Long distance migration has evolved in many organisms moving through different media and using various modes of locomotion and transport. Migration continues to evolve or become suppressed as shown by ongoing dynamic and rapid changes of migration patterns. This great evolutionary flexibility may seem surprising for such a complex attribute as migration. Even if migration in most cases has evolved basically as a strategy to maximise fitness in a seasonal environment, its occurrence and extent depend on a multitude of factors. We give a brief overview of different factors (e.g. physical, geographical, historical, ecological) likely to facilitate and/or constrain the evolution of long distance migration and discuss how they are likely to affect migration. The basic driving forces for migration are ecological and biogeographic factors like seasonality, spatiotemporal distributions of resources, habitats, predation and competition. The benefit of increased resource availability will be balanced by costs associated with the migratory process in terms of time (incl. losses of prior occupancy advantages), energy and mortality (incl. increased exposure to parasites). Furthermore, migration requires genetic instructions (allowing substantial room for learning in some of the traits) about timing, duration and distance of migration as well as about behavioural and physiological adaptations (fuelling, organ flexibility, locomotion, use of environmental transport etc) and control of orientation and navigation. To what degree these costs and requirements put constraints on migration often depends on body size according to different scaling relationships. From this expos it is clear that research on migration warrants a multitude of techniques and approaches for a complete as possible understanding of a very complex evolutionary syndrome. In addition, we also present examples of migratory distances in a variety of taxons. In recent years new techniques, especially satellite radio telemetry, provide new information of unprecedented accuracy about journeys of individual animals, allowing re-evaluation of migration, locomotion and navigation theories. (Less)

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Long-distance migration: evolution and determinants

The effects of hormones on sex differences in infection: from genes to behavior.

Testing the immunocompetence handicap hypothesis: A review of the evidence

A fragment of the mitochondrial cytochrome b gene of avian malaria (genera Haemoproteus and Plasmodium) was amplified from blood samples of 12 species of passerine birds from the genera Acrocephalus, Phylloscopus and Parus. By sequencing 478 nucleotides of the obtained fragments, we found 17 different mitochondrial haplotypes of Haemoproteus or Plasmodium among the 12 bird species investigated. Only one out of the 17 haplotypes was found in more than one host species, this exception being a haplotype detected in both blue tits (Parus caeruleus) and great tits (Parus major). The phylogenetic tree which was constructed grouped the sequences into two clades, most probably representing Haemoproteus and Plasmodium, respectively. We found two to four different parasite mitochondrial DNA (mtDNA) haplotypes in four bird species. The phylogenetic tree obtained from the mtDNA of the parasites matched the phylogenetic tree of the bird hosts poorly. For example, the two tit species and the willow warbler (Phylloscopus trochilus) carried parasites differing by only 0.6% sequence divergence, suggesting that Haemoproteus shift both between species within the same genus and also between species in different families. Hence, host shifts seem to have occurred repeatedly in this parasite host system. We discuss this in terms of the possible evolutionary consequences for these bird species.

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Host specificity in avian blood parasites: a study of Plasmodium and Haemoproteus mitochondrial DNA amplified from birds

LETTERS to the EDITORPublication bias

Immunosuppressive effects of testosterone lead to a rediction of male-biased parasitism. To test this prediction, prevalences of blood parasites were compared between male and female birds using statistically correct vote counts of data from 33 studies. We found no overall difference in prevalence between males and females, in either breeding or non-breeding birds. However, infections by Haemoproteus (the most common genus of blood parasite found) were significantly more common among breeding females than breeding males, Restricting the analysis to breeding birds of polygynous species, females again were more likely than males to be infected by blood parasites: this result held for an intra-family comparison that controlled for phylogenetic effects. In comparison, measures of sexual size dimorphism did not relate to sex biases in parasitism as predicted, after controlling for phylogeny using independent comparisons. Because testosterone is often implicated in suppressing the immune system, female biases in parasitism are unexpected. Female biases in parasitism by blood parasites could result from differential exposure of the sexes to vectors, or from oestrogen-based effects on immunity.

