Invasion of an Avian Nest Parasite, Philornis downsi, to the Galapagos Islands: Colonization History, Adaptations to Novel Ecosystems, and Conservation Challenges

Feßl, Birgit; Heimpel, George E.; Causton, Charlotte E.

doi:10.1007/978-3-319-65909-1_9

Cited by 74 publications

(132 citation statements)

References 136 publications

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“…Under this situation, first instars could either wait until nestlings hatch or feed on parent birds, as has already been demonstrated through the presence of anti-Philornis antibodies in brooding females (Huber et al, 2010;Koop et al, 2013b) and through the finding of P. downsi larvae and pupae in which eggs failed to hatch (Cimadom et al, 2016;Fessl et al, 2018). We suggest that increased larval longevity in Philornis may facilitate exploitation of ephemeral and unpredictable resources such as nestlings.…”

Section: Discussionsupporting

confidence: 60%

“…The study system Philornis downsi attacks dozens of bird species in various orders, particularly the Passeriformes (Bulgarella & Heimpel, 2015;Fessl et al, 2018). In-nest video analyses and nest inspections have shown that P. downsi females deposit eggs ( Figure 1) within bird nests on nesting material (O'Connor et al, 2010a;Lincango et al, 2015).…”

Section: Methodsmentioning

confidence: 99%

“…In various species of Darwin's finches in Gal apagos (Fessl et al, 2006) and in society finches in captivity (Bulgarella et al, 2017) the first instars feed within the nares or ears of nestling birds and feed externally on the body of nestlings in the second and third instars. There is some recent evidence from Darwin's finches that young P. downsi larvae can feed on brooding females as well (Huber et al, 2010;Koop et al, 2013b;Cimadom et al, 2016) but the dynamics of this behaviour are not well understood (Fessl et al, 2018). The development time of their nestling hosts (taking Darwin's finches as an example) ranges between 12 and 14 days (Fessl & Tebbich, 2002).…”

Section: Methodsmentioning

confidence: 99%

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Environmentally cued hatching in the bird‐parasitic nest fly Philornis downsi

Sage

Boulton

Lahuatte

et al. 2018

Entomologia Exp Applicata

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Under the hypothesis of environmentally cued hatching (ECH), eggs are stimulated to hatch by cues favouring larval survival. Here we investigated whether the bird-parasitic nest fly Philornis downsi Dodge & Aitken (Diptera: Muscidae) exhibits ECH in response to the presence of suitable hosts and environmental conditions. Philornis downsi is an invasive in the Galapagos Islands and ECH could help to explain its success in a novel habitat. We found that the presence of hosts (nesting birds) per se does not accelerate hatching time in P. downsi, but that nesting birds do produce a microclimate, in terms of temperature and/or humidity that is conducive to faster hatching and higher hatching success. Eggs that are laid under extremely dry conditions die rather than delay their hatching time. We also found that P. downsi eggs hatch more rapidly when the substrate is very wet. Furthermore, larvae that hatch rapidly survive longer under starvation conditions. We suggest that eggs hatching more rapidly can either take advantage of optimal conditions for larval growth (host presence) or escape unfavourable microclimatic conditions (as larvae are mobile).

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Section: Discussionsupporting

confidence: 60%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Environmentally cued hatching in the bird‐parasitic nest fly Philornis downsi

Sage

Boulton

Lahuatte

et al. 2018

Entomologia Exp Applicata

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“…Here we focus on natural selection for small body size in the fly, Philornis downsi (Diptera: Muscidae) (Dodge and Aitken), which is an invasive myiasis-causing parasite of Darwin's finches on the Galápagos Islands. Philornis downsi larvae consume the blood and tissue of nestling birds, causing up to 100% in-nest mortality in some of its Darwin's finch hosts (Dudaniec & Kleindorfer, 2006;Fessl, Heimpel, & Causton, 2018;Kleindorfer, Peters, Custance, Dudaniec, & O'Connor, 2014;O'Connor, Sulloway, Robertson, & Kleindorfer, 2010). The adult fly has been present in the Galápagos since at least 1964 (Causton et al, 2006), but its larvae were first reported in Darwin's finch nests on Santa Cruz Island in 1997 (Fessl, Couri, & Tebbich, 2001) despite long-term field study into Darwin's finches on other islands since 1973 (Grant & Grant, 2002).…”

