CONTENT - International Society of Zoological Sciences

S3 ICZ2008 - Abstracts
Male terminalia variation in the rainforest dwelling Drosophila
teissieri contrasts with the sperm pattern and species stability
Dominique Joly 1 , Marie-Louise Cariou 1 , Tendai Mhlanga-
Mutangadura 2,3 and Daniel Lachaise 1,#
1 CNRS UPR 9034, Laboratoire Evolution, Génomes et Spéciation,
91198 Gif-sur-Yvette Cedex, France, and Université Paris-Sud 11,
91405 Orsay Cedex, France
2 Department of Biological Sciences, University of Zimbabwe, P.O.
Box MP 167, Mount Pleasant, Harare, Zimbabwe ; 3 Present adress:
Department of Veterinary Pathobiology, University of Missouri,
Columbia, MO 65211
# Our late colleague and friend
It is commonly recognized that speciation does not necessarily result
from extensive variation between populations, and what the
speciation process per se consists of still remained an outstanding
question. We advocate here that the variation of male terminalia
does not necessarily result in noticeable reproductive isolation. Here
we report on the strictly Afrotropical forest-dwelling continental
species Drosophila teissieri whether there is invariance or variance
of traits central to sexual selection processes (i.e. male terminalia
and sperm length) compared to traits which are generally assumed
to vary more neutrally (i .e. allozymes). Three geographic categories
can be recognized: the central populations of the Guineo-Congolese
forest block (Cameroon-Congo), the outlying large populations of
West Africa to the west of the Dahomey gap (Guinea and Ivory
Coast), and isolated marginal populations scattered in East Africa
(e.g. Silinda in Zimbabwe). Although we concur with the argument
that the species integrity requires some degree of stability, our data
suggest that its components do not obey the variance/invariance
alternative consistently. Male terminalia and allozymes show
extensive variation while sperm length distribution is strikingly similar
between the categories. It is therefore inferred that this trait might be
one of the major targets of stabilizing selection. The relative
invariance of sperm distribution feature between populations is only
made possible due to considerable and consistent variance within.
Finally, it is suggested that the striking fit between the extent of
sperm heteromorphism (within male) and sperm polymorphism
(between males) is instrumental in maintaining the species integrity.
Evolutionary causes and consequences of mating plugs in
spiders
Stefan H. Nessler 1 , Jutta M. Schneider 1 and Gabriele Uhl 2
1
University of Hamburg, Biocenter, Department of Ethology, Bonn,
Germany
2
University of Bonn, Institute of Zoology, Department of
Neuroethology, Bonn, Germany
In animal mating systems there is a high selective advantage for any
mechanism that helps to avoid sperm competition. Relatively obvious
means by which males can secure their fertilization success is to
prevent or impede the female from re-mating with rival males by
plugging her copulatory opening. Mating plugs are a common
phenomenon for spider taxonomists: plugs made of secretion are
often found on the female copulatory opening and in some taxa
males are known to mutilate their genitalia in order to leave the
broken off parts inside the female genitalia. In this talk we will review
the information available to date on the effectiveness of the two
types of plugs. As to secretory plugs there is preliminary evidence
that in some species the mating plug is only effective when male and
female substances interact. These observations strongly suggest
that cryptic female mate choice can shape the effectiveness of male
secretions. As to male genital mutilation there is a recent increase in
experimental and comparative data. Since male genital mutilation
predominantly occurs in sexually cannibalistic species we will ask if
genital mutilation in males is the cause or the consequence of sexual
cannibalism.
- 16 -
Insect genitalia, sexual selection and sperm ageing
Klaus Reinhardt
Western Bank, S10 2TN, Sheffield, UK
Bill Eberhard has both united and revolutionised taxonomy and
evolutionary biology by proposing that animal genitalia have evolved
by sexual selection context, particularly so through male genitalic
courtship enabling cryptic female choice. Using several insect
species, I will here test some of Bill Eberhard's explicit predictions
about male genitalia allometry and about corresponding female
genitalia diversification. Cryptic female choice also incorporates the
specific case of sperm choice by females. I will explore the possibility
that genitalia have functions other than courtship and will propose
that intra-ejaculate variation in sperm quality may also be related to
genitalia complexity.
Functional Morphology of Copulatory Organs in Coleoptera
Phytophaga (Insecta)
Michael Schmitt and Susanne Düngelhoef
Zoologisches Forschungsmuseum Alexander Koenig, Adenauerallee
160, 53113 Bonn, Germany
Originally, the male copulatory organ (aedeagus) of the
Curculionoidea and the Chrysomeloidea is composed of a median
lobe and a tegmen with basal struts and distal parameres. Within the
taxon Phytophaga (= Pseudotetramera), the parameres have been
reduced several times. Comparison of different types of parameres
and median lobes and aedeagi lacking parameres and investigation
of dissected pairs in copula revealed that (1) parameres do not
provide mechanical coupling, (2) mechanical footing is provided by
the endophallus, (3) the flagellum serves as a means for sperm
transfer, and (4) the male possibly perceives tactile stimuli from the
bursa copulatrix (inside the female) during copulation by means of
sensilla in the membrane of the endophallus.
In several evolutionary lines the sclerotization of the aedeagus has
been reduced. Mechanical and behavioural interaction between male
and female copulatory organs have been studied morphologically
and by observation of live copulating pairs of beetles.