Darwin's Finch Begging Intensity Does Not Honestly Signal Need in Parasitised Nests

O’Connor, Jody A.; Robertson, Jeremy; Kleindorfer, Sonia

doi:10.1111/eth.12196

Cited by 54 publications

(66 citation statements)

References 41 publications

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“…Medium tree finch nests had more P. downsi larvae compared with most other Darwin's finch species (Dudaniec et al, 2007;Kleindorfer et al, 2014b). Although higher body condition is often linked with fewer parasites or higher survival under conditions of parasitism (Brown et al, 2000;Møller et al, 1998), this does not directly apply here because the parasite P. downsi consumes the blood of nestling birds and not adults Fessl et al, 2006;Huber, 2008;O'Connor et al, 2014). Therefore, even if adult small and medium tree finches had better body condition and higher adult survival than the hybrid birds, their numbers could still be declining due to low nesting success.…”

Section: Discussionmentioning

confidence: 97%

Divergent foraging behavior in a hybrid zone: Darwin’s tree finches (Camarhynchus spp.) on Floreana Island

Peters

Kleindorfer

2015

Current Zoology

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Hybrid speciation is increasingly recognized as a mechanism for novel evolutionary trajectories. However, we know very little about the ecology of a contact zone that has arisen in sympatry. This study examines the foraging behavior and fitness of two species of Darwin's tree finches (Camarhynchus parvulus, C. pauper) and hybrid offspring on Floreana Island. Previous study showed that the percentage of hybrids in the tree finch population increased from 19% in 2005 to 41% in 2010, and their body and beak size increased by ~5% (parental phenotype did not change). In 2005-2006, all three tree finch groups (two parental species and hybrid birds) used the same foraging substrate, technique, and height. By 2010-2013, the small tree finch C. parvulus had changed its foraging technique and the medium tree finch C. pauper had changed its foraging height. Both parental species had higher body condition when foraging at (divergent) mean foraging heights per species but hybrid birds did not. We discuss the implications of conserving forest to facilitate vertical niche expansion and the role of hybridization for genetic persistence [Current Zoology 61 (1): [181][182][183][184][185][186][187][188][189][190] 2015].

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Section: Discussionmentioning

confidence: 97%

Divergent foraging behavior in a hybrid zone: Darwin’s tree finches (Camarhynchus spp.) on Floreana Island

Peters

Kleindorfer

2015

Current Zoology

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“…Adult flies, which are not parasitic, lay their eggs in the nests of finches and other land birds in the Galápagos. In some years, 100% of finch nests fail to produce fledglings due to P. downsi (Koop et al 2011, 2013a, O'Connor et al 2013. Several studies have shown that P. downsi reduces the reproductive success of the medium ground finch (Geospiza fortis) and other species of Darwin's finches (reviewed in Koop et al 2011).…”

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confidence: 99%

Galápagos mockingbirds tolerate introduced parasites that affect Darwin's finches

Knutie

Owen

McNew

et al. 2016

Ecology

161

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Introduced parasites threaten native host species that lack effective defenses. Such parasites increase the risk of extinction, particularly in small host populations like those on islands. If some host species are tolerant to introduced parasites, this could amplify the risk of the parasite to vulnerable host species. Recently, the introduced parasitic nest fly Philornis downsi has been implicated in the decline of Darwin's finch populations in the Galápagos Islands. In some years, 100% of finch nests fail due to P. downsi; however, other common host species nesting near Darwin's finches, such as the endemic Galápagos mockingbird (Mimus parvulus), appear to be less affected by P. downsi. We compared effects of P. downsi on mockingbirds and medium ground finches (Geospiza fortis) on Santa Cruz Island in the Galápagos. We experimentally manipulated the abundance of P. downsi in nests of mockingbirds and finches to measure the direct effect of the parasite on the reproductive success of each species of host. We also compared immunological and behavioral responses by each species of host to the fly. Although nests of the two host species had similar parasite densities, flies decreased the fitness of finches but not mockingbirds. Neither host species had a significant antibody-mediated immune response to P. downsi. Moreover, finches showed no significant increase in begging, parental provisioning, or plasma glucose levels in response to the flies. In contrast, parasitized mockingbird nestlings begged more than nonparasitized mockingbird nestlings. Greater begging was correlated with increased parental provisioning behavior, which appeared to compensate for parasite damage. The results of our study suggest that finches are negatively affected by P. downsi because they do not have such behavioral mechanisms for energy compensation. In contrast, mockingbirds are capable of compensation, making them tolerant hosts, and a possible indirect threat to Darwin's finches.

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“…() showed that provisioning in 2010 did not differ between treatments, as found in other Darwin's finch systems (O'Connor et al. ).…”

Section: Discussionmentioning

confidence: 68%

“…, , O'Connor et al. ), is harmless to birds, including newly hatched nestlings. Nests were sprayed soon after the first nestling hatched, then again 4–6 d later.…”

Section: Methodsmentioning

confidence: 99%

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Relationships among introduced parasites, host defenses, and gut microbiota of Galapagos birds

Knutie

2018

Ecosphere

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Parasites can cause significant damage to their hosts. Hosts can reduce the damage that parasites cause by either resisting parasites (e.g., with an immune response) or tolerating parasites (e.g., with energy compensation). Recent work suggests that host‐associated microbiota (bacteria) affect parasites, and vice versa, which can be mediated by host defense mechanisms. Although there are many possible interactions among parasites, host defenses, and host‐associated microbiota, few studies have explored these interactions in non‐model systems. Such studies are important for understanding disease risk, especially when considering emerging diseases. The parasitic nest fly Philornis downsi, which was introduced to the Galapagos Islands, causes considerable damage to Darwin's finches. In contrast, P. downsi has little effect on tolerant hosts, such as Galapagos mockingbirds, which increase nestling provisioning to compensate for energy lost to the parasite. Although host defenses against P. downsi have been relatively well‐studied, the importance of host‐associated microbiota in host–P. downsi interactions is unknown. In this study, an experimental manipulation of P. downsi was used to test the effect of parasitism on the fecal bacterial community (proxy for the gut) of Galapagos mockingbird and Darwin's finch nestlings. The relationships between the bacterial community and nestling provisioning or the antibody response were also determined. Galapagos mockingbirds and Darwin's finches harbor different gut bacterial communities. P. downsi decreased bacterial diversity of mockingbird nestlings, presumably in response to increased provisioning, which was negatively correlated with bacterial diversity. Lower bacterial diversity was related to lower antibody levels in mockingbirds. In contrast, P. downsi did not affect bacterial communities of finch nestlings, but bacterial diversity was negatively related to antibody levels. Overall, this study demonstrates that introduced parasites can affect host‐associated bacterial communities and that host defenses can correlate with changes in the gut microbiota.

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Darwin's Finch Begging Intensity Does Not Honestly Signal Need in Parasitised Nests

Cited by 54 publications

References 41 publications

Divergent foraging behavior in a hybrid zone: Darwin’s tree finches (Camarhynchus spp.) on Floreana Island

Divergent foraging behavior in a hybrid zone: Darwin’s tree finches (Camarhynchus spp.) on Floreana Island

Galápagos mockingbirds tolerate introduced parasites that affect Darwin's finches

Relationships among introduced parasites, host defenses, and gut microbiota of Galapagos birds

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