among the lines in longevity. This divergence was mostly associated with the host genetic background rather than the Wolbachia infection, although there were also interactions between the host and Wolbachia genomes. Development time, viability, and productivity were not altered by selection. The implications of these results are discussed in light of the intended use of w MelPop for suppressing disease transmission.     

Archaeal diversity and a gene for ammonia oxidation are coupled to oceanic circulation

Evidence of microbial zonation in the open ocean is rapidly accumulating, but while the distribution of communities is often described according to depth, the other physical factors structuring microbial diversity and function remain poorly understood. Here we identify three different water masses in the North Water (eastern Canadian Arctic), defined by distinct temperature and salinity characteristics, and show that they contained distinct archaeal communities. Moreover, we found that one of the water masses contained an increased abundance of the archaeal alpha-subunit of the ammonia monooxygenase gene ( amoA ) and accounted for 70% of the amoA gene detected overall. This indicates likely differences in putative biogeochemical capacities among different water masses. The ensemble of our results strongly suggest that the widely accepted view of depth stratification did not explain microbial diversity, but rather that parent water masses provide the framework for predicting communities and potential microbial function in an Arctic marine system. Our results emphasize that microbial distributions are strongly influenced by oceanic circulation, implying that shifting currents and water mass boundaries resulting from climate change may well impact patterns of microbial diversity by displacing whole biomes from their historic distributions. This relocation could have the potential to establish a substantially different geography of microbial-driven biogeochemical processes and associated oceanic production.     

Parasite species richness in carnivores: effects of host body mass, latitude, geographical range and population density

Aim  Comparative studies have revealed strong links between ecological factors and the number of parasite species harboured by different hosts, but studies of different taxonomic host groups have produced inconsistent results. As a step towards understanding the general patterns of parasite species richness, we present results from a new comprehensive data base of over 7000 host–parasite combinations representing 146 species of carnivores (Mammalia: Carnivora) and 980 species of parasites.
Methods  We used both phylogenetic and non-phylogenetic comparative methods while controlling for unequal sampling effort within a multivariate framework to ascertain the main determinants of parasite species richness in carnivores.
Results  We found that body mass, population density, geographical range size and distance from the equator are correlated with overall parasite species richness in fissiped carnivores. When parasites are classified by transmission mode, body mass and home range area are the main determinants of the richness of parasites spread by close contact between hosts, and population density, geographical range size and distance from the equator account for the diversity of parasites that are not dependent on close contact. For generalist parasites, population density, geographical range size and latitude are the primary predictors of parasite species richness. We found no significant ecological correlates for the richness of specialist or vector-borne parasites.
Main conclusions  Although we found that parasite species richness increases instead of decreases with distance from the equator, other comparative patterns in carnivores support previous findings in primates, suggesting that similar ecological factors operate in both these independent evolutionary lineages.     

Trichogramma zahiri (Hymenoptera: Trichogrammatidae) an egg parasitoid of the rice hispa Dicladispa armigera (Coleoptera: Chrysomelidae) in Bangladesh

Trichogramma zahiri Polaszek sp. n. is described from Bangladesh. It has been collected at several localities from the major pest of rice Dicladispa armigera (Olivier) on which it has an important controlling impact. Trichogramma zahiri is compared with known Trichogramma species from the region, and diagnostic differences are presented. Data on developmental period, adult longevity, egg-laying frequency, host egg age preference and seasonal parasitism rate are presented and discussed. Other records of parasitoids of D. armigera are briefly reviewed and discussed.     

Opening the Social Gateway: Early Vocal and Social Sensitivities in Brown-Headed Cowbirds (Molothrus ater)

The organization of cowbird ( Molothrus ater ) social groups affords individuals living in the groups different opportunities for learning and also structures trajectories of social development. Here, we studied the influence of adults on social organization of very young cowbirds. In three experiments, we housed juvenile birds in large, seminatural environments that either contained or did not contain adult conspecifics. We then observed the social associations and vocalizations of juveniles in each environment. The presence of adults in the social environment influenced the assortment and singing patterns of juveniles, although throughout the three experiments adults rarely interacted physically with juveniles. Juveniles housed with adults interacted with other juveniles more often and sang significantly less often than juveniles housed without adults. Effects of adult presence or absence on social organization and singing patterns emerged extremely rapidly and could be reversed quickly. Taken as a whole, the experiments revealed that very young cowbirds, in the first days of independence from their hosts, were sensitive to, and reacted rapidly to, the composition of their social environment. Specifically, presence of other age classes of individuals within the group increased juvenile associations and delayed production of vocalizations by juvenile males. Self-organization within the social group produced different social environments, which could in turn create different gateways for social learning and vocal development.     

The Development of Local Song Preferences in Female Cowbirds (Molothrus ater): Flock Living Stimulates Learning

We carried out two experiments across 2 yr on song perception in female cowbirds (Molothrus ater). In the first experiment, juvenile and adult female brown‐headed cowbirds, living in same‐sex flocks in outdoor aviaries, were periodically tutored with recordings of local male cowbirds’ songs. In the spring, four adult male cowbirds were placed with half of the females for a 12‐d period. We then tested song preferences of all females by measuring copulation solicitation displays during the breeding season. We found that the females exposed only to tape‐tutor songs preferred those songs to those of the unfamiliar males used as companions and that the females allowed to interact with males preferred their songs over the familiar tape‐tutor songs. These data establish the modifiability of female cowbirds’ song preferences at the level of local song. In a second experiment, we studied the playback responses of juvenile females, hand‐reared from the egg, who were tape‐tutored only in the spring in the presence or absence of adult females. There were no differences between the responses of juveniles housed with or without adult females and the hand‐reared juveniles were significantly less responsive to song than adult females. Adult females responded more to familiar songs than to the unfamiliar songs: juvenile females made no such distinction. Taken as a whole, these data are the first to document that female cowbirds’ song preferences for local song can be reshaped by post‐natal experience. These data complement recent study in cowbirds and other species showing that socially more complex contexts reveal plasticity in female song preferences that are not apparent when learning opportunities are constrained by impoverished laboratory settings.