Luis Arriaga (MS student)
Female mate choice has been
studied a great deal, but male mate choice has been
historically neglected. My first project
focused on the evolution of male mate preference as it
relates to female fecundity. Theory predicts that the
strength of male mate choice should be correlated to
female quality. In other words, males should prefer
females based on how big a bang for their buck they get.
In poeciliids, female quality in terms of fecundity is
highly correlated with female size. What's interesting
is that this correlation is different depending on the
habitat from which the population originates. For
example, females from toxic environments have evolved to
have fewer and larger offspring than females from
nontoxic environments. That means that the difference
between the fecundity of small vs. large females in the
cave is smaller than that of fish from the nontoxic
environments. Males from nontoxic environments therefore
have a comparatively bigger incentive to choose larger
females, and they should therefore have a stronger
preference for larger females than cave males. Whether
this is true or not is the question that this project
Female Limia vittata
second project focused on Limia.
Limia is a very
cool genus of poeciliids from the greater Antilles, but
it has been severely neglected in terms of research. I
wanted to begin to rectify this situation, so I looked
at the behavior of three species (L. sulphurophila,
L. perugiae, and L. vittata) in three
different scenarios- male/male, male/male/female, and
third project involved Poecilia mexicana.
This species has a number of populations living in all
combinations of cave/surface and toxic/nontoxic
environments. These populations have evolved a number of
different adaptations to deal with their respective
environments, and as such they are undergoing the
process of speciation. Interestingly, there is
practically no gene flow between the toxic cave/nontoxic
surface populations, even though there are no
significant barriers to it. I therefore created hybrids
between a population of toxic cave fish and another
population of nontoxic surface fish, and I tested their
fitness under food and light conditions meant to
simulate cave and surface environments. Some of the
variables measured were: survival, maturation rates,
growth rates, fat content, number of babies, interbrood
interval, fat content of the embryos and babies, among
I also worked on the website,
including taking the photos in the "pictures"
is what the website used to look like.
I got my Master's in the
spring of 2013.
project uses the Amazon molly, Poecilia
formosa, to analyze the effects of an audience on
sexual behavior. The question I am trying to answer is do
males and females adjust their sexual behavior due to the
presence of other individuals? I will use different
combinations of Poecilia
latipinna males and females along with the P. formosa to
documents the interactions among them. The results of my
experience will help us to understand factors that allow
the stable co-existence between a sexual species and an
asexual, sperm-dependant associate.
of the more puzzling questions in ecology is the
existence of species or lineages through time.
Especially, how sexual species can coexist with asexual
species, although the latter should have a clear
advantage in reproductive output?
diploma thesis focused on P.
formosa, a clonal but sperm-dependent
gynogenetic vertebrate species, which coexists with
closely related sexual species like P.
latipinna. Ecological differences could reduce
competition between both species directly or indirectly
through different mortality rates.
studied both species in the field and tested
experimentally for differences in thermal tolerance,
differences in the susceptibility to predators and
differences in food preferences as well as food
I am studying
the behavioral and hormonal mechanisms behind a
conditional signal in male green swordtails, X.
hellerii. The lateral stripe on adult green swordtails
is important for social interactions, and has been
considered a static, unchanging trait. However, males
from a single observed population in Veracruz, Mexico
can reversibly change the color of their stripe, and
within a matter of minutes. I am investigating the
modality with which males perceive each other and that
triggers color change, as well as female preference for
stripe color. Additionally, I am comparing color
shifting in the presence of males from the same
population and with two, non-shifting populations.
Finally, I will be isolating hormones that may explain
the physiological changes that occur in shifting males,
specifically examining chromatophore expression.
coexistence of gynogenetic Amazons and its sexual host
species may occur under weak male mate discrimination,
density dependent mating, or ecological niche
partitioning. In the current project, we study frequency
dependent mechanisms that may regulate long-term
coexistence of sexual and asexual females. Simulating
the colonization of new habitats in a patchy
environment, we are testing population regulation and
coexistence of sperm-dependent asexual females and
sexually reproducing females in a mesocosm experiment.
of sex, its origin and maintenance are part of the major
puzzle of modern evolutionary biology. Compared to
asexual reproduction, sex is a costly and at first sight
ineffective mechanism, since it involves disadvantages
like the production of males, leading to a reduced
overall number of offspring. This leads to the question
why the majority of species reproduces sexually.
The coexistence of the gynogenetic Amazon Molly (Poecilia
formosa) and its sexual host species (P.
latipinna and P.
mexicana) represents a suitable model to
explain how sexuality can persist despite its costs. For
my diploma project I investigated which factors,
especially on the behavioral level, might regulate the
stability of the mating system by addressing the
following main questions:
• Do males from populations dominated
by Poecilia formosa
differ in mate choice decisions from males from
populations in which P.
formosa is rare?
