Interactions between frequency–dependent and vertical transmission in host–parasite systems

Altizer, Sonia; Augustine, David J.

doi:10.1098/rspb.1997.0113

Cited by 40 publications

(40 citation statements)

References 23 publications

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“…Number as an alternative to density plays an acknowledged role in disease transmission (Thrall et al 1995;Altizer and Augustine 1997), and its importance in animal behavior is evidenced by discussions of frequency-dependent foraging strategies (Church et al 1996;Marini and Weale 1997;Smithson and Macnair 1997;Allen et al 1998;Belisle 1998). Ecologists have explored effects of group size on survivorship (e.g., Henschel 1998), and commonly demonstrate both costs and benefits of living in groups (reviewed in Radakov 1973;Bertram 1978).…”

Section: Discussionmentioning

confidence: 97%

Regulation of local populations of a coral reef fish via joint effects of density- and number-dependent mortality

Shima

2001

Oecologia

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Density-dependent mortality can regulate local populations - effectively minimizing the likelihood of local extinctions and unchecked population growth. It is considered particularly important for many marine reef organisms with demographically open populations that lack potential regulatory mechanisms tied to local reproduction. While density-dependent mortality has been documented frequently for reef fishes, few studies have explored how the strength of density-dependence varies with density, or how density-dependence may be modified by numerical effects (i.e., number-dependent mortality). Both issues can have profound effects on spatial patterns of abundance and the regulation of local populations. I address these issues through empirical studies in Moorea, French Polynesia, of the six bar wrasse (Thalassoma hardwicke), a reef fish that settles to isolated patch reefs. Per capita mortality rates of newly settled wrasse increased as a function of density and were well approximated by the Beverton-Holt function for both naturally formed and experimentally generated juvenile cohorts. Average instantaneous mortality rates were a decelerating function of initial densities, indicating the per capita strength of density-dependence decreased with density. Results of a factorial manipulation of density and group size indicate that per capita mortality rates were simultaneously density- and number-dependent; fish at higher densities and/or in groups had higher probabilities of disappearing from patch reefs compared with fish that were solitary and/or at lower densities. Mortality rates were ~30% higher for fish at densities of 0.5 fish/m than at 0.25 fish/m. Similarly, mortality rates increased by ~45% when group size was increased from 1 to 2 individuals per patch, even when density was kept constant. These observations suggest that the number of interacting individuals, independent of patch size (i.e., density-independent effects) can contribute to regulation of local populations. Overall, this work highlights a greater need to consider numerical effects in addition to density effects when exploring sources of population regulation.

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Section: Discussionmentioning

confidence: 97%

Regulation of local populations of a coral reef fish via joint effects of density- and number-dependent mortality

Shima

2001

Oecologia

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“…High host density can have several effects on disease dynamics. For example, it is most often associated with greater rates of horizontal transmission [54–56], leading to localized increases in prevalence. High coral cover reduces the distance between neighboring coral colonies [57] and thus between infected and healthy hosts, increasing the potential for horizontal disease transmission between corals in close proximity.…”

Section: Discussionmentioning

confidence: 99%

Thermal Stress and Coral Cover as Drivers of Coral Disease Outbreaks

et al. 2007

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Very little is known about how environmental changes such as increasing temperature affect disease dynamics in the ocean, especially at large spatial scales. We asked whether the frequency of warm temperature anomalies is positively related to the frequency of coral disease across 1,500 km of Australia's Great Barrier Reef. We used a new high-resolution satellite dataset of ocean temperature and 6 y of coral disease and coral cover data from annual surveys of 48 reefs to answer this question. We found a highly significant relationship between the frequencies of warm temperature anomalies and of white syndrome, an emergent disease, or potentially, a group of diseases, of Pacific reef-building corals. The effect of temperature was highly dependent on coral cover because white syndrome outbreaks followed warm years, but only on high (>50%) cover reefs, suggesting an important role of host density as a threshold for outbreaks. Our results indicate that the frequency of temperature anomalies, which is predicted to increase in most tropical oceans, can increase the susceptibility of corals to disease, leading to outbreaks where corals are abundant.

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“…On the other hand, Altizer et al (2004) found that for females that mated with heavily parasitized males, up to 90% of the progeny were infected for eggs laid immediately (1 day) following mating. Although this percentage declined to zero by 5 days post-mating, mathematical models of host-parasite dynamics indicate that even low rates of paternal transmission can prevent a virulent parasite from going extinct when maternal transmission is high, and hence could be important for explaining parasite persistence in migratory populations, and the high prevalence observed in some resident populations (Altizer and Augustine 1997;Altizer et al 2004).…”

Section: (B) (A)mentioning

confidence: 96%

Strength in numbers: high parasite burdens increase transmission of a protozoan parasite of monarch butterflies (Danaus plexippus)

et al. 2009

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Parasites often produce large numbers of offspring within their hosts. High parasite burdens are thought to be important for parasite transmission, but can also lower host fitness. We studied the protozoan Ophryocystis elektroscirrha, a common parasite of monarch butterflies (Danaus plexippus), to quantify the benefits of high parasite burdens for parasite transmission. This parasite is transmitted vertically when females scatter spores onto eggs and host plant leaves during oviposition; spores can also be transmitted between mating adults. Monarch larvae were experimentally infected and emerging adult females were mated and monitored in individual outdoor field cages. We provided females with fresh host plant material daily and quantified their lifespan and lifetime fecundity. Parasite transmission was measured by counting the numbers of parasite spores transferred to eggs and host plant leaves. We also quantified spores transferred from infected females to their mating partners. Infected monarchs had shorter lifespans and lower lifetime fecundity than uninfected monarchs. Among infected females, those with higher parasite loads transmitted more parasite spores to their eggs and to host plant leaves. There was also a trend for females with greater parasite loads to transmit more spores to their mating partners. These results demonstrate that high parasite loads on infected butterflies confer a strong fitness advantage to the parasite by increasing between-host transmission.

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Interactions between frequency–dependent and vertical transmission in host–parasite systems

Cited by 40 publications

References 23 publications

Regulation of local populations of a coral reef fish via joint effects of density- and number-dependent mortality

Regulation of local populations of a coral reef fish via joint effects of density- and number-dependent mortality

Thermal Stress and Coral Cover as Drivers of Coral Disease Outbreaks

Strength in numbers: high parasite burdens increase transmission of a protozoan parasite of monarch butterflies (Danaus plexippus)

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