­­­­­­­­­Introduction between rearing light and lateral display and quiver.

­­­­­­­­­Introduction

Speciation
is the formation of distinct species within the course of evolution. Geographical
changes, barries (allopatric) or sexual selection (sympatric) are examples of
factors which are the driving process behind speciation. Previous studies
indicate that sympatric speciation could be driven by heterogeneous
environments when geographical obstacles are missing. An example of sympatric
speciation in a heterogeneous environment is the sensory speciation in two
species of Chichlids in Lake Victoria. Two closely related Chichlids, Pundamilia
nyererei and Pundamilia pundamila live in the same lake but differ in
preference of waterdepth, and thus light intensity. Both species behave as
‘real’ species when they are present in their prefered habitat but hybridize in
turbid habitat where.

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State of the art

Although the aquatic ecosystem shows evidence in
visial communication, reproductive isolation due to visual adaptation hasn’t
been proved yet. Previous research to the effect of changing visual conditions
on mate choice for killifish did not show a comprehensive result but suggested
a small effect of sensory development on color choice. This promissing
suggestion is why the link between visual system properties and visual mate
preferences should be further investigated.

Another study has found that p. nyererei expresses higher long-wavelength-sensitive visual
pigment and is more sensitive to red colors compared to P. pundamila. Furthermore, the characteristics of male coloration,
photic environment and female preferences are correlated with the visial
systems which the Chichlids prefer. Botch Chichlids species and their
crossbreeds are used in this experiment. The Chichlids were reared under
simulated red colored deep- (turbid) and blue colored shallow (clear) water
conditions. Afterwards the preference of females for red or blue males under
different light settings was tested.

 

Recent findings

Female preference was significantly
affected by the rearing light conditions. Quiver and courtship behaviour for P. pundamila and P. nyererei
was prefered by both deep and shallow reared females however P. pundamila was more in favor by
females which were reared in simulated shallow water habitat. The female
Chichlids which were reared in deep water habitat did not have a specific
preference for any of the male Chichlids species.  Furthermore, when female species are brood in natural habitat
circumstances there is a significant interaction between rearing light and
lateral display and quiver. Female chechlids do more frequently respond to males
of the same species in reared lighting than when they are reared in artificial
lighting. Whenever P. pundamila
was raised in shallow water the females preferred males of the same species but
when P. pundamila was raised in deep
water it did not. P. nyererei did not
have any preference for either red or blue males in either shallow- or deep
reared habitat. When both P. pundamila and
P. nyererei are combined in one group
and are re-organising to the natural and unnatural deep and shallow lake rearing
conditions, it turned out that non random mating occurd. Sexual selection for
quivering male chichlids with the same phenotype occured significantly more
often than that females wanted to mate with a male with a different phenotype. It
turned out that females which were reared in light conditions that simulated
their natural habitat preferred mating with males who have a similar phenotype
but did not have a preference for any phenotype when brood under unnatural
light circumstances.

Repeatability of male preferency by hybrid and P. pundamila females was higher than when
compared to P. nyererei. Still,
overall the repeatability of female preference was small. This wasn’t caused by
the different set ups nor did examinating females in two contrasting light
conditions influence the experiment. Repeatability was low in both of each
tested set up and each light condition. Although the the experimental set ups
did not influence female preference it did influence fish activity. 

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