Lajos Rózsa

Quantifying parasites in samples of hosts.

Whereas terminological recommendations require authors to use mean intensity or mean abundance to quantify parasites in a sample of hosts, awkward statistical limitations also force them to use either the median or the geometric mean of these measures when making comparisons across different samples. Here, we propose to reconsider this inconsistent practice by giving priority to biological realism in the interpretation of different statistical descriptors and choosing the statistical tools appropriate to our decisions. Prevalence, mean intensity, and indices of parasite distribution (such as median intensity) are suitable descriptors to quantify parasites in a sample of hosts. These measures have different biological interpretations and need different statistical methods to be compared between samples.

Relationship of host coloniality to the population ecology of avian lice (Insecta: Phthiraptera)

We test the hypothesis that avian social system (territorial vs. colonial) has an impact on the ecological characteristics of avian lice. We compared the louse loads of two congeneric host species, the territorial hooded crow (Corvus corone cornix L.) and the colonial rook (C. frugilegus L.). Each species harboured the same five genera of lice ; one species of louse was shared, while the other four species on each host were host-specific. More rooks harboured Myrsidea, Philopterus, Brueelia and Allocolpocephalum spp. than crows. Rooks harboured more species-rich louse loads than crows. Louse loads were also more diverse on rooks than on crows. The frequency distributions of lice on rooks were less aggregated than on crows. Sex ratios of lice were less biased on rooks than on crows. Biased sex ratios were correlated with the subpopulation size of lice on individual hosts, making it necessary to control for subpopulation size in comparative analyses. These findings may result from the increased frequency of horizontal transmissions via increased body-to-body contacts among colonial rooks, compared to territorial hooded crows.

Measures of sociality : two different views of group size

*Department of Biomathematics and Informatics, Faculty of Veterinary Science, Szent Istva´n UniversityyNomogram LtdzAnimal Ecology Research Group of the Hungarian Academy of SciencesxCollegium Budapest e Institute for Advanced Study**Department of Ecology, Faculty of Sciences, University of Debrecen(Received 4 January 2007; initial acceptance 31 January 2007;final acceptance 20 May 2007; published online 5 November 2007; MS. number: SC-1307R)

The Feather Holes on the Barn Swallow Hirundo rustica and Other Small Passerines are Probably Caused by Brueelia Spp. Lice

Abstract Barn swallows Hirundo rustica often have characteristic feather holes on wing and tail feathers. During the past 15 yr, several influential papers have been based on the assumption that these holes were chewed by the louse Machaerilaemus malleus. We gathered feather-hole data from barn swallows and other passerines at 2 sites in Hungary and correlated the presence of holes with louse infestations and, more specifically, with the occurrence of M. malleus versus other species of avian lice. The shape of frequency distribution of holes was left-biased, and this bias was more pronounced in large swallow colonies that in a random sample, in accordance with the view that the causative agent of the ‘feather hole symptom’ is a contagious macroparasite. However, both intra- and interspecific comparisons suggest that the causative agent of the symptom had probably been misidentified. The occurrence of Brueelia spp. ‘wing lice’ provides the best fit to the distribution and abundance of feather holes, both in barn swallows and across some other small passerines. This identification error does not challenge the results of the former evolutionary–ecological studies based on this model system, although it has important implications from the viewpoint of louse biology.

HOST-MEDIATED SITE SEGREGATION OF ECTOPARASITES: AN INDIVIDUAL-BASED SIMULATION STUDY

Site segregation of coexisting ectoparasite species may result either from a direct interaction such as resource competition between them or from a host-mediated interaction. Here we present an individual-based model for the coevolution of 1 host and 2 parasite species to study this latter hypothesis. Parasite species are generalists at the start of the simulation and develop site specificities under the following assumptions. Parasite populations are not subject to resource limitations but are limited directly by host defense as predation. Hosts have 2 sites that need different defensive abilities to reduce their parasite burden. Parasites need to exhibit different evasive abilities to survive on different sites. Host grooming selects parasites for an increasing capability for evasion, whereas parasites select hosts for an increasing efficiency of grooming. Two trade-offs are incorporated into the model: one between host defensive abilities on the 2 sites, and another between parasite evasive abilities on the 2 sites. We conclude that, under these assumptions, the optimization of host defense and parasite evasion strategies may select ectoparasites for site segregation and this may stabilize the coexistence of parasite species.