• Does the social environment
influence conspecific and heterospecific sperm transfer
in Poecilia latipinna
males and what are the consequences for the
fertilization success in Poecilia
• Which association preferences do
males show when confronted with shoals of different
am studying audience effects in sailfin mollies,
P. latipinna, and amazon mollies, P.
formosa. Audience effects is essentially
two individuals interacting with an audience present and
how the interacting pair changes their behavior
according to the type of audience. I am focusing
on sexual harassment and whether or not harassment is
influenced with the presence of a male audience or the
size of these males. The audiences that I use are
movies that are play back on a computer screen to the
I am doing honors research with Amazon and Sailfin
Mollies. I am interested in male mate choice in the
Sailfin Mollies. Many studies have shown that male
Sailfins prefer conspecific Sailfin female over the
asexual, heterospecific Amazon Molly. Other studies have
shown no preference. However, the Amazon Molly mating
system is dependent upon male choice. I am interested in
how male preference changes when a cost is involved. I
would predict that when males have to spend more energy
to get to the female, they will show a greater
preference for conspecific females over heterospecifics.
In my experiment, males will be made to swim against a
current to get to the female. I expect that the energy
the male spends will alter with the female's value. To
this end, I will vary the female species, size, and
quality in my experiment. I may also show videos of
different audiences to see how they affect male choice.
Such audiences would be other males, predators, Amazon
females or Sailfin females.
project I study adaptations of fishes to life in
lightless subterranean habitats. In a comparative
approach I examine the ecology, behavior, parasitology
and reproductive life history traits in the cave molly
and in surface-dwelling mollies.
The habitat of the cave molly, the south Mexican “Cueva del Azufre”
is unique in its combination of darkness and toxic
H2S. My major interests are the evolution of male
mating tactics and male and female (non-visual) mating
preferences in relation to extreme environmental
conditions and lightlessness.
I am interested in two aspects of Poecilia-life
What life history traits contribute to the stability
in a sexual/asexual mating complex of fishes (Amazon
formosa & Sailfin mollies, Poecilia
latipinna). To understand how stable
coexistence in the P.
latipinna/ P. formosa–mating complex can be
maintained, it is important to obtain thorough
information concerning life-history traits of both
species. For my dissertation project, I address the
following questions: (1) Are there differences in
the life histories of P.
P. latipinna? (2) How do life history
traits relate to the maintenance of the stable
coexistence in the P.
latipinna/ P. formosa–mating complex?
What life history adaptations allow for colonization
of extreme habitats? In Tabasco, southern Mexico,
two populations of the Atlantic molly (Poecilia
mexicana) have invaded a toxic
(H2S-rich) and a non-toxic cave. In this system
I am studying toxic (H2S) and non-toxic surface- and
cave-habitats to investigate how extreme
environments (darkness and toxicity) have selected
for different life history traits.
Amazon mollies are gynogens and reproduce asexually but
require sperm, commonly from male Sailfins, to trigger
embryogenesis. Sailfin mollies are a sexual species that
commonly live in the same habitat as Amazon mollies.
Theoretically, Amazon mollies should cause Sailfin
mollies to go extinct because of their ability to
increase in numbers more quickly. In turn, Amazon
mollies would go extinct because of their need for a
sperm donor. I’m interested in how these two species are
able to live in stable coexistence. One possible
mechanism is male choice. In theory, males should not
mate with Amazon mollies because they gain no
fitness-relevant offspring. Also, Amazon mollies must
compete with female Sailfin mollies. Currently, my
project is trying to determine if larger male Sailfin
mollies force smaller male Sailfin mollies into
proximity and mating situations with Amazon mollies.
Tobler (Ph. D. student)
evolution and maintenance of sex and recombination is
still a major and unresolved paradox in evolutionary
biology. Currently, one of the most widely accepted
hypotheses, the Red Queen hypothesis, states that
recombination provides an immediate advantage in biotic
interactions. More specifically, the Red Queen
hypothesis argues that recombination results in
genetically diverse offspring that, contrary to the
uniform offspring of asexuals, are difficult targets for
parasites and diseases.
The Amazon molly, Poecilia
formosa, is one of the few clonal
vertebrates, reproduces gynogenetically and thus
always has to coexist with a closely related sexual
species. The mating system of P.
formosa and its sexual relatives is an ideal
model system to investigate advantages of sexual
reproduction and testing the predictions of the Red
Current projects focus on: