10.5061/DRYAD.9GHX3FFHW
Common, Lauren K
0000-0001-8551-5107
Flinders University
Sumasgutner, Petra
0000-0001-7042-3461
University of Vienna
Dudaniec, Rachael Y
Macquarie University
Colombelli-Negrel, Diane
0000-0002-9572-1120
Flinders University
Kleindorfer, Sonia
Flinders University
Avian vampire fly (Philornis downsi) intensity and mortality
Dryad
dataset
2021
2021-07-25T00:00:00Z
2021-07-25T00:00:00Z
en
45553 bytes
4
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
In invasive parasites, generalism is considered advantageous during the
initial phase of introduction. Thereafter, fitness costs to parasites,
such as host-specific mortality, can drive parasites towards specialism to
avoid costly hosts. It is important to determine changes in host
specificity of invasive populations to understand host-parasite dynamics
and their effects on vulnerable host populations. We examined changes in
mortality in the introduced avian vampire fly (Philornis downsi) (Diptera:
Muscidae), a generalist myasis-causing ectoparasite, between 2004 and 2020
on Floreana Island (Galápagos). Mortality was measured as the proportion
of immature larvae found upon host nest termination. Over the time period,
the avian vampire fly was most abundant and had low mortality in nests of
the critically endangered medium tree finch (Camarhynchus pauper) and had
the highest mortality in nests of hybrid tree finches (Camarhynchus spp.).
Low larval mortality was also found in small tree (Camarhynchus parvulus)
and small ground finch (Geospiza fuliginosa) nests. Selection could favour
avian vampire flies that select medium tree finch nests and/or avoid
hybrid nests. Overall, the finding of differences in avian vampire fly
survival across host species is parsimonious with the idea that the
introduced fly may be evolving towards host specialisation.
Avian vampire fly (Philornis downsi) intensity (total number of parasites
collected per nest) was collected from nests of Darwin's finches
monitored in the highlands of Floreana Island, Galapagos across 10 years:
2004, 2005, 2006, 2008, 2010, 2012, 2013, 2014, 2016 and 2020. Floreana
rainfall data (sum of annual rainfall; mm) were collected via satellite
sourced from CPC Global Unified Precipitation Data provided by
NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, downloaded from the Galápagos
Vital Signs website by the Galápagos Conservancy. Nests of three host
species and one hybrid, small ground finch (Geospiza fuliginosa), small
tree finch (Camarhynchus parvulus), medium tree finch (C. pauper) and the
hybrid tree finch (C. parvulus x C. pauper including introgressed
individuals) were monitored during incubation and nesting. Host species
was determined morphologically in the field and hybrids were confirmed via
microsatellite analysis. Brood size was collected using borescope. Upon
nest termination (host death, as determined via borescope, or fledging)
nests were collected and dismantled to collect the total number of P.
downsi (larvae, pupae, puparia and adult flies). Dead nestlings were
soaked in ethanol for 24 hours to collect any larvae residing in the nares
or ear canals and these larvae were added to the total intensity. For a
subset of these nests, all P. downsi larvae were identified to age class:
first instar, second instar and third instar. First and second instar are
unable to survive to adulthood upon termination of the nest and therefore
were used to caculate to proportion of unsuccessful P. downsi per nest.