and also:
Acoustic adaptations of periodical cicadas (Hemiptera: Magicicada)
UTA OBERDÖRSTER & PETER R. GRANT
Biological Journal of the Linnean Society, 2007, 90, 15–24.
Abstract
We studied the trade-off between traits that function in mate attraction
and those that function in enemy avoidance by contrasting features of
acoustic communication in cicadas differentially at risk to predators in
the same environment. Two genera of North American cicadas were studied:
Magicicada and Tibicen. Magicicada species of periodical cicadas, with
17-year life cycles, seek mates in dense aggregations of calling males
that are made possible by the relative ineffectiveness of predators to
control their numbers. During the breeding season, Magicicada are so
abundant that they satiate their predators. From their relative freedom
from predation, it is to be expected that traits for attracting mates
are emphasized in Magicicada compared with the more solitary genus
Tibicen, which reproduce at much lower densities. Males of solitary
species are expected to sing more loudly and at low pitch because both
features enhance long-distance transmission. These two features were
confirmed by measurement. Magicicada septendecim appears to be the most
divergent species, evolutionarily, in terms of an unusually sharply
tuned sound resonating system, low resonant frequency, and quietness of
its song that cannot be entirely explained by body size. These
characteristics represent adaptations to the problem of communicating
unambiguously to females at close range in a loud and heterogeneous
sound environment. Sensitivity to predators, parasitoids, and congeneric
species may also have shaped the evolution of their communication systems.
Alan McElligott a écrit :
Song divergence at the edge of Amazonia: an empirical test of the
peripatric speciation model
NATHALIE SEDDON
Biological Journal of the Linnean Society, 2007, 90, 173-188.
Abstract
The evolutionary divergence of mating signals provides a powerful basis for
animal speciation. Divergence in sympatry strengthens reproductive isolation, and
divergence in allopatry can reduce or eliminate gene flow between populations on
secondary contact. In birds, the first of these processes has empirical support,
but the second remains largely hypothetical. This is perhaps because most studies
have focused on oscine passerines, whose song learning ability may reduce the
influence of vocalizations in reproductive isolation. In suboscine passerines, the
role of learning in song development is thought to be minimal, and the resultant
signals are relatively fixed. To investigate the role of song in the early stages
of peripatric speciation, we therefore studied a suboscine, the chestnut-tailed
antbird Myrmeciza hemimelaena. We recorded male songs in a natural forest island
(isolated for < 3000 years) at the southern fringe of Amazonia, and at two
nearby sites in continuous
forest. A previous study found the isolated population to be weakly
differentiated genetically from the ancestral population suggesting that
peripatric speciation was underway. In support of this, although we detected
minor but significant differences in song structure between each site, the most
divergent songs were those of island birds. On simulating secondary contact
using playback, we found that pairs from the forest island responded more
strongly to island (i.e. local) songs than to those from both non-island sites,
and vice versa. This pattern was not observed in pairs from one non-island
site, which responded with equal strength to local songs and songs from the
other non-island site. Island females were more likely to approach and sing
after hearing local male songs, rather than songs from the non-island
populations, and vice versa; non-island females did not appear to discriminate
between local songs and those from the other non-island site. These findings
are cons
istent with the idea that vocal divergence arising in small populations at the
edge of Amazonia may result in partial reproductive isolation when contact is
resumed. They also suggest the possibility that song divergence in peripatry
may, after much longer time-frames, act as a barrier to gene flow in
suboscines, perhaps because of an inability to learn or recognize divergent
songs on secondary contact.
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
Dr. Alan McElligott
The School of Biology
Biology Building
The University of Nottingham
University Park
Nottingham NG7 2RD
UK
Tel + 44 (0) 115 951 3231
Fax + 44 (0) 115 951 3251
http://www.nottingham.ac.uk/biology/
--
__________________________________________________
Institut de Recherche sur la Biologie de l'Insecte
CNRS UMR 6035
Université de Tours, faculté des Sciences
Parc Grandmont
37200 Tours
http://www.univ-tours.fr/irbi/
http://sueur.jerome.neuf.fr
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