Clever birds are lousy: Co-variation between avian innovation and the taxonomic richness of their amblyceran lice

Lice (Insecta: Phthiraptera) are ectoparasites that reduce host life expectancy and sexual attractiveness. Their taxonomic richness varies considerably among their hosts. Previous studies have already explored some important factors shaping louse diversity. An unexplored potential correlate of louse taxonomic richness is host behavioural flexibility. In this comparative study, we examine the relationship between louse generic richness, innovative capabilities (as a proxy for behavioural flexibility), and brain size while controlling for host species diversity, phylogeny, body size and research effort. Using data for 108 avian families, we found a highly significant positive relationship between host innovative capabilities and the taxonomic richness of amblyceran lice, but a lack of a similar relationship in ischnoceran lice. Host brain size had only a marginal impact on amblyceran diversity and no correlation with ischnoceran diversity. This suggests that the effect in Amblycera is not mediated by metabolic limitations due to the energetic costs of brain size and maintenance, rather directly caused by the ecological differences between hosts with differing cognitive capabilities. We propose four alternative and mutually non-exclusive hypotheses that may explain this phenomenon.

An experimental test of the site specificity of preening to control lice in feral pigeons.

Site specificities of ectoparasites on the host may have evolved due to the selective pressure exerted by host grooming. The present study demonstrates that the efficiency of avian preening varies among sites on the host. The study relies on the simple idea that the effectiveness of preening behavior to control lice can be quantified by the removal rate of dead lice glued onto the feathers of living birds. Two treatments were done to document site-specific differences in the efficiency of preening for louse control. The first treatment showed that lice disappear from the underwing covert feathers significantly more than from the tail feathers. A second treatment showed that preening was responsible for the differential removal of lice. There seems to be some correspondence in the site specificity of the louse species Columbicola columbae and that of the efficiency of preening by the host, which is the feral pigeon (Columba livia).

Co-extinct and critically co-endangered species of parasitic lice, and conservation-induced extinction: should lice be reintroduced to their hosts?

The co - extinction of parasitic taxa and their host species isconsideredacommon phenomenon inthecurrent global extinction crisis. However, information about the conservation status of parasitic taxa is scarce. We prese nt a global list of co - extinct and critically co - endangered parasitic lice (Phthiraptera), based on published data on their host - specificity and their hosts’ conservation status according to the IUCN Red List. We list six co - extinct and 40 (possibly 41) cr itically co - endangered species. Additionally, we recognize 2 – 4 species that went extinct as a result of conservation efforts to save their hosts. Conservationists should consider preserving host - specific lice as part of their efforts to save species.

Evolutionary co-variation of host and parasite diversity—the first test of Eichler’s rule using parasitic lice (Insecta: Phthiraptera)

The taxonomic richness of lice (Phthiraptera) varies considerably among their avian and mammalian hosts. Previous studies explored some factors shaping louse diversity; however, the so-called Eichler’s rule—according to which taxonomic richness of parasites co-varies with that of their hosts—has never been tested. Our study incorporates all families of birds and mammals and the whole order of lice to test this co-variation, thus we present the widest taxonomic range to test any correlates of louse richness. Louse richness data were controlled for uneven sampling effort. We used the method of independent contrasts to control for phylogenetic effects. We found a strong correlation between the species richness of avian and mammalian families and generic richness of their lice. We discuss some alternative macroevolutionary and macroecological hypotheses that may explain this phenomenon that may well be a general feature of parasitism and it seems possible that this effect contribute considerably to global biodiversity.

Distribution of the myrmecoparasitic fungus Rickia wasmannii(Ascomycota: Laboulbeniales) across colonies, individuals,and body parts of Myrmica scabrinodis

The ant species Myrmica scabrinodis plays a markedly important ecological role through much of the humid grasslands of Eurasia. It hosts a species-rich community of pathogens and parasites, including Rickia wasmannii, an enigmatic member of entomoparasitic laboulbenialean fungi. This study provides a descriptive ecology of R. wasmannii by characterizing its prevalence and distribution across several hierarchical levels: colonies, individuals, and anatomic body parts. Infections were restricted to a single ant species, M. scabrinodis, and infected colonies occurred predominantly in wet habitats. Infections tended to be highly prevalent within infected colonies, often reaching 100% sample prevalence among workers. Individual infections exhibited an aggregated distribution typical to host-parasite systems. Workers from the aboveground part of nests (presumably older ones acting as foragers) were more infected than those from the belowground part. Fungal thalli could be found all over the body of the hosts, the head and the abdomen being the most infected parts of the body. The fungis distribution among host body parts statistically differed between low versus high-intensity infections: the initial dominance of the head decreased with advancing infection. These findings may provide baseline data for future comparative or monitoring studies.