10.5061/DRYAD.1JWSTQJRV
Taverne, Maxime
0000-0003-3355-6200
Musée National d'Histoire Naturelle
King-Gillies, Nina
Muséum National d'Histoire Naturelle
Krajnovic, Marija
University of Zagreb
Lisicic, Duje
University of Zagreb
Mira, Oscar
University of Zagreb
Petricioli, Donat
DIIV Ldt. for Marine, Freshwater and Subterranean Ecology, Zadar
Sabolic, Iva
University of Zagreb
Stambuk, Anamaria
0000-0002-3177-7694
University of Zagreb
Tadic, Zoran
University of Zagreb
Vigliotti, Chloé
Muséum National d'Histoire Naturelle
Wehrle, Beck
University of California, Irvine
Herrel, Anthony
0000-0003-0991-4434
Muséum National d'Histoire Naturelle
Data from: Proximate and ultimate drivers of variation in bite force in
the insular lizards Podarcis melisellensis and Podarcis sicula
Dryad
dataset
2020
Podarcis melisellensis
Podarcis sicula
National Geographic Society
https://ror.org/04bqh5m06
Explorer Grant
Croatian Science Foundation
https://ror.org/03n51vw80
HRZZ-IP-2016-06-9177
2020-06-03T00:00:00Z
2020-06-03T00:00:00Z
en
https://doi.org/10.5061/dryad.2b1g52j
13390 bytes
3
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
Bite force is a key performance trait in lizards since biting is involved
in many ecologically relevant tasks, including foraging, fighting, and
mating. Several factors have been previously suggested to impact bite
force in lizards, such as head morphology (proximate factors), or diet,
intraspecific competition, and habitat characteristics (ultimate factors).
However, these have been generally investigated separately and mostly at
the interspecific level. We tested which factors drive variation in bite
force at the population level and to what extent. Our study includes 20
populations of two closely-related lacertid species, Podarcis
melisellensis and Podarcis sicula, which inhabit islands in the Adriatic.
We found that lizards with more forceful bites have relatively wider and
taller heads, and consume more hard prey and plant material. Island
isolation correlates with bite force, likely by driving the resource
availability. Bite force is only poorly explained by proxies of
intraspecific competition. The linear distance from a large island and the
proportion of difficult-to-reduce food items consumed are the ultimate
factors that explain most of the variation in bite force. Our findings
suggest that the way in which morphological variation affects bite force
is species-specific, likely reflecting the different selective pressures
operating on the two species.
In-vivo bite force was measured using an isometric Kistler force
transducer (type 9203) connected to a Kistler charge amplifier (type 5995,
Kistler Inc., Winterthur, Switzerland). Lizards were made to bite the
plates of the transducer, left bare, at least five times, and the greatest
bite force across the five trials was retained as an estimate of an
individual’s maximum bite force. Gape angle was standardized across trials
by adjusting the distance between the bite plates for each individual to
maintain gape angle constant at around 30°. Bite position was standardized
by assuring that the tips of the jaws of each lizard were up against the
metal stop mounted on the device. Bite force was log10-transformed before
statistical analyses. The maximum hardness of each food item was estimated
using the regression equations proposed by Herrel & O’Reilly
(2006) that relate prey length and hardness, according to the item
hardness category. We measured all individuals using digital calipers
(Mitutoyo absolute digimatic; ± 0.01mm; see Supplementary Fig. 1) and
recorded snout-vent length (SVL) and linear head dimensions including head
length (HL), head width (HW), head height (HH), lower jaw length (LJL),
quadrate to jaw tip length (QT), and coronoid to jaw tip length (CT). Two
other functionally relevant variables were calculated: the in-lever for
jaw opening (open = LJL – QT) and the in-lever for jaw closing (close= QT
– CT). For both species separately, a principal component analysis (PCA)
was run on head dimensions. The contribution of each specimen along the
three first principal components (PC) was extracted and used to calculate
the mean contribution of each sex of each population on these axes. The
sexual dimorphism in head dimensions (SDh) for each site was determined as
follows: where mi and fi refer respectively to the mean contribution of
the males and the females of the population of interest along with the
PCi. Two other proxies for intraspecific competition were estimated: the
proportion of individuals which missed the longest toe on one of the hind
feet and the proportion of individuals with a regenerated tail.
Data has been log-10 transformed, expect for the proportions which have
been arcsin transformed.