Artificial illumination near rivers may alter bat-insect trophic interactions
2019
Аутори:
Russo, DaniloConsentino, Francesca
Festa, Francesca
De Benedetta, Flavia
Bajić, Branka
Cerretti, Pierfilippo
Ancillotto, Leonardo
Тип документа:
Конференцијски прилог (Објављена верзија)
,
©2019 Associazione Teriologica Italiana onlus
Метаподаци
Приказ свих података о документуАпстракт:
Artificial lighting at night (ALAN) has undergone a broad and
rapid expansion. By altering natural environmental lighting,
ALAN significantly interferes with some key aspects of animal
physiology and ecology.
Bats, as obligate nocturnal taxon, are very sensitive to ALAN,
and so are the insects they feed on: thus, the presence of artificial
light may have direct effects on different bat behaviors such as
foraging, drinking, commuting, emergency, and roosting.
Insect attraction to light also leads more opportunistic bat species to use illuminated foraging sites, which alters their normal
routes and exposes them to a greater risk of predation. In
freshwater ecosystems, this alteration may have massive repercussions on the trophic relationship between foraging bats and
their insect prey.
We used bats and their insect prey as models to investigate the
effects of LED lighting on prey-predator interactions at riverine
ecosystems.
The experiment was carried out by installing a portable LED
outdoor lamp on a bank along the river Sangro and its tributary
stream Zittola (Abruzzo, Lazio and Molise National Park), in
summer 2017.
We compared through a paired design bat and insect reactions
in terms of bat activity and prey insect abundance and diversity,
respectively, on artificially lit vs. unlit nights. We surveyed bat
activity at each sampling point with stationary, automatically
triggered D500X bat detectors, and sampled insects using sticky
traps placed transversally along the river channel, 4 for each site
and treatment, for 3 hours after sunset.
We used generalized linear mixed models to test for the effect
of artificial illumination at night on bat activity and adopted
paired Student t-tests to examine differences in insect abundance
under dark and light conditions. We also calculated a BrayCurtis dissimilarity index to look at changes in insect assemblage
composition at family level between the two conditions, and used
non-metric multidimensional scaling (NMDS) to analyse insect
assemblage composition among sites and conditions. Finally, we
conducted a two-way analysis of similarity to test whether insect
assemblages differed under different light conditions, sites and
trap positions.
Our experiment shows that artificial light influenced both insect and bat assemblages in taxon-specific directions. Total bat
activity showed a significant decrease under lit conditions, but
this change was mainly due to the response of Myotis daubentonii, the most abundant species at the sites we investigated,
while light-opportunistic species showed no reaction or even an
opposite pattern as in the case of Pipistrellus kuhlii.
The total number of sampled insects, especially that of dipterans,
had a significantly increase under lit conditions. Moreover,
insect assemblage composition differed between dark and lit
conditions.
The increase of insects under artificial illumination mainly concerned Chironomidae, typical Myotis daubentonii prey, therefore the decline in activity we observed in this species is best
explained as direct avoidance of artificial lighting rather than a
food-induced reaction. In fact, M. daubentonii is a relatively
slow flier and mostly moves along rivers when hunting, so artificial light at night may act as a barrier fragmenting this species’
foraging habitat and increasing vulnerability to predation.
On the other hand, the increase in P. kuhlii activity we observed
on light sessions was most likely due to the increase in small
dipterans which concentrated especially near the light, since the
latter had the effect of promoting prey availability along riparian
vegetation, the optimal foraging habitat for this edge specialist.
We conclude that ALAN affects adversely some bat species,
whereas others exploit the greater availability of insects near
light sources. ALAN also implies qualitative and quantitative
alterations of insect assemblages, overall potentially altering
prey-predator interactions, which in turn implies changes in
ecosystem functions and dynamics.
У:
- IV convegno italiano sui chirotteri; 2019 Oct 17-19; Padova, Italy. Gruppo Italiano Ricerca Chirotteri – Associazione Teriologica Italiana; 2019. p. 29.