/pdf/sex-biased-parasitism-of-avian-hosts-relations-to-blood-6ut57f9hre.pdf

Sex-Biased Parasitism of Avian Hosts: Relations to Blood Parasite Taxon and Mating System

Testing alternative hypotheses for variation in amphipod behaviour and life history in relation to parasitism.

We studied feeding site selection and impacts by benthic fish (flounder and skates) on the amphipod Corophium volutator, an ecologically-important species in muddy intertidal communities. We determined that benthic fish foraged mainly in areas that had high densities of amphipods, on a mudflat in Nova Scotia, Canada. This observation was based on recording sediments displaced by benthic fish in areas where samples of amphipods also were taken. From gut-content analysis, we found that benthic fish fed almost entirely on C. volutator, and most consumed smaller amphipods than expected based on samples of amphipods collected from the substrate. Benthic fish also fed on male amphipods more than expected. We determined that daily foraging pressure by benthic fish on amphipods was low (about 0.3% per day) by measuring the new appearance of feeding traces made by fish. Nonetheless, fish are expected to have substantial impacts on demography of C. volutator due to the length of the fish foraging season an...

Foraging and impacts by benthic fish on the intertidal amphipod corophium volutator

We found evidence that a nematode (Skrjabinoclava morrisoni) adaptively manipulates the behavior of its intermediate host (the amphipod Corophium volutator) to increase its likelihood of transmission to its final host (the semipalmated sandpiper, Calidris pusilla). We found that male and female amphipods parasitized by nematodes increased their surface activity in the field during daytime, but not during nighttime hours. Increased surface activity is known to increase susceptibility of amphipods to predation by sandpipers during the day, but not at night, when sandpipers do not feed visually. Also, as predicted by the manipulation hypothesis, only late-stage (infective) larvae of nematodes were associated with behavioral changes of amphipods. We found no evidence that parasites were associated with other amphipod behaviors in the laboratory, such as trail complexity, distance traveled, or burrow-probing activity of crawling males as would be expected if parasitized hosts altered their own behavior. Survivorship of amphipods was also unaffected by parasitism, which may favor parasite transmission. Thus, behavioral changes of parasitized hosts were simple, and their expression was context-dependent and related to likelihood of predation. We argue that maturation times of nematodes in relation to migration schedules of sandpipers provide a narrow window of opportunity and may explain why nematodes manipulate amphipod behavior. Key words: amphipod, Bay of Fundy, Calidris pusilla, Corophium volutator, host behavior, nematodes, parasite manipulation, sandpipers, Skrjabinoclava morrisoni. [Behav Ecol 10:351‐357 (1999)]

Evidence that the parasitic nematode Skrjabinoclava manipulates host Corophium behavior to increase transmission to the sandpiper, Calidris pusilla

In this paper, we describe the occurrence of a microsporidian parasite in female-biased populations of an intertidal amphipod, Corophium volutator (Pallas), at mudflat sites in the Bay of Fundy, Canada. Sequence data for the parasite's 16S rDNA indicate that it is a novel microsporidian species. This parasite was found principally in female host gonads, indicating that it might be a vertically transmitted, sex-distorting microparasite. At 4 sites each sampled in early and mid-summer, parasite prevalence varied from 0 to 21%. In the lab, infected mothers gave rise to more female-biased broods, than did uninfected mothers. Infection was not associated with size of females or with lowered survivorship of their young. Surprisingly, infected mothers actually had higher fertility controlling for body length than did uninfected mothers. Taken together, our results suggest that this novel microsporidian is likely a feminizing microparasite and is a contributing factor to local and widespread sex ratio distortion in C. volutator.

Dean G. McCurdy

Papers

Sex-Biased Parasitism of Avian Hosts: Relations to Blood Parasite Taxon and Mating System

Testing alternative hypotheses for variation in amphipod behaviour and life history in relation to parasitism.

Foraging and impacts by benthic fish on the intertidal amphipod corophium volutator

Evidence that the parasitic nematode Skrjabinoclava manipulates host Corophium behavior to increase transmission to the sandpiper, Calidris pusilla

Evidence for sex ratio distortion by a new microsporidian parasite of a Corophiid amphipod.