Section: Introductionmentioning

confidence: 99%

Evidence for rapid downward fecundity selection in an ectoparasite (Philornis downsi) with earlier host mortality in Darwin’s finches

Common

O’Connor

Dudaniec

et al. 2020

J of Evolutionary Biology

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Fecundity selection is a critical component of fitness and a major driver of adaptive evolution. Trade‐offs between parasite mortality and host resources are likely to impose a selection pressure on parasite fecundity, but this is little studied in natural systems. The ‘fecundity advantage hypothesis’ predicts female‐biased sexual size dimorphism whereby larger females produce more offspring. Parasitic insects are useful for exploring the interplay between host resource availability and parasite fecundity, because female body size is a reliable proxy for fecundity in insects. Here we explore temporal changes in body size in the myiasis‐causing parasite Philornis downsi (Diptera: Muscidae) on the Galápagos Islands under conditions of earlier in‐nest host mortality. We aim to investigate the effects of decreasing host resources on parasite body size and fecundity. Across a 12‐year period, we observed a mean of c. 17% P. downsi mortality in host nests with 55 ± 6.2% host mortality and a trend of c. 66% higher host mortality throughout the study period. Using specimens from 116 Darwin's finch nests (Passeriformes: Thraupidae) and 114 traps, we found that over time, P. downsi pupae mass decreased by c. 32%, and male (c. 6%) and female adult size (c. 11%) decreased. Notably, females had c. 26% smaller abdomens in later years, and female abdomen size was correlated with number of eggs. Our findings imply natural selection for faster P. downsi pupation and consequently smaller body size and lower parasite fecundity in this newly evolving host–parasite system.

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“…The first‐instar larvae of P. downsi feed on the inside of the nestling beak and cause massive deformation; the few hosts that fledge generally have severely enlarged naris size (Kleindorfer & Sulloway, ). High mortality caused by P. downsi is the biggest threat to the survival of Galapagos land birds (Causton et al., ) and is thought to be the principal cause of recent declines in Galápagos passerines, making this novel host–parasite association a critical invasive species conservation battle (Causton, Cunninghame, & Tapia, ; Fessl, Heimpel, & Causton, ; Kleindorfer & Dudaniec, ).…”

Section: Introductionmentioning

confidence: 99%

Host‐specific associations affect the microbiome of Philornis downsi, an introduced parasite to the Galápagos Islands

et al. 2017

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The composition and diversity of bacteria forming the microbiome of parasitic organisms have implications for differential host pathogenicity and host-parasite co-evolutionary interactions. The microbiome of pathogens can therefore have consequences that are relevant for managing disease prevalence and impact on affected hosts. Here, we investigate the microbiome of an invasive parasitic fly Philornis downsi, recently introduced to the Galápagos Islands, where it poses extinction threat to Darwin's finches and other land birds. Larvae infest nests of Darwin's finches and consume blood and tissue of developing nestlings, and have severe mortality impacts. Using 16s rRNA sequencing data, we characterize the bacterial microbiota associated with P. downsi adults and larvae sourced from four finch host species, inhabiting two islands and representing two ecologically distinct groups. We show that larval and adult microbiomes are dominated by the phyla Proteobacteria and Firmicutes, which significantly differ between life stages in their distributions. Additionally, bacterial community structure significantly differed between larvae retrieved from strictly insectivorous warbler finches (Certhidea olivacea) and those parasitizing hosts with broader dietary preferences (ground and tree finches, Geospiza and Camarhynchus spp., respectively). Finally, we found no spatial effects on the larval microbiome, as larvae feeding on the same host (ground finches) harboured similar microbiomes across islands. Our results suggest that the microbiome of P. downsi changes during its development, according to dietary composition or nutritional needs, and is significantly affected by host-related factors during the larval stage. Unravelling the ecological significance of bacteria for this parasite will contribute to the development of novel, effective control strategies.

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Invasion of an Avian Nest Parasite, Philornis downsi, to the Galapagos Islands: Colonization History, Adaptations to Novel Ecosystems, and Conservation Challenges

Cited by 74 publications

References 136 publications

Environmentally cued hatching in the bird‐parasitic nest fly Philornis downsi

Environmentally cued hatching in the bird‐parasitic nest fly Philornis downsi

Evidence for rapid downward fecundity selection in an ectoparasite (Philornis downsi) with earlier host mortality in Darwin’s finches

Host‐specific associations affect the microbiome of Philornis downsi, an introduced parasite to the Galápagos Islands

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